Milk-Derived miR-22–3p Promotes Proliferation of Human Intestinal Epithelial Cells (HIECs) by Regulating Gene Expression

Abstract

ObjectivesMicroRNAs (miRNAs) are small non-coding RNA involved in RNA silencing and post-transcriptional regulation of gene expression. Milk exosomes are microvesicles containing miRNAs, and miR-22–3p (miR-22) abundantly appears in human milk exosomes. Both human milk exosomes and miR-22 survive in vitro gastrointestinal digestion. The aim of the current study was to evaluate effects of milk derived miR-22 on intestinal epithelial cells in early life. MethodsTo evaluate effects of miR-22 on intestinal epithelial cells and mimic uptake of miR-22 in exosomes by intestinal epithelial cells, miR-22 was transfected to human intestinal epithelial cells (HIECs) using Lipofectamine, and then total RNA was isolated after 24 h for microarray assay. After microarray results were verified by qRT-PCR, microarray they were analyzed using the Bioconductor package limma and compared with miR-22 predicted target genes to identify a direct target gene for miR-22 in HIECs. ResultsTotally, 608 genes were markedly regulated by miR-22. Based on Gene Ontology terms, the roles of miR-22 in HIECs include promotion of proliferation and regulation of immune functions. A proliferation assay (BrdU) was subsequently conducted to confirm the effect of miR-22 on promotion of proliferation of HIECs. Based on analysis of the microarray results and miR-22 predicted target genes, C/EBPδ, a transcription factor, may be a direct target for miR-22. In miR-22 transfected HIECs, transcription and translation of the C/EBPδ gene was significantly inhibited, and cell proliferation was increased when the C/EBPδ gene was silenced by siRNA. A luciferase assay showed that miR-22 specifically bound to the 3’-untranslated region of the C/EBPδ gene. ConclusionsMilk-derived miR-22 promotes intestinal proliferation by modifying gene expression, and C/EBPδ may be an important direct target for miR-22 in human intestinal epithelial cells. Funding SourcesIntramural funds.