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Quantitative assessments of articular cartilage function are needed to aid clinical decision making. Our objectives were to develop a new electromechanical grade to assess quantitatively cartilage quality and test its reliability. Electromechanical properties were measured using a hand-held electromechanical probe on 200 human articular surfaces from cadaveric donors and osteoarthritic patients. These data were used to create a reference electromechanical property database and to compare with visual arthroscopic International Cartilage Repair Society (ICRS) grading of cartilage degradation. The effect of patient-specific and location-specific characteristics on electromechanical properties was investigated to construct a continuous and quantitative electromechanical grade analogous to ICRS grade. The reliability of this novel grade was assessed by comparing it with ICRS grades on 37 human articular surfaces. Electromechanical properties were not affected by patient-specific characteristics for each ICRS grade, but were significantly different across the articular surface. Electromechanical properties varied linearly with ICRS grade, leading to a simple linear transformation from one scale to the other. The electromechanical grade correlated strongly with ICRS grade (r = 0.92, p < 0.0001). Additionally, the electromechanical grade detected lesions that were not found visually. This novel grade can assist the surgeon in assessing human knee cartilage by providing a quantitative and reliable grading system.

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Recent advances in the development of new drugs to halt or even reverse the progression of Osteoarthritis at an early-stage requires new tools to detect early degeneration of articular cartilage. We investigated the ability of an electromechanical probe and an automated indentation technique to characterize entire human articular surfaces for rapid non-destructive discrimination between early degenerated and healthy articular cartilage. Human cadaveric asymptomatic articular surfaces (four pairs of distal femurs and four pairs of tibial plateaus) were used. They were assessed ex vivo: macroscopically, electromechanically, (maps of the electromechanical quantitative parameter, QP, reflecting streaming potentials), mechanically (maps of the instantaneous modulus, IM), and through cartilage thickness. Osteochondral s were also harvested from healthy and degenerated regions for histological assessment, biochemical analyses, and unconfined compression tests. The macroscopic visual assessment delimited three distinct regions on each articular surface: Region I was macroscopically degenerated, region II was macroscopically normal but adjacent to regions I and III was the remaining normal articular surface. Thus, each extracted was assigned to one of the three regions. A mixed effect model revealed that only the QP (p?<?0.0001) and IM (p?<?0.0001) were able to statistically discriminate the three regions. Effect size was higher for QP and IM than other assessments, indicating greater sensitivity to distinguish early degeneration of cartilage. When considering the mapping feature of the QP and IM techniques, it also revealed bilateral symmetry in a moderately similar distribution pattern between bilateral joints.  Read More

Purpose: Mechanical testing of articular cartilage is recommended by the FDA for products intended for the repair or replacement of knee cartilage. One experimental configuration that has many practical advantages is indentation. However, one limitation is the need to perpendicularly position the articular surface to the indenter. The objective of this study was to investigate the ability of a novel technique to automatically characterize mechanical properties of an entire articular surface with rapidity, precision, and reproducibility in indentation.  Read More

Early Post-traumatic Osteoarthritis (PTOA) can be asymptomatic but represents a possible window of opportunity for therapeutic intervention before disease progression. Impact models are ideal for studying these strategies because the location and severity of impact can be controlled. Streaming potentials generated during cartilage compression are a sensitive measure of degeneration, which may be valuable in detecting early PTOA. An arthroscopic device, the (Fig. 1) permits non-destructive electromechanical measurements and computes a Streaming Potential Integral (SPI) that reflects cartilage function, structure and composition. A custom-built Impactor device, consisting of a spring loaded shaft and a sterilizable, 6.5 mm diameter plane-ended tip with rounded edges, was developed to facilitate the delivery of local impact stresses to the articular surface in both in vitro and in vivo studies. Consistent impacts were successfully delivered with the custom-built Impactor device at two levels: low impact, 15.0 ± 1.4 MPa (n=6) and high impact, 41.3 ± 5.3 MPa (n=8). India ink revealed surface cracking and diffuse staining at high impact sites compared with faint or no staining at low impact sites (Fig. 4C). SPI decreased at all high impact sites (p<0.0001) and a nominal increase was observed due to low impact (p=0.002). Small increases in SPI may indicate alterations to the extracellular matrix but is unlikely to influence tissue function (Fig. 5). High impact caused a reduction in Ef (p=0.04), which reflects collagen network stiffness, an increase in k (p=0.03), but no change in Em (p=0.21), which reflects proteoglycan matrix stiffness. This suggests immediate damage to the collagen network but insufficient time for proteoglycan depletion to occur10 (Fig. 6). Detrimental changes to both electromechanical (SPI) and biomechanical properties of articular cartilage were detected immediately following impact injury.Read More

Introduction: The biochemical composition and mechanical/electromechanical properties of articular cartilage evolve during growth. The objective of this study was to examine the age-dependence in the distribution pattern of electromechanical properties of ovine articular cartilage. To achieve this goal, we used a hand-held medical device (), designed to be used during arthroscopy, to measure compression-induced streaming potentials on articular cartilage. The device sensor has 37 microelectrodes evenly distributed over the surface of a semi-spherical indenter. Streaming potentials are recorded by each microelectrode when the indenter is manually compressed against the articular cartilage surface. From each point measurement, the device calculates a quantitative parameter (QP) corresponding to the number of microelectrodes in contact with the cartilage (contact area) when the sum of their streaming potential reaches 100 mV. It should be mentioned that this calculation means that high QP cartilage has low stiffness and vice-versa. Previous studies have demonstrated the reproducibility and user independence of the and the relation between the QP and the electromechanical properties of human [1] and ovine articular cartilage [2].  Read More

Introduction: It is challenging to identify and grade degenerated regions of the entire articular surface both quantitatively and non-destructively. Therefore, the objective of this study was to investigate the ability of a novel technique to automatically characterize mechanical properties of entire articular surfaces in indentation to rapidly discriminate between damaged articular cartilage (AC) and healthy ones.  Read More

Purpose: The output of the was originally streaming potentials integral (SPI) parameter (Abedian-2013). Since then, the output has changed to a quantitative parameter (QP) (Sim-2014). The purpose of this study was to reanalyzed old data to investigate whether QP values are reliable for assessing articular cartilage in a clinical context. Read More

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In a recent study, our group has highlighted the importance of considering the natural topographic variability of the mechanical properties over the articular surface, particularly in the context of cartilage repair, where it can screen the effect of a treatment [1]. Moreover, the availability of test sample is limited in those repair studies since the regions of interest are often limited in size. A solution to overcome this problematic is to perform multiple tests at a single location over the articular surface. Therefore, the objective of this study was to develop such a sequence of mechanical tests to characterize articular cartilage at a single location.  Read More

Recent advances in the development of new drugs to halt or even reverse the progression of Osteoarthritis at an early-stage requires new tools to detect early degeneration of articular cartilage. We investigated the ability of an electromechanical probe and an automated indentation technique to characterize entire human articular surfaces for rapid non-destructive discrimination between early degenerated and healthy articular cartilage. Human cadaveric asymptomatic articular surfaces (four pairs of distal femurs and four pairs of tibial plateaus) were used. They were assessed ex vivo: macroscopically, electromechanically, (maps of the electromechanical quantitative parameter, QP, reflecting streaming potentials), mechanically (maps of the instantaneous modulus, IM), and through cartilage thickness. Osteochondral s were also harvested from healthy and degenerated regions for histological assessment, biochemical analyses, and unconfined compression tests. The macroscopic visual assessment delimited three distinct regions on each articular surface: Region I was macroscopically degenerated, region II was macroscopically normal but adjacent to regions I and III was the remaining normal articular surface. Thus, each extracted was assigned to one of the three regions. A mixed effect model revealed that only the QP (p?<?0.0001) and IM (p?<?0.0001) were able to statistically discriminate the three regions. Effect size was higher for QP and IM than other assessments, indicating greater sensitivity to distinguish early degeneration of cartilage. When considering the mapping feature of the QP and IM techniques, it also revealed bilateral symmetry in a moderately similar distribution pattern between bilateral joints.

