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.
