Los espermatozoides de ratón realizan la exocitosis acrosomal en istmos proximal del oviducto

LA SPINA FA; ROMAROWSKI A; PUGA MOLINA L; VITALE A; HIROHASHI N; BUFFONE MG

Lima

Congreso; Reunión Bienal Asociación Latinoamericana de Investigadores en Reproducción Humana (ALIRH).; 2015

Asociación Latinoamericana de Investigadores en Reproducción Humana (ALIRH)

Mammalian sperm are not able to fertilize oocytes immediately after ejaculation; they must first undergo a complex process called capacitation in the female reproductive tract or in vitro. These changes include the development of hyperactivated motility and the ability to undergo acrosomal exocytosis (AE) in response to specific stimuli. Recent evidence demonstrated that most fertilizing sperm undergo AE before binding to the zona pellucida (ZP) of the eggs. However, the sites where fertilizing sperm could initiate AE and what stimuli trigger it remain unknown. Therefore, the aim of this study was to determine physiological sites of AE by using double transgenic mouse sperm, which carried EGFP in the acrosome and DsRed2 fluorescence in mitochondria. Using live imaging of EGFP/DsRed2 sperm during in vitro fertilization of cumulus-oocyte complexes, it was observed that most sperm in the cumulus did not undergo AE. In the ex-vivo experiments, the occurrence of AE within the female reproductive tract was evaluated in the physiological context where this process occurs. Most sperm that migrated through the uterotubal junction (UTJ) into the oviductal isthmus and formed the sperm reservoir were acrosome-intact; however, a significant number of sperm that reached the upper isthmus had undergone AE. In the ampulla, very few sperm were detected and only 5% of the sperm in this region were acrosome-intact. These results support our previous observations that sperm do not initiate AE close to or on the ZP, and further demonstrate that most sperm initiate AE in the upper segments of the oviductal isthmus.