Age-related Impairment in Paracrine Regulation of Angiogenesis by Androgens

Background: Ageing is associated with a marked reduction in capacity for angiogenesis and vascular regeneration. In elderly males, ageing is also associated with a decline in androgen levels. We examined the effects of ageing on androgenmodulation of angiogenesis in young and old human fibroblasts. Methods:Human dermal fibroblasts were isolated from young (30 yrs) and older males (>65 yrs). Cells were incubated with 40nM dihydrotestosterone (DHT), with or without hydroxyflutamide (HF), or a phosphoinositide 3-kinase (PI3-kinase) inhibitor. Fibroblasts and fibroblastconditioned media was used to stimulate HUVECs, and analysed by ELISA and western blotting. Nuclear fractionation and fluorescencemicroscopywere used to study androgen receptor (AR) localisation. Results: Young male fibroblasts treated with DHT doubled HUVEC tubulogenesis and migration through increased VEGF secretion (p< 0.05). Older male fibroblasts were unresponsive to DHT treatment with a lack of VEGF production and could not stimulate enhanced angiogenesis in HUVECs. DHT-induced stimulation of VEGF secretion from young fibroblasts was dependent on AR binding and increased nuclear AR translocation (p< 0.01). Thiswas associatedwith increasedAKTproduction (p< 0.05) and phosphorylation (p< 0.01), all of which was abrogated by PI3-kinase inhibition. Despite comparable level of ARs, fibroblasts from older males treated with DHT displayed reduced AR nuclear translocation, resulting in a lack of AR-mediated VEGF production. Conclusion: Unlike young male fibroblasts, older male cells cannot respond to DHT treatment with increased VEGF production and angiogenic promotion of endothelial cellsdue todefectivenuclear translocationof androgen receptors.