Oxidative markers in cryopreservation medium from frozen-thawed embryos: a possible tool for improved embryo selection in in vitro fertilization?

Abstract

Purpose The present study evaluated the association between oxidative parameters in embryo cryopreservation medium and laboratory and clinical outcomes. Methods This prospective laboratory study was conducted in an IVF unit in a university-affiliated hospital with 91 IVF patients undergoing a frozen-thawed embryo transfer cycle. Following thawing, 50 μL of embryo cryopreservation medium was retrieved from each cryotube and tested by the thermochemiluminescence (TCL) assay. TCL amplitudes after 50 (H1), 150 (H2), and 280 s (H3) were recorded in counts per second (CPS) and the TCL ratio determined for comparison with implantation and pregnancy rates. Results A total of 194 embryos were transferred in 85 frozenthaw cycles. Twenty-one pregnancies (24.7 %) occurred. Implantation and overall and clinical pregnancy rates were higher when the median TCL H1 amplitude was <32 CPS compared to ≥32 CPS (14.6 vs. 5.3 %, 37.5 vs. 17 %, 28.1 vs. 9.4 %, respectively). No pregnancies occurred when the H1 amplitude was ≥40 CPS. Logistic regression multivariate analysis found that only the median TCL H1 amplitude was associated with the occurrence of pregnancy (OR = 2.93, 95 % CI 1.065-8.08). The TCL ratio inversely correlated with the duration of embryo cryopreservation (r = −0.37).Conclusions The results indicate that thawed embryos may express oxidative processes in the cryopreservation medium, and higher oxidative levels are associated with lower implantation rates. These findings may aid in the improved selection of frozen-thawed embryos for IVF.

Oxidative Stress and Assisted Reproduction: A Comprehensive Review of Its Pathophysiological Role and Strategies for Optimizing Embryo Culture Environment

“…These include dilution of sperm samples (and seminal fluid), exposure to toxic cryoprotectants, and pH and osmotic changes induced by cooling to cryogenic temperatures and rewarming for thawing. In line with this, a significantly increased ROS production has been reported in human gametes, as well as in mice and human embryos, during cryopreservation [61][62][63][64]. In contrast, the formation of ice crystals is lower when vitrification is performed, with lower osmotic shock due to ultra-rapid cooling [65].…”

Influence of different post-thaw culture time on the clinical outcomes of different quality embryos

“…We also hypothesize that the suboptimal embryos may express oxidative stress in the cryopreservation medium, and higher oxidative stress levels are associated with lower implantation rates. 24 Therefore, we think that the implantation rate for optimal day-3 embryo transfers after 2 h of culture can be improved.…”

Effect of post‐warming culture time on the live birth rate after frozen embryo transfer

“…Although the embryo culture medium has been optimized to resemble that of the uterus, there is still the potential for this post‐thawing culture to have adverse effects on the embryo 8 . It was suggested that embryos might respond poorly to the culture medium and be susceptible to oxidative stress, leading to lower implantation rates 9 . Some studies have shown that post‐warming embryo culture for 2–5 h results in higher implantation and live birth rates than culturing overnight 10,11 .…”

“…8 It was suggested that embryos might respond poorly to the culture medium and be susceptible to oxidative stress, leading to lower implantation rates. 9 Some studies have shown that post-warming embryo culture for 2-5 h results in higher implantation and live birth rates than culturing overnight. 10,11 However, other studies showed no differences in clinical outcomes between the short and long culture duration groups.…”