Messages stored in the bovine male gamete: effects of heat stress, role of epididymis-spermatozoa interactions and the paternal contribution to embryo development

• Grant number: 21/08759-2
• Support Opportunities: Regular Research Grants
• Start date: February 01, 2022
• End date: July 31, 2024
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Reproduction
• Principal Investigator: Felipe Perecin
• Grantee: Felipe Perecin
• Host Institution: Faculdade de Zootecnia e Engenharia de Alimentos (FZEA). Universidade de São Paulo (USP). Pirassununga , SP, Brazil
• Associated researchers: Flávio Vieira Meirelles ; Juliano Coelho da Silveira ; Luís Miguel Águila Paredes ; Maíra Bianchi Rodrigues Alves ; Maria Elena Arias Cea ; Ricardo Felmer ; Ricardo Perecin Nociti

Abstract

While morphological and functional sperm attributes are associated with semen quality and male fertility potential, sperm molecular features have recently been included as determinant for those factors. In this regard, sperm convey RNA molecules, mainly ncRNAs (non-coding RNAs), which are related to early embryonic development. Since sperm cells are typically assorted as transcriptionally inert because they display a highly-condensed DNA, these cells acquire most of RNA molecules during the transit across the epididymis mediated through extracellular vesicles (named epididymosomes) released by the epididymal epithelium. Using two different experimental models, we have shown that microRNAs (miRNAs), a specific subpopulation of ncRNAs, (1) are altered in sperm and extracellular vesicles (EVs) isolated from seminal plasma of bulls exposed to scrotal heat stress and (2) are delivered by the sperm from low fertility bulls to the embryo, influencing early embryonic development. However, the results of the first model were scanty to demonstrate if the molecular profile of the epididymal epithelium could also be altered by heat stress. Additionally, although we demonstrated in the second model the influence of the sperm molecular signature in embryonic development, we could not conclude about the involvement of EVs. From this, although our studies have demonstrated that the molecular profile from sperm and seminal plasma EVs are altered by heat stress, it remains to be known mechanisms leading to these alterations and their impact on embryonic development. Since the effects of heat stress are well described impairing sperm quality and male fertilization potential and are unknown regarding the epididymis-spermatozoa interactions mediated by the epididymosomes, the hypothesis here is that the heat stress triggers molecular changes in the epididymis and in the sperm cells, mediated by epididymosomes, and impact early embryonic development. It will be outlined two studies to shed light on this proposition. In Study 1, the effects of scrotal heat stress on the epididymis, spermatozoa and embryos' paternal transmitted traits will be investigated using an in vivo model. The aim of this study is to characterize the molecular changes (mainly in RNA levels) promoted by scrotal heat stress in epididymis, spermatozoa and paternal traits transmitted to preimplantation embryos. The results of this study will show new pathways involved in epididymis-spermatozoa interaction that impact embryonic development. In Study 2, the epididymis-spermatozoa interaction under heat stress conditions will be investigated in vitro model. The aim of this study is to investigate if the epididymis-spermatozoa interaction is impacted by altered epididymosomes. The results of this study will show the effects of heat stress on epididymosomes content and release by epididymal epithelium. The results of this project will provide new insights regarding the regulation of the molecular content of sperm cells and its impact on embryonic development. With these results, we expected to open new avenues to understand the paternal contribution to embryonic development and fertility in mammals. (AU)