Robust pan-junctional reinforcement preserves the gut epithelial barrier under mechanical stress

Epithelia are specialized tissue barriers that safeguard the organism's internal milieu from the external environment, a function critically dependent on intercellular junctions. In the colon, this barrier is repeatedly challenged by mechanical distension from feces, but it is unknown whether and how the colon adapts to this stress, which could otherwise compromise barrier integrity. Here, we show that feces-mediated mechanical distension triggers coordinated remodeling at cell and tissue scales, consistent with a mechanoadaptative response. This response includes recruitment of junctional proteins at all three types of adhesive cell-cell junctions (tight junctions, adherens junctions, and desmosomes). We identified protein-specific temporal profiles of junctional enrichment during distension, with ZO-1, E-cadherin, desmocollin 2, and plakoglobin exhibiting sustained junctional enrichment, whereas desmoplakin and keratin 8 showed progressive accumulation peaking at 15 min of distension. Distension was also accompanied by perijunctional recruitment and activation of nonmuscle myosin II (NMMII). Through genetic, pharmacological, and mechanical perturbations, we demonstrated that NMMII activation is required for epithelial mechanoadaptation. This process depends on extracellular calcium availability and mechanosensitive ion channel activity, supporting a role for calcium-dependent mechanosensitive signaling in NMMII-mediated junctional reinforcement. Loss of NMMII function impaired the junctional response to distension across all three junctional complexes, including desmosomes, resulting in disorganized junctions and barrier breach. Together, our findings uncover a robust physiological mechano-adaptive response of the adult colonic epithelium to an extrinsic mechanical stress, whereby coordinated reinforcement of all junctional complexes, requiring myosin II activity and calcium-dependent mechanosensitive signaling, preserves intestinal barrier integrity.