Differentiation and mineralization in osteogenic precursor cells derived from fetal rat mandibular bone.

The process of mineralization in cells prepared either by neutral protease digestion (Pro I) or by collagenase digestion (fifth cycle, Col V) from fetal rat mandible was studied in vitro. Alkaline phosphatase (ALPase) activity of cells in Pro I was low on day 3, increased rapidly from day 8, and reached a maximum on day 16, whereas that in Col V was high on day 2, then declined and thereafter elevated to reach a maximum on day 13. Both cell populations synthesized type I collagen in cell matrix and medium. Type III collagen was observed in cell matrix of Pro I on day 14 and 21. There was alpha 2 band of type V collagen in cell matrix of Pro I on day 21. Calcium deposition could be detected from day 14 in Pro I and from day 19 in Col V. The von Kossa-positive nodules were found on day 17 in Pro I and day 21 in Col V, respectively. The extracellular matrix in Pro I electron-microscopically consisted of well-banded collagen fibrils with a large number of calcified spherules. An elevation of ALPase activity, collagen synthesis, and mineral deposition occurred sequentially with a time lapse in Col V, and almost simultaneously in Pro I. The number of mineralized nodules was correlated with the density of plated cells in Pro I, but not in Col V. Dexamethasone caused an increase in the number of mineralized nodules in Pro I, but not in Col V, suggesting that Pro I contained osteoprogenitor cells.(ABSTRACT TRUNCATED AT 250 WORDS)