Unlocking Oocyte Potential: L-Asp's Protective Role Against Heat-Induced Meiotic Disruption

Global warming has made heat stress (HS) an unavoidable challenge in livestock production, significantly impacting animal feed intake, growth, reproduction, and health. Germ cells, including oocytes, are particularly sensitive to HS, with impaired oocyte maturation being a primary cause of reproductive dysfunction. This study examines the effects of HS on porcine oocyte meiotic maturation and evaluates the protective role of L-aspartic acid (L-Asp) supplementation during this process. Here, we report that L-Asp supplementation improves the quality of porcine oocytes under heat stress. More specifically, we found that heat stress resulted in oocyte maturation failure by disturbing the dynamics of meiotic organelles, including the spindle assembly, chromosome structure and mitochondrial function. Moreover, heat stress triggered the overproduction of reactive oxygen species (ROS) and caused DNA damage, resulting in apoptosis in oocytes and halting embryonic development. Importantly, our findings showed that L-Asp supplementation during heat stress alleviated the meiotic defects in porcine oocyte maturation. These findings demonstrate that L-Asp supplementation is a beneficial strategy for improving oocyte quality under HS by facilitating both nuclear and cytoplasmic maturation. This approach holds promise as a practical strategy for mitigating the reproductive challenges posed by global warming in livestock production. Overall design: After L-Asp treatment, MII oocytes were collected from the control, HS, and L-Asp-supplemented groups (25 oocytes per group). The single-cell collection mixture contained cell lysate to disrupt the cell membranes and release RNA and RNase inhibitors to prevent RNA degradation. Total RNA was isolated, and reverse transcription was performed using nucleic acids bound to Oligo dT to synthesize first-strand cDNA. PCR amplification of the first-strand cDNA enriched the nucleic acids, and the amplified products were purified for library construction. The library preparation process included DNA fragmentation, end repair, the addition of “A” splices, PCR amplification, and quality control. The constructed library was sequenced on an Illumina platform