Evaluation of the in vitro fertilization potential of bovine sperm preconditioned in medium supplemented with oviductal fluid

• Grant number: 24/05440-3
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: September 01, 2024
• End date: August 31, 2025
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Reproduction
• Principal Investigator: Maíra Bianchi Rodrigues Alves
• Grantee: Maria Julia Aparecida Daniel
• Host Institution: Faculdade de Ciências Agrárias e Veterinárias (FCAV). Universidade Estadual Paulista (UNESP). Campus de Jaboticabal. Jaboticabal , SP, Brazil

Abstract

The cattle livestock in Brazil is one of the sectors that significantly contributes to the country's economy. With this in mind, it is evident the need for the development and improvement of new techniques to enhance livestock productivity. Out of the techniques, we can highlight reproductive biotechniques, such as in vitro embryo production, which has proven to be an important tool for genetic progression and herd productivity. However, this biotechnique can still be improved to result in the production of embryos with higher viability, since blastocysts produced in vitro have lower pregnancy rates after transfer than those produced in vivo. One of the differences is that spermatozoa do not establish contact with the female reproductive tract at the moment preceding fertilization in vitro. Although poorly explored, this period of interaction could positively conditionate sperm cells by contacting oviductal factors, as occurs in vivo. Examples of these oviductal factors include glycosaminoglycans (GAGs), which are components of the uterine-oviductal microenvironment and are essential for sperm capacitation and acrosomal reaction. In vitro, GAGs are replaced by heparin, and preconditioning spermatozoa with heparin and/or other oviductal components could positively impact in vitro embryo production. To explore the possible effects of this preconditioning, two experiments will be conducted in this project. In the first experiment, the fertilization and polyspermy rates will be evaluated after spermatozoa incubation previous to in vitro fertilization (IVF) step in IVF medium containing 0 µg/mL, 5 µg/mL, and 10 µg/mL of heparin. In the second experiment, the IVF medium that results in the lowest polyspermy rate in experiment 1 will be used for spermatozoa preconditioning in a medium supplemented with oviductal fluid (OF). For this, two pools of oviductal fluid (OF) will be formed from 20 reproductive tracts of bovine females, to obtain one pool with OF from females in the follicular phase and another from females in the luteal phase. Both pools will be formed after perfusion of the isthmus region of the oviduct with PBS. Subsequently, spermatozoa will be incubated in three treatments with IVF medium supplemented with (1) 10% of follicular phase OF pool, (2) 10% of luteal phase OF pool, or (3) 10% PBS (control). Fertilization and polyspermy rates (12 hours after IVF), cleavage (D4), and blastocyst (D7) will be evaluated. It is expected that the preconditioning of spermatozoa with follicular phase oviductal fluid will result in better fertilization rates and embryo production.