The aim of this study is to find out the activity of autoproliferation of ratfibroblast exposed to crystalline silica and the role of mediators secreted from rat fibroblast.

The effect of alpha-quartz on production of growth factor (platelet-derived growth factor-AA and transforming growth factor beta)from rat fibroblasts were evaluated by ELISA and immunocytochemical analysis. Gene expression of these growth factors in rat fibrobast exposed to crystalline silica was evaluated by RT-PCR. Furthermore, fibroblast proliferation by culture supernatant of rat fibroblast was assayed by the neutral red test.

The amounts of H2O2 and growth factors synthesized in rat fibroblasts were significantly increased by the stimulation of crystalline silica(alpha-quartz), which showed the dose-dependent manner to the concentration of alpha-quartz with the maximum response at the dosage of 100 microgram/cm2. The result of RT-PCR demonstrated that alpha-quartz induced gene expression of PDGF-AA and TGFbeta in rat fibroblast. We also found that supernatant of alpha-quartz-cocultured rat fibroblast induced a significant proliferation of fibroblast.

Crystalline silica directly induce functional change in fibroblast such as increased release of reactive oxygen species and growth factors. The products of these functional change promote fibroblast proliferation via autocrine loop.