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OBJECTIVE:The hand-held ? device is used to map electromechanical properties of articular cartilage. The purpose of the study was to evaluate correlation of electromechanical properties with histological, biochemical and biomechanical properties of cartilage.

METHOD:Electromechanical properties (quantitative parameter (QP)) of eight human distal femurs were mapped manually ex vivo using the (1 measure/site, 5 s/measure, 3209 sites). Osteochondral s were then harvested from different areas on the femurs and assessed with the Mankin histological s. Prior to histoprocessing, s were tested in unconfined compression. A subset of the s was analyzed with polarized light microscopy (PLM) to assess collagen structure. Biochemical assays were done on additional s to obtain water content and glycosaminoglycan (GAG) content. The QP corresponding to each was calculated by averaging all QPs collected within 6 mm of the center.

RESULTS:The electromechanical QP correlated strongly with both the Mankin s and the PLM s (r = 0.73, P < 0.0001 and r = -0.70, P < 0.0001 respectively) thus accurately reflecting tissue quality and collagen architecture. Electromechanical QP also correlated strongly with biomechanical properties including fibril modulus (r = -0.76, P < 0.0001), matrix modulus (r = -0.69, P < 0.0001), and log of permeability (r = 0.72, P < 0.0001). The QP correlated weakly with GAG per wet weight and with water content (r = -0.50, P < 0.0003 and r = 0.39, P < 0.006 respectively).

CONCLUSION:Non-destructive electromechanical QP measurements correlate strongly with histological ss and biomechanical parameters providing a rapid and reliable assessment of articular cartilage quality.

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Introduction: Histological scoring, biochemical analyses and biomechanical testing (unconfined compression) are often seen as gold standard characterizations for articular cartilage but can present major drawbacks in the context of animal and human studies where characterization of complete intact articular cartilage surfaces is required. In particular, histology, biochemical and mechanical testing involve destructive processing of samples, do not represent the entire joint surface and require significant time to complete. The purpose of this study was to correlate measurements obtained with a hand-held electromechanical device (TM) that maps electromechanical properties of cartilage across an entire surface non-destructively, to histological, biochemical and biomechanical properties of osteochondral s harvested at different locations from 8 human distal femurs obtained from RTI Surgical.  Read More

Purpose: Due to their size (~1mm), mouse models pose significant challenges to map biomechanical properties over their articular surfaces. The purpose of this study was to determine if an automated indentation technique could be used to map the biomechanical properties of the articular surfaces in murine knees and to identify early alterations of the articular cartilage of a mouse strain (STR/ort) that spontaneously develops osteoarthritis (OA) on the medial side of their knees.  Read More

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Purpose: To demonstrate the ability of non-destructive electromechanical device and automated indentation technique in assessing the quality of cartilage in a sheep model of cartilage repair.  Read More

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Purpose: An important measure of articular cartilage function in health and disease is its biomechanical properties. While much research has mouse models of osteoarthritis, the assessment of biomechanical properties in these small joints is quite challenging. We have previously developed novel and easily implemented indentation technique on sheep stifle joints and rat knee joints. The purpose of this study was to determine if this novel technique could be used to map the biomechanical properties of entire mice articular surfaces in indentation.  Read More

Hyaline-like cartilage repair can be occasionally elicited by bone marrow stimulation procedures however mainly in younger patients, indicating the need for further treatments to improve success rates in middle-aged patients. Traditional scaffold-guided repair approaches use a solid material to fill the wound void and to provide a mechanically stable substrate for cell attachment, ingrowth and differentiation. However it is repeatedly observed that solid scaffolds persist and interfere with bone regeneration and chondroinduction. In this study, a novel paradigm was used to design an implant to promote anabolic osteochondral regeneration in aged knees. It was conceived that delivery of dispersed microparticles of biodegradable chitosan with a molecular weight timed for slow clearance in a large animal defect could guide subchondral bone repair responses that lead to bone-induced chondroinduction and improved articular cartilage resurfacing. A unique approach was used to deliver chitosan microparticles to bleeding subchondral bone. Chitosan (80% degree of deacetylation, 80 kDa) was aseptically freeze-dried (FD) to form an ultraporous scaffold that could be d into small cylinders that slowly and spontaneously disperse as microparticles when submerged in whole blood. Using an aged sheep model of bone marrow stimulation, we tested the hypothesis that sub-chondral FD-chitosan implants are retained in bleeding microdrill holes, increase mid-term drill hole bone remodeling, and enhance defect resurfacing with hyaline-like cartilage. All protocols were approved by institutional ethics review boards. Sequential small arthrotomies were used to create bilateral full-thickness ~10x10mm chondral defects in the medial femoral condyles of N=12 female sheep with advanced age (8-9 years, 66 ±6 kg). Chondral defects were perforated with 11, 1.4 mm drill holes. In one knee each drill hole was treated with FD-chitosan implant generated with 5, 10, or 20 mg/mL initial chitosan concentration; holes in the other knee were left to bleed as controls. Sheep were euthanized after 1 day (N=2), 3 months (N=5), and 9 months (N=5), and the osteochondral repair tissues analyzed for macroscopic % fill, biomechanics, micro-CT, repair tissue histomorphometry, and ICRS-II Histological Scoring. Chitosan microparticles were visualized to reside in drill defects at 1 day. Implant treatment improved macroscopic soft tissue resurfacing at 9 months in 4 out of 5 treated lesions (P < 0.05, N=5). Drill hole volume enlarged by approximately 2.6-fold at 3 months versus day 1 post-operative (P < 0.005), then mostly healed over with mineralized bone at 9 months except for one animal (Fig. 1). Treated drill holes tended to show more woven bone and less callus formation compared to drilling alone at 3 months. At 9 months, treated defects were resurfaced with more soft tissue (p=0.04, N=5) and had higher ICRS-II overall histological assessment ss in 4 out of 5 sheep (Fig.2). In these aged sheep with structural changes similar to early osteoarthritis, histological and biomechanical analyses showed that microdrilling following a bone remodeling phase elicits hyaline-like cartilage repair with viscoelastic properties (Fig. 3), while implant improved cartilage volume. These results support the hypothesis that FD-chitosan microparticles can enhance articular cartilage resurfacing in letally aged sheep by guiding or altering the subchondral bone wound repair response without exaggerating the transient bone resorption response to microdrilling.Read More

Introduction: In cartilage regeneration and repair, mechanical testing of articular cartilage characterizes functional restoration of the repair site [1] and can detect early degeneration of articular cartilage [2]. However, the experimental design often incorporates the use of cartilage adjacent to the treated site or at contralateral sites as normal references to evaluate the effect of treatment [1]. In doing so, the natural spatial distribution of the properties of the normal articular cartilage is rarely taken into account. Neglecting this spatial variation of the cartilage properties will increase variability of the results and could compromise study outcome. The purpose of this study was therefore to assess the importance of taking into account the spatial distribution of the mechanical properties of normal articular cartilage in animal models of cartilage repair, specifically the distributions of thickness and instantaneous modulus.  Read More

