Epigenetic Mechanisms Inhibit Smad7 and Contribute to Fibrosis in Crohn's Disease

DNMT1-dependent Smad7 promoter hypermethylation and miR-21–mediated Smad7 mRNA degradation silence Smad7 in subepithelial myofibroblasts from fibrostenotic Crohn’s disease.

• Why it matters: Smad7 normally restrains TGF-beta1 profibrotic signaling, yet fibrostenotic Crohn’s disease mesenchymal cells show sustained TGF-beta1 activity without elevated Smad7, leaving the mechanism unclear.
• What they did: Paired ileal tissues and primary cultured SEMFs were analyzed for gene expression, promoter methylation, protein stability, and miR-21 localization; antagomiR-21, 5-Azacytidine, DNMT1 knockdown, and p300/HDAC1 modulation were used to test regulation.
• The result: Restoring Smad7 with antagomiR-21, demethylation, or DNMT1 knockdown reduced TGF-beta1-dependent profibrotic gene expression, implying epigenetic and post-translational Smad7 loss sustains intestinal fibrosis in fibrostenotic Crohn’s disease.

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