Intra-Articular Delivery of Quercetin Using Thermosensitive Hydrogel Attenuate Cartilage Degradation in an Osteoarthritis Rat Model.

OBJECTIVE: Quercetin (Que), a bioflavonoid, is both anti-inflammatory and antioxidative. Que has been used as an oral supplement for osteoarthritis (OA) with inconsistent findings because of its low bioavailability. We encapsulated Que in a mPEG-polypeptide thermogel to prolong its bioactivity. The efficacy of this formulation was evaluated in a posttraumatic OA rat model. DESIGN: Methoxy-poly(ethylene glycol)-l-poly(alanine) (mPEG-PA) polymer was synthesized and characterized in terms of cytotoxicity and release kinetics in vitro. At 12 weeks old, Sprague-Dawley rats underwent anterior cruciate ligament transection (ACLT). At 24 weeks post-operation, rats received either an intra-articular (IA) injection of saline, hydrogel, or hydrogel with Que (50 or 500 µg). Gait analysis was performed at pre-ACLT, pre-treatment, and at 4, 8, and 12 weeks post-treatment. At 12 weeks post-treatment, knee joints were collected for histopathological evaluation. RESULTS: In vitro studies showed that chondrocytes were viable after 72 hours of incubation with mPEG-PA, and the release of Que could be sustained for >28 days. Among all OA rats, the limb idleness index (LII) were significantly increased at 24 weeks post-ACLT. Rats that received hydrogel with Que (50 µg) showed the most reduction in LII at both 4 and 8 weeks post-treatment. The Osteoarthritis Research Society International score of rats received hydrogel with Que (50 µg) was significantly lower than the control group. All rats suffered from low-grade synovitis (Krenn score: 2-4). CONCLUSION: This study suggests that a sustained delivery of Que (50 µg) could provide symptom relief and also delay the progression of OA in the knee.

The non-reconstructive treatment of complete ACL tear with biological enhancement in clinical and preclinical studies: A systematic review.

INTRODUCTION: There is still controversy regarding the bio-enhanced non-reconstructive ACL treatment. MATERIALS AND METHODS: A search for articles in databases was performed in February 2017. The objective and subjective evaluations of clinical studies and biomechanical and histological data of preclinical studies were extracted. RESULTS: Eighteen articles were included for analysis. In clinical studies, although subjective scores were significantly improved, the rate of re-operation rate was high. In preclinical studies, bio-enhancing techniques demonstrated promotion of the healing of ACL. CONCLUSIONS: The efficacy of biological enhancement cannot be validated in clinical studies. Preclinical studies showed improved biomechanical and healing potential.

Muscle-Secreted Factors Improve Anterior Cruciate Ligament Graft Healing: An In Vitro and In Vivo Analysis.

One of the ligaments most often damaged during sports-the anterior cruciate ligament (ACL)-has poor healing capacity. On damage, reconstructive surgery is performed to restore the mechanical stability of the knee and to reduce the inflammatory milieu otherwise present in the joint. A return to normal activities, however, takes between 9 and 12 months. Thus, strategies capable of improving ACL graft healing are needed. Embryonic development of tendon and ligament (T/L) is regulated by a crosstalk between different cell types. We hypothesized that terminally differentiated skeletal-derived cells such as osteoblasts, chondrocytes, and myoblasts modulate T/L healing. Using an indirect coculture system, we discovered that myoblast-secreted signals-but not osteoblasts, chondrocytes, or stromal-secreted signals-are capable of upregulating classical T/L markers such as scleraxis and tenomodulin on human hamstring tendon-derived cells (hTC), which contribute to ACL graft healing. Transcriptome analysis showed that coculturing hTC with myoblasts led to an upregulation of extracellular matrix (ECM) genes and resulted in enhanced ECM deposition. In vivo, using a rat model of ACL reconstruction showed that conditioned media derived from human muscle tissue accelerated femoral tunnel closure, a key step for autograft integration. Collectively, these results indicate that muscle-secreted signals can be used to improve ACL graft healing in a clinical setting where muscle remnants are often discarded.

Optimisation of platelet concentrates therapy: Composition, localisation, and duration of action.

