Extended In Vitro Maturation Enhances Oocyte Developmental Competence but Alters Gene Expression in Bovine Embryos...

Area of Science:

• Veterinary Science
• Reproductive Biology
• Biotechnology

Background:

• In vitro maturation (IVM) is crucial for bovine oocyte development.
• Nuclear maturation speed (NMS) varies among oocytes, affecting developmental potential.
• Machine learning can predict NMS, enabling tailored IVM protocols.

Purpose of the Study:

• To determine the optimal IVM duration for bovine oocytes based on predicted NMS.
• To assess the impact of IVM duration on oocyte developmental competence and embryo quality.
• To correlate IVM duration with gene expression in resulting blastocysts.

Main Methods:

• Machine learning was used to classify bovine oocytes into fast- or slow-predicted NMS groups.
• Oocytes were subjected to IVM for 24, 28, or 32 hours.
• Developmental competence (cleavage, blastocyst formation) and embryo quality (gene expression) were evaluated.

Main Results:

• Extending IVM to 28 hours significantly improved cleavage rates and accelerated first cleavage timing in slow NMS oocytes.
• Blastocyst formation rates for slow NMS oocytes matured for 24 hours improved to levels comparable to fast NMS oocytes at 28 hours IVM.
• Extended IVM (28 and 32 hours) decreased the expression of pluripotency genes (NANOG, OCT4) in blastocysts, irrespective of NMS.

Conclusions:

• A 28-hour IVM duration enhances the developmental competence of slow NMS bovine oocytes.
• Optimizing IVM duration based on predicted NMS is key for efficient bovine embryo production.
• While improving developmental rates, extended IVM may compromise embryonic developmental potential by reducing pluripotency gene expression.