Serosal mast cells maintain their viability and promote the metabolism of cartilage proteoglycans when cocultured with chondrocytes

Objective. To determine the consequences of mast cell (MC)–chondrocyte interactions. Methods. Cocultured cells were analyzed histochemically, morphologically, biochemically, and functionally. Results. Cocultured MC adhered to the chondrocytes and remained viable. Chondrocytes cocultured with nonactivated MC produced more proteoglycans than did chondrocytes cultured alone, and these proteoglycans possessed an intact hyaluronic acid—binding region. In contrast, most of the proteoglycans produced by chondrocytes cocultured with activated MC were degraded. Conclusion. These studies indicate that a complex interaction occurs in which the nonactivated MC stimulates biosynthesis and the activated MC degrades cartilage proteoglycans.