Investigation The Changes In Chromatin Configuration During In Vitro Growth Of Forcine Oocyte Derived From Pre-Antral Follicle (0.3-0.7mm)

Abstract

High-quality oocytes are necessary for the efficient creation of embryos from IVG oocytes; thus, the researchers worked to perfect the in vitro settings for their development. As one may anticipate, a significant factor in determining the quality of the mature oocyte is the immature oocyte's quality. Therefore, high-quality immature oocytes were identified using morphological and biochemical analyses. According to earlier research, the follicular size and chromatin profile of mammalian oocytes has been linked to the completion of meiosis. Based on the chromatin architecture of GV oocytes in antral follicles, two kinds may be distinguished: two types of nuclei exist: the surrounded nucleolus (SN) type, in which the GV chromatin surrounds the nucleolus in a ring, and the non-surrounded nucleolus (NSN) type, in which the GV chromatin is distributed around the nucleolus. However, only a few analysts have taken pre-Antral follicles, 0.3-0.7mm, particularly in IVG. Therefore, this study will focus on performing chromatin morphological classification of the pre-Antral follicle and look at the development of porcine oocytes to clarify the effects of porcine oocyte chromatin formation on growing ability. The OGCs were cultured in vitro in two different time marks, including 7 and 10 days. After each time mark, oocyte diameter and cells surrounding proliferation were examined. As a result, the oocyte size on day 10 was significantly larger than on day 7, although all treatments could not reach the size of fully-grown oocytes. The proliferation of cells surrounding was increased on day 10. After each time point, the oocytes were stained with orcein staining and immunofluorescent staining with histone acetylation to determine the chromatin configuration. All chromatin phases, including filamentous chromatin (FC), stringy chromatin (SC), and germinal vesicle (GV), were exhibited by the oocytes. Oocytes cultured for ten days (50.9%) had a higher proportion of the GVI stage than oocytes cultured for seven days (13.3%). And the ratio of GVI of oocytes cultured for 7 and 10 days was significantly lower (P < 0.05) than that of fully-grown oocytes (80.3%). The proportion of GVI of oocytes cultured for ten days corresponds to the ratio of GVI stage of oocytes derived from 2-<3mm follicles (41.1%). In conclusion, on day 7 of IVG, the majority were FC or SC stage, and on day ten, the most significant proportion of GVI.