Research Of The Localization And Expression Of EGF And EGFR In Bovine Estrus Cycle

Epidermal growth factor(EGF)is one of the important regulatory factors of EGF family.Studies on its reproductive regulation in animals indicate that EGF binds to the EGF domain of epidermal growth factor receptor(EGFR).It can effectively inhibit the apoptosis of follicular cells,promote the proliferation of granulosa cells and the maturation of oocytes,so as to induce ovulation process.It is of great significance to make clear the development process and regulation mechanism of ovarian follicles in order to improve the fecundity of female animals and cultivate excellent offspring.At present,there is no systematic study on the expression,distribution and functional significance of EGF and EGFR in cow ovary.In this study,the microstructure and ultrastructure of ovarian follicles in estrus cycle of dairy cows were observed by means of histology and transmission electron microscopy(TEM).The cellular localization and relative expression of EGF and EGFR in follicles and luteum of ovaries in estrus cycle of dairy cows were observed by immunohistochemical staining.RT-PCR technique was used to study the expression of EGFR mRNA in ovarian follicles and corpus luteum in order to explore its functional significance in the development of ovarian follicles in estrus cycle of dairy cows.The results are as follows:1.There was no significant difference in micromorphology between follicular follicles and luteal follicles in bovine estrus cycle.During the observation of subcellular structure of follicles,a large number of interstitial junctions and microvilli were observed between oocytes and surrounding granulosa cells at the stage of primordial follicles,and even desmosomes could be observed.This indicates that there is a close material exchange and information exchange between the oocytes and the surrounding granulosa cells at this stage.2.During estrus cycle,the relative protein and mRNA expression of EGF and EGFR in follicles changed regularly in different days of estrus cycle in bovine ovaries.At the early stage of follicular growth wave,the relative protein expression of EGF and its receptor in tertiary follicles was higher than that in other follicles,but the expression of EGFR mRNA in all follicles had no significant change.The expression of EGFR mRNA in secondary follicles increased at the stage of follicular growth after the beginning of follicular growth wave.In the middle stage of follicular growth wave(dominant follicular selection stage),the expression of EGF and EGFR in oocytes and granulosa cells of tertiary follicles was significantly increased,and the expression of EGFR mRNA in tertiary follicles of follicular stage was also significantly increased.In the corpus ovaries,the growth of follicles is inhibited in the stage of corpus development.When the corpus is in the stage of degeneration,the expression of EGF and EGFR in the secondary follicles is higher than that in the secondary follicles,and the expression of EGFR is higher in the secondary follicles than in the secondary follicles when the corpus is in the stage of degeneration.The morphological results showed that oocytes had close material and information exchange with the surrounding granulosa cells at the early stage of follicular development.The expression of protein and mRNA in ovarian follicles during estrus cycle suggested that it can promote follicular development in follicular growth wave and may mediate the selection of dominant follicles.