CHONDROCYTE-DERIVED APOPTOTIC BODIES AND CALCIFICATION OF ARTICULAR-CARTILAGE

Chondrocytes exposed to nitric oxide (NO) or antibody to Fas undergo c ell death by apoptosis. This study examines structural and functional properties of chondrocyte-derived apoptotic bodies. In NO treated cart ilage, the dense pericellular matrix that normally surrounds the cells is degraded and apoptotic bodies accumulate within and in the vicinit y of the chondrocyte lacunae. Functional analysis shows that apoptotic bodies isolated from NO-treated chondrocytes or cartilage produce pyr ophosphate. The levels of pyrophosphate produced by apoptotic bodies a re increased by pretreatment of the chondrocytes with transforming gro wth factor beta and decreased by interleukin 1. Apoptotic bodies conta in alkaline phosphatase and NTP pyrophosphohydrolase activities and ca n precipitate calcium. These results suggest that chondrocyte-derived apoptotic bodies express functional properties that may contribute to the pathologic cartilage calcification observed in aging and osteoarth ritis.