Effects of cumulus cells on the in vitro cytoplasmic maturation of immature oocytes in pigs

Seon Ah Ryu; Song Baek; Keun Cheon Kim; Eun Song Lee; Seung Tae Lee

doi:10.1016/j.theriogenology.2023.04.021

Effects of cumulus cells on the in vitro cytoplasmic maturation of immature oocytes in pigs

Theriogenology. 2023 Aug:206:133-139. doi: 10.1016/j.theriogenology.2023.04.021. Epub 2023 May 12.

Authors

Seon Ah Ryu¹, Song Baek¹, Keun Cheon Kim², Eun Song Lee³, Seung Tae Lee⁴

Affiliations

¹ Department of Applied Animal Science, Kangwon National University, Chuncheon, 24341, Republic of Korea.
² Department of Obstetrics, Gynecology and Women's Health, University of Missouri, Columbia, 65201, USA.
³ College of Veterinary Medicine, Kangwon National University, Chuncheon, 24341, Republic of Korea. Electronic address: eslee@kangwon.ac.kr.
⁴ Department of Applied Animal Science, Kangwon National University, Chuncheon, 24341, Republic of Korea; Kustogen, Chuncheon, 24341, Republic of Korea. Electronic address: stlee76@kangwon.ac.kr.

PMID: 37209433
DOI: 10.1016/j.theriogenology.2023.04.021

Abstract

The exposure of cumulus cells to nuclear matured oocytes can be regulated through the forced delay of nuclear maturation or the alteration of in vitro maturation (IVM) time in cumulus-oocyte complexes (COCs). However, to date, no evidence has been presented for the enhancement of cytoplasmic maturation by them, indicating irrelevance of cumulus cells in cytoplasmic maturation. Therefore, in order to identify the requirement of cumulus cells in achieving the cytoplasmic maturation of immature oocytes, this study investigated the effects of cumulus cells on the in vitro cytoplasmic maturation of oocytes within COCs derived from porcine medium antral follicles (MAFs) post-the completion of nuclear maturation. For these, with IVM of COCs for 44 h (control), cumulus cell-free oocytes with completed nuclear maturation were in-vitro-matured additionally for 0, 6, or 12 h, and then a variety of factors representing the cytoplasmic maturation of oocytes were analyzed and compared. As the results, the IVM of COCs for 32 h showed complete nuclear maturation and incomplete cytoplasmic maturation. Moreover, after the removal of cumulus cells from COCs with the completion of nuclear maturation, IVM for an additional 6 or 12 h resulted in significant increases in the size of the perivitelline space, the proportion of oocytes with a normal intracellular mitochondrial distribution and a normal round first polar body, and the preimplantation development into the 2-cell and blastocyst stages after parthenogenetic activation. Simultaneously, they showed significant reduction in the level of intracellular reactive oxygen species and no significant differences in the total number of blastocysts. Furthermore, oocytes obtained by this approach did not significantly differ from control oocytes produced by IVM of COCs for 44 h. Our results demonstrate that the cumulus cells enclosing COCs derived from porcine MAFs are not essential for the completion of cytoplasmic maturation after complete nuclear maturation by COCs.

Keywords: Cumulus cells; Cytoplasm; Nuclear; Oocyte maturation; Pig.

MeSH terms

Animals
Cumulus Cells / physiology
Cytoplasm
Embryonic Development
Female
In Vitro Oocyte Maturation Techniques* / methods
In Vitro Oocyte Maturation Techniques* / veterinary
Oocytes* / physiology
Ovarian Follicle
Swine