TSG-6 promotes fascin-1-mediated microvascular repair in murine airway allografts

Bronchial anastomotic complications, including stenosis, necrosis, and dehiscence, remain major contributors to morbidity and poor graft outcomes following lung transplantation. These complications are primarily driven by microvascular disruption, causing hypoxia, epithelial injury, and impaired wound healing at the anastomosis. Tumor necrosis factor-stimulated gene 6 (TSG-6) protein is a secreted anti-inflammatory mediator with immunomodulatory and tissue-reparative properties; however, its role in transplant-associated vascular and epithelial regeneration remains incompletely defined. In this study, we investigated the therapeutic potential of exogenous TSG-6 in preserving airway microvasculature and promoting immunoregulation in a murine orthotopic tracheal transplant model that mimics the clinical setting of bronchial anastomosis following lung transplantation. BALB/cJ→C57BL/6J allografts were treated intranasally with recombinant TSG-6 (5 µg per transplant) on days -1, 2, 5, and 8 posttransplantation. Exogenous TSG-6 therapy significantly increased the recruitment of M2 macrophages, regulatory T cells, and subsets of regulatory B cells, shifting the graft microenvironment toward an IL-10-dominant anti-inflammatory state. These immunoregulatory effects were accompanied by improved microvascular perfusion, increased Fascin-1 and β-catenin expression in CD31+ endothelial cells, and preserved epithelial architecture with reduced inflammation and airway lumen narrowing, in contrast to untreated allografts that showed epithelial disruption with dense mononuclear infiltration. These findings suggest that TSG-6 coordinates vascular and epithelial repair after transplantation via IL-10-mediated immunoregulation and Fascin-1-dependent endothelial remodeling. These results highlight TSG-6 as a promising immunoregulatory factor with therapeutic potential to mitigate ischemia-related airway injury and offer a novel strategy for preventing bronchial anastomotic complications following lung transplantation.