DIFFERENTIAL INDUCTION OF CELL-MEDIATED MINERALIZATION IN RAT MARROW STROMA BY SERA FROM WOMEN OF LOW AND HIGH-RISK FOR VERTEBRAL FRACTURE

The purpose of this study was to analyze the ability of sera to reflec t the state of bone metabolism by testing the osteogenic response of m esenchymal cells in culture. Sera of 20 peri- and postmenopausal women were tested before the initiation of hormone replacement therapy. The responding cells were osteoprogenitors (OPC) of rat marrow stroma whi ch normally respond to dexamethasone (DEX) and beta-glycerophosphate ( beta CP) by proliferation, differentiation, and mineralization in cult ure. Instead of DEX, diluted sera (1:50) were applied to rat stromal c ell cultures for analysis of their ability to affect cell proliferatio n, specific alkaline phosphatase (ALP) activity, and cell-mediated min eralization. The results were compared individually with the respectiv e values of vertebral bone mineral density (BMD), expressed as the num ber of standard deviations above or below the mean BMD of reference po pulations (positive or negative Z-score). Serum donors were divided in two; the group with positive Z-scores was considered to have a low ri sk, and that with negative Z-scores was considered to have a higher ri sk for vertebral fractures. No significant difference was found betwee n the two groups in the ability of their sera to induce cell prolifera tion or specific ALP activity. However, sera representing negative Z-s cores induced sixteenfold less mineralization than those of positive Z -scores. The scatter of individual mineralization values was highly di scriminatory between the two groups (alpha < 0.00). These results indi cate that the serum-induced, cell-mediated mineralization in culture m ight be suitable for initial evaluation of fracture risk and thus dese rve further investigation. (C) 1996 Wiley-Liss, Inc.