Impaired biomechanical properties correlate with neoangiogenesis as well as VEGF and MMP‐3 expression during rat patellar tendon healing

Recent studies reveal an important role of vascular endothelial growth factor (VEGF)‐induced angiogenesis in degenerative tendon diseases. The way how VEGF influences mechanical properties of the tendons is not well understood yet. We here hypothesized that tendinopathy results in a hypoxia‐mediated stimulation of VEGF and that the mechanical stability of the tendon is impaired in an angiogenic process by VEGF‐induced matrix metalloproteinases (MMPs). A modified in situ freezing model of patellar tendon was used to create a tendinopathy. 0, 7, 14, and 28 days post‐surgical animals were sacrificed and patellar tendons were dissected for biomechanical and immunohistochemical analysis. Native tendons were used as controls. Immunohistochemical staining revealed a peak in HIF‐1α stabilization immediately after surgery. Both VEGF and MMP‐3 were increased 7 days after surgery. Angiogenesis was also abundant 7 days after surgery. In contrast, biomechanical stability of the tendon was decreased 7 days after surgery. The current results reveal a time‐dependent correlation of HIF‐1/VEGF‐induced and MMP‐3‐supported angiogenesis with decreased biomechanical properties during tendon healing. The therapeutical modulation of neoangiogenesis by influencing the level of VEGF and MMP‐3 might be a promising target for new approaches in degenerative tendon diseases. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1952–1957, 2012     

Minimal mechanical load and tissue culture conditions preserve native cell phenotype and morphology in tendon—a novel ex vivo mouse explant model

Appropriate mechanical load is essential for tendon homeostasis and optimal tissue function. Due to technical challenges in achieving physiological mechanical loads in experimental tendon model systems, the research community still lacks well‐characterized models of tissue homeostasis and physiological relevance. Toward this urgent goal, we present and characterize a novel ex vivo murine tail tendon explant model. Mouse tail tendon fascicles were extracted and cultured for 6 days in a load‐deprived environment or in a custom‐designed bioreactor applying low magnitude mechanical load (intermittent cycles to 1% strain, at 1 Hz) in serum‐free tissue culture. Cells remained viable, as did collagen structure and mechanical properties in all tested conditions. Cell morphology in mechanically loaded tendon explants approximated native tendon, whereas load‐deprived tendons lost their native cell morphology. These losses were reflected in altered gene expression, with mechanical loading tending to maintain tendon specific and matrix remodeling genes phenotypic of native tissue. We conclude from this study that ex vivo load deprivation of murine tendon in minimal culture medium results in a degenerative‐like phenotype. We further conclude that onset of tissue degeneration can be suppressed by low‐magnitude mechanical loading. Thus a minimal explant culture model featuring serum‐free medium with low mechanical loads seems to provide a useful foundation for further investigations. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1383–1390, 2018.

     

组织工程化肌腱体外构建的环境优化及系统设计

目的 设计一套构建具有一定功能和形态的肌腱组织的体外培养方法。方法 根据肌腱细胞体内的生物力学环境，在细胞的培养过程中，设计一套能够提供张力和参数测量系统的生物反应器，在肌腱的培养过程中对肌腱施加不同形式的张应力作用，以期在体外获得力学性能优化的自体肌腱。结果 细胞培养和张应力控制系统是由完全透明的有机材料制成的，整个系统由细胞培养室、测量系统和排换液系统等部分构成，在长期的肌腱细胞培养中，可提供肌腱一材料支架动态的培养方式。细胞培养室能很方便与气动肌腱连接，产生持续的脉冲张力作用。结论 用肌腱生物反应器可以使肌腱组织复合物在形成过程中始终处于力学环境中，促进肌腱组织中胶原纤维的平行排列，提高肌腱的力学性能，为组织工程化肌腱的产业化提供一种新的方法。     

Dose–response effect of an intra‐tendon application of recombinant human platelet‐derived growth factor‐BB (rhPDGF‐BB) in a rat Achilles tendinopathy model

