Yak milk–derived exosomal microRNAs regulate intestinal epithelial cells on proliferation in hypoxic environment

摘要

Intestinal epithelial cells (IEC) act as an importantintestinal barrier whose function can be impaired uponinduction by hypoxia. Although intestinal barrier injuriesare preventable by milk-derived exosomal microRNAs(miRNAs), the underlying mechanism remainspoorly understood. This study aimed to characterize theeffect of yak and cow milk–derived exosomal miRNAon the barrier function of IEC-6 under hypoxic conditions,and explore the mechanism of yak milk exosomalmiRNA to relieve the hypoxia stress. First, by IlluminaHiSeq 2500 (Illumina Inc., San Diego, CA) sequencing,the miRNA expression was systematically screened,and differential expression of 130 miRNAs was identifiedwith 51 being upregulated and 79 downregulatedin yak and cow milk–derived exosomes. Furthermore,the top 20 miRNAs that had a relatively consistenthigh expression in yak milk exosome were identified,and bta-miR-34a was found to be an effective regulatorfor alleviating hypoxic injury of IEC-6. In vitroassay of the role of bta-miR-34a on survival of IEC-6in hypoxia by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) confirmed its effectivenessto significantly increase IEC-6 survival up to 13% for12 h, and up to 9.5% for 24 h. Investigation on theregulatory relationship between bta-miRNA-34a andthe hypoxia-inducible factor/apoptosis signaling pathwayprovided insights into the possible mechanismsby which bta-miR-34a activated the hypoxia-induciblefactor and apoptosis signaling pathway, thus promotingIEC-6 survival. The results of this study suggestan important relationship between miRNA expressionand intestine barrier integrity, which facilitated furtherunderstanding of the physiological function of yak andcow milk exosomal miRNAs, as well as mechanisms ofhypoxia-driven epithelial homeostasis.