Hayashi M et al. (2008) Weekly intra-articular injections of bone morphogenetic-7 protein inhibits osteoarthritis progression. Arth Res Ther 10: R118

A well-designed study suggests that intra-articular injections of bone morphogenetic protein 7 (BMP7) prevents the progression of cartilage damage in a rabbit anterior cruciate ligament transection model of knee osteoarthritis. In the study by Hayashi and colleagues, 12 weekly injections of 50 ng, 500 ng or 5,000 ng of recombinant human BMP7, or saline (control), were administered to 36 knees of 18 rabbits. Morphological and histological examination revealed that the two highest doses of BMP7 inhibited the progression of osteoarthritis to a similar extent. No evidence of increased synovial fibrosis, formation of ectopic bone or cartilage, or increased osteophyte size was detected in BMP7-treated knees. Furthermore, BMP7 concentrations in the cartilage of treated knees were still measurable by enzyme-linked immunosorbent assay 7 days after the last injection.

The authors addressed the issue of individual variability in osteoarthritis progression by use of a matched-pair analysis, whereby weekly 500 ng injections of BMP7 in the right knees of 15 rabbits were compared with saline injected into the left knees of the same animals. At 12 weeks, knees injected with BMP7 had fewer cartilage erosions, which were limited to either the medial or the lateral condyle, than control knees, in which severe lesions were present in both locations. In addition, histological scores were better in treated knees compared to the contralateral control knees.

Intra-articular injection of BMP7, therefore, has potential as a nonsurgical alternative for inhibiting cartilage degradation in osteoporosis. Future in vivo studies should investigate the optimal duration of this approach for osteoporosis of the knee.