Effect of vitrification temperature and cryoprotectant concentrations on the mRNA transcriptome of bovine immature oocytes

The present study mainly aimed to investigate the effect of vitrification temperature (VT) and cryoprotective agent concentrations (CPAs) on the mRNA transcriptome of bovine immature oocytes (BIOs). Cumulus oocyte complexes (COCs) were randomly divided into the following five groups: fresh oocytes (control), oocytes vitrified in liquid helium (LHe; -269?) with 5.6 M CPAs (LHe 5.6 M), oocytes vitrified in LHe with 6.6 M CPAs (LHe 6.6 M), oocytes vitrified in liquid nitrogen (LN; -196?) with 5.6 M CPAs (LN 5.6 M), and oocytes vitrified in LN with 6.6 M CPAs (LN 6.6 M). mRNA transcriptomes of each sample were analyzed by Smart-seq4, and the di?erentially expressed genes (DGEs) were detected by edgeR (p=0.05; fold-change=2). Compared with the control group, 505 DGEs were detected with 342 up-regulated and 163 down-regulated genes in LHe 5.6 M; 609 DGEs were detected with 493 up-regulated and 116 down-regulated gene in LHe 6.6 M; 218 DGEs were determined with 101 up-regulated and 117 down-regulated genes in LN 5.6 M; and 221 DGEs were detected with 104 up-regulated and 117 down-regulated genes in LN 6.6 M. LHe vitrification affected the mRNA transcriptome of vitrified BIOs mainly by up-regulating gene expression. Reduced CPAs (5.6 M) decreased the effect of vitrification on mRNA transcriptome when LHe vitrification was used. Among all the DGEs closely related to bovine immature oocytes, the genes possibly related to VT were ND2, MPV17L2, PIF1, LPIN1, IMP3, BRD1, DCTN3, DERA, ATP7B, NEK5, HVCN1 and MARK2. The gene that may be associated with CPAs is CC2D2A. Genes that may be affected by both VT and CPAs were PGK1, SLC7A3, FITM2, NPM3, ISCU, CWC15 and PSAP. DERA was up-regulated when reduced VT (-269 °C) was used, which may have contributed to the recovery and stress prevention of vitrified oocyte. Overall design: Examination the effect of vitrification temperature and cryoprotectant concentrations on the mRNA transcriptome of bovine immature oocytes