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Mol Med. 2015 Nov;21(1):676-687. doi: 10.2119/molmed.2015.00147. Epub 2015 Aug 3.

Transgenic Expression of miR-222 Disrupts Intestinal Epithelial Regeneration by Targeting Multiple Genes Including Frizzled-7.

Chung HK1,2, Chen Y1,2, Rao JN1,2, Liu L1,2, Xiao L1,2, Turner DJ1,2, Yang P3, Gorospe M4, Wang JY1,2,5.

Author information

1
Cell Biology Group, Department of Surgery, University of Maryland School of Medicine, Baltimore, Maryland, United States of America.
2
Baltimore Veterans Affairs Medical Center, Baltimore, Maryland, United States of America.
3
Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Maryland School of Medicine, Baltimore, Maryland, United States of America.
4
Laboratory of Genetics, National Institute on Aging (NIA)-Intramural Research Program (IRP), National Institutes of Health, Baltimore, Maryland, United States of America.
5
Department of Pathology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America.

Abstract

Defects in intestinal epithelial integrity occur commonly in various pathologies. miR-222 is implicated in many aspects of cellular function and plays an important role in several diseases, but its exact biological function in the intestinal epithelium is underexplored. We generated mice with intestinal epithelial tissue-specific overexpression of miR-222 to investigate the function of miR-222 in intestinal physiology and diseases in vivo. Transgenic expression of miR-222 inhibited mucosal growth and increased susceptibility to apoptosis in the small intestine, thus leading to mucosal atrophy. The miR-222-elevated intestinal epithelium was vulnerable to pathological stress, since local overexpression of miR-222 not only delayed mucosal repair after ischemia/reperfusion-induced injury, but also exacerbated gut barrier dysfunction induced by exposure to cecal ligation and puncture. miR-222 overexpression also decreased expression of the Wnt receptor Frizzled-7 (FZD7), cyclin-dependent kinase 4 and tight junctions in the mucosal tissue. Mechanistically, we identified the Fzd7 messenger ribonucleic acid (mRNA) as a novel target of miR-222 and found that [miR-222/Fzd7 mRNA] association repressed Fzd7 mRNA translation. These results implicate miR-222 as a negative regulator of normal intestinal epithelial regeneration and protection by downregulating expression of multiple genes including the Fzd7. Our findings also suggest a novel role of increased miR-222 in the pathogenesis of mucosal growth inhibition, delayed healing and barrier dysfunction.

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