Fibrosis of corpus cavernosum in animals following cavernous nerve ablation

To investigate alterations of smooth muscle cells and collagen fibers in corpus cavernosum following cavernous neurectomy and its relation to the expression of transforming growth factor-beta1 (TGF-beta1).

Ten adult male SD rats (neurectomy group) were subject to a bilateral cavernous nerve (CN) resection aseptically under an operating microscope, with 6 sham-operated rats as the control. Fifteen weeks after the operation, the penile specimens were collected and prepared for quantitative-analyzing of ratio of smooth muscle to collagen fibers in corpus cavernosum with confocal microscopy, and for detecting the expression of TGF-beta1 by RT-PCR and western-blot.

Smooth muscle cells that show red color after fluorescent-labeling with tetramethylrhodamine isothiocyanate-phalloidin and collagen fibers that produce green autofluorescence after paraformaldehyde fixation were clearly identified under the confocal microscope. Quantification of fluorescent intensity showed that the ratio of smooth muscle to collagen fibers in corpus cavernosum in neurectomy group was 0.265 +/- 0.125, which was significantly lower than that in sham-operated group (0.760 +/- 0.196, P<0.01). RT-PCR and western-blot analyses revealed a significantly higher expression of TGF-beta1 in the penile tissues of the neurectomy animals than that in sham-operated group.

Bilateral ablation of CN can lead to fibrosis of corpus cavernosum, which may be related to an increased expression of TGF-beta1 induced by hypoxia in cavernous tissue after denervation.