Exploring the dynamics of progenitor cells in the urethra after simulated birth trauma in mice.

OBJECTIVE: To examine the alteration in the cellular dynamics of the urethral tissue after a simulated birth trauma in a mouse model. MATERIALS AND METHODS: A total of 36 B6 mice received vaginal distention treatment, and four untreated mice were used as controls. Specimens were collected every 24 hours after the injury for 9 consecutive days and examined using immunofluorescent staining for cell markers including c-kit, smooth muscle actin (SMA), and vimentin. Confocal microscopy was used to localize the stained cells and determine the cell number. RESULTS: The number of c-kit positive cells increased after the 1st day and peaked on the 3rd day. The amount of SMA positive cells rapidly reduced to its lowest count on the 1st day and maintained a statistically significant low cell number than that at the basal level for 4 days after vaginal distension. The cell number finally returned to basal level on the 9th day. The amount of vimentin positive cells increased dramatically after the 1st day and plateaued from the 3rd day to the 9th day. The number of vimentin positive cells in the plateau phase was significantly higher than that of the control group. CONCLUSION: Our study confirmed that the dynamic change in different cell types after the urethral injury was dependent on the nature and physiology of the wound repairing cells during the tissue healing process. It might be a simple animal model to study birth trauma repair; however, the varied progenitor cell activity in different species should also be considered.