The purpose of this study was to assess whether intra‐tendon delivery of recombinant human platelet‐derived growth factor‐BB (rhPDGF‐BB) would improve Achilles tendon repair in a rat collagenase‐induced tendinopathy model. Seven days following collagenase induction of tendinopathy, one of four intra‐tendinous treatments was administered: (i) Vehicle control (sodium acetate buffer), (ii) 1.02 µg rhPDGF‐BB, (iii) 10.2 µg rhPDGF‐BB, or (iv) 102 µg rhPDGF‐BB. Treated tendons were assessed for histopathological (e.g., proliferation, tendon thickness, collagen fiber density/orientation) and biomechanical (e.g., maximum load‐to‐failure and stiffness) outcomes. By 7 days post‐treatment, there was a significant increase in cell proliferation with the 10.2 and 102 µg rhPDGF‐BB‐treated groups (p = 0.049 and 0.015, respectively) and in thickness at the tendon midsubstance in the 10.2 µg of rhPDGF‐BB group (p = 0.005), compared to controls. All groups had equivalent outcomes by Day 21. There was a dose‐dependent effect on the maximum load‐to‐failure, with no significant difference in the 1.02 and 102 µg rhPDGF‐BB doses but the 10.2 µg rhPDGF‐BB group had a significant increase in load‐to‐failure at 7 (p = 0.003) and 21 days (p = 0.019) compared to controls. The rhPDGF‐BB treatment resulted in a dose‐dependent, transient increase in cell proliferation and sustained improvement in biomechanical properties in a rat Achilles tendinopathy model, demonstrating the potential of rhPDGF‐BB treatment in a tendinopathy application. Consequently, in this model, data suggest that rhPDGF‐BB treatment is an effective therapy and thus, may be an option for clinical applications to treat tendinopathy. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31: 413–420, 2013     

In-Vivo Efficacy of Recombinant Human Hyaluronidase (rHuPH20) Injection for Accelerated Healing of Murine Retrocalcaneal Bursitis and Tendinopathy

The deposition of aggrecan/hyaluronan (HA)-rich matrix within the tendon body and surrounding peritenon impede tendon healing and result in compromised biomechanical properties. Hence, the development of novel strategies to achieve targeted removal of the aggrecan-HA pericellular matrix may be effective in treating tendinopathy. The current study examined the therapeutic potential of a recombinant human hyaluronidase, rHuPH20 (FDA approved for reducing HA accumulation in tumors) for treating murine Achilles tendinopathy. The 12-week-old C57Bl/6 male mice were injected with two doses of rHuTGF-β1 into the retrocalcaneal bursa (RCB) to induce a combined bursitis and tendinopathy. Twenty-four hours following induction of injury, treatment groups were administered rHuPH20 Hyaluronidase (rHuPH20; Halozyme Therapeutics) into the RCB. At either 6 h (acute), 9 days, or 25 days following hyaluronidase treatment, Achilles tendons were analyzed for gene expression, histology and immunohistochemistry, fluorophore-assisted carbohydrate electrophoresis, and biomechanical properties. The rHuPH20 treatment was effective, particularly at the acute and 9-day time points, in (a) removing HA deposits from the Achilles tendon and surrounding tissues, (b) improving biomechanical properties of the healing tendon, and (c) eliciting targeted increases in expression of specific cell fate, extracellular matrix metabolism, and inflammatory genes. The potential of rHuPH20 to effectively clear the pro-inflammatory, HA-rich matrix within the RCB and tendon strongly supports the future refinement of injectable glycosidase preparations as potential treatments to protect or regenerate tendon tissue by reducing inflammation and scarring in the presence of bursitis or other inducers of damage such as mechanical overuse. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:59–69, 2020     

Efficacy of Combining PRP and MMP Inhibitors in Treating Moderately Damaged Tendons Ex Vivo

