Surgical resection of longitudinal vaginal septum improves fertility and reproductive capacity in mice.

Abstract: Longitudinal vaginal septum is a fibrous tissue band that bisects the vaginal canal and is associated with poor breeding in mice, leading to considerable waste of research time and resources in affected colonies. We observed a very high incidence (34.2%) of longitudinal vaginal septum in one of our mixed backgrounds inbred mice colonies that suffered from poor breeding. We hypothesized that vaginal septum resection would lead to normalization of fertility and reproductive outcomes in affected mice. Female mice were evaluated for vaginal septum and divided into three groups: septum surgery, septum no surgery, and no septum control. Surgical septum excision was done under general anesthesia using microscissors. Breeding began 7 days following septum surgery, and reproductive outcomes were assessed. Histopathological analysis of septate and non-septate reproductive tracts revealed no other abnormalities apart from the vaginal septum. Septum surgery mice had increased copulatory plug rates (82 vs 46%, P = 0.036), pregnancy rates after 30 days (95.2 vs 36.3%, P = 0.0001), pregnancy rates after 75 days (100 vs 72.7%, P = 0.01), and delivery rates (100 vs 72.7%, P = 0.01), as well as shorter time to pregnancy (P < 0.01) compared to septum mice without surgery. There were no differences in litter size, viability, or pup weight between the groups. In conclusion, our findings indicate that the reproductive capacity of mice is adversely affected by the presence of a vaginal septum. Surgical resection of longitudinal vaginal septum can normalize reproductive outcomes in mice. This simple procedure can save substantial time and financial resources in laboratory mice research impacted by poor breeding. Lay summary: A vaginal septum is a birth defect consisting of a tissue band that crosses the vaginal canal, dividing it. It is associated with poor breeding in mice, which affects animal research timelines. We tested whether vaginal septum excision would improve fertility and reproductive outcomes in our laboratory mouse colony which had a high septum rate (34%). Surgical septum excision was done under general anesthesia. Breeding began 7 days following septum surgery, and reproductive outcomes were evaluated. Mice that had septum excision surgery had increased breeding activity, pregnancy rates, delivery rates, and shorter time to pregnancy compared to septum mice without surgery. In conclusion, we found that excision of the vaginal septum can improve reproductive outcomes in mice. This simple procedure of vaginal septum resection can save substantial time and financial resources in laboratory mouse research impacted by poor breeding.