Physiological and Functional Roles of Neurotrophin-4 During In Vitro Maturation of Porcine Cumulus-Oocyte Complexes

Mirae Kim; Seon-Ung Hwang; Junchul David Yoon; Joohyeong Lee; Eunhye Kim; Lian Cai; Hyerin Choi; Dongjin Oh; Gabsang Lee; Sang-Hwan Hyun

doi:10.3389/fcell.2022.908992

Physiological and Functional Roles of Neurotrophin-4 During In Vitro Maturation of Porcine Cumulus-Oocyte Complexes

Front Cell Dev Biol. 2022 Jul 8:10:908992. doi: 10.3389/fcell.2022.908992. eCollection 2022.

Authors

Mirae Kim^{1

2}, Seon-Ung Hwang³, Junchul David Yoon⁴, Joohyeong Lee^{1

2}, Eunhye Kim⁵, Lian Cai^{1

6}, Hyerin Choi^{1

2}, Dongjin Oh^{1

2}, Gabsang Lee⁷, Sang-Hwan Hyun^{1

2

6}

Affiliations

¹ Veterinary Medical Center and College of Veterinary Medicine, Laboratory of Veterinary Embryology and Biotechnology (VETEMBIO), Chungbuk National University, Cheongju, South Korea.
² Institute of Stem Cell & Regenerative Medicine (ISCRM), Chungbuk National University, Cheongju, South Korea.
³ Department of Biological Sciences, College of Arts and Sciences, University at Buffalo, The State University of New York (SUNY), Buffalo, NY, United States.
⁴ Division of Animal Sciences, University of Missouri, Columbia, MO, United States.
⁵ Laboratory of Molecular Diagnostics and Cell Biology, College of Veterinary Medicine, Gyeongsang National University, Jinju, South Korea.
⁶ Graduate School of Veterinary Biosecurity and Protection, Chungbuk National University, Cheongju, South Korea.
⁷ Department of Neurology, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, United States.

Abstract

Neurotrophin-4 (NT-4), a granulosa cell-derived factor and a member of the neurotrophin family, is known to promote follicular development and oocyte maturation in mammals. However, the physiological and functional roles of NT-4 in porcine ovarian development are not yet known. The aim of this study was to investigate the physiological role of NT-4-related signaling in the in vitro maturation (IVM) of porcine cumulus-oocyte complexes (COCs). The NT-4 protein and its receptors were detected in matured porcine COCs via immunofluorescence analysis. NT-4 was shown to promote the maturation of COCs by upregulating NFKB1 transcription via the neurotrophin/p75^NTR signaling pathway. Notably, the mRNA expression levels of the oocyte-secreted factors GDF9 and BMP15, sperm-oocyte interaction regulator CD9, and DNA methylase DNMT3A were significantly upregulated in NT-4-treated than in untreated porcine oocytes. Concurrently, there were no significant differences in the levels of total and phosphorylated epidermal growth factor receptor and p38 mitogen-activated protein kinase between NT-4-treated and untreated cumulus cells (CCs); however, the level of phosphorylated ERK1/2 was significantly higher in NT-4-treated CCs. Both total and phosphorylated ERK1/2 levels were significantly higher in NT-4-treated than in untreated oocytes. In addition, NT-4 improved subsequent embryonic development after in vitro fertilization and somatic cell nuclear transfer. Therefore, the physiological and functional roles of NT-4 in porcine ovarian development include the promotion of oocyte maturation, CC expansion, and ERK1/2 phosphorylation in porcine COCs during IVM.

Keywords: cumulus cell; in vitro fertilization; in vitro maturation; neurotrophin-4; oocyte; pig; somatic cell nuclear transfer.