Platelet‐rich plasma (PRP) and broad‐spectrum matrix metalloproteinase inhibitors (MMPIs) have been used as therapeutic options for tendinopathy. However, mixed results have been reported regarding their efficacy. We posited that the combination of these two treatment strategies would be more beneficial for healing tendons than each treatment alone. Rat tail tendons were harvested and cultured without mechanical stress for 0, 4, or 10 days. Single and combination treatment with PRP and MMPIs with either broad‐ or narrow‐spectrum (MMP‐13 selective), was administered to 4‐day stress‐deprived (SD) tendons, an ex vivo model for moderate tendinopathy. This treatment was applied to the damaged tendons over 6 days. At the end of their culture time, the tendons were subjected to traction testing and pathohistology, immunohistochemistry, and viability assays. The results showed better histological features for the PRP + narrow‐spectrum MMPI group compared with all individual treatment modalities. Moreover, higher fiber density, more elongated nucleus shape, smaller space between fibers, and a trend toward higher mechanical strength were noted for PRP + narrow‐spectrum MMPI group compared with 10‐day SD tendons. This study shows that the combination of PRP + narrow‐spectrum MMPI is a potentially effective treatment approach for tendinopathy. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1838–1847, 2019     

Aging does not alter tendon mechanical properties during homeostasis,but does impair flexor tendon healing

Aging is an important factor in disrupted homeostasis of many tissues. While an increased incidence of tendinopathy and tendon rupture are observed with aging, it is unclear whether this is due to progressive changes in tendon cell function and mechanics over time, or an impaired repair reaction from aged tendons in response to insult or injury. In the present study, we examined changes in the mechanical properties of Flexor Digitorum Longus (FDL), Flexor Carpi Ulnaris (FCU), and tail fascicles in both male and female C57Bl/6 mice between 3 and 27 months of age to better understand the effects of sex and age on tendon homeostasis. No change in max load at failure was observed in any group over the course of aging, although there were significant decreases in toe and linear stiffness in female mice from 3 to 15 months, and 3 to 27 months. No changes in cell proliferation were observed with aging, although an observable decrease in cellularity occurred in 31‐month old tendons. Given that aging did not dramatically alter tendon mechanical homeostasis we hypothesized that a disruption in tendon homeostasis, via acute injury would result in an impaired healing response. Significant decreases in max load, stiffness, and yield load were observed in repairs of 22‐month old mice, relative to 4‐month old mice. No changes in cell proliferation were observed between young and aged, however, a dramatic loss of bridging collagen extracellular matrix was observed in aged repairs suggest that matrix production, but not cell proliferation leads to impaired tendon healing with aging. Results © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2716–2724, 2017.

     

Genome‐wide analysis identifies differential promoter methylation of Leprel2, Foxf1, Mmp25, Igfbp6, and Peg12 in murine tendinopathy

We have used a murine Achilles tendinopathy model to investigate whether tissue changes (such as collagen disorganization, chondroid metaplasia, and loss of tensile properties) which are broadly characteristic of human tendinopathies, are accompanied by changes in the expression of chromatin‐modifying enzymes and the methylation status of promoter regions of tendon cell DNA. Tendinopathy was induced by two intra‐tendinous TGF‐β1 injections followed by cage activity or treadmill running for up to 28 days. Activation of DNA methyltransferases occurred at 3 days after the TGF‐β1 injections and also at 14 days, but only with treadmill activity. Genome‐wide Methyl Mini‐Seq™ analysis identified 19 genes with differentially methylated promoters, five of which perform functions with an apparent direct relevance to tendinopathy (Leprel2 , Foxf1 , Mmp25, Igfbp6 , and Peg12) . The functions of the genes identified included collagen fiber assembly and pericellular interactions, therefore their perturbation could play a role in the characteristic disorganization of fibers in affected tendons. We postulate that a study of the functional genomics of these genes in animal and human tendon could further delineate the pathogenesis of this multi‐factorial complex disease. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:947–955, 2017.

     

Zonal variation in primary cilia elongation correlates with localized biomechanical degradation in stress deprived tendon

Tenocytes express primary cilia, which elongate when tendon is maintained in the absence of biomechanical load. Previous work indicates differences in the morphology and metabolism of the tenocytes in the tendon fascicular matrix (FM) and the inter‐fascicular matrix (IFM). This study tests the hypothesis that primary cilia in these two regions respond differently to stress deprivation and that this is associated with differences in the biomechanical degradation of the extracellular matrix. Rat tail tendon fascicles were examined over a 7‐day period of either stress deprivation or static load. Seven days of stress deprivation induced cilia elongation in both regions. However, elongation was greater in the IFM compared to the FM. Stress deprivation also induced a loss of biomechanical integrity, primarily in the IFM. Static loading reduced both the biomechanical degradation and cilia elongation. The different responses to stress deprivation in the two tendon regions are likely to be important for the aetiology of tendinopathy. Furthermore, these data suggest that primary cilia elongate in response to biomechanical degradation rather than simply the removal of load. This response to degradation is likely to have important consequences for cilia signalling in tendon and as well as in other connective tissues. © 2016 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 34:2146–2153, 2016.     

