Involvement of Rho-Kinase/LIM Kinase/Cofilin Signaling Pathway in Corporal Fibrosis after Cavernous Nerve Injury in Male Rats

Introduction. The molecular mechanism of corporal fibrosis leading to erectile dysfunction (ED) following cavernous nerve (CN) injury is poorly understood. Aim. To determine whether the LIMK2/cofilin pathway, the downstream effectors of ROCK1, was involved in ED and corporal fibrosis following bilateral CN injury in male rats. Methods. Forty-eight 10-week-old male Sprague-Dawley rats were equally divided into three groups: sham surgery (S); bilateral CN crush injury (I); and bilateral CN resection (R). Within each groups, two subgroups were analyzed at 1 and 4 weeks postoperatively. Main Outcome Measures. Electrostimulation was performed to assess erectile function by the ratio of maximal intracavernous pressure to mean arterial pressure (ICP/MAP) and areas under the ICP curve to MAP (AUC/MAP). Penile tissue was processed for Masson's trichrome staining, Western blot (ROCK1, total LIMK2, phospho-LIMK2, total cofilin, phospho-cofilin), immunohistochemistry (alpha-SM actin [alpha-SMA]), and double immunofluorescent staining (ROCK1, phospho-LIMK2, vimentin). Results. At each time point, both I and R groups showed a significantly lower percent of ICP/MAP and AUC, and decreased SM cell/collagen ratio and expression of alpha-SMA than S group. Densitometry revealed a significantly higher expression of ROCK1 in I and R groups compared with S group at all time points. The LIMK2 phosphorylation in I and R groups significantly increased at 1 week, but not at 4 weeks. The cofilin phosphorylation in R group significantly increased to that in S group starting at 1 week, while that in I group was increased significantly at 4 weeks. The double immunofluorescent staining noted that coexpression of vimentin with ROCK1 or phospho-LIMK2 in I and R groups was significantly increased mainly in the subtunical area at 1 week but not at 4 weeks. Conclusions. The ROCK1/LIMK2/cofilin pathway may be involved in ED related to corporal fibrosis, and it appears to be functional particularly in the early period after CN injury. Song SH, Park K, Kim SW, Paick J-S, and Cho MC. Involvement of Rho-kinase/LIM kinase/cofilin signaling pathway in corporal fibrosis after cavernous nerve injury in male rats.