Intra-articular administration of EP2 enhances the articular cartilage repair in a rabbit model.

We have reported the usefulness of chondrocyte sheets on articular cartilage repair in animal experiments. Here, we investigated the regenerative effects of EP2 signalling with or without chondrocyte sheets. Forty-five rabbits were used, with six rabbits in each of the six groups and nine rabbits for chondrocytes and synovial cells harvesting to fabricate triple-layered chondrocyte sheets: osteochondral defect only (control, Group A), EP2 agonist (Group B), EP2 antagonist (Group C), chondrocyte sheets (Group D), EP2 agonist and chondrocyte sheets (Group E), and EP2 antagonist and chondrocyte sheets (Group F). After surgery, the weight distribution ratio was measured as an indicator of pain alleviation. Injections of the EP2 agonist or EP2 antagonist were given from 4 weeks after surgery. The rabbits were sacrificed at 12 weeks, and the repaired tissues were evaluated for histology. The weight distribution ratio and International Cartilage Repair Society grading were as follows: Group A: 40.5% ± 0.2%, 14.8 ± 0.5; Group B: 43.4% ± 0.7%, 25.4 ± 0.8; Group C: 38.7% ± 0.7%, 13.7 ± 0.3; Group D: 48.6% ± 0.6%, 40.2 ± 0.5; Group E: 49.1% ± 0.3%, 40.5 ± 0.4; and Group F; 46.8% ± 0.4%, 38.7 ± 0.5. Significant differences in histology and pain alleviation were observed between groups except between Groups A and C, between Groups D and E, and between Groups D and F. These findings show that the intra-articular administration of an EP2 agonist achieved pain alleviation and tissue repair. However, no synergistic effect with chondrocyte sheets was observed.

Effects of a cell-free method using collagen vitrigel incorporating TGF-ß1 on articular cartilage repair in a rabbit osteochondral defect model.

We studied the ability of collagen vitrigel material to repair cartilage in vivo when used alone or with transforming growth factor-ß (TGF-ß). We measured the time course and quantity of TGF-ß1 released from the collagen vitrigel in vitro to quantify the controlled release of TGF-ß1. Over 14 days, 0.91 ng of TGF-ß was released from the collagen vitrigel. Osteochondral defects were made in the femoral trochlear groove in 36 Japanese white rabbits, which were divided into three groups: untreated group (group A), collagen vitrigel-implanted group (group B), and TGF-ß1-incorporated collagen vitrigel-implanted group (group C). The weight distribution ratio between the affected and unaffected limbs served as an indicator of pain. Animals were sacrificed at 4 and 12 weeks after surgery, and their tissues were assessed histologically. The weight distribution ratio increased in all groups and did not differ significantly between groups at 12 weeks. Group A needed 6 weeks to attain maximum improvement, and groups B and C showed near-maximum improvement at 4 and 2 weeks, respectively. The International Cartilage Repair Society II score improved significantly in group C relative to the other groups. These findings suggest that sustained, slow release of TGF-ß caused early pain mitigation and cartilage repair. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2592-2602, 2017.

Assessment of the Safety of Chondrocyte Sheet Implantation for Cartilage Regeneration.

We have previously studied the effects of chondrocyte sheets on the repair and regeneration of articular cartilage by using temperature-responsive culture inserts. On the basis of this work, we succeeded in rapid fabrication of chondrocyte sheets with the use of a coculture method in which inserts were placed between synoviocytes and chondrocytes. Treatment of cartilage defects using layered chondrocyte sheets promotes repair and regeneration; this method is compatible with in vivo osteoarthritis models that reproduce partial-thickness defects. In human stem cell clinical research guidelines, the Ministry of Health, Labour and Welfare (MHLW) approved several applications related to this technology. Indeed, its translation to a clinical setting is already yielding favorable results. In this study, we evaluated the risk of tumorigenesis associated with this treatment and characterized the dynamics of biological processes associated with the posttransplantation cell sheets in vivo. Furthermore, we also confirmed the safety of the procedure by using array comparative genomic hybridization (array CGH) and G-band staining to screen for deleterious genetic aberrations during prolonged subculture of cells. The safety of chondrocytes that were cultured for longer than normal was confirmed by the array CGH and G-band staining results. In addition, tumorigenicity testing confirmed that culture chondrocyte sheets are not tumorigenic. Furthermore, from the evaluation of bioluminescence imaging following implantation of the cell sheets, it was confirmed that the transplanted chondrocytes and synoviocytes remained in the knee joint and did not transfer elsewhere over time. We believe that the technique used in this study is a highly useful method for evaluating the safety of not only chondrocytes but also extensive subculturing in general.

Bevacizumab, an anti-vascular endothelial growth factor antibody, inhibits osteoarthritis.

INTRODUCTION: Angiogenesis is an important factor in the development of osteoarthritis (OA). We investigated the efficacy of bevacizumab, an antibody against vascular endothelial growth factor and an inhibitor of angiogenesis, in the treatment of OA using a rabbit model of anterior cruciate ligament transection. METHODS: First, we evaluated the response of gene expression and histology of the normal joint to bevacizumab treatment. Next, in a rabbit model of OA induced by anterior cruciate ligament transection, we used macroscopic and histological evaluations and real-time polymerase chain reaction (PCR) to examine the responses to intravenous (systemic) administration of bevacizumab (OAB IV group). We also investigated the efficacy of intra-articular (local) administration of bevacizumab in OA-induced rabbits (OAB IA group). RESULTS: Histologically, bevacizumab had no negative effect in normal joints. Bevacizumab did not increase the expression of genes for catabolic factors in the synovium, subchondral bone, or articular cartilage, but it increased the expression of collagen type 2 in the articular cartilage. Macroscopically and histologically, the OAB IV group exhibited a reduction in articular cartilage degeneration and less osteophyte formation and synovitis compared with the control group (no bevacizumab; OA group). Real-time PCR showed significantly lower expression of catabolic factors in the synovium in the OAB IV group compared with the OA group. In articular cartilage, expression levels of aggrecan, collagen type 2, and chondromodulin-1 were higher in the OAB IV group than in the OA group. Histological evaluation and assessment of pain behaviour showed a superior effect in the OAB IA group compared with the OAB IV group 12 weeks after administration of bevacizumab, even though the total dosage given to the OAB IA group was half that received by the OAB IV group. CONCLUSIONS: Considering the dosage and potential adverse effects of bevacizumab, the local administration of bevacizumab is a more advantageous approach than systemic administration. Our results suggest that intra-articular bevacizumab may offer a new therapeutic approach for patients with post-traumatic OA.