Influence of different oxygen concentrations on mouse embryo development using time-lapse-imaging

Purpose:

Estimate the influence of oxygen concentration on embryo development in ART using mouse embryo assay and morphokinetics provided by time lapse imaging.

Material and methods:

Female mice (BI6/CBAca) were sacrificed and zygotes were isolated 20 hours after mating. 314 zygotes were arranged randomly into three parallel groups consisted of atmospheric oxygen concentration (21%-high group) (n = 93), low oxygen (5%) (n = 129), and mixed (7% from day 1 to 2 and 2% from day 3 to 5) (n = 92). Zygotes were cultured in Primovision micro-well culture dishes using GTL Medium (Vitrolife) and were observed in the Primovision time-lapse system. All statistical analyses were performed using the R program.

Results:

Blastocyst rate at 120 hours in mixed group (91.3%) was significantly increased compared to high (76.3%) and low group (74.4%, p= 0.009 and 0.001), respectively. Blastocyst size was enlarged in mixed group (p < 0.001 compared to high and low group). Morphokinetics showed significantly faster cell division of mixed group in almost every cleavage stage compared to high or low groups.

Conclusions:

This study demonstrated that the oxygen concentrations, which mimic the changes in the oviduct (7% from day 1 to day 2) and uterus (2% from day 3 to day 5), significantly improved the blastocyst rate, the blastocyst size and speeded up time to cell divisions compared to routinely used conditions. Time lapse imaging is a highly sensitive measure to evaluate embryo development and changes in culture conditions.