In vitro effects of glutamate and N‐methyl‐d‐aspartate receptor (NMDAR) antagonism on human tendon derived cells

It is known that extracellular glutamate concentrations are increased in tendinopathy but the effects of glutamate upon human tendon derived cells are unknown. The primary purpose was to investigate the effect of glutamate exposure on human tendon‐derived cells in terms of viability, protein, and gene expression. The second purpose was to assess whether NMDAR antagonism would affect the response of tendon‐derived cells to glutamate exposure. Human tendon‐derived cells were obtained from supraspinatus tendon tissue obtained during rotator cuff repair (tendon tear derived cells) and from healthy hamstring tendon tissue (control cells). The in vitro impact of glutamate exposure and NMDAR antagonism (MK‐801) was measured using the Alamar blue cell viability assay, immunocytochemistry, and quantitative real‐time PCR. Glutamate reduced cell viability at 24 h in tendon tear derived cells but not in control cells at concentrations of 7.5 mM and above. Cell viability was significantly reduced after 72 h of 1.875 mM glutamate in both cell groups; this deleterious effect was attenuated by NMDAR antagonism with 10 µM MK‐801. Both 24 and 72 h of 1.875 mM glutamate exposure reduced Type 1 alpha 1 collagen (COL1A1) and Type 3 alpha 1 collagen (COL3A1) gene expression, but increased Aggrecan gene expression. We propose that these effects of glutamate on tendon derived cells including reduced cell viability and altered matrix gene expression contribute to the pathogenesis of tendinopathy. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1515–1522, 2015.     

Flexor digitorum profundus tendon to bone tunnel repair: a vascularization and histologic study in canines

PURPOSE: Recent in vivo canine studies have shown incomplete restoration of the flexor digitorum profundus (FDP) insertion site after transection and repair to the cortical surface of the distal phalanx. Previous biomechanical analyses of tendon to bone surface repair have suggested that repair site gap formation of greater than 3 mm occurs frequently under physiologic loads. A recent ex vivo investigation into a novel repair of the FDP tendon into a bone tunnel in the distal phalanx showed improved tensile properties with a decrease in repair site gap formation. Time-zero data, however, do not always accurately reflect in vivo responses. The repair response of the FDP tendon when placed in an osseous compartment is not known. The purpose of this study was to analyze the histologic and vascular anatomic properties of the FDP insertion site after transection and repair in a bone tunnel within the distal phalanx. METHODS: Twenty-six FDP tendon to bone repairs were performed in 13 adult mongrel dogs after insertion site transection. The tendons were repaired in a bone tunnel in the distal phalanx. Vascular analysis of the tendon and repair site was performed by using a modified Spalteholtz technique and routine hematoxylin-eosin staining was used to assess histologic properties of the repair. RESULTS: In normal specimens the vascular analysis showed that there was a distal network of vessels extending 1- to 2-cm proximal to the FDP insertion site. At 10 days after repair the distal tendon segment tendon remained avascular. By 21 days after repair there was proximal migration of an unorganized reticular network of tendon surface vessels with sparse intratendinous communications. At 6 weeks after repair the structure of the distal tendon vascular network resembled that of normals. The vascular response of the tendon within the bone tunnel followed a similar time frame. Histologic analysis showed an inflammatory reaction in the bone tunnel leading to a progressive degradation of that portion of the FDP tendon that resided in the tunnel. Tendon necrosis was not seen. CONCLUSIONS: The FDP tendon, after insertion site transection and repair in a bone tunnel, undergoes a process of neovascularization and revascularization over a period of 6 weeks. There is a progressive loss of tendon parenchyma within the bone tunnel and the suture tracks appeared to serve as conduits for the ingrowth of inflammatory tissue. Restoration of the normal 4-zone tendon-bone interface was not seen. Although ex vivo biomechanical assessment of tendon repair in a bone tunnel appears promising, the repair response in vivo may not be favorable for tendon to bone healing. The progressive tendon degeneration that was observed here may have detrimental effects on repair site tensile properties, increasing the potential for early failure.     

