Human adipose-derived mesenchymal stromal cells improved wound healing in enterocutaneous fistulizing disease mouse model

A significant complication of Crohns disease is the formation of perianal fistulas. While local application of human adipose tissue-derived mesenchymal stromal cells (AT-MSC INN Darvadstrocel, Takeda) is an approved therapy for this condition, challenges in studying human clinical tissue and the absence of a robust experimental model have hindered deeper understanding of the preclinical efficacy and mechanisms behind the therapy. We have developed a model that closely mimics the clinical scenario, using human gut tissue transplanted subcutaneously into SCID mice. In this model, enterocutaneous fistulas are reliably induced by combining imiquimod-induced psoriatic dermatitis above the transplant with systemic lipopolysaccharide (LPS), a major component of the bacterial cell wall. Similar to clinical observations, local application of AT-MSC significantly improved fistula wound healing and re-epithelialization. This model system enabled comprehensive tissue harvesting for histopathological analysis, spatial transcriptomics, and protein profiling. Our findings demonstrate that AT-MSC applied around the fistula wound survive for up to three weeks, migrating into the fistula tract and further into the inflamed human gut tissue. Within the fistula tract, AT-MSCs acquired immune-active properties, with increased expression of SOD2 and CCL2, and were associated with a substantial population of M2 macrophages. In contrast, AT-MSC located in healthy tissue near the fistula remained stationary, adopting a fibroblast-like phenotype within a collagen-rich extracellular matrix. These preclinical results support the safety and efficacy of AT-MSC for treating fistulizing gut disease. Furthermore, our data suggest that the inflamed fistula tract acts as a scaffold promoting AT-MSC activity and migration. Enhancing SOD2 and CCL2 expression through pre-activation or genetic modification may further improve the therapeutic potential of these cells.