Platelet concentrates (PC) generally refers to a group of products that are prepared from autologous blood intended to enhance healing activities. PC therapy is now very popular in treating musculoskeletal injuries; however, inconsistent clinical results urge the need to understand the working mechanism of PC. It is generally believed that the platelet-derived bioactive factors are the active constituents, and their bioavailability in the vicinity of the lesion sites determines the treatment efficacies. Therefore, the composition, localisation, and duration of the action of PC would be key determinants. In this review, we discuss how different preparations and delivery methods of PC would affect the treatment outcomes with respect to clinical evidence about PC therapy for osteoarthritis, tendinopathies, rotator cuff tears, anterior cruciate ligament injuries, and bone fractures. This review can be used as a quick guide for the use of PC therapy and provide insights for the further optimisation of the therapy in the near future.

Intra-articular injection of an antioxidant formulation did not improve structural degeneration in a rat model of post-traumatic osteoarthritis.

BACKGROUND/OBJECTIVE: Oxidative stress plays an important role in osteoarthritis (OA), causing inflammation and matrix degradation in joints. Previous studies have shown that antioxidants such as quercetin and vitamin C are potential candidates for treating OA. We aimed to determine whether a formulation of quercetin and vitamin C, together with an iron chelator, could retard OA progression in a post-traumatic OA rat model. METHODS: Twelve rats received anterior cruciate ligament transection for OA induction. At 20 weeks postoperation, weekly intra-articular injection of 50 µL of either saline or a formulation of quercetin dehydrate, sodium-L-ascorbate, and deferoxamine mesylate was given consecutively for 4 weeks (n = 5). Gait analysis was performed at pretreatment, and at 1 week and 5 weeks post-treatment. Microcomputed tomography scanning and histological scoring were performed at 5 weeks post-treatment. RESULTS: Gait analysis showed that intra-articular injections of antioxidant formulation did not improve pain-associated Limb Idleness Index over time (p = 0.449, Friedman test). However, at 5 weeks post-treatment, the treatment group exhibited a significantly lower Limb Idleness Index than the control group (p = 0.047, Mann-Whitney U test). At 5 weeks post-treatment, microcomputed tomography analysis revealed that there was no difference in any parameter between the treatment and control groups (p > 0.05, Student t test). Severe OA histopathological changes were found in both groups. The Osteoarthritis Research Society International scores of the treatment and control groups were 20 (range, 20-26) and 20 (range, 9-26), respectively (p = 0.382, Mann-Whitney U test). CONCLUSION: Intra-articular injection of an antioxidant formulation containing quercetin, vitamin C, and deferoxamine did not retard OA progression in advanced-stage OA. Future studies should aim to determine whether giving antioxidants in early OA, with prolonged drug retention, would be effective in retarding OA progression.

Peri-tunnel bone loss: does it affect early tendon graft to bone tunnel healing after ACL reconstruction?

PURPOSE: The clinical relevance and mechanisms of local bone loss early post-anterior cruciate ligament (ACL) reconstruction remain unclear. The early spatial and temporal changes of peri-tunnel bone, its molecular mechanisms and its relationships with graft-bone tunnel healing were investigated in a 12-week-old rat model. METHODS: At various times, the reconstructed ACL complex was harvested for vivaCT imaging, biomechanical test, histology and immunohistochemical staining of CD68+ cells (a monocyte-macrophage lineage marker), MMP1 and MMP13. RESULTS: The peri-tunnel bone resorbed simultaneously with improvement of graft-bone tunnel healing. There were 30.1 ± 17.4, 46.8 ± 10.5 and 81.5 ± 12.3 % loss of peri-tunnel BMD as well as 43.2 ± 21.7, 78.7 ± 8.5 and 92.4 ± 17.7 % loss of peri-tunnel bone volume/total volume (BV/TV) at week 6 at the distal femur, epiphysis and metaphysis of tibia, respectively. MMP1, MMP13 and CD68+ cells were expressed at the graft-bone tunnel interface and peri-tunnel bone and increased with time post-reconstruction at the tibia. The ultimate load and stiffness of the healing complex positively correlated with tibial tunnel bone formation and negatively correlated with tibial peri-tunnel bone. Tunnel BV/TV at the tibial metaphysis and epiphysis showed the highest correlation with ultimate load (ρ = 0.591; p = 0.001) and stiffness (ρ = 0.427; p = 0.026) of the complex, respectively. CONCLUSION: There was time-dependent loss of peri-tunnel bone early post-reconstruction, with the greatest loss occurring at the tibial metaphysis. This was consistent with high expression of MMP1, MMP13 and CD68+ cells at the graft-bone tunnel interface and the peri-tunnel region. The significant loss of peri-tunnel bone, though not critically affecting early tunnel healing, suggested the need to protect the knee joint early post-reconstruction.

