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The Frequency of Common Progenitors for Adipocytes and Osteoblasts and of Committed and Restricted Adipocyte and Osteoblast Progenitors in Fetal Rat Calvaria Cell Populations *
Author(s) -
Bellows C. G.,
Heersche J. N. M.
Publication year - 2001
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1359/jbmr.2001.16.11.1983
Subject(s) - calvaria , adipocyte , progenitor cell , osteoblast , endocrinology , population , medicine , biology , progenitor , microbiology and biotechnology , chemistry , stem cell , adipose tissue , biochemistry , in vitro , environmental health
In fetal rat calvaria (RC) cell populations, adipocyte differentiation is stimulated by both dexamethasone (Dex) and 1,25 dihydroxyvitamin D 3 [1,25(OH) 2 D 3 ], whereas osteoblast differentiation is stimulated by Dex but inhibited by 1,25(OH) 2 D 3 . We examined whether the osteoblastic and adipocytic colonies were derived from a common progenitor, from committed and restricted adipocyte and osteoblast progenitors, or from both and whether the adipocyte progenitors stimulated by 1,25(OH) 2 D 3 constitute a population of progenitors that is different from that stimulated by Dex. RC cells were isolated by sequential enzyme digestion yielding five populations designated I‐V. In population I the effect of Dex on adipocyte formation was greater than that of 1,25(OH) 2 D 3 , whereas the effect of 1,25(OH) 2 D 3 was greater than that of Dex in populations III‐V. We next applied replica plating techniques to further investigate the response characteristics of individual osteoprogenitors and adipocyte progenitors by looking at the fate of duplicate colonies derived from the same progenitor under different culture conditions. RC cells were plated at 1000–1500 cells/100 mm culture dish and a 17‐μm mesh polyester membrane overlaid onto master dishes on day 4 or day 5 and removed on day 11 or day 12. Then, replicas and master dishes were cultured separately in medium containing either Dex, 1,25(OH) 2 D 3 , or Dex plus 1,25(OH) 2 D 3 for a further 17–21 days and then fixed and stained with both Sudan IV and the von Kossa technique. Nine hundred twenty‐seven matched colonies present on both master dishes and replica membranes were screened and colonies were classified as either adipocytic, osteoblastic (bone or osteoid), or fibroblastic. Results show convincingly that most of the osteoprogenitors present in fetal RC cells are committed and restricted to the osteoblastic cell lineage (95.29%); that the 1,25(OH) 2 D 3 ‐responsive adipocyte progenitors are different from the Dex‐responsive adipocyte progenitors, but both are restricted to form adipocytes and finally; and that a common osteoblast/adipocyte progenitor is present in a low frequency (4.71% of osteoprogenitors).