Changes in growth factor expression in the ageing prostate may disrupt epithelial-stromal homeostasis

The alterations in expression of six growth factors known to be regulators of prostatic function have been examined in the ventral lobe of prostates from young adult (14 week) and ageing (1.5 year) Wistar rats. The selected growth factors were transforming growth factor beta (TGFbeta1), insulin-like growth factor I (IGF-I), insulin-like growth factor II (IGF-II), platelet derived growth factor (PDGF), basic fibroblast growth factor (FGF2) and epidermal growth factor (EGF). The extracellular matrix growth co-factor thrombospondin (TSP) was also examined. Our study demonstrated a 2.9-fold up-regulation of TGFbeta1 (p < 0.0001), a 2.0-fold increase in FGF2 (p < 0.0002), an 8.3-fold increase in IGF-II (p < 0.0007) and a 5.4-fold increase in EGF (p < 0.0001) in ageing compared to adult prostate tissue. Conversely, we observed a 2.7-fold down-regulation of IGF-I (p < 0.0005), a 1.7-fold decrease in PDGF (p < 0.0097) and a 5.8-fold decrease in TSP (p < 0.0079) in ageing rat prostate tissue. The observed alterations in growth factor expression in this study may be the result or cause of, an imbalance in the proliferative-apoptotic balance during ageing. This imbalance may explain the increase in epithelial proliferation that is characteristic of the normal ageing prostate. As in other systems it seems likely that these factors work synergistically rather than in isolation.