The purpose of the study was to investigate if electromechanical properties of human tibial plateau correlate strongly with histological ss and with biomechanical properties as in human distal femurs (Sim et al., 2014). Six pairs of tibial plateau from human donors (5 males and 1 female, average age 48 years) were provided by RTI Surgical (FL, USA). Ex vivo electromechanical properties were mapped across entire articular surfaces using the . The device calculates a quantitative parameter (QP) which corresponds to the number of microelectrodes in contact with the cartilage when the sum of their streaming potential reaches 100 mV (inversely proportional to electromechanical activity). A total of 56 osteochondral s were then harvested to be tested in unconfined compression to obtain the fibril modulus (Ef), equilibrium modulus (Em), and permeability (k) prior to histoprocessing. Safranin O-Fast Green-stained paraffin sections were assessed with the Mankin s. The QP corresponding to the d site was calculated as the average of all QPs measured within 6 mm from the center. Safranin O-Fast Green-stained sections showed a decrease in matrix GAG staining and worse structural integrity as the QP increased as expected (Fig.1). The QP decreased with increasing Ef (r = ?0.73, p<0.0001; Fig.2A) and Em (r=?0.30, p=0.0186; Fig.2C) whereas the QP increased with Mankin S (r=0.50, p=0.0004), permeability (r=0.64, p<0.0001; Fig.2B) and thickness (r=0.42, p=0.0006; Fig.2D). Similar correlations of the QP with histological s and mechanical parameters were observed in human tibial plateau as in distal femurs, thus reinforcing the interpretation of QP as an accurate assessment of cartilage quality. In addition, there was a positive correlation between QP and cartilage thickness, which could be related to variations present on the tibial plateau surface. Considering these results, we believe that the can provide a reliable tool.Read More

Introduction: The identification and quantitative grading of early degenerated regions over an entire articular surface remains a challenging quest. The objective of this study was to investigate the ability of a novel technique to automatically characterize mechanical properties of entire human articular surfaces in indentation in order to rapidly and non-destructively discriminate between damaged and healthy articular cartilage regions.  Read More

Introduction: A currently unsatisfied need in Arthritis and cartilage research is to assess the function of the entire articular cartilage surface both quantitatively and non-destructively. The objective of this study was to investigate the ability of a novel automatic technique to characterize mechanical properties of entire articular surfaces in indentation in order to rapidly discriminate between degenerated versus healthy articular cartilage.  Read More

Introduction: We describe the design of bioinspired lubricating and wear protecting fluids based on synergistic mixtures of bottle brushes (BB) and linear polymers solutions. To illustrate this concept we used hyaluronic acid (HA) - a naturally occurring linear polyelectrolyte, and water soluble synthetic BB polymers. Individually, these two polymers exhibit poor wear protecting capabilities compared to saline solutions. Mixture of the two polymers in pure water or in saline allows to drastically increase wear protection of surfaces under a wide range of shearing conditions. We demonstrate that this synergy between the BB and HA polymer emerges from a strong, yet transient, cohesion between the two components forming the boundary film due to entanglements between both polymers. We show that this concept can be applied to other types of linear polymers and surfaces and is independent of the chemical and mechanical properties of the surfaces. Most importantly, we show that these fluids can be injected into articular joints to improve chondroprotection and wear protection. Methods: We used the surface forces apparatus (SFA) to elucidate the molecular conformation and the interaction forces of the BB polymers and their mixtures with hyaluronic acid. These experiments were complemented with larger scale tribological measurements on a lab-made tribometer. In vivo testing of the fluids was performed on rats with surgically induced osteoarthritis (anterior cruciate ligament transection). Results: Force measurements show that the BB polymers conformation can be tuned by the architecture of the polymer. Triblocks polymers tend to form loop on surfaces while monoblock and diblocks adopt a brush like conformation. When mixed with HA, nanotribology and macro tribology results show a strong improvement of wear protection compared to components alone. In vivo testing show that these polymer mixtures have the remarkable capacity to stop cartilage degradation and to preserve joints mechanical properties.Introduction:We describe the design of bioinspired lubricating and wear protecting fluids based on synergistic mixtures of bottle brushes (BB) and linear polymers solutions. To illustrate this concept we used hyaluronic acid (HA) - a naturally occurring linear polyelectrolyte, and water soluble synthetic BBpolymers. Individually, these two polymers exhibit poor wear protecting capabilities compared to saline solutions. Mixture of the two polymers in pure water or in saline allows to drastically increase wear protection of surfaces under a wide range of shearing conditions. We demonstrate that this synergy between the BB and HA polymer emerges from a strong, yet transient, cohesion between the two components forming the boundary film due to entanglements between both polymers. We show that this concept can be applied to other types of linear polymers and surfaces and is independent of the chemical and mechanical properties of the surfaces. Most importantly, we show that these fluids can beinjected into articular joints to improve chondroprotection and wear protection. Methods: We used the surface forces apparatus (SFA) to elucidate the molecular conformation and the interaction forces of the BB polymers andtheir mixtures with hyaluronic acid. These experiments were complemented with larger scale tribological measurements on a lab-made tribometer. In vivo testing of the fluids was performed on rats with surgically induced osteoarthritis (anterior cruciate ligament transection). Results: Force measurements show that the BB polymers conformation can be tuned by the architecture of the polymer. Triblocks polymers tend to form loop on surfaces while monoblock and diblocks adopt a brush like conformation. When mixed with HA, nanotribology and macro tribology results show a strong improvement of wear protection compared to components alone. In vivo testing show that these polymer mixtures have the remarkable capacity to stop cartilage degradation and to preserve joints mechanical properties.Read More

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Cartilage mechanical function relies on a composite structure of a collagen fibrillar network entrapping a proteoglycan matrix. Previous biphasic or poroelastic models of this tissue, which have approximated its composite structure using a homogeneous solid phase, have experienced difficulties in describing measured material responses. Progress to date in resolving these difficulties has demonstrated that a constitutive low that is successful for one test geometry (confined compression) is not necessarily successful for another (unconfined compression). In this study, we hypothesize that an alternative fibril-reinforced composite biphasic representation of cartilage can predict measured material responses and explore this hypothesis by developing and solving analytically a fibril-reinforced biphasic model for the case of uniaxial unconfined compression with frictionless compressing platens. The fibrils were considered to provide stiffness in tension only. The lateral stiffening provided by the fibril network dramatically increased the frequency dependence of disk rigidity in dynamic sinusoidal compression and the magnitude of the stress relaxation transient, in qualitative agreement with previously published data. Fitting newly obtained experimental stress relaxation data to the composite model allowed extraction of mechanical parameters from these tests, such as the rigidity of the fibril network, in addition to the elastic constants and the hydraulic permeability of the remaining matrix. Model calculations further highlight a potentially important difference between homogeneous and fibril-reinforced composite models. In the latter type of model, the stresses carried by different constituents can be dissimilar, even in sign (compression versus tension) even though strains can be identical. Such behavior, resulting only from a structurally physiological description, could have consequences in the efforts to understand the mechanical signals that determine cellular and extracellular biological responses to mechanical loads in cartilage.Read More

