Retinoic acid-induced differentiation of porcine prospermatogonia in vitro.

Spermatogenesis is an intricate developmental process occurring in testes by which spermatogonial stem cells (SSCs) self-renew and differentiate into mature sperm. The molecular mechanisms for SSC self-renewal and differentiation, while have been well studied in mice, may differ between mice and domestic animals including pigs. To gain knowledge about the molecular mechanisms for porcine SSC self-renewal and differentiation that have so far been poorly understood, here we isolated and enriched prospermatogonia from neonatal porcine testes, and exposed the cells to retinoic acid, a direct inducer for spermatogonial differentiation. We then identified that retinoic acid could induce porcine prospermatogonial differentiation, which was accompanied by a clear transcriptomic alteration, as revealed by the RNA-sequencing analysis. We also compared retinoic acid-induced in vitro porcine spermatogonial differentiation with the in vivo process, and compared retinoic acid-induced in vitro spermatogonial differentiation between pigs and mice. Furthermore, we analyzed retinoic acid-induced differentially expressed long non-coding RNAs (lncRNAs), and demonstrated that a pig-specific lncRNA, lncRNA-106504875, positively regulated porcine spermatogonial proliferation by targeting the core transcription factor ZBTB16. Taken together, these results would help to elucidate the roles of retinoic acid in porcine spermatogonial differentiation, thereby contributing to further knowledge about the molecular mechanisms underlying porcine SSC development and, in the long run, to optimization of both long-term culture and induced differentiation systems for porcine SSCs.

Potential dual protective effects of melatonin on spermatogonia against hexavalent chromium.

Hexavalent chromium (Cr (VI)) is a widely used metal and has been shown to cause male reproductive abnormalities. However, the underlying mechanisms for the Cr (VI)-induced reproductive toxicity remain incompletely understood. In this study, we investigated the spermatogonial damage caused by Cr (VI) as well as the protective effect of melatonin against Cr (VI)-triggered toxicity. We observed that Cr (VI) caused spermatogonial damage in a time- and dose-dependent manner. Results further showed that melatonin could protect spermatogonia from Cr (VI)-triggered damage via elimination of reactive oxygen species (ROS) as well as via suppression of ATM-p53 phosphorylation and the mitogen-activated protein kinase (MAPK) pathway. Prior administration of melatonin also prevented the Cr (VI)-caused enrichment of H3K9me3 in the Mad1, Mad2 and Bcl2 gene promoter regions, precluding the G2/M arrest and apoptosis in spermatogonia. Taken together, this study demonstrates that melatonin can effectively protect spermatogonia against the damage and against the histone modification changes induced by Cr (VI). This, along with the uncovered molecular mechanism, provide important implications for male infertility induced by environmental pollution.

Sperm-derived RNAs improve the efficiency of somatic cell nuclear transfer (SCNT) through promoting R-loop formation.

Mammalian sperm and oocytes are haploid cells that carry parental genetic and epigenetic information for their progeny. The cytoplasm of oocytes is also capable of reprograming somatic cells to establish totipotency through somatic cell nuclear transfer (SCNT). However, epigenetic barriers seriously counteract SCNT reprogramming. Here, we found that sperm-derived RNAs elevated chromatin accessibility of nuclear donor cells concurrent with the appearance of increased RNA amount and decreased cell proliferation, instead of activating DNA damage response. Additionally, tri-methylation of lysine 9 on histone H3 (H3K9me3) and the H3K9 methyltransferase SUV39H2 were significantly downregulated by the sperm-derived RNA treatment. Our findings thus raise a fascinating possibility that sperm RNA-induced R-loops may activate gene expression and chromatin structure, thereby promoting SCNT reprogramming.