Isolation and characterization of smooth muscle cells from rat corpus cavernosum tissue for the study of erectile dysfunction

Purpose

Primary culture of the cavernous smooth muscle cells from corpus cavernous tissues is known to be difficult, mainly because of contamination with fibroblasts. We applied a new method for better isolation of rat penile smooth muscle cells (RPSMCs) from rat corpus cavernosum tissue for reliable ex vivo research on erectile dysfunction.

Materials and Methods

With the use of 8-week-old adult male Sprague-Dawley rats, ex vivo migrations of rat cavernous tissue were measured by penis and aortic ring assay by use of a Matrigel-based D-valine-modified culture method. The expression of α-smooth muscle actin (α-SMA) and platelet/endothelial cell adhesion molecule (PECAM)-1 in the RPSMCs was determined by standard immunofluorescent staining and immunoblotting. The expression patterns of phosphodiesterase (PDE) family mRNA in RPSMCs were compared with patterns in rat aortic smooth muscle cells (RASMCs) by use of quantitative real-time reverse transcription polymerase chain reaction.

Results

Immunocytochemical staining showed greater α-SMA-positive and PCAM-1-negative fluorescence. Moreover, whereas the expression of α-SMA was detected in the RPSMCs, that of PECAM-1 was not. The levels of PDE1A, PDE1B, PDE1C, PDE2A, PDE3A, PDE4A, PDE4B, PDE4C, PDE4D, and PDE5A mRNA in the RPSMCs were about 3.2-, 4.4-, 3.4-, 29.0-, 3.5-, 2.8-, 2.9-, 6.1-, 45.0-, and 6.0-fold the corresponding expression in RASMCs.

Conclusions

We developed a two-stage tissue culture method utilizing a Matrigel-based sprouting culture system to facilitate stromal cell sprouting and an adherent culture system using D-valine to eliminate the contamination of fibroblasts into the smooth muscle cells.

Spontaneous recovery of cavernous nerve crush injury

Purpose

To investigate pathophysiological consequences and spontaneous recovery after cavernous nerve crush injury (CNCI) in a rat model.

Materials and Methods

Twenty 4-week-old male Sprague-Dawley rats were divided into the following groups: sham-operated group (n=10) and bilateral CNCI groups (n=10) for two different durations (12 and 24 weeks). At both time points, CN electrical stimulation was used to assess erectile function by measuring the intracavernous pressure. The expression of hypoxia inducible factor (HIF)-1α and sonic hedgehog (SHH) was examined in penile tissue. Immunohistochemical staining was performed for nerve growth factor (NGF), endothelial nitric oxide synthase (eNOS), neuronal nitric oxide synthase (nNOS), and smooth muscle α-actin.

Results

CNCI significantly decreased erectile function at 12 weeks (51.7% vs. 71.9%, mean ICP/BP ratio, p<0.05) and increased the expression of HIF-1α and decreased the expression of eNOS, nNOS, and SHH. At 24 weeks, erectile function in the CNCI group was improved with no significant difference versus the sham group (70.5% vs. 63.3%, mean ICP/BP ratio, p<0.05) or the CN group at 12 weeks (51.7% vs. 63.3%, mean ICP/BP ratio, p<0.05). By RT-PCR, the increase in HIF-1α and decrease in SHH mRNA was restored at 24 weeks. By immunohistochemistry, the expression of eNOS and nNOS was increased at 24 weeks.

Conclusions

CN injury induces significantly impaired erectile function and altered gene and protein expression, which suggests that local hypoxic and inflammatory processes may contribute to this change. Significant spontaneous recovery of erectile function was observed at 6 months after CN crush injury.