Tripeptide-copper complex GHK-Cu (II) transiently improved healing outcome in a rat model of ACL reconstruction.

After anterior cruciate ligament reconstruction (ACLR), the biological healing of the graft is a rate-limiting step which can contribute to graft failure. The tripeptide-copper complex glycyl-L-histidyl-L-lysine-Cu(II) (GHK-Cu) is a well-known activator of tissue remodeling. We investigated whether GHK-Cu can improve graft healing following ACLR. Seventy-two rats underwent unilateral ACLR were randomized to saline, 0.3 or 3 mg/ml GHK-Cu groups (n = 24). Post-operational intra-articular injections were given from week 2, once a week, for 4 weeks. Gait analysis was performed pre-injury and at harvesting time. At 6 or 12 weeks post-operation, knee specimens were harvested for knee laxity test, graft pull-out test, and histology. At 6 weeks post-ACLR, GHK-Cu groups resulted in a smaller side-to-side difference in knee laxity as compared to the saline group (p = 0.009), but there was no significant difference at 12 weeks post-operation. The graft complex in the 0.3 mg/ml GHK-Cu group had higher stiffness than saline group at 6 weeks post-operation (p = 0.026), but there was no significant difference in ultimate load, gait parameters, and histological scores among treatment groups. All grafts failed mid-substance during pull-out test. Intra-articular supplementation with a bioactive small molecule GHK-Cu improved graft healing following ACLR in rat, but the beneficial effects could not last as treatment discontinued.

Systematic Review of Biological Modulation of Healing in Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Whether biological modulation is effective to promote healing in anterior cruciate ligament (ACL) reconstruction remains unclear. PURPOSE: To perform a systematic review of both clinical and experimental evidence of preclinical animal studies on biological modulation to promote healing in ACL reconstruction. STUDY DESIGN: Systematic review; Level of evidence, 2. METHODS: A systematic search was performed using the PubMed, Ovid, and Scopus search engines. Inclusion criteria were clinical and animal studies involving subjects with ACL injury with the use of biological modulation to promote healing outcomes. Methodological quality of clinical studies was evaluated using the Critical Appraisal Skill Programme (CASP) appraisal tool, and animal studies were evaluated by a scoring system based on a published checklist of good animal studies. RESULTS: Ten clinical studies and 50 animal studies were included. Twenty-five included studies were regarded as good quality, with a methodological score ≥5. These studies suggested that transforming growth factor-beta (TGF-ß), mesenchymal stem cells, osteogenic factors, and modalities that reduce local inflammation may be beneficial to promote graft healing in ACL reconstruction. CONCLUSION: This systematic review suggests that biological modulation is able to promote healing on top of surgical treatment for ACL injuries. This treatment strategy chiefly works through promotion of healing at the tunnel-graft interface, but the integrity of the intra-articular midsubstance of the graft would be another target for biological modulation.

Local administration of alendronate reduced peri-tunnel bone loss and promoted graft-bone tunnel healing with minimal systemic effect on bone in contralateral knee.

Continued systemic administration of alendronate was reported to reduce peri-tunnel bone resorption and promoted graft-bone tunnel healing at the early stage post-anterior cruciate ligament (ACL) reconstruction. However, systemic increase in bone mineral density (BMD) in the contralateral intact knee was observed. We tested if single local administration of alendronate into the bone tunnel during ACL reconstruction could achieve similar benefits yet without the systemic effect on bone. Seventy-two rats with unilateral ACL reconstruction were divided into three groups: saline, low-dose (6 µg/kg) and mid-dose (60 µg/kg) alendronate. For local administration, alendronate was applied to the bone tunnels for 2 min before graft insertion and repair. At weeks 2 and 6, the reconstructed complex was harvested for high-resolution computed tomography (vivaCT) imaging followed by biomechanical test or histology. Our results showed that local administration of low-dose alendronate showed comparable benefits on the reduction of peri-tunnel bone loss, enhancement of bone tunnel mineralization, tunnel graft integrity, graft osteointegration and mechanical strength of the reconstructed complex at early stage post-reconstruction, yet with minimal systemic effect on mineralized tissue at the contralateral intact knee. A single local administration of alendronate at the low-dose therefore might be used to promote early tunnel graft healing post-reconstruction.

Effect of graft tensioning on mechanical restoration in a rat model of anterior cruciate ligament reconstruction using free tendon graft.

