MODULATION OF GROWTH-FACTOR INCORPORATION INTO ECM OF HUMAN OSTEOBLAST-LIKE CELLS IN-VITRO BY 17-BETA-ESTRADIOL

Human fetal osteoblast-like cells formed a regular multilayered struct ure in vitro with an extensive collagen-based extracellular matrix. Wi th colloidal gold immunocytochemistry, labels for alkaline phosphatase and osteocalcin were distributed in a relatively diffuse pattern, in contrast to the bone growth factors, insulin-like growth factors I and II (IGF-I and IGF-II), transforming growth factor-beta 1 (TGF-beta 1) , and basic fibroblast growth factor, which were colocalized in the co llagenous matrix of the multilayer. The inclusion of 17 beta-estradiol (10(-11) to 10(-9) M) in the culture medium increased multilayer dept hs, increased labeling for IGF-I, IGF-II, and TGF-beta 1, and resulted in earlier detection of TGF-beta 1 label. In contrast, the increase i n multilayer depth resulting from treatment with human platelets, an e xogenous source of growth factors, was not accompanied by an increase in matrix IGF-I, IGF-II, or TGF-beta 1 label, suggesting a particular effect of estradiol to facilitate this process. Because growth factors in bone matrix may act as coupling agents when released during resorp tion, reduced growth factor incorporation in the presence of reduced s ex steroid concentrations may lead to uncoupling of resorption and sub sequent formation.