Mechanisms of collagen fibril alignment in tendon injury: From tendon regeneration to artificial tendon

The process by which collagen fibrils are aligned following tendon injury remains unknown. Therefore, we analyzed the process of tendon regeneration by transmission electron microscopy, using a film model method. In mice, the Achilles tendon of medial head was transected. On day 3, after only the proximal end of the transected tendon was placed on film and kept in vivo, a translucent substance containing granules, called tendon gel, was secreted. On day 5, the granules assembled in a loose (L) layer, and coalesced tightly in a dense (D) layer, forming an L‐D‐L layered pattern. On day 10, granules showed high electron density in H layers, which developed into D‐H‐D layers on day 13. The distal end was placed on film to face the proximal end. On day 10, the tendon gel showed a D‐H‐D layer pattern. On day 11, mechanical stress from muscular constriction changed the tendon gel to aligned collagen fibrils (6 ± 2 nm in diameter). Thereafter, the diameter of the fibrils increased. Tendon gel harvested on day 5 or day 10 was pulled manually or by hanging weights (about 0.6 MPa). Aligned collagen fibrils (32 ± 7 nm in diameter) were created by traction using tendon gel harvested on day 10. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29:1944–1950, 2011     

Chondroitin‐6‐sulfate incorporation and mechanical stimulation increase MSC‐collagen sponge construct stiffness

Using functional tissue engineering principles, our laboratory has produced tendon repair tissue which matches the normal patellar tendon force‐displacement curve up to 32% of failure. This repair tissue will need to withstand more strenuous activities, which can reach or even exceed 40% of failure force. To improve the linear stiffness of our tissue engineered constructs (TECs) and tissue engineered repairs, our lab is incorporating the glycosaminoglycan chondroitin‐6‐sulfate (C6S) into a type I collagen scaffold. In this study, we examined the effect of C6S incorporation and mechanical stimulation cycle number on linear stiffness and mRNA expression (collagen types I and III, decorin and fibronectin) for mesenchymal stem cell (MSC)‐collagen sponge TECs. The TECs were fabricated by inoculating MSCs at a density of 0.14 × 10⁶ cells/construct onto pre‐cut scaffolds. Primarily type I collagen scaffold materials, with or without C6S, were cultured using mechanical stimulation with three different cycle numbers (0, 100, or 3,000 cycles/day). After 2 weeks in culture, TECs were evaluated for linear stiffness and mRNA expression. C6S incorporation and cycle number each played an important role in gene expression, but only the interaction of C6S incorporation and cycle number produced a benefit for TEC linear stiffness. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:1092–1099, 2010     

Culture of human septal chondrocytes in a rotary bioreactor

Objectives (1) To show that extracellular matrix deposition in 3-dimensional culture of human septal chondrocytes cultured in a rotary bioreactor is comparable to the deposition achieved under static culture conditions. (2) To demonstrate that the biomechanical properties of human septal chondrocytes cultured in a bioreactor are enhanced with time and are analogous to beads cultured under static culture. Study Design Prospective, basic science. Setting Research laboratory. Methods Human septal chondrocytes from 9 donors were expanded in monolayer and seeded in alginate beads. The beads were cultured in a rotary bioreactor for 21 days in media supplemented with growth factors and human serum, using static culture as the control. Biochemical and biomechanical properties of the beads were measured. Results Glycosaminoglycan (GAG) accumulation significantly increased during 2 measured time intervals, 0 to 21 days and 10 to 21 days (P < .01). No significant difference was seen between the static and bioreactor conditions. Substantial type II collagen production was demonstrated in the beads terminated at day 21 of culture in both conditions. In addition, the biomechanical properties of the beads were significantly improved at 21 days in comparison to beads from day 0. Conclusion Human septal chondrocytes cultured in alginate beads exhibit significant matrix deposition and improved biomechanical properties after 21 days. Alginate bead diameter and stiffness positively correlated with GAG and type II collagen accretion. Matrix production in beads is supported by the use of a rotary bioreactor.     

