Mechanical stress induces DNA synthesis in PDL fibroblasts by a mechanism unrelated to autocrine growth factor action.

Periodontal regeneration is thought to require the proliferation of stress-sensitive periodontal ligament (PDL) fibroblast cells. The influence of physiological amounts of mechanical stretching on the DNA synthesis potential of human PDL fibroblasts was examined by means of an established, simple in vitro system of stretch application. A significant increase in the relative levels of incorporation of tritiated thymidine was observed in cultures stretched for 1-6 h. Neutralising antibodies for platelet-derived growth factor (PDGF) and transforming growth factor-beta (TGF-beta) did not blunt the DNA synthesis induction. This mitogenic response to stretch appears to be independent of an autocrine mechanism involving growth factors in general, because stretch-conditioned medium, when transferred to non-stretched fibroblasts, did not mimic the mitogenic effect of stretch.