ROLE OF CHONDROITIN SULFATE GLYCOSAMINOGLYCANS IN MINERALIZING OSTEOBLAST-LIKE CELLS - EFFECTS OF HORMONAL MANIPULATION

A monoclonal anti-chondroitin sulfate antibody (CS-56) that recognizes native chondroitin sulfate glycosaminoglycans (CSGAG) was used to qua ntify changes in CSGAG labeling levels in mineralizing human fetal ost eoblast-like cell multilayers up to 40 days postconfluence. In control cultures, mean labeling of CSGAG increased in nonmineralized areas fr om around eight gold probes per mu m(2) (gpm) at 20 days to 26 gpm at 40 days. Labeling was markedly increased in the mineralized tissue, to 560 gpm at 30 days and 580 gpm at 40 days. In beta-glycerophosphate-t reated cultures, the mineralized areas were increased and appeared ear lier (20 days) than in the control cultures. In these cultures, mean C SGASG labeling increased in nonmineralized areas from around 5 gpm at 20 days to 26 gpm at 30 days and was further increased in mineralized areas to 270 gpm at 20 days and 298 gpm at 30 days. Mineralization was not noted in cultures treated with 10(-8) M 1,25-dihydroxyvitamin D, and CSGAG labeling remained low (<5 gpm) during the study period. Thes e results indicate that an increase in immunoreactive CSGAG is associa ted with mineralization in this culture system. One possible interpret ation of these findings is that proteoglycan molecules or at least the ir CSGAG side chains may be involved in the mineralization process.