PURPOSE: Initial graft tensioning is important in anterior cruciate ligament reconstruction (ACLR), but its effect on graft healing is still not clear. Since all previous animal studies on graft tensioning used bone-patellar tendon-bone, this study aimed to investigate the effect of initial graft tensioning on ACLR using tendon graft. METHODS: Fifty-five Sprague-Dawley rats underwent ACLR using flexor digitorum longus tendon graft. A constant force of 2 or 4 N was applied during graft fixation. At 0, 2, and 6 weeks, knee samples were harvested (n = 6) for static knee laxity test and graft pull-out test. Histological examination was performed at 2 and 6 weeks post-injury (n = 4). RESULTS: At time zero, knee laxity was restored by ACLR with 2 or 4 N tensioning as compared to ACL-deficient group (p < 0.001), and the 4 N group exhibited a better restoration as compared to 2 N group (p = 0.031). At week 2 post-operation, the 4 N group still exhibited a better restoration in knee laxity (p = 0.001) and knee stiffness (p = 0.002) than the 2 N group; the graft pull-out force (p = 0.032) and stiffness (p = 0.010) were also higher. At week 6 post-operation, there was no significant difference between the 2 and 4 N group in knee laxity and graft pull-out strength. Histological examination showed that the beneficial effect of higher initial graft tension may be contributed by maintenance of graft integrity at mid-substance and reduction in adverse peri-graft bone changes in the femoral tunnel region. CONCLUSIONS: A higher initial graft tension favours the restoration of knee laxity and promotes graft healing in ACLR using free tendon graft in the rat model.

Ectopic chondro-ossification and erroneous extracellular matrix deposition in a tendon window injury model.

The acquisition of chondro-osteogenic phenotypes and erroneous matrix deposition may account for poor tissue quality after acute tendon injury. We investigated the presence of chondrocyte phenotype, ossification, and the changes in the expression of major collagens and proteoglycans in the window wound in a rat patellar tendon window injury model using histology, von Kossa staining and immunohistochemistry of Sox 9, major collagens, and proteoglycans. Our results showed that the repair tissue did not restore to normal after acute injury. Ectopic chondrogenesis was observed in 33% of samples inside wound at week 4 while ectopic ossification surrounded by chondrocyte-like cells were observed in the window wound in 50% of samples at week 12. There was sustained expression of biglycan and reduced expression of aggrecan and decorin in the tendon matrix in the repair tissue. The erroneous deposition of extracellular matrix and ectopic chondro-ossification in the repair tissue, both might influence each other, might account for the poor tissue quality after acute injury. Higher expression of biglycan and aggrecan were observed in the ectopic chondro-ossification sites in the repair tissue, suggesting that they might have roles in ectopic chondro-osteogenesis.

Use of allogeneic scaffold-free chondrocyte pellet in repair of osteochondral defect in a rabbit model.

Cell-based therapies are currently being used in treating osteochondral defect (OCD), but technical advances are needed to tackle the problems of scaffold and grafting technique. This study aimed to test the potential of allogeneic scaffold-free bioengineered chondrocyte pellet (BCP) in treating OCD. BCP was fabricated from rabbit costal cartilage and implanted into 3 mm × 3 mm OCD in medial femoral condyle of 20 rabbits. Samples were harvested at 2, 4, 8, and 16 weeks for histology, histological scoring and histomorphometric analysis. At treated side, cartilage score was significantly better at week 4 (p = 0.027), and cartilage thickness measured in histomorphometric analysis was significantly thicker at week 4 (p = 0.028) and week 16 (p = 0.028) compared to the empty controls. At treated side, bone score remained significantly lower from week 8 onwards (p = 0.024 at week 8, p = 0.02 at week 16) whereas bone area was significantly smaller from week 4 onwards compared to the empty controls (p = 0.028 at week 4, 8, 16). No immunorejection was observed throughout the experiment. The results demonstrated that the BCP enhanced cartilage repair at early stage. Press-fitting of allogeneic BCP was a simple method for OCD repair without immunorejection. Further optimization of the treatment is required before clinical application.

Deciphering the pathogenesis of tendinopathy: a three-stages process.