To assess the electromechanical properties of human knee articular cartilage with compression-induced streaming potentials for reliability among users and correlation with macroscopic and histological evaluation tools and sulfated glycosaminoglycan (sGAG) content.Streaming potentials are induced in cartilage in response to loading when mobile positive ions in the interstitial fluid temporarily move away from negatively charged proteoglycans. Streaming potential integrals (SPIs)were measured with an indentation probe on femoral condyles of 10 human knee specimens according to a standardized location scheme. Interobserver reliability was measured using an interclass correlation coefficient (ICC). The learning curves of 3 observers were evaluated by regression analysis. At each SPI measurement location the degradation level of the tissue was determined by means of the International Cartilage Repair Society (ICRS) s, Mankin s, and sGAG content. The computed ICC was 0.77 (0.70-0.83) indicating good to excellent linear agreement of SPI values among the 3 users. A significant positive linear correlation of the learning index values was observed for 2 of the 3 users. Statistically significant negative correlations between SPI and both ICRS and Mankin ss were observed (r=0.502, P < 0.001, and r=0.255, P=0.02, respectively). No correlation was observed between SPI and sGAG content (r = 0.004, P =0.973).SPI values may be used as a quantitative means of cartilage evaluation with sufficient reliability among users. Due to the significant learning curve, adequate training should be absolved before routine use of the technique.
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Purpose: By applying 3D in vitro chondrogenesis in a model using human bone marrow mesenchymal stem cells (hBMSC), it was demonstrated that excess thyroid hormone (T3) and the upregulation of deiodinase iodothyronine type-2 (D2) gene (DIO2), had similar detrimental effects on cartilage matrix deposition. Moreover, an in vivo rat model further indicated that this unfavourable effect of DIO2 upregulation on articular cartilage is likely modulated by mechanical loading. In the current study our aim was to investigate the effect of excess T3 in a human ex vivo explant model in interaction with mechanical loading. Methods: Full thickness osteochondral explants were isolated from the macroscopically preserved condyles of three human osteoarthritic (OA) donors included in the RAAK study. From day 0 to 5 the explants were kept under standardized conditions in chondrogenic medium to normalize expression levels. All explants were loaded from day 6 to 9, with a regime of 1 hz (MachOne mechanical testing system, BMM ) at 30% strain, during 10 min. To determine the effect of thyroid hormone, 10 nM T3 was added to the culture medium. As primary output, RT-PCR was performed to measure changes in COL2A1 (anabolism), MMP13 (catabolism) and EPAS1 (hypertrophy) gene expression. To determine structural damage, paraffin sections of the cartilage were stained with hematoxylin and eosin (HE), Safranin O and Alcian blue staining. Results: In our human explants, excess T3 resulted in a significant upregulation of EPAS1 (P ? 0.037) whereas for MMP13 and COL2A1 suggestive evidence for upregulation was found (P ? 0.065 and P ? 0.065, respectively). Additionally, staining with Safranin O, confirmed that excess T3 was detrimental to cartilage homeostasis as reflected by a loss of proteoglycans. Conclusions: Similar to our 3D in vitro chondrogenesis model with hBMSC, we here show that excessive T3 while applying 30% strain is detrimental to cartilage matrix homeostasis in a human explant culture model. The DIO2 gene, resulting in excessive T3 levels, has previously been identified as a susceptibility gene for OA and our results here further recognize the thyroid homeostasis as a potential therapeutic target of OA.Read More

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Osteoarthritis is one of the leading causes of disability in adults over the age of 40 years, and there is currently no curative measure for the disease. As a result, there is a critical need for a strategy that can promote cartilage regeneration. Of particular interest is an injectable, in situ gelling hydrogel for cell encapsulation that can be delivered with low cytotoxicity to native chondrocytes and encapsulated cells. Adipose-derived stem cells are an attractive cell population for delivery because they secrete a wide array of soluble factors and they have the ability to differentiate down the chondrogenic lineage. Chemotaxis of passage 0 and passage 2 bovine chondrocytes toward bovine ASCs was measured using a modified Boyden chamber assay. Passage 0 chondrocyte migration was less than 3% of seeded cells for all conditions investigated with no significant differences between groups. Passage 2 chondrocytes exhibited significantly higher migration than P0 chondrocytes, but migration towards bASCs was actually lower than media controls. PDGF-BB and IGF-I promoted chemotaxis of passage 2 chondrocytes at 5 ng/mL and up to 100 ng/mL. Acrylate-poly(trimethylene carbonate)-block-poly(ethylene glycol)-block- poly(trimethylene carbonate)-acrylate (A-PTMC-PEG-PTMC-A) tri-block copolymers were synthesized from 3.4 and 20 kg/mol PEG-diol initiators. Methacrylate chondroitin sulphate (MCS) modified with collagen integrin peptides RGD, GLOGEN, and GVOGEA was blended with A-PTMC-PEG-PTMC-A to form hydrogels for ASC encapsulation. Conjugation of peptides onto MCS resulted in higher ASC viability in A-PTMC-PEG-PTMC-A/MCS hydrogels as assessed by LIVE/DEAD stain. The 20k/MCS hydrogels exhibited higher equilibrium water content, ultimate strain, and toughness, but lower equilibrium moduli than MCS and 3.4k/MCS hydrogels. In addition, 3.4k/MCS hydrogels were tougher than MCS hydrogels but had a comparable equilibrium modulus. The present work showed that ASCs do not encourage chemotaxis of bovine chondrocytes in 2-D culture. This finding provides early evidence that ASCs may be unsuitable for promoting chondrocyte migration in a cartilage defect model. The viability and mechanical measurements demonstrate that A-PTMC-PEG-PTMC-A/MCS hydrogels modified with integrin peptides can maintain ASC viability following encapsulation. However, further experiments are necessary to assess the suitability of peptide-modified A-PTMC-PEG-PTMC-A/MCS hydrogels as a viable cartilage regeneration strategy.Read More

BACKGROUND: Clinical arthroscopic probes based on indentation testing are being developed. However, the biological effects of certain design parameters (i.e., tip geometry and size) and loading protocols (i.e., indentation depth, rate, and repetition) on human articular cartilage are unclear.  Read More

Background: Osteochondral allograft transplantation has a good clinical outcome, however, there is still debate on optimization of allograft storage protocol. Storage temperature and nutrient medium composition are the most critical factors for sustained biological activity of grafts before implantation. In this study, we performed a time-dependent in vitro experiment to investigate the effect of various storage conditions on electromechanical, histological and histochemical properties of articular cartilage.  Read More

The articular cartilage of autologous osteochondral grafts is typically different in structure and function from local host cartilage and thereby presents a remodeling challenge. The hypothesis of this study was that properties of the articular cartilage of trochlear autografts and adjacent femoral condyle are associated with the 3-dimensional (3-D) geometrical match between grafted and contralateral joints at 6 and 12 months after surgery. Design: Autografts were transferred unilaterally from the lateral trochlea (LT) to the medial femoral condyle (MFC) in adult Spanish goats. Operated and contralateral nonoperated joints were harvested at 6 and 12 months and analyzed by indentation testing, micro–computed tomography, and histology to compare 1) histological indices of repair, 2) 3-D structure (articular surface deviation, bone-cartilage interface deviation, cartilage thickness), 3) indentation stiffness, and 4) correlations between stiffness and 3-D structure. Results: Cartilage deterioration was present in grafts at 6 months and more severe at 12 months. Cartilage thickness and normalized stiffness of the operated MFC were lower than the nonoperated MFC within the graft and proximal adjacent host regions. Operated MFC articular surfaces were recessed relative to the nonoperated MFC and exhibited lower cartilage stiffness with increasing recession. Sites with large bone-cartilage interface deviations, both proud and recessed, were associated with recessed articular surfaces and low cartilage stiffness. Conclusion: The effectiveness of cartilage repair by osteochondral grafting is associated with the match of 3-D cartilage and bone geometry to the native osteochondral structure.Read More

