Production of transforming growth factor-beta by cultured rat mesangial cells.

The purpose of this study was to examine whether transforming growth factor-beta (TGF beta) acts as an autocrine cytokine in cultured mesangial cells. Measangial cell conditioned media (CM) were prepared and tested for their effect on mesangial cell proliferation. CM showed a concentration dependent inhibition on mesangial cell proliferation and the activity was enhanced by treating conditioned media with acid. Gel filtration analysis showed peak inhibitory activity to reside in fractions with an estimated molecular weight range of 16-30 KD. The activity was partially blocked by anti-TGF beta antibody, but not nonimmune control IgG. The presence of TGF beta was confirmed using the mink lung epithelial cell assay. Furthermore, the addition of anti-TGF beta antibody directly into culture media significantly enhanced mesangial cell proliferation. These results demonstrate that measangial cell produce both active and latent forms of TGF beta, which functions as an autocrine growth inhibitor for mesangial cells.