MiR-21-5p ameliorates Busulfan-induced testicular dysfunction and maintains spermatogenesis1

Spermatogonial stem cells (SSCs) are the key to maintaining production of the sperms and healthy offsprings, and also treating breeding livestock's reproductive damage and infertility. MicroRNAs act a decisive role in regulating gene expression in many cells and tissues, including in processes such as proliferation, self-renewal, differentiation, and apoptosis of stem cells. However, the miRNA mechanism in regulation of SSCs is still unclear. Here, high-throughput sequencing was used to identify specific miRNAs. We confirmed that miR-21-5p was concentrated in both goat and mouse SSCs, and enhanced the proliferation and antiapoptotic ability of SSCs. In vivo experiments have shown that miR-21-5p resisted the damage of the chemotherapy drug Busulfan to germ cells, ameliorated Busulfan-induced testicular dysfunction, and maintained spermatogenesis. Further RNA-seq and target gene prediction revealed that SPRY1 and FASLG are targets of miR-21-5p, thereby activating downstream signaling pathways such as MAPK/ERK, PI3K-AKT, and apoptosis. In summary, miR-21-5p is crucial for the self-renewal and maintenance of SSCs. This study provides new avenues for treating breeding livestock's reproductive damages, infertility, oligospermia, and other conditions.