The effect of adeno-associated virus mediated brain derived neurotrophic factor in an animal model of neurogenic impotence

Purpose: We tested the hypothesis that transfecting penile tissue with brai n derived neurotrophic factor may facilitate neural recovery and erectile c apability after cavernous nerve injury. Materials and Methods: Of the 34 Sprague-Dawley rats used 10 underwent sham operation and 24 underwent bilateral cavernous nerve freezing and intracav ernous injection of adenoassociated virus-lacZ (12) or adeno-associated vir us-brain derived neurotrophic factor (12). Erectile function was assessed b y cavernous nerve electrostimulation at 4 and 8 weeks, and samples of penil e tissue and the major pelvic ganglia were evaluated histologically. Results: In the brain derived neurotrophic factor group mean maximal intrac avernous pressure plus or minus standard deviation was significantly higher than in the LacZ group at 4 and 8 weeks (58.5 +/- 11.7 cm, water versus 28 .4 +/- 5.5 and 61.3 +/- 12.5 versus 37.7 +/- 7.9, respectively). In additio n, in the brain derived neurotrophic factor group reduced nicotinamide aden ine dinucleotide phosphate diaphorase staining and neuronal nitric oxide sy nthase immunostaining revealed significantly more positive nerve fibers in the dorsal nerves and cavernous tissue than in the LacZ group at each time point and the percent of neuronal nitric oxide synthase positive neurons in the major pelvic ganglia was also significantly greater. Moreover, in the LacZ group most neurons showed a light staining pattern with irregular cont ours and numerous vacuoles in the cytoplasm. Conclusions: Intracavernous injection of adeno-associated virus-brain deriv ed neurotrophic factor may prevent the degeneration of neuronal nitric oxid e synthase containing neurons in the major pelvic ganglia and facilitate th e regeneration of neuronal nitric oxide synthase containing nerve fibers in penile tissue, thus, enhancing the recovery of erectile function after bil ateral cavernous nerve injury.