The Effect of Hyperbaric Oxygen Therapy on Erectile Function Recovery in a Rat Cavernous Nerve Injury Model

Abstract

Cavernosal oxygenation appears to be important for preservation of erectile tissue health. Hyperbaric oxygen therapy (HBOT) has been shown to improve tissue oxygenation and has neuromodulatory effects. This study was designed to define the effects of HBOT on erectile function (EF) and cavernosal tissue in the rat cavernous nerve (CN) injury model. Four groups of Sprague-Dawley rats were studied: rats with bilateral CN crush, HBOT treated (Crush+/HBOT+); bilateral CN-crush/no HBOT (C+/H-); no crush/no HBOT (C-/H-); and no crush/HBOT (C-/H+). HBOT was delivered daily for 90 minutes at three atmospheres for 10 days commencing the day of CN crush. Ten days after CN injury, the animals underwent CN stimulation measuring the maximal intracavernosal pressure/mean arterial pressure (ICP/MAP) ratios. Corporal tissue was harvested pre-sacrifice, and immunohistochemically stained for nerve growth factor (NGF), endothelial nitric oxide synthase (eNOS), and cluster of differentiation molecule (CD31). Histologic analysis was performed for Masson's trichrome to assess the smooth muscle-collagen ratio. Terminal deoxynucleotidyl transferase Biotin-dUTP Nick End Labeling assay was used to define apoptotic indices (AIs). The C+/H- group had significantly lower ICP/MAP ratios compared with C-/H- rats, (31% vs. 70%, P < 0.001). C+/H+ rats had significantly higher ICP/MAP ratio recovery compared with the C+/H- group (55% vs. 31%, P = 0.005). NGF and eNOS staining densities were higher in C+/H+ rats compared with C+/H- rats (P < 0.05 and P < 0.001, respectively). No difference was seen in CD31 expression. Staining density for MT displayed a trend toward higher smooth muscle preservation after HBOT. AIs were significantly increased by HBOT (P < 0.05). HBOT following a CN injury improved EF preservation in this model, supporting the cavernosal oxygenation concept as protective mechanism for EF. The effects appear to be mediated via preservation of neurotrophic and endothelial factor expression.