Introduction: Inflammatory Bowel Disease (IBD) is characterized by chronic inflammation in the gastrointestinal tract (GIT) via dysbiosis of the gut microbiome and weakening of the epithelial and mucosal barriers. Although the causative nature of IBD remains unknown, several studies have demonstrated that aberrant host-microRNA (miRNA) activity contributes to its pathophysiology. For example, miRNA-21 contributes to IBD through three mechanisms. Firstly, by increasing gut permeability via the ARF4 pathway. Secondly, by decreasing gut mucosal secretions via interfering with host goblet cells. Finally, by regulating proteins that inhibit host autophagy and decreasing immune response via the Phosphatase and Tensin Homolog (PTEN) and Akt pathway. The proposed study aims to answer the following question: how does aberrant expression of miRNA-21 in IBD contribute to the disease?
Methods: This review highlights and summarizes relevant studies on the miRNA-21 regulation of key pathways in the pathogenesis of IBD. Searches used electronic databases including PubMed, and Google Scholar for keywords such as “Inflammatory bowel disease” and “miRNA-21” and other additional relevant terms from years 2016 to 2022. Review papers that met our criteria and the relevant papers they referenced, regardless of their publication date, were manually searched for. Figures were made in part using KeyNote and Serveir Medical Art.
Discussion: Intracellular pathways contribute to chronic inflammation in IBD such as the PTEN pathway and pro-inflammatory cytokines like TNF-α. These pathways have been shown to influence the mucosal barrier, epithelial barrier, and the immune system in the gut. These pathways are regulated by miRNA-21, demonstrating miRNA-21 as a key regulator in IBD. Both PTEN and TNF-α also contribute to levels of angiogenesis in the gut through the regulation of vascular endothelial growth factor (VEGF) and hypoxia-inducible factor (HIF), further demonstrating the intricacies of the miRNA-21 pathway regulation in IBD.
Conclusion: The research highlighted in this review provides insight into the mechanisms of aberrant miRNA expression in IBD. Furthermore, knowledge of such molecular mechanisms has clinical and research applications, including identifying diagnostic biomarkers, less invasive screening techniques, and novel drug therapies.
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