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Oxidative stress is a significant factor affecting reproductive efficiency in dairy cows, contributing to conditions such as endometritis that impair fertility and milk production. This study investigates the molecular mechanisms by which bta-let-7d modulates the oxidative stress responses induced by potassium permanganate (KMnO₄) in bovine endometrial epithelial cells (BEECs). Using KMnO₄ to induce oxidative stress, we observed significant increases in reactive oxygen species (ROS) and malondialdehyde (MDA) levels, accompanied by decreased activities of the antioxidant enzymes glutathione peroxidase (GPx) and superoxide dismutase (SOD). Quantitative PCR and Western blot analyses indicated a negative correlation between IGF1R and bta-let-7d expression in oxidative-stress-affected tissues, suggesting opposing roles in managing stress responses. Following KMnO₄ treatment, there was marked downregulation of anti-apoptotic genes and an upregulation of pro-apoptotic markers, alongside diminished antioxidant capacity. Mechanistically, bta-let-7d targets IGF1R, leading to the suppression of the PI3K/AKT signaling pathway and exacerbating oxidative damage. In vivo experiments further confirmed the impact of KMnO₄ exposure on IGF1R expression. These findings provide novel insights into the mechanisms by which KMnO₄ induces oxidative stress and apoptosis in bovine uterus. They highlight the potential for therapeutic strategies targeting the bta-let-7d/IGF1R axis to enhance reproductive health management in dairy cows, offering a promising avenue for mitigating oxidative-stress-related reproductive disorders. Full article

Successful fertilization and subsequent embryo development rely on complex molecular processes starting with the development of oocyte competence through maturation. MicroRNAs (miRNAs) are small non-coding RNA molecules that function as gene regulators in many biological systems, including the oocyte and embryo. In order to further explore the roles of miRNAs in oocyte maturation, we employed small RNA sequencing as a screening tool to identify and characterize miRNA populations present in pools of bovine germinal vesicle (GV) oocytes, metaphase II (MII) oocytes, and presumptive zygotes (PZ). Each stage contained a defined miRNA population, some of which showed stable expression while others showed progressive changes between stages that were subsequently confirmed by quantitative reverse transcription polymerase chain reaction (RT-PCR). Bta-miR-155, bta-miR-222, bta-miR-21, bta-let-7d, bta-let-7i, and bta-miR-190a were among the statistically significant differentially expressed miRNAs (p < 0.05). To determine whether changes in specific primary miRNA (pri-miRNA) transcripts were responsible for the observed miRNA changes, we evaluated pri-miR-155, -222 and let-7d expression. Pri-miR-155 and -222 were not detected in GV oocytes but pri-miR-155 was present in MII oocytes, indicating transcription during maturation. In contrast, levels of pri-let-7d decreased during maturation, suggesting that the observed increase in let-7d expression was likely due to processing of the primary transcript. This study demonstrates that both dynamic and stable populations of miRNAs are present in bovine oocytes and zygotes and extend previous studies supporting the importance of the small RNA landscape in the maturing bovine oocyte and early embryo. Full article