Characterization of age-related penile microvascular hemodynamic impairment using laser speckle contrast imaging: possible role of increased fibrogenesis.

Abstract

Current technology for penile hemodynamic evaluations in small animals is invasive and has limitations. We evaluated a novel laser speckle contrast imaging (LSCI) technique to determine age‐related changes in penile microvascular perfusion (PMP) and tested the role of cavernosal muscle (CC) fibrosis mediated by Wnt‐TGF β1 signaling pathways in a mouse model. Ten young (2–3 months) and old (24–28 months) wild‐type C57BL6 male mice were subjected to PMP measured using a LSCI system. Penile blood flow (PBF, peak systolic velocity, PSV) was also measured using a color Doppler ultrasound for comparison. Measurements were made before and after injection of vasoactive drugs: prostaglandin E1 (PGE 1) and acetylcholine (ACh). CC was processed for immunohistochemical studies for markers of endothelium and fibrosis. Protein levels were quantified by Western blot.PMP and PBF increased significantly from baseline after injection of vasoactive drugs. Peak PMP after PGE 1 and ACh was higher in young mice (225.0 ± 12.0 and 211.3 ± 12.1 AU) compared to old (155.9 ± 7.1 and 162.6 ± 5.1 AU, respectively). PSV after PGE 1 was higher in young than old mice (112.7 ± 8.5 vs. 78.2 ± 4.6 mm/sec). PSV after ACh was also higher in young (112.7 ± 5.6 mm/sec) than older mice (69.2 ± 7.1 mm/sec). PMP positively correlated with PSV (r = 0.867, P = 0.001). Immunostaining and Western blot showed increased protein expression of all fibrosis markers with aging. LSCI is a viable technique for evaluating penile hemodynamics. Increased cavernosal fibrosis may cause impaired penile hemodynamics and increased incidence of erectile dysfunction in older men.