Bone marrow mesenchymal stem cell-derived circHECTD1 targets claudin1 through the CTCF/METTL3 axis to alleviate...

Ulcerative colitis (UC) is an inflammatory bowel disease that lacks satisfactory treatment. This study aimed to investigate the role of bone marrow mesenchymal stem cell-derived exosomal circHECTD1 (Exo-circHECTD1) in UC and its mechanism of action.

An inflammatory model was created using LPS-stimulated MODE-K cells and an UC mouse model was established using dextran sodium sulfate (DSS). Cell proliferation was assessed using CCK-8. Apoptosis and Th17/Treg cell differentiation were analyzed by flow cytometry. Inflammatory factors were detected using ELISA. FITC fluorescence intensity was measured to evaluate permeability. m⁶A modification and molecular binding were detected using immunoprecipitation methods. Luciferase reporters were used to evaluate METTL3 promoter activity. RT-qPCR was used to detect RNA expression and western blotting was used to detect METTL3, CTCF, claudin1, and tight junction proteins (ZO-1, occludin).

Exo-circHECTD1 enhanced viability and permeability and reduced apoptosis and inflammation factor levels in LPS-treated MODE-K cells. Moreover, it reduced the Th17/Treg ratio, regulated gut microbiota, and promoted the recovery of mice with DSS-induced UC. Claudin1 knockdown reversed the protective effect of Exo-circHECTD1 on UC models. CircHECTD1 binds to CTCF, which binds to the METTL3 promoter and promotes METTL3 promoter activity. METTL3 upregulates the level of claudin1 m⁶A modification and inhibits claudin1 expression. CTCF or METTL3 knockdown alleviated LPS-induced MODE-K cell damage.

Exo-circHECTD1 inhibits METTL3 transcription by binding to CTCF to reduce claudin1 m⁶A modification and promote claudin1 expression, thereby regulating the balance of gut microbiota and Th17/Treg cells and alleviating UC.