Spontaneous Recovery of Cavernous Nerve Crush Injury

ABSTRACT

PURPOSE: To investigate pathophysiological consequences and spontaneous recovery after cavernous nerve crush injury (CNCI) in a rat model. MATERIALS AND METHODS: Twenty 4-week-old male Sprague-Dawley rats were divided into the following groups sham-operated group (n=10) and bilateral CNCI groups (n=10) for two different durations (12 and 24 weeks). At both time points, CN electrical stimulation was used to assess erectile function by measuring the intracavernous pressure. The expression of hypoxia inducible factor (HIF)-1alpha and sonic hedgehog (SHH) was examined in penile tissue. Immunohistochemical staining was performed for nerve growth factor (NGF), endothelial nitric oxide synthase (eNOS), neuronal nitric oxide synthase (nNOS), and smooth muscle alpha-actin. RESULTS: CNCI significantly decreased erectile function at 12 weeks (51.7% vs. 71.9%, mean ICP/BP ratio, p<0.05) and increased the expression of HIF-1alpha and decreased the expression of eNOS, nNOS, and SHH. At 24 weeks, erectile function in the CNCI group was improved with no significant difference versus the sham group (70.5% vs. 63.3%, mean ICP/BP ratio, p<0.05) or the CN group at 12 weeks (51.7% vs. 63.3%, mean ICP/BP ratio, p<0.05). By RT-PCR, the increase in HIF-1alpha and decrease in SHH mRNA was restored at 24 weeks. By immunohistochemistry, the expression of eNOS and nNOS was increased at 24 weeks. CONCLUSIONS: CN injury induces significantly impaired erectile function and altered gene and protein expression, which suggests that local hypoxic and inflammatory processes may contribute to this change. Significant spontaneous recovery of erectile function was observed at 6 months after CN crush injury.