RAC1-YAP1-PIEZO1 signaling axis links intrauterine inflammation to uterine hypercontractility and preterm labor

Preterm birth is a leading cause of neonatal morbidity and mortality, yet its underlying mechanisms remain incompletely understood. Our previous studies have demonstrated that the mechanosensitive ion channel PIEZO1 plays a critical role in regulating intracellular calcium levels and amplifying inflammation in uterine smooth muscle (USM) cells, thereby promoting USM contractility and preterm labor. However, the upstream regulatory mechanisms driving PIEZO1 expression during infection-induced preterm labor remain unclear. Here, we established an infection-induced preterm birth mouse model using intrauterine lipopolysaccharide (LPS) injection and assessed USM contractility via ex vivo tension measurements. Western blotting and immunofluorescence were employed to assess the expression and cellular localization of PIEZO1, YAP1, and RAC1 in both uterine tissue and cultured USM cells. Pharmacological inhibitors (Verteporfin for YAP1 and NSC23766 for RAC1) and Rac1 siRNA were utilized to investigate the functional roles and regulatory relationships among these molecules. We found that LPS induced YAP1 dephosphorylation and nuclear translocation, which was inhibited by Verteporfin, reducing PIEZO1 expression and USM contractility, and prolonging gestation. Elevated RAC1 expression in LPS-treated tissues drove YAP1 nuclear translocation and PIEZO1 overexpression. Our findings suggest that RAC1 is involved in regulating YAP1 activation and nuclear localization, which is associated with increased PIEZO1 expression and uterine smooth muscle contractility. Thus, targeting the RAC1-YAP1-PIEZO1 axis might represent a novel strategy for preventing infection-induced preterm birth.