Plant-derived miR166a-3p packaged into exosomes to cross-kingdom inhibit mammary cell proliferation and promote apoptosis by targeting APLNR gene.

Plant-derived microRNAs (miRNAs) have attracted significant attention for their potential in cross-kingdom gene regulation, but the mechanisms of their entry, stability, and function in animal bodies need further investigation. We provided an in-depth analysis of tissue-specific miRNA expression in dairy cows, identifying 347 miRNAs, including 16 novel candidates, across 21 normal tissues. Our findings revealed that specific miRNAs, such as miR-192, miR-143, miR-148a, miR-486, and miR-21-5p, showed distinct tissue enrichment. In addition, a total of 167 maize-derived miRNAs were identified in dairy cow tissues, particularly in the rumen, mammary glands, serum, and exosomes. These exogenous miRNAs, which are abundant and conserved among plants, may be absorbed by the SLC46A2 transporter in the rumen epithelium during feeding and distributed to other tissues via exosomal encapsulation. The maize-derived miR166a-3p was highly abundant. Transfection experiments confirmed that miR166a-3p reduces the expression of proliferation markers (PCNA, Cyclin D, and Cyclin E) and the anti-apoptotic gene Bcl2, while upregulating the pro-apoptotic gene Bax. Moreover, exosomes derived from bovine serum were found to mediate these effects, as miR166a-3p-enriched exosomes inhibited cell proliferation and promoted apoptosis, further supporting the cross-kingdom role of plant-derived miRNAs in regulating biological processes. This study enhances the understanding of miRNA regulatory mechanisms, particularly the absorption and systemic transport of plant-derived miRNAs in dairy cows. The findings underscore the potential for using exogenous miRNAs, like miR166a-3p, in agricultural and medical contexts, warranting further investigation into their functions and cross-species interactions.