Rat incisor dentine contains a factor which alters the phenotypic expression and stimulates chondrogenesis in fibroblast-like cells in vitro.

Abstract

A low molecular weight protein fraction isolated under dissociative conditions during the demineralization of rat incisor dentine has the ability to modulate, in culture, the expression of fibroblast-like cells explanted from neonatal rat muscle. The protein fraction enhances the incorporation of 35S-sulphate into a proteoglycan larger in weight than that produced by the uninduced cells; furthermore it induces the production of type II collagen. These changes take place in the absence of cell proliferation as measured by 3H-thymidine incorporation. The altered fibroblast-like cells form nodules and secrete an abundant extracellular matrix which stains for proteoglycan after 7-9 days in culture. These data show that the dentine matrix does contain a factor which can initiate a mitogenesis-independent alteration in the expression of the muscle-explant outgrowth cells. Those changes are consistent with a shift to a chondrogenic mode.