Simulated childbirth injuries in an inbred rat strain

Vaginal distension (VD) in outbred rats has been shown to decrease urethral resistance, as well as increase the expression of the stem cell-homing chemokine, monocyte chemotactic factor 3 (MCP-3), but not stromal derived factor 1 (SDF-1). The aim of this study was to determine if similar responses are induced by VD in an inbred rat strain.

Forty female Lewis rats underwent VD or sham VD followed by leak point pressure (LPP) testing 4 or 10 days later. Ten additional rats served as controls. The urethra and vagina were then dissected for histology. To examine chemokine expression, eight additional rats underwent VD with organs harvested immediately or 1 day after the procedure for reverse transcriptase polymerase chain reaction (RT-PCR) of MCP-3 and SDF-1. Four age-matched rats served as controls.

Four days after VD, LPP was significantly lower in VD rats (14.3 +/- 1.6 cm H(2)O) than controls (18.7 +/- 1.3 cm H(2)O). Ten days after VD, LPP in both VD (19.7 +/- 2.6 cm H(2)O) and sham (18.4 +/- 1.3 cm H(2)O) groups was not significantly different from controls. Urethral histology demonstrated marked disruption and atrophy of smooth and striated muscle in VD rats compared to shams and controls. RT-PCR yielded a 25-fold significant increase in expression of urethral MCP-3 immediately following VD. SDF-1 was significantly decreased in the urethra and vagina immediately after VD and in the bladder 24 hr after VD.

VD in Lewis rats produces functional, histological and molecular results similar to that of outbred rats. This model could be utilized in future studies investigating cellular transplant methods of improving urethral function.