DIFFERENTIAL CHEMOTACTIC RESPONSES OF DIFFERENT POPULATIONS OF FETAL-RAT CALVARIA CELLS TO PLATELET-DERIVED GROWTH-FACTOR AND TRANSFORMING GROWTH-FACTOR-BETA

We tested the chemotactic response to platelet-derived growth factor (PDGF) and transforming growth factor beta (TGFbeta) of cells released enzymatically from fetal rat calvaria (RC). Both factors were chemotactic for RC cells, but the magnitude of the chemotactic response differed markedly between different populations and varied with time in culture of the cell populations. Cells released earlier from the calvaria showed a greater response than osteoblast-enriched populations released later. The optimal concentration of PDGF was the same for both alkaline phosphatase (AP)-positive and AP-negative cells within the populations. However AP-positive cells showed two peaks of response to TGFbeta; one peak coincided with the TGFbeta concentration also maximally affecting AP-negative cells, while the other occurred at a concentration 50-100 times higher. The results indicate that PDGF and TGFbeta are chemotactic for both AP-positive and AP-negative cells in populations of cells derived from fetal calvariae, that chemotactic response declined with longer periods of time in culture, and that AP-positive osteoblast-like cells respond to a concentration of TGFbeta that does not affect the AP-negative cells in the population.