ObjectiveTo investigate the protective effect of human urine-derived stem cells (USCs) on erectile function and cavernous structure in rats with cavernous nerve injury (CNI).

METHODSSixty adult male SD rats with normal sexual function were randomly divided into four groups of equal number: sham operation, bilateral CNI (BCNI) model control, phosphate buffered saline (PBS), and USC. The BCNI model was established in the latter three groups of rats by clamping the bilateral cavernous nerves. After modeling, the rats in the PBS and USC groups were treated by intracavernous injection of PBS at 200 μl and USCs at 1×106/200 μl PBS respectively for 28 days. Then, the maximum intracavernous pressure (mICP) and the ratio of mICP to mean arterial pressure (mICP/MAP) of the rats were calculated by electrical stimulation of the major pelvic ganglions, the proportion of nNOS- or NF200-positive nerve fibers in the total area of penile dorsal nerves determined by immunohistochemical staining, the levels of endothelial cell marker eNOS, smooth muscle marker α-SMA and collagen I detected by Western blot, and the smooth muscle to collagen ratio and the cell apoptosis rate in the corpus cavernosum measured by Masson staining and TUNEL, respectively.

RESULTSAfter 28 days of treatment, the rats in the USC group, as compared with those in the PBS and BCNI model control groups, showed significant increases in the mICP (［81 ± 9.9］ vs ［31 ± 8.3］ and ［33 ± 4.2］ mmHg, P <0.05), mICP/MAP ratio (0.72 ± 0.05 vs 0.36 ± 0.03 and 0.35 ± 0.04, P <0.05), the proportions of nNOS-positive nerve fibers (［11.31 ± 4.22］% vs ［6.86 ± 3.08］% and ［7.29 ± 4.84］% , P <0.05) and NF200-positive nerve fibers in the total area of penile dorsal nerves (［27.31 ± 3.12］% vs ［17.38 ± 2.87］% and ［19.49 ± 4.92］%, P <0.05), the eNOS/GAPDH ratio (0.52 ± 0.08 vs 0.31 ± 0.06 and 0.33 ± 0.07, P <0.05), and the α-SMA/GAPDH ratio (1.01 ± 0.09 vs 0.36 ± 0.05 and 0.38 ± 0.04, P <0.05), but a remarkable decrease in the collagen I/GAPDH ratio (0.28 ± 0.06 vs 0.68 ± 0.04 and 0.70 ± 0.10, P <0.05). The ratio of smooth muscle to collagen in the corpus cavernosum was significantly higher in the USC than in the PBS and BCNI model control groups (17.91 ± 2.86 vs 7.70 ± 3.12 and 8.21 ± 3.83, P <0.05) while the rate of cell apoptosis markedly lower in the former than in the latter two (3.31 ± 0.83 vs 9.82 ± 0.76, P <0.01; 3.31 ± 0.83 vs 9.75 ± 0.91, P <0.05).

CONCLUSIONSIntracavernous injection of USCs can protect the erectile function of the rat with cavernous nerve injury by protecting the nerves, improving the endothelial function, alleviating fibrosis and inhibiting cell apoptosis in the cavernous tissue.