The oviduct provides the environment to support gamete maturation, fertilisation and early embryo development. As there is a high incidence of early embryonic death in lactating dairy cows, this study compared expression of IGF family members in the oviduct between lactating Holstein-Friesian dairy cows (n=16, 81±2.4 days in milk) and nulliparous heifers (n=16, age 1.6±0.07 years) at three stages of the oestrous cycle: A) newly selected dominant follicle in the luteal phase, B) follicular phase before the LH surge and C) pre-ovulatory phase after the LH surge. Expression of IGF1, IGF2, IGF binding protein 2 (IGFBP2), IGFBP3 and IGFBP6 mRNA was determined in the ampulla of the oviduct. Oviduct side (ipsilateral or contralateral) with respect to the dominant follicle did not affect gene expression. Expression of IGF1 and all three IGFBPs increased significantly between the luteal and the pre-ovulatory phases, with no further significant alteration post-LH surge. Concentrations of circulating IGF1 were higher in heifers than in cows, as was the mRNA expression of IGF1, IGFBP3 and IGFBP6. The pre-LH surge rise in IGFBP2 mRNA was only observed in heifers. IGF2 expression was not influenced by either age or stage of cycle. These three IGFBPs are generally considered to inhibit IGF action. These results indicate tight regulation of IGF bioavailability in the oviductal environment around oestrus, with pronounced differences between cows and heifers, which are likely to influence early embryonic development. Further studies are required to assess the implications for embryo survival.
Theerawat Swangchan-Uthai, Siobhan W Walsh, Sarah L H Alexander, Zhangrui Cheng, Mark A Crowe, Alexander C O Evans, and D Claire Wathes
Noof Abdulrahman Alrabiah, Alexander C O Evans, Alan G Fahey, Niamh Cantwell, Patrick Lonergan, Janet McCormack, John A Browne, and Trudee Fair
Ovulation has been described as an inflammatory event, characterized by an influx of leukocytes into the ovulatory follicle and changes in the expression of immune factors in both the theca and granulosa tissue layers. Since information on this process is limited in cattle, our objective was to elucidate the contribution of the immune system to dominant follicle luteinization, ovulation and corpus luteum formation in cattle. Beef heifers (n=50) were oestrous synchronized, slaughtered and ovarian follicular or luteal tissue collected during a 96h window around ovulation. Follicular fluid cytokine concentration, temporal immune cell infiltration and inflammatory status were determined by Luminex multiplex analysis, immunohistochemistry and quantitative real time PCR-analysis, respectively, in pre- and peri-ovulatory follicular tissues. The concentrations of CXCL10 and VEGF-A were highest in pre-ovulatory follicular fluid samples. The pre and peri -ovulatory follicles play host to a broad repertoire of immune cells, including T-cells, granulocytes and monocytes. Dendritic cells were the most abundant cells in ovulatory follicular and luteal -tissue at all times. The mRNA expression of candidate genes associated with inflammation was highest in pre- and peri-ovulatory tissue, whereas tissue growth and modelling factors were highest in the post-ovulatory follicular and early luteal tissue. In conclusion, ovulation in cattle is characterized by the presence of neutrophils, macrophages and dendritic cells in the ovulatory follicle, reflected in compartmentalized cytokine and growth factor expression. These findings indicate a tightly regulated sterile inflammatory response to the LH surge in the ovulatory follicle which is rapidly resolved during early corpus luteum formation.