The regulation effects of fibroblast growth factor on podocyte proliferation and expressions of bone morphogenetic protein-7 and cytoskeletal proteins in podocytes

Objective To investigate the effect of fibroblast growth factor (bFGF) on podocyte prolifera- tion and on expressions of bone morphogenetic protein-7 (BMP-7) and cytoskeletal proteins in podocytes.Method We employed a cell line of mouse podocytes immortalized with the simian virus 40 large tumor antigen gene,and examined the cell proliferation using colony-forming and MTT assays following treatment with various concentra- tions of bFGF.BMP-7,alpha-smooth muscle actin (α-SMA),and vimentin in the podocytes were detected by western blot.Methyl blue staining was used for the observation of cell morphology.Results After being treated with 1.25 to 20 ng/ml bFGF for 10 days,the podocytes showed significant increase of colony formation in a dose- dependent manner (r=0.844).When bFGF in culture reached 20ng/ml,the number of colonies was 4.2 times higher than that of the controls.Similar results were obtained from MTT assay.On methyl blue staining,the colonies showed larger diameter and contained higher cell density after bFGF stimulation.A part of the cells also had vacuolation change.Western blot demonstrated that bFGF (1.25 to 20 ng/ml) treatment for 96 hours caused the decrease of BMP-7 in a dose-dependent manner,and that 20ng/ml bFGF stimulation resulted in the decrease of BMP- 7 by90%.bFGF treatment for 96 hours also inhibitedα-SMA expression,but without significant change in vimentin expression.Conclusion Our data suggest that bFGF induces podocyte proliferation and vacuolation,and down-regulates BMP-7 andα-SMA expressions in podocytes.Based on the renal protective function of BMP-7,the down-regulation of BMP-7 in podocytes by bFGF stimulation may be an important mechanism in mediating bFGF- induced renal injury.