Intra-articular injections of bone morphogenetic protein-7 retard progression of existing cartilage degeneration.

We investigated the effect of weekly intra-articular injections of bone morphogenetic protein-7 (BMP-7) on prevention of progression of existing cartilage degeneration in an osteoarthritis model in rabbits. An anterior cruciate ligament transection (ACLT) model was used to create a progressive osteoarthritis model. BMP-7 was intra-articular injected weekly into the right knee and PBS into the left knee from 4 weeks after ACLT. Both sides of the knees were compared macroscopically, histologically, immunohistochemically, and by micro CT. Macroscopically, fibrillation in the femoral condyle was observed 4 weeks after ACLT. In the control knees, cartilage degeneration further progressed throughout the 12-week period. In the BMP-7 treated knee, osteoarthritis progression was milder than in the control knees. Histologically, safranin-O staining was decreased in the surgical knees at 4 weeks. Obvious erosions in both medial and lateral condyles were revealed in the control knees at 12 weeks, while cartilage matrix was predominantly retained in the BMP-7 treated knees. The macroscopic and microscopic OA score in the BMP-7 treated knee was better than that in the control in each rabbit. Immunohistochemical analysis demonstrated that both type II collagen and BMP-7 were more expressed in cartilage treated with BMP-7. Micro CT analysis showed that osteophytes were smaller in the BMP-7 treated knee compared to that of the control. Weekly intra-articular injections of BMP-7 inhibited progression of existing cartilage degeneration.