Long-term applicability of current surgical interventions for the repair of articular cartilage is jeopardized by the formation of mechanically inferior repair tissue. Cartilage tissue engineering offers the possibility of developing functional repair tissue, similar to that of native cartilage, enabling long-lasting repair of cartilage defects. Current techniques, however, rely on the need for a large number of cells, requiring substantial harvesting of donor tissue or a separate cell expansion phase. As routine cell expansion methods tend to elicit negative effects on cell function, the following study describes an approach to generate large-sized engineered cartilage constructs (? 3 cm2) directly from a small number of immature rabbit chondrocytes (approximately 20,000), without the use of a scaffold. After characterizing the hyaline-like engineered constructs, the in vivo repair capacity was assessed in a chondral defect model in the patellar groove of rabbits. In vitro remodeling of the constructs developed in the bioreactor occurred as early as 3 weeks, with the histological staining exhibiting zonal differences throughout the depth of the tissue. With culturing parameters optimized (3 weeks growth under 15 mM NaHCO3), constructs were grown and implanted into critical-sized 4 mm chondral defects. Assessed after 1, 3 and 6 months (n=6), implants were sd macroscopically to evaluate integration and survival of the implants. Out of 18 rabbits, 16 received normal or nearly normal over-all repair assessment. Histological and immunohistochemical evaluation showed good integration with surrounding cartilage and underlying subchondral bone. Architectural remodeling of the constructs was present at each time point, with the presence of flattened chondrocytes at the implant surface and columnar arrangement of chondrocytes in deeper zones. The observation of in vivo remodeling was also supported by the changes in biochemical composition of the constructs. At each time point, constructs had a collagen to proteoglycan ratio similar to that of native cartilage (3:1 collagen to proteoglycan). In contrast, the repair tissue for each control group was inferior to that produced with treated defects. These initial results hold promise for the generation of engineered articular cartilage for the clinical repair of cartilage defects without the limitations of current surgical repair strategies.Read More

In healthy joints, a zone of calcified cartilage (ZCC) provides the mechanical integration between articular cartilage and subchondral bone. Recapitulation of this architectural feature should serve to resist the constant shear force from the movement of the joint and prevent the delamination of tissue-engineered cartilage. Previous approaches to create the ZCC at the cartilage-substrate interface have relied on strategic use of exogenous scaffolds and adhesives, which are susceptible to failure by degradation and wear. In contrast, we report a successful scaffold-free engineering of ZCC to integrate tissue-engineered cartilage and a porous biodegradable bone substitute, using sheep bone marrow stromal cells (BMSCs) as the cell source for both cartilaginous zones. BMSCs were predifferentiated to chondrocytes, harvested and then grown on a porous calcium polyphosphate substrate in the presence of triiodothyronine (T3). T3 was withdrawn, and additional predifferentiated chondrocytes were placed on top of the construct and grown for 21 days. This protocol yielded two distinct zones: hyaline cartilage that accumulated proteoglycans and collagen type II, and calcified cartilage adjacent to the substrate that additionally accumulated mineral and collagen type X. Constructs with the calcified interface had comparable compressive strength to native sheep osteochondral tissue and higher interfacial shear strength compared to control without a calcified zone. This protocol improves on the existing scaffold-free approaches to cartilage tissue engineering by incorporating a calcified zone. Since this protocol employs no xenogeneic material, it will be appropriate for use in preclinical large-animal studies.Read More

Objective: The structure–function relationship in the healthy temporomandibular joint (TMJ) disc has been well established, however the changes in dysfunctional joints has yet to be systematically evaluated. Due to the poor understanding of the etiology of temporomandibular disorders (TMDs) this study evaluated naturally occurring degenerative remodeling in aged female porcine temporomandibular joint (TMJ) discs in order to gain insight into the progression and effects on possible treatment strategies of TMDs.  Read More

Objectives: To evaluate the effects of low-magnitude high-frequency vibration (LMHFV) on degenerated articular cartilage and subchondral bone in anterior cruciate ligament transection (ACLT) induced osteoarthritis (OA) rat model.  Read More

Terminal sterilization induces physical and chemical changes in the extracellular matrix (ECM) of ex vivo-derived biomaterials due to their aggressive mechanism of action. Prior studies have focused on how sterilization affects the mechanical integrity of tissue-based biomaterials but have rarely characterized effects on early cellular interaction, which is indicative of the biological response. Using a model fibrocartilage disc scaffold, these investigations compare the effect of three common sterilization methods [peracetic acid (PAA), gamma irradiation (GI), and ethylene oxide (EtO)] on a range of material properties and characterized early cellular interactions. GI and EtO produced unfavorable structural damage that contributed to inferior cell adhesion. Conversely, exposure to PAA resulted in limited structural alterations while inducing chemical modifications that favored cell attachment. Results suggest that the sterilization approach can be selected to modulate biomaterial properties to favor cellular adhesion and has relevance in tissue engineering and regenerative medicine applications. Furthermore, the study of cellular interactions with modified biomaterials in vitro provides information of how materials may react in subsequent clinical applications.  Read More

Purpose: Clinical outcome of osteochondral allograft transplantation (OAT) depends on allograft quality. There is a lack of rapid and reliable non-destructive methods for intraoperative evaluation of repaired cartilage. Measurement of cartilage electromechanical properties offers novel possibilities to monitor cartilage healing after OAT. The purpose of our study was to evaluate in vivo performance of fresh and stored allografts and determine whether allograft electromechanical properties have relationship with macroscopic and histological findings after OAT.  Read More

Degenerative joint diseases, like osteoarthritis, are characterized by progressive cartilage degeneration, which can lead to pain and loss of mobility. Low-grade cartilage deterioration occurs early in disease progression and may be treatable. However, current clinical assessment methodologies, including physical exam, synovial fluid analysis and imaging, may not be sensitive enough to detect early degenerative changes. Electroarthrography (EAG) is a new technology capable of measuring streaming potentials produced by cartilage during compression through electrodes applied to skin surrounding an articular joint. Streaming potentials arise from interactions among constituents of the cartilage extracellular matrix during load bearing and provide a sensitive measure of cartilage degeneration. Consequently, EAG may provide a sensitive, non-invasive method for detecting low-grade cartilage degeneration. Its response to trypsin degradation of cartilage was explored here in an equine model. EAG coefficients were significantly reduced (p<0.05) following trypsin degradation of cartilage duringstanding (1630±81 N) & walking (3082±134 N) loads. More dramatic reductions were observed during walking, 48%±6%, compared to standing, 27%±4%, at palmar sites (CH 1, CH 2, CH 7, CH 8) (Fig. 5). Higher QP, indicating lower cartilage stiffness, were measured in degraded cartilage on both the cannon (p<10-4, n=40) & phalanx (p<10-5, n=35) (Fig. 6), which corroborates reductions in EAG. Both indirect and direct measurements of cartilage streaming potentials, by EAG and the , respectively, detected cartilage damage that was not visible to the unaided eye. These data demonstrate the potential for EAG to provide a sensitive, non-invasive diagnostic of cartilage health that could contribute to the early detection and treatment of osteoarthritis and other degenerative joint diseases.Read More

