The role of platelet-derived growth factor in the development of mouse molars.

Platelet-derived growth factor (PDGF) is a potent mitogen that functions in cytodifferentiation and wound healing. PDGF receptor-alpha (PDGFR-alpha) is required for the normal development of the dental ectomesenchyme (Stephenson et al., Proc. Natl. Acad. Sci. USA 88: 6-10, 1991). To investigate the regulatory potential of PDGF on tooth development, the expression of PDGF-AA was determined by reverse transcription-polymerase chain reaction (RT-PCR), the PDGF ligands and receptors were localized by immunohistochemistry. The growth-promoting effects of exogenous PDGF-AA on molar explants were determined by assaying for tritiated thymidine incorporation, the presence of type I collagen and amelogenin messenger RNA transcripts, and total DNA, RNA and protein accumulation. Based upon the temporal and spatial localization, PDGFs and their receptors are present in the enamel epithelia and pulpal mesenchyme of developing mouse molars. Exogenous PDGF-AA administration increased the total protein accumulation of mouse molar explants but produces no discernible effect on amelogenin and type I collagen expression.