MicroRNAs espermáticos relacionados à fertilidade

Abstract

Spermatozoa is a cell type that carry much more than just male genomic DNA during the fertilization process. In recent years, epigenetic mechanisms related to sperm quality have been extensively studied. Among the mechanisms, microRNAs deserve to be highlighted because they act as powerful post-transcriptional regulation of their target genes, being correlated with spermatogenesis, sperm functionality and reproductive success in different species. It is hypothesized that changes in sperm kinetic and morphofunctional parameters, as well as in testicular physiology, may disturb sperm microRNA levels. Thus, the main objective was to elucidate whether the levels of microRNAs related to fertility is affected exogenous DNA transfected-sperm, and in sperm samples from transgenic animals overexpressing growth hormone. In the first study, through a systematic review of scientific literature, it was possible to identify the microRNAs let-7c, let-7d, let-7g, miR-1, miR-100, miR-148b-3p, miR-151-3p, miR-20a, miR-26a-5p, miR-30b-5p, miR-30c-5p, miR-34c-5p, and miR-378, with different levels according to the contrasting sperm motility profile in livestock species, such as cattle and pigs. In a second study, through sperm-mediated gene transfer technique, it was observed that transfection of exogenous DNA associated with cationic nanostructure affects not only kinetic and morphofunctional parameters, but also the microRNA levels related to sperm functionality in bovine, such as, bta-miR-30b-5p and bta-miR-34c. Finally, in a third study, using a transgenic zebrafish model overexpressing growth hormone, it was observed a reduction in sperm quality parameters and a modulation of twenty two sperm microRNAs levels, among them, dre-miR-20a-5p, dre-miR-202-5p, dre-miR-146b, and dre-miR-200a-5p. Based on the results achieved using bovine and zebrafish model organisms, it was possible to infer that sperm exogenous DNA uptake by sperm, and physiological changes in testicular tissue affects some microRNAs. Finally, it is important to note that a better understanding of relationship of sperm microRNAs with fertility becomes a stimulus for validation and using these small RNA molecules as a biotechnological tool.