The immunohistochemical localization of phospholipase C gamma and the epidermal growth-factor, platelet-derived growth-factor and fibroblast growth-factor receptors in the cells of the rat molar enamel organ during early amelogenesis

Findings on the localization and possible roles of the major growth factors , epidermal (EGF), platelet-derived (PDGF) and fibroblast (FGF) in early am elogenesis are contradictory and inconclusive. This study sought to localiz e immunohistochemically phospholipase (PLC gamma) and the EGF, PDGF and FGF receptors in the cells of the enamel organ during the events leading direc tly to early enamel formation in rat molars. PLC gamma, is an immediate, do wnstream, signal-transduction pathway effector unique to the three receptor s. A whole-head, freeze-dried sectioning method was used to reduce the poss ibilities of false-negative staining. A modification of the avidin/biotin c omplex method of immunohistochemical localization was used. Anti-PLC gamma and antibodies to each of EGF, PDGF and FGF receptors colocalized in the pr eameloblasts of the cervical loop, adjacent to the undifferentiated mesench ymal cells of the dental pulp. This staining disappeared shortly after the beginning of dentine mineralization. Staining for all four antibodies appea red on the proximal ends of the differentiating presecretory ameloblasts at the level of the beginning of predentine matrix deposition and continued i n the secretory ameloblasts. It appears that EGF, PDGF and FGF have roles i n the differentiation of ameloblasts and in control of cellular functions i n presecretory and secretory ameloblasts. Their :roles may represent redund ancy of the kind seen in highly conserved tissues. (C) 1999 Published by El sevier Science Ltd. All rights reserved.