Embryo development and the mechanisms behind the improvements in In Vitro dynamic culture systems

Mammalian embryo culture is influenced by autocrine and paracrine effects and the diffusion of harmful byproducts. The physiological development of the embryo occurs in the Fallopian tube under dynamic conditions. To obtain high quality embryos in in vitro culture, dynamic culture systems (DCSs) have been developed which mimic the dynamic physiological conditions. In this review, embryo culture using DCSs in vitro and their culture results are discussed. From the culture results of DCSs that move the medium and embryos, we deduced that an increase in the diffusion rate is one of the reasons for an improvement in embryo development. Diffusion around the embryos could be investigated by monitoring pH changes in the medium during embryo culture. Application of moderate mechanical stimuli to embryos using DCSs would induce improvement in embryo development. To understand mechanosensing of mammalian embryos, mechanical stimuli and intracellular calcium concentrations in the embryos should be quantitatively evaluated. Finally, strategies to apply these insights and technologies to human embryo development are briefly discussed.