184 GDF9 mitigates LPS-induced negative effects during bovine oocyte maturation

Clinical metritis and mastitis caused by gram-negative bacteria such as Escherichia coli represent an important cause for decreased reproductive performance in dairy cows. Lipopolysaccharide (LPS), an outer cell wall component of gram-negative bacteria, accumulates in follicular fluid and negatively affects meiosis and mitochondrial function of oocytes, as well as their subsequent capacity to develop to the blastocyst stage. In contrast, the oocyte-secreted growth differentiation factor 9 (GDF9) acts as a key regulator of follicular development and its addition during bovine oocyte IVM increases developmental competence and the number of blastocysts produced. As one of the noncanonical signaling pathways of GDF9 is represented by the nuclear factor-kB (NF-kB), which is also a pathway used by LPS to mediate its effects, we hypothesized that GDF9 supplementation during IVM could mitigate the negative effects of LPS on bovine oocytes and restore blastocyst development. Bovine ovaries were collected at the slaughterhouse (n = 6 replicates), and oocytes (min. 50/group/replicate) underwent the following treatments during IVM: control, GDF9, LPS, and GDF9+LPS. Following IVM, standardized IVF and IVC were performed, and blastocyst formation was assessed 7 days after IVF. Data were analyzed using a General Linear Model followed by Bonferroni post-hoc tests in SPSS 29. As expected, LPS treatment decreased cumulus expansion and cleavage and blastocyst rates, as well as the percentages of code 1 embryos and transferable embryos compared with control and GDF9 treatment, respectively (P < 0.01 in all cases). The combination of GDF9+LPS increased the blastocyst rate and the percentage of code 1 embryos compared with LPS alone (P < 0.05 in both cases) and yielded similar results to control regarding all analyzed parameters (P > 0.05 in all cases). Addition of GDF9 during IVM led to similar results compared with control (P > 0.05), but higher blastocyst rate and percentage of code 1 embryos compared with GDF9+LPS (P < 0.01 in both cases). In conclusion, our results demonstrate that GDF9 addition during IVM of bovine oocytes mitigates the LPS-induced reduction in blastocyst rate and percentage of code 1 embryos, respectively. Further studies should clarify the mechanisms by which LPS and GDF9 interact during bovine oocyte maturation and whether similar observations can be made in cows naturally infected with E. coli.