Abstract
25 CHARACTERIZATION OF THE RESPONSIVENESS OF THE PREOSTEOBLASTS IN HUMAN BONE MARROW TO TGF-BETA AND CALCITRIOL IN VITRO A Battmann, H. Resch, D.J. Baylink, J. Wergedal Mineral Metabolism(151), Jerry L. Pettis Memorial Veterans Hospital, Loma Linda, CA 92357, USA Bone formation occurs through the action of osteoblasts. These are identified as cuboid cells resting on the forming surface oftrabecular bone. The origin of these cells is considered to be pluripotent stem cells in marrow, but the regulation of osteoblastic differentiation is not well known. Earlier studies had shown that calcitriol and TGFBeta stimulate differentiation as measured by alkaline phosphatase activity. To determine if these agents act on an early stage of differentiation, we compared human bone cells isolated from marrow with those isolated from bone surface by collagenase digestion and with cells that grow out of collagenase denuded bone samples. Osteocalcin production was low in marrow cells cultures even in the presence of calcitriol ( 60%) and this activity was increased in all three populations by calcitriol (10 nM) treatment (180% to 220% of control). TGF-Beta (10-100 pg/ml) increased the stimulation of alkaline phosphatase by calcitriol in all three populations The greatest response was seen in the cells obtained from the bone outgrowth cultures. TGF-Beta inhibited the production of osteocalcin in all three ceils preparations. In conclusion: Human marrow cell cultures contain osteoblast-like cells in that are mostly early preostoblast, preosteocalcin production stage. Alkaline phosphatase is present or can be induced by calcitriol of TGF-Beta and calcltriol in combination.
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