Oral Microcapsules Encapsulating Endometrial Regenerative Cell-Derived Exosomes Promote Intestinal Epithelial Barrier Repair and Ameliorate Experimental Colitis

Background: Endometrial regenerative cell-derived exosomes (ERC-Exos) exhibit tissue repair and anti-inflammatory properties for ulcerative colitis (UC) treatment, but oral administration is limited by gastrointestinal degradation. This study first developed chitosan-sodium alginate microcapsules (CSE) for ERC-Exos delivery and explored the role of milk fat globule-EGF factor 8 (MFGE8). Methods: MFGE8-knockdown ERC-Exos (MFGE8 −/− -ERC-Exos) were constructed via lentiviral transfection. Colitis-targeted exosomes (CSE) were prepared, and their in vivo stability and targeting ability were verified. A dextran sulfate sodium (DSS)-induced murine colitis model was used to evaluate the effects of CSE. Immunofluorescence staining was utilized to assess colon DC infiltration; Flow cytometry was employed to detect CD4 ⁺ T cell proliferation and dendritic cell (DC) maturation. EdU/TUNEL staining and Western blotting were performed to determine intestinal epithelial cell proliferation and apoptosis, as well as the activation level of the PI3K/AKT/mTOR pathway. Results: CSE achieved 89.2%± 1.5% encapsulation efficiency and 78% colon-targeted release, resisting gastric degradation. Oral CSE significantly alleviated DSS-induced weight loss ( P < 0.001), colon shortening ( P < 0.0001), and histopathological damage, while restoring intestinal barrier function (reduced permeability, P < 0.0001; upregulated tight junction proteins ZO-1/Occludin/Claudin-1). It also inhibited DC maturation (MLN: P < 0.0001; LP: P < 0.0001) and CD4⁺T cell proliferation (MLN: P < 0.001; LP: P < 0.01), and normalized cytokine profiles (reduced IL-6/IL-1β/TNF-α, P < 0.001; increased IL-10, P < 0.0001). MFGE8 knockdown significantly attenuated these effects. Mechanistically, MFGE8 mediated ERC-Exos uptake by intestinal epithelial cells via αvβ 5 integrin, activating PI3K/AKT/mTOR to inhibit apoptosis (P< 0.0001) and promote proliferation (P< 0.0001). Conclusion: This study is the first to confirm that the CSE carrier achieves colonic targeted release, overcoming the limitations of oral exosome delivery. MFGE8 mediates the intestinal epithelial repair effect of ERC-Exos via the PI3K/AKT/mTOR pathway. Keywords: oral administration, ulcerative colitis, endometrial regenerative cells, exosomes, milk fat globule-EGF factor 8, intestinal barrier