Activation of the FAK-MAPK/ERK1 pathway promotes intestinal epithelial cell sheet migration during fistula tract repair

Postoperative fistula tracts remain a significant clinical challenge, yet the molecular mechanisms governing their healing are poorly understood. This study aimed to investigate the regulatory role of focal adhesion kinase (FAK) in intestinal mucosal epithelial cell migration during drainage tube-induced fistula tract healing and to elucidate its underlying mechanisms through the MAPK/ERK1 signaling pathway. A rabbit small intestinal fistula tract model was established and tissues were collected at 0, 7, 14, and 28 days post-surgery. Tissue characterization included histopathological evaluation (H&E and Masson trichrome staining) and molecular assessment of FAK phosphorylation, collagen deposition, and epithelial-mesenchymal transition (EMT) markers via immunohistochemistry, immunofluorescence, and Western blot analysis. In vitro, primary intestinal epithelial cells were isolated and FAK activity was modulated using pharmacological activation (ZINC40099027) or shRNA knockdown. Cell proliferation and migration were assessed via CCK-8, EdU, wound healing, and Transwell assays. Mechanistic involvement of the MAPK/ERK1 signaling pathway was validated using inhibitor (MAPK-IN-1) and agonist (C16-PAF) rescue experiments. In vivo, local injection of sh-FAK adenovirus evaluated FAK's role in fistula tract healing. FAK phosphorylation (p-FAK) and Collagen I expression increased progressively during fistula tract maturation, exhibiting clear spatial co-localization in tissue sections. Pharmacological FAK activation enhanced epithelial cell proliferation, migration, MMP2/9 and Vimentin expression, and reduced E-cadherin levels, while shRNA-mediated FAK knockdown produced the opposite effects. Mechanistically, FAK activity positively correlated with MEK/ERK phosphorylation. Bidirectional rescue experiments using pathway inhibitors and agonists demonstrated that MAPK/ERK1 signaling is essential for FAK-induced cell migration. In vivo, local sh-FAK adenovirus injection suppressed MAPK/ERK1 activity, reduced granulation tissue and collagen deposition, and delayed fistula tract healing. FAK facilitates fistula tract repair by activating the MAPK/ERK1 pathway, driving epithelial cell proliferation, migration, and EMT-like transformation during the healing process. Targeting the FAK-MAPK/ERK1 axis represents a promising therapeutic strategy for managing refractory postoperative fistulas.