Electroarthrography (EAG) is a new technique formeasuring electrical potentials appearing on the knee surface during loadingthat reflects cartilage quality and joint contact force. Our objective was toinvestigate the evolution of EAG signals during successive loading cycles. Thestudy was conducted on 20 standing subjects who shifted their body weight toachieve knee loading. Their EAG signals were recorded during 10 successiveloading cycles, and during a subsequent sequence of 10 cycles recorded after a15 min exercise period. Multiple linear regression models estimated theelectro-mechanical ratio (EMR) interpreting the ability of cartilage togenerate a certain potential for a given ground reaction force by taking intoaccount this force and the center of pressure displacements during unipedalstance. The results showed that the EMR values slowly decreased with successivecycles: during the initial sequence, the correlation coefficients between EMRvalues and sequence numbers were significant at 3 of the 4 electrode sites (P<0.05); for the post-exercise sequence, the EMR values still decreased and were significantly lower than during the initial sequence (P<0.001). The reduction of EMR values could arise from muscle activity and habituation of the stretch reflex, and also from the time dependent electromechanical properties of cartilage. In conclusion, refraining from physical activity before the EAG measurements is important to improve measurement repeatability because of the EMR decrease. The electromechanical model confirmed the role of EAG as a natural sensor of the changes in the knee contact force and also improved EAG measurement accuracy.
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Electroarthrography (EAG) consists of recording electrical potentials on the knee surface that originate from streaming potentials within articular cartilage while the joint is undergoing compressive loading. The aim was to investigate how the contraction of specific leg muscles affects the contact force of the knee joint and, in turn, the EAG values.
For six normal subjects, voluntary isometric muscle contractions were repeatedly conducted to activate four leg muscle groups while the subject was lying on his back. Two EAG signals were recorded on the medial and lateral sides of the knee, as well as four EMG signals (gastrocnemius, hamstring, quadriceps, tensor fascia latae), and the signal from a force plate fixed against the foot according to the direction of the force.
The EAG and force signals were very well correlated: the median of the correlation coefficients between an EAG signal and the corresponding force signal during each loading cycle was 0.91, and 86% of the correlation coefficients were statistically significant (P<5%). Isolated muscle contraction was possible for the gastrocnemius and hamstring, but not always for the quadriceps and tensor fascia latae. Using the clinical loading protocol which consists of a one-legged stance, the quadriceps and hamstring EMGs showed minimal activity; loading cycles with increased EAG amplitude were associated with higher EMG activity from the gastrocnemius, which is involved in antero-posterior balance.
These results document the role of the EAG as a “sensor” of the knee contact force and contribute to the development of clinical loading protocols with improved reproducibility. 
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Introduction: During joint articulation, cartilage, particularly that near the articular surface, undergoes a complex combination of compression, shear, and sliding.1,2 In vitro analyses have focused on cartilage biomechanics in response to relative surface movement at a constant velocity after startup. However, joint movement typically involves variability in the relative surface velocity. Cartilage also exhibits a variety of biological responses to shear and articulation, including increased matrix and lubricant secretion at low amplitudes but cell death at high amplitudes.3,4 Chondrocyte death and survival generally involves mechanisms of apoptosis and autophagy, with high amplitude torsional shear causing cell apoptosis and mechanical impact attenuating autophagy but stress-related responses to articulation are unclear.4,5 Microtubule-associated protein 1 light chain (LC3) correlates with autophagosome formation and PARP-p85 is a nuclear enzyme involved in DNA repair.6,7 The objective of the present study was to assess the biomechanics and mechanobiology of articular cartilage when subjected to time-varying articulation in the form of low and high amplitude oscillations.  Read More

Animal models of osteoarthritis have been used for understanding diseaseprogression and are essential for assessing potential new therapies. Ovine models, such as the lateral meniscectomy model, are of interest because meniscectomy models often follow a disease progression similar to that in humans, and joint size is sufficient for multiple analyses of cartilage including biomechanical, biochemical & histological evaluations. Current evaluation methods do not allow for non-destructive, sequential, quantitative assessment of cartilage function. We have used a new arthroscopic device, , to non-destructively evaluate cartilage at multiple positions in ovine knee (stifle) joints. Topographical patterns were consistent among users, with a high reliability as determined by the Intraclass Correlation Coefficient of 0.64. Values of the quantitative parameter, cartilage mechanical properties & cartilage thickness all depend on location and meniscal coverage (Table 1). Some variability among users could be attributed to user-specific differences in positioning the device on the relatively small cartilage surfaces and the broad range of mechanical properties and cartilage thickness observed on these joint surfaces (Table 1). The mechanical properties measured in this study are consistent with mechanical measurements of cartilage on human tibial plateau, where thinner, stiffer cartilage was found in regions beneath the meniscus. Cartilage QP maps, generated with the , were related to meniscal coverage in the sheep stifle. In future studies, additional parameters such as water content & collagen cross-links will be assessed to further describe the relationship between QP and cartilage functional mechanical properties.Read More

Purpose: Menisci are structurally complex and play an essential weight-??bearing role in the knee joint. Although there has been a recent increase in the number of meniscus repairs performed yearly in the US [1], only a small number of all meniscal tears are repairable so that current surgical treatment of meniscal tears often involves partial meniscectomy which increases the risk of developing osteoarthritis (OA) [2]. Trephination and meniscus wrapping techniques have had some success in pre-??clinical models [3] and in clinical studies [4] to augment the rate of healing for complex tears [5]. We have developed a freeze-??dried chitosan polymer that can be resuspended in PRP to produce a homogeneous mixture that coagulates once implanted and sustains recruitment of host cells to the site. The purpose of this study was to investigate whether healing of ovine meniscus tears can be repaired by applying chitosan-??PRP implants and/or wrapping the meniscus with a collagen membrane. Electromechanical properties of the tibial plateau and the distal femurs were mapped across the articular surfaces using the Arthro-?BST device. The average quantitative parameters (QP) calculated for the medial femoral condyles and for the tibial plateau were similar in all treatment groups and in the contralateral intact menisci, suggesting the surgically induced meniscus tear does not cause severe cartilage degeneration within 6 weeks. Chitosan-??PRP implants showed evidence of a superior regenerative effect compared to wrapping the meniscus with a collagen membrane. Using the wrap in conjunction with chitosan-??PRP implants did not further improve repair and the additional sutures needed to secure the wrap created significant damage to the menisci. This suggests that chitosan-??PRP implants by themselves could be sufficient in overcoming the current limitations of meniscus repair. Further study is certainly required before we would recommend using this clinically.Read More

Introduction: Chondroitin sulphate is an important component GAG found in articular cartilage and has a chondroinductive effect on adipose derived stem cells (ASCs). Methacrylate chondroitin sulphate (MCS) has therefore been chosen as a basis for a polymer vehicle for ASC delivery for chondral defect repair. However, MCS lacks cell binding site as well as the required mechanical strength and swells extensively following crosslinking. To overcome these limitations, MCS was conjugated with the peptide sequences GVOGEA, GLOGEN, and GGRGDS, and blended with acrylated triblock copolymers of poly(ethylene glcol)-block-poly(trimethylene carbonate) (A-PTMC-PEG-PTMC-A) then crosslinked using a thermal initiator. The resulting gels were assessed for their mechanical properties and ability to retain encapsulated ASC viability.  Read More

Recent advances in murine molecular genetics has enabled the production of mice with targeted disruption of genes that regulate cartilage and bone metabolism. These mice represent excellent models to study the 0 16 Wild Type etiology and progression of complex diseases, including arthritis. Mice lacking FGFR3-/- exhibit defects in cartilage and bone metabolism by 4 months of age Novel technology has been developed to test the biomechanical properties of mouse articular cartilage. It was determined that the load bearing surface of the left humeral head of FGFR3-/- mice was significantly less stiff (p<0.005) than that of wild type littermatesRead More

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Introduction: During daily physical activities, joint articulation results in 3-10% compression in its overall thickness. There is also consensus that articulation is a combined process of shearing and sliding, with relative rotational and translational motions between femoral condyle and tibia cartilage at least at the millimeter scale 2,3. The macroscale motions in the joint which translates to microscale tissue deformation have been assessed in vitro to range from 2.8 to 41.0% depending on the tissue state and lubrication 4 . Biologically, dynamic shear at small amplitudes (±3%) markedly stimulates PRG4 secretion by immature bovine cartilage disks, but little evidence has been provided for similar effects in human cartilage, perhaps due to insufficiently large amplitudes of stimulation 5 . A prior study on the effects of torsional shear on chondrocyte apoptosis has suggested that superficial zone (SZ) cell apoptosis occurs in bovine explants when sheared without lubrication 6 . However, it is unknown whether (1) the degree of SZ cell death and amount of PRG4 secretion is a function of shear and sliding amplitudes and (2) how much resultant tissue deformation and sliding occurs during the chosen method of shear. Therefore, the hypothesis for this study was that articulation induces an amplitude-dependent effect on cartilage superficial zone health and responses, and that the variations in responses are due in part to the extent of tissue shear. Thus, the aims were to assess the effects of graded levels of articulation on chondrocyte viability and PRG4 secretion, and to relate these biological responses to the level of tissue shear.  Read More