Our understanding of the pathogenesis of "tendinopathy" is based on fragmented evidences like pieces of a jigsaw puzzle. We propose a "failed healing theory" to knit these fragments together, which can explain previous observations. We also propose that albeit "overuse injury" and other insidious "micro trauma" may well be primary triggers of the process, "tendinopathy" is not an "overuse injury" per se. The typical clinical, histological and biochemical presentation relates to a localized chronic pain condition which may lead to tendon rupture, the latter attributed to mechanical weakness. Characterization of pathological "tendinotic" tissues revealed coexistence of collagenolytic injuries and an active healing process, focal hypervascularity and tissue metaplasia. These observations suggest a failed healing process as response to a triggering injury. The pathogenesis of tendinopathy can be described as a three stage process: injury, failed healing and clinical presentation. It is likely that some of these "initial injuries" heal well and we speculate that predisposing intrinsic or extrinsic factors may be involved. The injury stage involves a progressive collagenolytic tendon injury. The failed healing stage mainly refers to prolonged activation and failed resolution of the normal healing process. Finally, the matrix disturbances, increased focal vascularity and abnormal cytokine profiles contribute to the clinical presentations of chronic tendon pain or rupture. With this integrative pathogenesis theory, we can relate the known manifestations of tendinopathy and point to the "missing links". This model may guide future research on tendinopathy, until we could ultimately decipher the complete pathogenesis process and provide better treatments.

Expression of bone morphogenetic protein-2 in the chondrogenic and ossifying sites of calcific tendinopathy and traumatic tendon injury rat models.

BACKGROUND: Ectopic chondrogenesis and ossification were observed in a degenerative collagenase-induced calcific tendinopathy model and to a lesser extent, in a patellar tendon traumatic injury model. We hypothesized that expression of bone morphogenetic protein-2 (BMP-2) contributed to ectopic chondrogenesis and ossification. This study aimed to study the spatial and temporal expression of BMP-2 in our animal models. METHODS: Seventy-two rats were used, with 36 rats each subjected to central one-third patellar tendon window injury (C1/3 group) and collagenase-induced tendon injury (CI group), respectively. The contralateral limb served as controls. At week 2, 4 and 12, 12 rats in each group were sacrificed for immunohistochemistry and RT-PCR of BMP-2. RESULTS: For CI group, weak signal was observed at the tendon matrix at week 2. At week 4, matrix around chondrocyte-like cells was also stained in some samples. In one sample, calcification was observed and the BMP-2 signal was observed both in the calcific matrix and the embedded chondrocyte-like cells. At week 12, the staining was observed mainly in the calcific matrix. Similar result was observed in C1/3 group though the immunopositive staining of BMP-2 was generally weaker. There was significant increase in BMP-2 mRNA compared to that in the contralateral side at week 2 and the level became insignificantly different at week 12 in CI group. No significant increase in BMP-2 mRNA was observed in C1/3 group at all time points. CONCLUSION: Ectopic expression of BMP-2 might induce tissue transformation into ectopic bone/cartilage and promoted structural degeneration in calcific tendinopathy.

Expression of transforming growth factor beta isoforms and their roles in tendon healing.

Transforming growth factor beta (TGF-beta) plays active roles in tendon healing. However, the differential effects of TGF-beta isoforms on tendon healing have not been investigated. In cultured tendon fibroblasts, we tested the effects of TGF-beta1, beta2, and beta3 on the mRNA levels of COL1A1 and COL3A1 by quantitative real-time polymerase chain reaction. We also investigated the expression of TGF-beta isoforms, TGF-beta receptors, procollagen Type I and Type III in a rat model of tendon healing. We found that TGF-beta3 exhibited the highest potency in stimulating COL1A1 and COL3A1. TGF-beta1 exerted antagonistic effects to TGF-beta2 and beta3. All TGF-beta isoforms and procollagen Type I were confined to the edges of the healing tendon at day 28 postinjury. Our results indicated that interaction of TGF-beta isoforms exist in the regulation of collagen synthesis in tendon fibroblasts. Their effects may be further complicated by uneven spatial distribution of TGF-beta and TGF-beta receptors in healing tendons.

Is cultured tendon fibroblast a good model to study tendon healing?

Cultured tendon fibroblasts (CTFs) from intact explants are widely used to study tendon healing in vitro. The significance of these findings may rely on similarities between CTFs and healing tendon fibroblasts in situ. Our purpose was to compare CTFs with fibroblasts cultured from healing tendons. We cultured CTFs from intact and healing tendons at day 7 and day 14 postinjury in a rat model of patellar donor site injury. The mRNA expression of COL1A1, COL3A1, decorin, and biglycan, with or without supplementation of 1 ng/mL TGF-beta1, was compared by quantitative real-time RT-PCR. The expression of proliferation cell nuclear antigen (PCNA) and alpha-smooth muscle actin (alpha-SMA) was determined by immunostain. COL3A1 and decorin mRNA in CTFs was lower as compared to day 7 healing fibroblasts, but its biglycan mRNA level was higher than day 14 healing fibroblasts. TGF-beta1 increased COL1A1 and decorin mRNA in CTFs, but decreased the mRNA of all four genes in day 7 healing tendon fibroblasts. CTFs exhibited lower PCNA immunopositivity as compared to day 7 and day 14 healing fibroblasts, but a higher alpha-SMA immunopositivity than cultured day 14 healing fibroblasts. These findings showed that CTFs did not resemble healing tendon cells with respect to major cellular activities related to tendon healing. Thus, fibroblasts from healing tendon may be a more appropriate model for studying cellular activities in tendon healing.

