Use of Senolytics for Amelioration of Parturition-Related Vaginal Changes in an Animal Model

Objectives: Parturition can accelerate changes in the vagina resulting in cellular senescence and eventual development of pelvic floor disorders. The use of senolytic agents at the time of delivery has the potential to target pathology associated with cellular senescence and improve post-partum tissue recovery. Our objective was to use an animal model to determine if senolytic administration affects markers of cellular senescence following parturition with and without simulated obstetrical injury.

Methods: 12 week-old non-pregnant (n=5) and parturient WT C57BL/6 female mice both with (n=41) and without (n=41) simulated obstetrical injury were assigned to either control group or treatment with the senolytics dasatinib (D) and quercetin (Q) via oral gavage at the time of delivery (D=5mg/kg, Q=50mg/kg). Vaginal tissue was collected at 4 hours, 24 hours, 72 hours, 7 days, and 4 weeks post-partum. Tissue analysis included immunostaining and cytokine analysis for markers of cellular senescence. ANOVA and t-tests were used for statistical analysis with post-hoc tests as appropriate. Quantitative data is presented as percentage area of expression and mean ± standard error of the mean.

Results: Immunostaining for markers of cellular senescence demonstrated increased expression of p16 in all parturient groups compared to non-pregnant mice (p=0.0002). Simulated obstetric injury increased p16 expression at 24h, 72h, and 4w post-partum. Treatment with senolytics following injury significantly decreased p16 expression at 24h and 7d compared to control (p=0.007). Though not statistically significant, γH2Ax expression following senolytic administration after injury was also decreased at 72h (9.47% vs 3.5% p=0.18) and 4w (8% vs 1.1%, p=0.29) compared to no treatment. p53 expression increased after injury, with the most notable increase observed at 72h. Senolytic treatment at this timepoint likewise resulted in significantly decreased post-partum p53 expression (7.02% vs 0.78%, p=0.016). Cytokine analysis of cellular senescence markers showed a significant increase in IL-6 expression at 4h post-partum in the injury group compared to no injury (3.1pg/mL ± 1.1 vs 0.59pg/mL ± 0.12, p=0.005). Senolytic treatment decreased expression of this marker after injury compared to no treatment (1.3pg/mL ± 0.3 vs 3.1pg/mL ± 1.1, p=0.18). IL-1b was similarly significantly elevated at 7d postpartum in the injury group compared to no injury (254.8pg/mL ± 107.9 vs 10.78pg/mL ± 2.06, p=0.005). At 4w postpartum, senolytic treament resulted in decreased expression of IFN-γ after injury compared to no treatment (2.67pg/mL ± 0.73 vs 8.96pg/mL ± 2.46, p=0.0009).

Conclusions: Use of senolytics at the time of delivery in the setting of simulated obstetrical injury decreased expression of markers of cellular senescence in this animal model. These results suggest senolytic agents may play a role in mitigating the contribution of parturition and obstetrical injury to cellular senescence and resultant tissue dysfunction associated with pelvic floor disorders.