Impact of a controlled culture temperature gradient on mouse embryo development and morphokinetics.

Abstract

Temperature control within the IVF laboratory is an important aspect of a quality control system, helping to reduce environmental stress and ensure good-quality embryo development. Temperature fluctuations are probably more common than expected and the optimal temperature for embryo culture is not known. Modern incubators offer the opportunity to examine the impact of culture temperature on preimplantation embryo development while controlling for other variables within the system. The purpose of this study was to examine the effect of a range of temperatures during extended embryo culture on resulting mouse embryo development and morphokinetic timings. Using a single time-lapse incubator with six individual chambers, frozen-thawed one-cell mouse embryos were cultured individually at temperatures adjusted by 0.5°C between chambers to cover the range of 35.0-37.5°C. Resulting blastocyst formation and embryo morphokinetic timings were recorded and compared. Changes in culture temperature had a significant impact on mouse blastocyst development and morphokinetic timings (P<0.05). Under the conditions used in this study, blastocyst development was best at 37.0°C. Mouse preimplantation embryo mitotic cell divisions were generally slower at cooler temperatures and accelerated as the temperature increased from 35.0°C to 37.5°C. Incubator culture temperature must be carefully controlled, as even slight variations of 0.5°C in the temperature used for extended embryo culture can have significant impacts on embryo development and mitotic cell divisions. These data have potential implications for application of universal morphokinetic selection algorithms and may help explain differences in mitotic errors/embryo mosaicism between laboratories.