Cell signalling in the developing mammalian palate appears to involve various growth factors and hormones. An important developmental role for the transforming growth factor-ß (TGF-ß) class of growth factors is suggested by the immunolocalization of TGF-ß1 in the palate during its ontogeny. This study examined the effects of TGF-ß stimulation of, as well as TGF-ß receptor profiles in, murine embryonic palate mesenchymal (MEPM) and human embryonic palate mesenchymal (HEPM) cells. Results showed that TGF-ß1 (1 ng/ml) stimulated proliferation of HEPM cells and inhibited proliferation of MEPM cells in a dose-dependent manner. The time course of 125I-TGF-ß1 binding to specific receptors was determined by incubating cells in the presence of 170 pM125I-TGF-ß1 for up to 4 h. In both cell types, at 37 °C, the binding of 125I-TGF-ß decreased linearly over 4 h, while at 4 °C, binding increased with time of incubation. Incubation of both cell types at 4 °C for 4 h, with increasing concentrations of 125I-TGF-ß1, resulted in binding which demonstrated saturation kinetics. Scatchard analyses revealed one class of receptors for HEPM (K 32.3 pM) and MEPM (K 26.3 pM). However, SDS-PAGE analyses of 125I-TGF-ß chemically crosslinked to specific receptor sites revealed that both cell types contained the types I (65,000 Mr) and III (230,000 Mr) TGF-ß receptors while MEPM also contained the type II (86,000 Mr) receptor. Binding studies further demonstrated the ability of platelet-derived growth factor to transmodulate TGF-ß binding. These results indicate that the HEPM cell line and primary cultures of MEPM cells, although obtained from palates at similar developmental stages, are dramatically different in their responsiveness to TGF-ß and have disparate TGF-ß receptor profiles.
Available at: http://works.bepress.com/marina_dangelo/15/