Impact of reducing lipid content during in vitro embryo production: A systematic review and meta-analysis.

There is still no consensus regarding the role of lipid modulators during in vitro embryo production. Thus, we investigated how lipid reducers during the in vitro maturation of oocytes (IVM) or in vitro culture (IVC) of embryos impact their cryotolerance. A literature search was performed using three databases, recovering 43 articles for the systematic review, comprising 75 experiments (13 performed in IVM, 62 in IVC) and testing 13 substances. In 39 % of the experiments, an increase in oocyte and/or embryo survival after cryopreservation was reported, in contrast to 48 % exhibiting no effect, 5 % causing negative effects, and 8 % influencing in a dose-dependent manner. Of the 75 experiments extracted during IVM and IVC, 41 quantified the lipid content. Of those that reduced lipid content (n = 26), 50 % increased cryotolerance, 34 % had no effect, 8 % harmed oocyte/embryo survival, and 8 % had different results depending on the concentration used. Moreover, 28 out of the 43 studies were analyzed under a meta-analytical approach at the IVC stage in cattle. There was an improvement in the cryotolerance of bovine embryos when the lipid content was reduced. Forskolin, l-carnitine, and phenazine ethosulfate positively affected cryotolerance, while conjugated linoleic acid had no effect and impaired embryonic development. Moreover, fetal bovine serum has a positive impact on cryotolerance. SOF and CR1aa IVC media improved cryotolerance, while mSOF showed no effect. In conclusion, lipid modulators did not unanimously improve cryotolerance, especially when used in IVM, but presented positive effects on cryotolerance during IVC when reaching lipid reduction.

Effect of antifreeze protein I in the freezing solution on in vivo-derived sheep embryos.

This study evaluated the effects of different antifreeze protein type I (AFP I) concentrations added to a slow freezing solution in sheep in vivo-derived embryos. Good-quality embryos were allocated into: AFP-free (CONT); 0.1 µg/mL of AFP I (AFP0.1); or 0.5 µg/mL of AFP I (AFP0.5). After thawing, embryos were in vitro cultured (IVC) for 48 h. At 24 h and 48 h of IVC, dead cells and apoptosis, mitochondrial activity, intracellular reactive oxygen species (ROS), and glutathione (GSH) evaluations were performed. At 24 h, evaluated embryos were submitted to RT-qPCR for metabolism (SIRT2, PRDX1, OCT4, CDX2) and quality (AQP3, CDH1, HSP70, BAX, BCL2) genes. The in vitro survival rate was 56% (22/39) for CONT, 60% (32/53) for AFP0.1, and 53% (23/43) for AFP0.5 (p > 0.05). A tendency (p = 0.09) for a higher blastocyst hatching rate was noted in AFP0.1 (62%) compared to AFP0.5 (33%), and both groups were similar to CONT (50%). An increased (p < 0.05) mitochondrial activity at 24 h was observed in AFP0.1 compared to CONT. No differences (p > 0.05) were observed in oxidative stress homeostasis and viability between treatments. A downregulation (p < 0.05) of CDH1 in AFP0.1 and a downregulation of AQP3 in AFP0.5 were observed in comparison to the other groups. An upregulation (p < 0.05) was detected in HSP70 and BCL2 on AFP0.5 compared to AFP0.1 group. The addition of AFP I in slow freezing solution can benefit cryopreserved sheep in vivo-derived embryos, without affecting embryonic survival.