Mechanical transapical coupling of endometrial epithelial cells during implantation

Epithelial cells lining the lumen of organs have an apical-basal polarity, and mechanical cell contacts are located in the lateral and basal regions. During early pregnancy in rodents, the luminal space of the uterus is closed, and opposing epithelial cells attach to each other at apical-apical surfaces. Here, we show that cells are mechanically coupled at the apical cell-cell contacts. The apical plasma membrane was intricately intertwined between opposing cells. Extracellular matrix and tight junction molecules were localized at apical contacts. Claudin inhibition resulted in impaired luminal closure, suggesting a functional requirement of claudins for the establishment of transapical coupling. The present results demonstrate a mechanical cell-cell interaction that occurs between apical-apical surfaces in addition to lateral and basal cell junctions. ### Competing Interest Statement The authors have declared no competing interest.