Extraordinary muscular structure leads to urethral injury after vaginal delivery in animal study.
OBJECTIVE
The aim of this study is to explore causality of birth trauma after vaginal delivery and anatomical findings.


METHODS
A total of 28 virgin mice were studied. Treatment groups received vaginal distention. Specimens were collected and subjected to the following fluorescence stains: progenitor cell (c-kit), smooth muscle (SMA), fibroblast (vimentin), and skeleton muscle (Masson's trichrome). Confocal microscopy was used to screen all of the urogenital tissue to localize the stained cells.


RESULTS
Fibroblasts were spread all over perivaginal and urethral surroundings. Progenitor cells appeared at urethral-vagina intersection and urethral circle. They were noticeable only within smooth muscle layer. Two extraordinary skeleton muscle bands appeared on the urethra bilaterally.


CONCLUSIONS
Our study demonstrates existence of muscle bands at the bilateral urethra. They can limit the mobility of urethra during vaginal delivery and thereby cause urethra injury. Progenitor cells are located only in the smooth muscle of the urethral circle.
Chin
Hung-Yen
HY
Medical School, Chang Gung University, Tao-Yuan, Taiwan, Republic of China. chin671009@gmail.com
Changchien
Eileen
E
Chiang
Chi-Hsin
CH
Yang
Hsiu-Ping
HP
D000818:Animals; D036861:Delivery, Obstetric / Q000009:adverse effects*; D005260:Female; D051379:Mice; D008810:Mice, Inbred C57BL; D009130:Muscle, Smooth / Q000473:pathology; D014521:Urethra / Q000293:injuries* / Q000473:pathology; D014550:Urinary Incontinence, Stress / Q000209:etiology*