Transforming growth factor-beta modulation of glycosaminoglycan production by mesenchymal cells of the developing murine secondary palate.

Development of the mammalian secondary palate requires proper production of the extracellular matrix, particularly glycosaminoglycans (GAGs) and collagen. Endogenous factors that regulate the metabolism of these molecules are largely undefined. A candidate for a locally derived molecule would be transforming growth factor beta 1 (TGF beta 1) by virtue of its potency as a modulator of extracellular matrix metabolism by several cell lines. We have thus attempted to assign a regulatory role for TGF beta 1 in modulation of GAG production and degradation by mesenchymal cells of the murine embryonic palate (MEPM). Treatment with TGF beta 1 or TGF beta 2, but not IGF-II, resulted in a stimulation of total GAG synthesis. Furthermore, cells treated with both TGF beta 1 and TGF alpha showed a synergistic increase in GAG synthesis if pretreated with TGF beta 1 but not TGF alpha. Simultaneous stimulation with TGF beta 1 and TGF beta 2 did not elicit a synergistic response. These studies demonstrate the ability of TGF beta, synthesized by embryonic palatal cells, to specifically stimulate GAG synthesis by MEPM cells. Other growth factors present in the developing craniofacial region may also modulate TGF beta-induced GAG synthesis, a biosynthetic process critical to normal development of the embryonic palate.