Introduction: Degenerative joint diseases, including osteoarthritis, are characterized by progressive cartilage degeneration, which can lead to pain and loss of joint function. Therapeutics administered early, when only low grade cartilage changes have occurred, may slow or reverse disease progression, however, current clinical assessment methodologies lack the sensitivity required to provide diagnostic information early enough in the disease process to permit successful intervention [1]. Electroarthrography (EAG) is a new technology that non-invasively measures streaming potentials produced during cartilage compression through electrodes contacting the skin surrounding an articular joint [2]. Streaming potentials arise from interactions among proteoglycan, collagen and interstitial fluid components of the cartilage extracellular matrix and are correlated to cartilage load bearing properties [3]. Study objectives were to assess EAG sensitivity to naturally occurring cartilage degeneration during simulated physiological loading and to compare EAG to direct measurements of cartilage streaming potentials obtained in weight bearing regions of the equine fetlock (metacarpophalangeal) joint.  Read More

Introduction/Purpose: Electroarthrography (EAG) is a new technology that non-invasively measures cartilage streaming potentials through electrodes contacting the skin surrounding an articular joint. Streaming potentials are produced during cartilage compression and directly reflect cartilage composition, structure and load bearing properties. Study objectives were to develop an approach for measuring EAG in the fetlock joints of live horses, as well as to compare externally measured EAG to direct measurements of cartilage quality.  Read More

Purpose: Articular cartilage distributes load in joints and provides a low-friction surface for joint movement. Glycosaminoglycan (GAG) in cartilage plays a critical role in its compressive stiffness. Loss of GAG is an early sign of osteoarthritis that leads to lower compressive stiffness and altered viscoelastic behavior. MRI and CT-based imaging techniques have been developed to quantify GAG content in cartilage in an effort to detect osteoarthritic changes early in the disease process. Contrast-Enhanced Computed Tomography (CECT) attenuation using a custom cationic contrast agent (CA4+) correlates with GAG content and equilibrium compressive modulus in bovine osteochondral plug. CA4+ demonstrates higher sensitivity to changes in GAGs than commercially available anionic contrast agents. Applicability of these results to in vivo human studies is not clear because the cartilage is nonhuman and the plug model affects both diffusion of the contrast agent and cartilage mechanics.  Read More

Objective

The objective of this study was to assess a novel 3D microstructured scaffold seeded with allogeneic chondrocytes (cells) in a rabbit osteochondral defect model.

Design

Direct laser writing lithography in pre-polymers was employed to fabricate custom silicon-zirconium containing hybridorganic-inorganic (HOI) polymer SZ2080 scaffolds of a predefined morphology. Hexagon-pored HOI scaffolds were seeded with chondrocytes (cells), and tissue-engineered cartilage biocompatibility, potency, efficacy and shelf-life in vitro was assessed by morphological, ELISA (enzyme-linked immunosorbentassay) and PCR (polymerase chain reaction) analysis. Osteochondral defect was created in the weight-bearing area of medial femoral condyle for in vivo study. Polymerized fibrin was added to every defect of 5 experimental groups. Cartilage repair was analyzed after 6 months using macroscopical (Oswestry Arthroscopy S [OAS]), histological, and electromechanical quantitative potential (QP) ss. Collagen scaffold (CS) was used as a positive comparator for in vitro and in vivo studies.

Results

Type II collagen gene up regulation and protein secretion was maintained up to 8 days in seeded HOI. In vivo analysis revealed improvement in all scaffold treatment groups. For the first time, electromechanical properties of a cellular-based scaffold were analyzed in a preclinical study. Cell addition did not enhance OAS but improved histological and QP ss in HOI groups.

Conclusions

HOI material is biocompatible for up to 8 days in vitro and is supportive of cartilage formation at 6 months in vivo. Electromechanical measurement offers a reliable quality assessment of repaired cartilage.

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Purpose 
This procedure describes a method to extract the thickness of cartilage from MachOne files generated during an automated thickness mapping of an articular surface (as per MA056-SOP02-D). It also describes the creation of a corresponding “.map” characterization file.  
Scope 
This procedure can be applied using any MachOne result file obtained following an automated thickness mapping of an articular surface. Some parameters must be specified in an associated protocol: the filename(s) containing the results from a find contact, the parameter for the calculation of the thickness and the *.map filename(s) (associated with the pixels coordinates for the characterization locations over sample surface). Read More

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Background Walking and running provide cyclical loading to the knee which is thought essential for joint health within a physiological window. However, exercising outside the physiological window, e.g. excessive cyclical loading, may produce loading conditions that could be detrimental to joint health and lead to injury and, ultimately, osteoarthritis. The purpose of this study was to assess the effects of a stepwise increase in speed and duration of treadmill training on knee joint integrity and to identify the potential threshold for joint damage. Methods Twenty-four Sprague-Dawley rats were randomized into four groups: no exercise, moderate duration, high duration, and extra high duration treadmill exercise. The treadmill training consisted of a 12-week progressive program. Following the intervention period, histologic serial sections of the left knee were graded using a modified Mankin Histology Scoring System. Mechanical testing of the tibial plateau cartilage and RT-qPCR analysis of mRNA from the fat pad, patellar tendon, and synovium were performed for the right knee. Kruskal-Wallis testing was used to assess differences between groups for all variables. Results There were no differences in cartilage integrity or mechanical properties between groups and no differences in mRNA from the fat pad and patellar tendon. However, COX-2 mRNA levels in the synovium were lower for all animals in the exercise intervention groups compared to those in the no exercise group. Conclusions Therefore, these exercise protocols did not exceed the joint physiological window and can likely be used safely in aerobic exercise intervention studies without affecting knee joint health.Read More

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Purpose: Cartilage has intrinsic poor healing capacity after injury, which can lead to the development of degenerative diseases such as osteoarthritis (OA). Current treatments for OA are unable to effectively stop or delay disease progression. Hence, the development of methods for regenerating cartilage with sustained effects is clinically relevant. Deletion of the p21CIP1/WAF1 gene in mice results in these animals having the ability to regenerate cartilage after injury, however, the underlying mechanisms of this phenomenon remains unclear. p21 is a critical cell cycle regulator, and its absence facilitates cell cycle progression. Whether this is implicit in cartilage regeneration is not known, and difficult to elucidate since p21 is tightly regulated and involved in other intricate cellular processes, such as inflammation and apoptosis. Therefore, to discriminate the potential role of cell cycle activation on cartilage regeneration, we focused downstream of p21 and investigated E2F1, a transcription factor previously linked to cartilage and bone development. In the p21 pathway, inhibition of p21 leads to enhanced activity of E2F1, and as a result, cell cycle progression. Thus, we examined the in vivo role of cell cycle activation on cartilage regeneration after injury by conditionally overexpressing E2F1 in quiescent mesenchymal stem cells (MSCs); as MSCs have the unique ability to differentiate into chondrocytes and therefore are a likely contributor to this cartilage regeneration phenotype. Read More