Use of an IL1‐receptor antagonist to prevent the progression of tendinopathy in a rat model

This study evaluated if inhibiting IL1‐β activity with an IL1‐receptor antagonist (IL1‐RA) will prevent pathologic changes commonly seen in tendinopathy. Thirty‐six Sprague–Dawley retired‐breeder rats were divided into three groups having weekly bilateral patellar tendon injections: CON (0.1 ml Saline), CAR (0.1 ml 2% carrageenan), IL1‐RA (0.1 ml 2% CAR plus 0.94 mg of the IL1‐RA, 2.5 mg/kg). Carrageenan was used to establish tendinopathy in two groups due to its ability to develop tendinopathy in prior studies. Animals were euthanized 3 weeks after initial injection. The CAR group demonstrated significantly (p < 0.05) shorter tendon lengths (8.61 ± 0.38 mm) relative to CON (8.94 ± 0.38 mm) that was prevented in the IL1‐RA (9.02 ± 0.30 mm) as well as significantly increased collagenase activity in the CAR (0.061 ± 0.043) compared to CON (0.027 ± 0.015) (p< 0.05). By histological evaluation, the CAR group demonstrated significantly greater inflammation than IL1‐RA, and CON (p < 0.05). CAR showed a trend for increased cross‐sectional area relative to CON that was absent in the IL1‐RA. IL1‐RA can effectively inhibit the development of mechanical, chemical, and histologic changes seen with carrageenan‐induced tendonitis. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:616–622, 2016.     

肌腱病的病理改变及凋亡的研究

肌腱病是由过度使用所引起的肌腱及腱周疼痛、肿胀和功能障碍的综合征。三十年来,它的发病率明显增加。尽管人们对肌腱病进行了广泛研究,但目前仍然不能完全阐明肌腱病的发病机制、病理改变和治疗方案。本文阐述了肌腱病的病理分类、形态学、光镜及电镜下的特点,以及光镜下凋亡细胞的形态学特点。并着重介绍了最近关于从各种刺激到凋亡再发展为肌腱退变这一热点问题的研究。     

BIO alleviated compressive mechanical force‐mediated mandibular cartilage pathological changes through Wnt/β‐catenin signaling activation

Osteoarthritis induced by compressive mechanical force is characterized by decreased chondrocyte proliferation and degradation of the ECM. To examine underlying mechanisms of the pathological changes of mandibular cartilage induced by compressive mechanical force, an established animal model was used to examine Wnt signaling activation by glycogen synthase kinase‐3 beta (GSK3β) inhibitor 6‐Bromoindirubin‐3′‐oxime (BIO) injection in vivo. Histological changes in mandibular cartilage were assessed via hematoxylin & eosin (HE), masson, and alcian blue staining. Immunohistochemistry and real‐time PCR were performed to evaluate activation of the Wnt signaling pathway and chondrocytes proliferation markers. Chondrocytes apoptosis was examined by TUNEL staining. During the compressive mechanical force loading‐mediated process, Wnt signaling was largely inhibited, which showed the inhibited expression of β‐catenin and the increased expression of GSK‐3β. The expression of chondrocytes proliferation markers Ki67, and proliferating cell nuclear antigen (PCNA) also decreased. With BIO injection, the Wnt signaling was restored and the proliferation of mandibular chondrocytes was also increased in the late stage (7 days) of compressive mechanical force loading. Finally, the decreasing mandibular cartilage thickness, the degradation of extracellular matrix, and the erosion of bone trabecula were subsequently restored. Also, the changes of extracellular matrix markers such as collagen II and collagen X, matrix metalloproteases, and inflammatory cytokines were reversed followed by the injection of BIO. In summary, compressive mechanical force decreased endogenously Wnt signaling, leading to impaired proliferation in chondrocytes and degradation in cartilage matrix. Restoration of Wnt signaling largely recovered the proliferation defects and alleviated the pathological changes of mandibular cartilage. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1228–1237, 2018.