Human renal fibroblasts modulate proximal tubule cell growth and transport via the IGF-I axis

Human renal fibroblasts modulate proximal tubule cell growth and transport via the IGF-I axis. To determine the paracrine interactions involved in the tubulointerstitial response to progressive renal disease, the role of insulin-like growth factor-I (IGF-I) and its binding proteins (IGFBPs) in in vitro interactions between human proximal tubule cells (PTC) and renal cortical fibroblasts (CF) were studied in primary cell culture. PTC growth and transport were increased in the presence of CF-conditioned media (CF-CM), as shown by increased thymidine incorporation, cellular protein content and sodium-hydrogen exchange (NHE) activity, to 185 ± 31% ( P P P P