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Contrast?enhanced computed tomography (CECT) using charged contrast?agents enables quantification of cartilage glycosaminoglycan content. Since glycosaminoglycan content is a key determinant of cartilage compressive stiffness, CECT measurements have the potential to non?invasively assess cartilage stiffness. The objective of this study was to determine whether CECT attenuation, using a cationic contrast?agent (CA4+), correlates with the stiffness of intact cartilage. Six fresh femoral and six fresh tibial compartments with intact cartilage were obtained from patients undergoing total knee replacement surgery. The instantaneous stiffness was determined for 25–50 points on the surface of each compartment using an established indentation technique. The samples were then immersed in CA4+ solution for 48?h, scanned in a micro?CT scanner, and the average CECT attenuation at each indentation site was found for the superficial cartilage. A significant (p?<?0.01) and positive correlation was observed between stiffness and CECT attenuation for sites from each individual cartilage surface, with correlation coefficients ranging from r?=?0.37–0.57 and r?=?0.48–0.69 (p?<?0.01) for the tibia and femur, respectively. When data for each type of cartilage surface were pooled together, the correlation coefficients were r?=?0.73 for femoral condyle data points and r?=?0.49 for tibial plateau data points. CECT provided a map of cartilage stiffness across each surface, which allows regions of low stiffness to be identified. These findings support continued evaluation and development of quantitative imaging techniques to assess the functional properties of cartilage.Read More

Mechanical properties of articular cartilage that are vital to its function are often determined by indentation tests, which can be performed at different scales. Cartilage tissue exhibits various types of structural, geometrical, and spatial variations that pose strict demands on indentation protocols. This study aims to define a reproducible micro-indentation protocol for measuring the effective (average) stiffness of the cartilage surface in a region around 1?mm2. We elucidated how different parameters such as indenter size, indenter depth, and the location of the indentation influence the effective elastic modulus measured in micrometer scale on rat knee cartilage. When an indentation was performed (50??m radial probe, ?10??m indentation depth) at exactly the same location, the variability was less than 10%, even with a recovery period of 30?s. However, there was a high spatial variation and a small change of around 60??m in location could change the modulus values up to as much as 10-20 fold. The effective elastic modulus of cartilage surface layer cannot therefore be reproducibly determined from a few indentations on a cartilage sample, and requires at least 144 (12×12) indentations for a soft spherical probe with a 50??m radius. With higher depths, the spatial variation is slightly lower, allowing slightly lower number of indentations (?80 measurements or a 9×9 frame) to provide a representative elastic modulus. Using this protocol, we determined an elastic modulus of 2.6±1.9?N/mm2 at the medial side versus a higher modulus of 4.2±2.6?N/mm2 at the lateral side of the tibia of 12 weeks old Wistar rats. Optimized indentation protocols similar to the one presented here are required for revealing such variations in the mechanical properties of cartilage with anatomical location.Read More

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Purpose: This procedure describes a standard method to realize an automated indentation mapping over the surface of a sample using the MachOne mechanical tester (model v500css or v500csst, with software add-on for Automated Indentation Mapping).

Scope: This procedure can be used for the ex vivo automated indentation mapping over the surface of a sample. Sample’s dimension and mechanical properties must be compatible with the MachOne configuration and must allow proper attachment in the testing chamber. It is highly recommended to use standard protocol for sample preparation to facilitate positioning in the chamber and facilitate eventual comparison between samples. Some mapping parameters must be specified in an associated protocol: filename, sample holder type, mapping dimensioning method, surface positioning template (if applicable), position grid (# columns X # rows), multiple-axis load cell type, spherical indenter type and normal indentation function parameters.
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(In Germany only) In der Materialprüfung sind Indentationsverfahren bereits seit Jahren g?ngige Praxis. Jedoch war es bisher nicht so ohne weiteres m?glich Gewebeproben, insbesondere Weichgewebe wie Knorpel zu untersuchen. Mit dem Mikroindenter MachOneTM von BMM k?nnen sowohl flexible Biomaterialien wie Kontaktlinsen oder Wundauflagen aus elektrogesponnenen Gelatinefliesen genauso wie biologische Proben, wie Knorpelgewebe im trockenen Zustand sowie in PBS untersucht werden. Au?erdem besteht die M?glichkeit einer vollautomatischen Oberfl?chenuntersuchung an vorher festgelegten Punkten der Probe, sowie eine anschlie?ende Dickenmessung an den gleichen Positionen. Es sollen zwei Beispiele für Untersuchungsm?glichkeiten vorgestellt werden. Für die Untersuchungen wurden elektrogesponnene Fliese aus 16% w/v Gelatine sowie dem Gemisch aus 50 w% Gelatine und 50 w% Polyethylenglycol (PEG) verwendet. Das PEG wurde in einem anschlie?enden Waschprozess wieder entfernt. Es wurden Proben mit 4mm Durchmesser ausgestanzt und einem Kompressionstest unterzogen. Für die Untersuchungen wurde der MachOne TM V500css von BMM Inc. mit einem zylindrischen Indenter mit 1,2 cm Durchmesser verwendet. In einer zweiten Versuchsreihe wurde der Gelenkknorpel auf humanen Tibia Plateaus untersucht. Dazu wurden im Rahmen der Implantation einer Knieprothese explantierte Tibia Plateaus untersucht. Es erfolgte zun?chst eine Ermittlung der mechanischen Kennwerte mit einem 1mm Kugelindenter und anschlie?end die Bestimmung der Knorpeldicke. Für die elektrogesponnenen Fliese aus Gelatine ergaben sich E-Module von 7-12 KPa. Die Gelatine-Fliese mit ausgewaschenem PEG zeigten EModule von 1,5 – 8 KPa. Bei der Auswertung der automatischen Indentation kam das Elastische Modul nach Hayes zum Einsatz. In Abb.1 ist der Fit (in blau) im Vergleich zu den gemessenen Werten (schwarz) dargestellt. Aus den Daten der Knorpeldickenmessung konnte ein Oberfl?chenprofil der Tibia erstellt werden, dieses ist in Abb.2 dargestellt. Der Bereich unterhalb des intakten Meniskus zeigt eine deutlich geringere Abnutzung als im Bereich der Kondylen.Read More

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Purpose: Osteoarthritis (OA) is a debilitating chronicdisease. Currently, there is no cure or disease modifying treatment for OA.Using a Sprague-Dawley rat model, it has been shown that ahigh-fat/high-sucrose (HFS) diet induced obesity leads to histological OA-likechanges in the knee, and an infiltration of fat, collagen, and macrophages intoletal muscle within 12-weeks. Additionally, there is preliminary evidencesuggesting that exercise might mitigate these histological OA-like changes inthe knee cartilage of rats fed a HFS diet.

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Articular cartilage is an intricate and remarkable tissue found within synovial joints. It is essential for providing low-friction and load bearing during movement, resulting in pain-free mobility. Chondrocytes are the sole cell population present within the articular cartilage and play a critical role in tissue homeostasis. As the cellular building blocks of cartilage, they direct the synthesis and maintenance of this tissues proteoglycan-rich collagenous extracellular matrix (ECM), which in turn confers the mechanical properties required for cartilage to withstand shear and compressive loadings generated about 1000’s of times per day.Read More

Purpose: 

Osteoarthritis (OA) is a joint disease characterized by cartilage degeneration and bone spur formation. Due to the fact that there are no disease modifying drugs, OA is placing a high burden on society occurring during diseases. By applying genetic analyses and functional follow up research, our group demonstrated that the upregulation of the type IIiodothyronine deiodinase (D2) gene (DIO2), likely enhancing thyroid signaling, affects propensity of joint tissues to engage on osteoarthritis (OA) state, particularly upon mechanical loading.

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A mixture of polymers with lubricating properties is provided. The polymer can be used to produce a lubricating fluid. They can also be born on a surface or embedded in a porous material. This mixture of polymers comprises (a) a pharmaceutically acceptable bottle-brush polymer comprising a back bone with polymeric pendant chains, and (b) a pharmaceutically acceptable linear polymer. In the lubricating fluid, the bottle-brush polymer and the linear polymer are dissolved together in a pharmaceutically acceptable solvent.

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