Androgens Promote Endothelial Progenitor Cell (EPC) Mobilisation in Response to Ischaemia

Abstract

Introduction: Chronic atrial stretch is associated with a heightened risk of atrial fibrillation (AF) and thrombosis. Asymmetrical dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase (NOS), which leads to decreasednitric oxide (NO) levels, andproduces endothelial dysfunction. Elevated ADMA levels are also linked to increased thrombotic risk. Therefore we investigated ADMA levels between peripheral and cardiac sites in chronic atrial stretch due to mitral stenosis and immediately after stretch reversal by balloon mitral valvuloplasty (BMV). Methods:Nineteen patients with mitral stenosis (32± 8 years, 8 males) in sinus rhythm undergoing a BMV were studied. Blood samples were withdrawn from the femoral vein (FV), right atria (RA) and left atria (LA) at the start of procedure and thenagain at the completionof the valvuloplasty. Plasma levels ofADMAweremeasured as amarker culating EPCs are decreased in hypogonadal men, and increased with testosterone treatment, suggesting a role for androgens in EPC-mediated angiogenesis. This study investigated the role of androgens in EPC mobilisation following ischaemia. Methods:Male C57Bl/6J mice were castrated twoweeks prior to the induction of unilateral hindlimb ischaemia (HLI) and implanted with a DHT or placebo implant. Laser Doppler Perfusion Imaging (LDPI) was performed to assess flow recovery. Mice were sacrificed and EPCs were harvested from blood, bone marrow and spleen. Sca1+/CXCR4+ EPCswere enumerated using flow cytometry and colony forming unit (CFU) progenitors were assessed using a methylcelluose based assay. Adductor muscle from the ischaemic and non-ischaemic limbs were harvested for qRT-PCR and western blotting. Results: FollowingHLI, animals givenDHT showed significantly increasedLDPIflowrecoveryvs. placebo treated mice (P< 0.05). Sca1+/CXCR4+ EPCs isolated from blood and bone marrow three days post-HLI were greater in DHT treated mice compared with those administered a placebo (P< 0.05). Spleen Sca1+/CXCR4+ cells were not significantly different between groups. The number of CFU progenitors from blood and bone marrow were greater in DHT treated mice than in placebo (P< 0.05). No significant difference in spleen CFU progenitor colonies were observed between treatment groups. Differences in