Age-related impairment in androgen-mediated paracrine regulation of angiogenesis — ASN Events
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Age-related impairment in androgen-mediated paracrine regulation of angiogenesis (#169)

Laura Lecce 1 2 , Yuen Ting Lam 1 2 , Laura A Lindsay 2 , Sui Ching G Yuen 1 2 , David J Handelsman 2 3 , Martin K Ng 1 2 4
  1. Heart Research Institute, Newtown, NSW, Australia
  2. The University of Sydney, Sydney, NSW, Australia
  3. ANZAC Research Institute, Concord West, NSW, Australia
  4. Department of Cardiology, Royal Prince Alfred Hospital, Sydney, NSW, Australia

Background: Ageing is associated with reduced angiogenesis and vascular regeneration. In unselected elderly men, ageing is also associated with a general decline in blood androgen levels. The current study investigated the effect of ageing on androgen-mediated paracrine modulation of angiogenesis by fibroblasts from young and old men. 
Methods: Human dermal fibroblasts were isolated from young (30yrs) and older (>65yrs) men. Cells were incubated for 48 hours with 40nM dihydrotestosterone (DHT), with or without hydroxyflutamide (HF), or a phosphoinositide 3-kinase (PI3-kinase) inhibitor. Fibroblasts and fibroblast conditioned media was analysed by western blotting and ELISA. Fibroblast conditioned media was also used to stimulate angiogenic functions in human umbilical vein endothelial cells (HUVECs) such as migration and tubule formation. Following 6 hours of 40nM DHT treatment, nuclear fractionation and fluorescence microscopy were used to study androgen receptor (AR) localisation following DHT treatment.
Results: Conditioned media from fibroblasts of young men treated with DHT doubled HUVEC tubulogenesis and migration through increased VEGF secretion (p<0.05). Fibroblasts from older men were unresponsive to DHT treatment and lacked both androgen-mediated VEGF production and enhanced angiogenic functions in HUVECs. DHT-induced stimulation of VEGF secretion from fibroblasts of young men was dependent on AR binding and increased nuclear AR translocation (p<0.01) as well as increased AKT production (p<0.05) and phosphorylation (p<0.01), all of which were abrogated by PI3-kinase inhibition. Despite comparable levels of ARs, fibroblasts from older men treated with DHT displayed reduced AR nuclear translocation and absent AR-mediated VEGF production.
Conclusion: Unlike fibroblasts from younger men, cells from older men are unresponsive to androgen-mediated stimulation of VEGF production and angiogenesis despite comparable fibroblast AR expression. This failure in DHT-enhanced paracrine stimulation of angiogenesis by fibroblasts from older men is due to defective nuclear translocation of the androgen receptor.

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