Spontaneous Regeneration of Nerve Fiber and Irreversibility of Corporal Smooth Muscle Fibrosis After Cavernous Nerve Crush Injury: Evidence From Serial Transmission Electron Microscopy and Intracavernous Pressure.

ABSTRACT

OBJECTIVE: To determine the pathophysiological progresses following bilateral cavernous nerve crushing injury, as an index for a treatment point and establishment of adequate treatment strategies for neurogenic erectile dysfunction. MATERIALS AND METHODS: Thirty-six rats were assigned to 1 of 6 groups, and bilateral cavernous nerve crushing or sham surgery was performed. Functional testing and ultrastructural analyses were performed immediately and at 7, 14, 21, and 28 days after the cavernous nerve (CN) injury (n = 6). RESULTS: Intracavernos pressure lowered progressively from 7 days to 14 days post-injury, and histologic staining revealed that the number of neuronal nitric oxide synthase-positive nerve fibers on the dorsal penile nerve decreased significantly and progressively from 7 days until 21 days post-injury. Furthermore, ultrastructural analyses revealed axon loss and demyelination of the CN at 7 and 14 days post-injury. However, it is followed by partial spontaneous recovery of erectile function and regeneration of the CN at 28 days post-injury, suggesting that these time points may be useful for evaluating the effects of drug treatments. Furthermore, we found that CN injury-induced damage to corporal smooth muscle cells was irreversible; therefore, focusing on protecting the corpus cavernosum from apoptosis may be more important than nerve protection when assessing treatment mechanisms in the CN injury model. CONCLUSION: Our study makes a significant contribution to the human diagnostic pathology literature because it describes characteristics of relevant tissue in the rat and provides information regarding time points that may be useful for future studies of pathologic mechanisms or treatment evaluations.