Abstract: The purpose of this study was to investigate the effect of lysophosphatidic acid(LPA) with different concentrations on the expression of hyaluronate synthase 2(HAS2), prostaglandin-endoperoxide synthase 2(PTGS2) and pentraxin 3(PTX3) in Yak cumulus cells (YCCs). The YCCs of healthy adult (3-4 years old) female yaks were taken as the research object. YCCs in logarithmic growth phase were taken, and different concentrations of LPA (blank control, negative control, 5, 15, 30, and 50 μmol·L^-1) were applied to the cultured YCCs in vitro. After 12, 24, 36, and 48 hours of cultivation, CCK-8 was used to detect the cellular viability of YCCs. The relative expression levels of HAS2, PTGS2, and PTX3 mRNA and protein in YCCs were detected by RT-qPCR and Western-blot assays. Immunofluorescence staining was used to detect the distribution of cumulus dilatation factors HAS2, PTGS2, and PTX3 in YCCs. In this experiment, each treatment group had 3 replicates. The results showed that, LPA incubation for 12, 24, 36, and 48 h had a significant promoting effect on the viability of YCCs. When the incubation time was 24 h, LPA had the most significant promoting effect on the viability of YCCs. Compared to the control group, when the LPA concentration was 15 μmol·L^-1, the viability of YCCs increased most significantly at different incubation times(P<0.05). Compared with the blank control group, the highest relative expression levels of HAS2, PTGS2, and PTX3 mRNA and protein were observed(P<0.05) when the LPA concentration was 15 μmol·L^-1, and the fluorescence intensity of HAS2, PTGS2, and PTX3 in YCCs was significantly enhanced. However, when the LPA concentration exceeded 15 μmol·L^-1, the relative expression levels of HAS2, PTGS2, and PTX3 mRNA and protein gradually decreased. The study results suggests that LPA has a promoting effect on the viability of YCCs. When the incubation time is 24 hours and the LPA concentration is 15 μmol·L^-1, the viability improvement is the most significant(P<0.05). LPA can enhance the expression of the cumulus expansion factors HAS2, PTGS2, and PTX3 in YCCs, and its effect is dose-dependent, with the optimal concentration being 15 μmol·L^-1. The research results provide a theoretical basis for elucidating the molecular mechanism of LPA promoting the expansion of yak cumulus cells, and for further improving the quality of yak oocytes and the success rate of in vitro fertilization (IVF).

Key words: yak, lysophosphatidic acid, cumulus cells, cumulus expansion factors