One morphogenetic protein 2 stimulates articular cartilage proteoglycan synthesis in vivo but does not counteract interleukin-1 alpha effects on proteoglycan synthesis and content

Objective. To study the effect of bone morphogenetic protein 2 (BMP-2) on articular cartilage proteoglycan (PG) synthesis in vivo and to investigate whether BMP-2 is able to counteract the effects of interleukin-1 (IL-1) on articular cartilage PG synthesis and content. Methods, BMP-2 alone or in combination with IL-1 alpha was injected into murine knee joints. PG synthesis was measured by S-35-sulfate incorporation using an ex vivo method or autoradiography. Cartilage PG content was analysed by measuring Safranin O staining intensity on histologic sections. Results. BMP-2 appeared to be a potent stimulator of articular cartilage PG synthesis in vivo. However, BMP-2 was not able to counteract the deleterious effects of IL-1 alpha on articular cartilage PG synthesis and content, In addition, intraarticular injections of BMP-2 induced chondrophytes. Conclusion. Although BMP-2 is a very potent stimulator of cartilage PG synthesis in vivo, the therapeutic applications of BMP-2 are limited due to the inability of BMP-2 to counteract the effects of IL-1 and the induction of chondrophytes.