Increased apoptosis at the late stage of tendon healing.

The mechanism for the clearance of excess healing fibroblasts at the end of tendon healing has not been reported despite the importance of maintaining tissue homeostasis. This study investigated the role of apoptosis in cell turnover in a rat central 1/3 patellar tendon donor site injury model. At days 4, 7, 14, 28, months 2 and 6, the rats were killed. Patellar tendons without injury served as control. Apoptotic cells were determined by an in situ terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) assay and anti-active caspase-3 antibodies, while proliferating cells were determined by anti-proliferating cell nuclear antigen antibodies. The total fibroblast-like cell density in the center of the wound increased from day 4 and thereafter steadily returned to normal. In situ TUNEL assay showed few positive staining cells in the wound at days 4 and 7. The percentages of TUNEL-positive fibroblast-like cells showing morphological characteristics of apoptosis increased sharply and reached the maximum on day 28 (median %: 31.38%). No fibroblast-like cell was stained at month 6 and the healed tissue was similar to that in a normal uninjured tendon. A similar trend was observed with active caspase-3 immunohistochemistry. In conclusion, an increase in apoptosis at the end of tendon healing coincided with a decrease in cellularity.

TGF-beta1 reverses the effects of matrix anchorage on the gene expression of decorin and procollagen type I in tendon fibroblasts.

Transforming growth factor-beta1 is known for its effect on the production of extracellular matrix in tendons. Elevated levels of transforming growth factor-beta1 have been reported in tendon adhesion and tendinosis, which suggests that transforming growth factor-beta1 plays an important role in matrix disturbances. Tendon adhesion involves excessive collagen deposition, whereas tendinosis is associated with increased proteoglycan deposition. It seems that other factors also may affect matrix deposition and modulate the effects of transforming growth factor-beta1. We assessed whether matrix anchorage to Type I collagen or fibronectin could change the gene expression of matrix proteins in tendon fibroblasts, and studied whether the effects of transforming growth factor-beta1 were altered by matrix anchorage. Human patellar tendon fibroblast cultures were prepared in different cell anchorages, and the cellular responses to transforming growth factor-beta1 were measured as gene expression of procollagen Type I, Type III, decorin, and biglycan by real-time reverse transcriptase-polymerase chain reaction. Fibronectin anchorage significantly increased the messenger ribonucleic acid level of decorin, and the messenger ribonucleic acid level of procollagen Type I was decreased by matrix anchorage to either fibronectin or Type I collagen. Transforming growth factor-beta1 increased the messenger ribonucleic acid level of procollagen Type I in Type I collagen-coated plates, but it suppressed the messenger ribonucleic acid level of decorin in fibronectin-coated plates. These findings suggest that interaction of matrix anchorage and transforming growth factor-beta1 is an important determinant of matrix deposition in healing tendons and the development of matrix disturbances in tendons.

The roles of bone morphogenetic protein (BMP) 12 in stimulating the proliferation and matrix production of human patellar tendon fibroblasts.

Recombinant human (rh) bone morphogenetic protein 12 (BMP12) is proved to induce the formation of tendon and ligament tissues in animal experiments. But the roles of BMP12 on tissue regeneration in human tendons remain unexplored. In the present study, healthy human patellar tendon samples were collected for histological examination and preparation of tendon fibroblast culture. Immunohistochemical staining showed that BMP12 was detected on healthy patellar tendon samples, only located on active tenoblasts and perivascular mesenchymal cells but not in interstitial tenocytes. The expression of PCNA and procollagen type I also exhibited a similar distribution. It indicates that BMP12 may be involved in matrix remodeling process in adult tissues. In vitro studies showed that rhBMP12 could increase proliferation of tendon fibroblasts and increase the gene expression of procollagen type I and type III, but decrease the gene expression of decorin in tendon fibroblasts culture. Our findings suggest that BMP12 may play a role in early phases of tissue regeneration in tendons.