Analysis of DNA Fragmentation of Porcine Embryos Exposed to Cryoprotectants

Abstract

The chemical toxicity of cryoprotectants to porcine embryos was examined by the evaluation of survival and DNA damage after exposure to cryoprotectants. Porcine blastocysts were exposed to 10% of ethylene glycol (EG), 1,2-propanediol (PD) or glycerol (GLY) for 1 h at room temperature (23-25 degrees C) and then cultured in vitro for 24 h. The survival rates of blastocysts exposed to PD and GLY were significantly lower than those of control blastocysts in which the embryos were exposed to carrier solution without cryoprotectants. Significantly more DNA-fragmented nuclei occurred in the cryoprotectant-exposed blastocysts, compared with the control blastocysts. Moreover, the indices of DNA-fragmented nuclei in the blastocysts without blastocoele re-formation after culture were significantly higher than those with blastocoele re-formation, irrespective of the exposure treatment. These results indicate that the exposure of porcine blastocysts to cryoprotectant decreases the survival rates and increases the DNA-fragmented nuclei in embryos.

Comparison of sucrose and trehalose media modification as an update of oocyte vitrification: A study of apoptotic level

“…In addition, the results of this study indicated that the exposure to the 16.5% EG, 16.5% DMSO and 0.5 mol/l trehalose as cryoprotectant media decreased their viability and increased the number of DNA-fragmented nuclei in the oocytes, lesser than sucrose. Moreover, this study confirmed the result of Rajaei et al, about the DNA fragmentation of embryos exposed to cryoprotectants [17]. …”

“…Furthermore, the high concentration of cryoprotectant media has potential toxicity and could be harmful to the oocytes [14,15]. Previous studies have shown that the purpose of diverse concentrations of cryoprotectant and thermal-cooling alteration could generate adverse effect on apoptosis [16,17]. If the apoptosis or programmed cell death attains a particular threshold, it may damage the oocytes.…”

Evaluation of post-thaw DNA integrity of mouse blastocysts after ultrarapid and slow freezing

“…Those investigators did not examine the degree of blastocysts expansion before considering the DNA damage, and no evaluation was made for blastocysts that were cryopreserved by slow freezing. As reported by Rajaei et al, the mere exposure of blastocysts to any of the cryoprotectants (DMSO, ethylene glycol, propanediol) without cryopreservation increases apoptotic index and impairs blastocele re-expansion in culture (39).…”

Effect of varying equilibration time in a two-step vitrification method on the post-warming DNA integrity of mouse blastocysts

“…This may be related to a vulnerability to highly concentrated cryoprotectants that progresses with blastocyst development (2). Two opposing mechanisms seem to coexist and affect the outcome of blastocyst vitrification: the permeation of the cryoprotectants and the toxicity of these agents (2,13). Although extending the exposure time can improve the cryoprotection, it increases the risks of toxicity.…”