Temporal profile of serum-induced S-phase entry and retinoblastoma protein phosphorylation in human skin fibroblasts.

Temporal profile of serum-induced S-phase entry and retinoblastoma protein phosphorylation in human skin fibroblasts. Cultured skin fibroblasts from type 1 diabetic patients with nephropathy have a hyperplastic growth phenotype in comparison with diabetics without nephropathy and controls. We studied the G1 phase cyclins in skin fibroblasts from control subjects to define the temporal profile of serum-induced pRB phosphorylation, cyclin D1 protein expression, and cyclin D1/CDK4(6) kinase activity as well as S-phase entry by FACS analysis. Our preliminary studies indicate that cultured skin fibroblasts from type 1 diabetic patients with nephropathy have an enhanced pRB phosphorylation, cyclin D1 protein expression, and cyclin D1/CDK4(6) kinase activity. This finding may become useful to identify patients at risk for the development of nephropathy.