Transcriptional Profiling of Cumulus Cells From FLI-Matured Porcine Oocytes Identifies Junctional Genes as Key Components in Oocyte Maturation

Abstract

In vitro oocyte maturation and embryo culture are critical for preserving and expanding genetic lines, and are necessary to produce genetically engineered pigs for biomedical and agricultural purposes. However, suboptimal in vitro conditions compromise oocyte and embryo viability. Recent improvements to in vitro maturation medium, including the addition of FGF2, LIF, and IGF1 (FLI), have increased the number of oocytes that reached the metaphase II stage, doubled the number of oocytes that reached the blastocyst stage, and quadrupled the number of piglets born after embryo transfer. Despite these benefits, the underlying cellular mechanisms remain not fully understood. Given the essential role of cumulus cells (CCs) in oocyte maturation, we investigated how FLI affects CCs gene expression. Cumulus-oocyte complexes were matured for 24 h in control or FLI media, and CCs from oocytes that reached the blastocyst stage underwent RNA sequencing. FLI altered 1257 transcripts (423 upregulated, 834 downregulated; adj-p < 0.05), with enrichment of junctional communication genes and downregulation of extracellular matrix organization. Immunofluorescence confirmed increased TJP1, TJP2, and GJA4 in FLI-treated complexes. Additionally, cortical granule localization suggested enhanced cytoplasmic maturation with FLI supplementation. These findings indicate that FLI promotes CC communication and supports improved oocyte competence in porcine in vitro maturation.