Distinct Heat Stress Responses of Porcine Cumulus Cells and The Oocyte Is Associated With Disrupted Intercellular Communication

Abstract

Cumulus cells (CCs) play critical roles in oocytes maturation through intercellular communication. The adverse effect of heat stress (HS) on oocyte maturation has been well documented, whereas the HS responses of CCs and the oocytes in association with cumulusoocyte communication remain unclear. In this study, cumulus‐oocyte complexes (COCs) were subjected to HS at 42°C for 24 h during in vitro maturation. Cumulus expansion was impaired and oocyte quality was reduced with lower survival rate, polar body extrusion rate and early embryo developmental potentials. Oocytes and cumulus cells isolated from COCs demonstrated distinct responses to HS. In oocytes, mitochondrial DNA (mtDNA)‐encoded genes and heat shock protein (HSP)‐related genes were significantly down‐regulated, with significantly lower ATP content yet higher mitochondria reactive oxygen species (mROS) and caspase 3 activity. In contrast, CCs isolated from heat‐exposed COCs showed significant activation of mtDNAencoded genes and HSP‐related genes, which was accompanied by increased ATP content and caspase 3 activity yet unaltered mROS content. When denuded oocytes and isolated CCs were subjected to HS separately, ATP content in denuded oocytes decreased more extensively than that in oocytes isolated from heat‐exposed COCs. Also, mROS was significantly increased in CCs but not in denuded oocytes, which coincided with less pronounced increase of caspase 3 in denuded oocytes. Moreover, F‐actin, a marker of trans‐zonal projections, and occludin, a tight junction protein, and their co‐localization, were significantly reduced in heat‐exposed COCs. These results indicate that cumulus cells and oocytes show distinct HS responses, indicating disrupted cumulus‐oocytes communication in heat‐exposed porcine oocytes.Support or Funding InformationThis work was supported by the National Key Research and Development Program of China (2016YFD0500502), the National Basic Research Program of China (2014CB138502), the Priority Academic Program Development of Jiangsu Higher Education Institutions, and Jiangsu Collaborative Innovation Center of Meat Production and Processing, Quality and Safety Control.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.