Molecular and histomorphological evaluation of female rats' urethral tissues after an innovative trauma model of prolonged vaginal distention: immediate, short-term and long-term effects

Abstract

Introduction and hypothesis: An animal model of vaginal distention (VD) was developed to reproduce the acute urethral injury and deficiency underlying stress urinary incontinence (SUI). Data on the chronic effects of urethral trauma and the recovery process are still scarce. We investigated acute, short- and long-term histomorphological and molecular changes in the urethra of rats post 12-h intermittent VD.

Methods: We evaluated the urethra of four groups of female rats (n = 72): control without trauma, 1 h, 7 days and 30 days post VD. We compared the gene and protein expression of the VEGF and NGF growth factors, collagens (COL1a1 and COL3a1), desmin, smooth muscle myosin (MYH11), skeletal muscle myosins (MYH1, MYH2 and MYH3) and cell proliferation marker MKi67. We used real-time RT-qPCR, and immunohistochemistry.

Results: Histology showed urethral damage after VD mainly involving the muscular layers. VEGF, NGF, desmin and MKi67 mRNA were significantly upregulated in the urethras of rats 1-h post VD compared with controls (P < 0.05 for all). By 7 days post trauma, COL1a1, MYH11 and MYH3 genes were overexpressed compared with controls (p < 0.05 for all). The COL3a1 protein level was increased by 2.6 times by day 7, while MYH2 protein was significantly decreased (around two times) from 7 to 30 days post VD compared with controls (p < 0.05 for both).

Conclusions: The 12-h intermittent VD causes chronic alterations in the urethra represented by increased COL3a1 and decreased MYH2 protein levels in the long term. The model can potentially be used to study the mechanisms of urethral injury and recovery as well as the physiopathology of SUI.

Keywords: Collagen; Muscle; Trauma; Urethra; Urinary incontinence.