Cytoplasmic dynamics as a new marker of embryonic quality

Quality of an oocyte’s cytoplasm is an important factor affecting preand postimplantation development of the future embryo. It can be compromised for example by aging, both maternal (i.e. related to the female's age) and postovulatory (i.e. related to the time between ovulation and fertilization). Recently, we have establish a new non-invasive method to assess cytoplasmic quality of fertilized oocytes. It involves a Particle Image Velocimetry (PIV)-based analysis of cytoplasmic movements triggered by a fertilizing sperm. PIV method is commonly used in fluid dynamics to follow movements of amorphous objects. We have found that cytoplasmic movements depend on Ca2+ oscillations that are also induced by fertilization. Each time Ca2+ level increases, a contraction of the actomyosin occurs and this in turn induces a directional cytoplasmic flow. Therefore, analysis of cytoplasmic flows provides unique information about functionality of Ca2+ siganlling and cytoskeleton in the oocytes. In experiments performed on a mouse model, we have shown that a specific temporal pattern of the cytoplasmic movements (very frequent fast twitches with very slow movements in the intervening periods) correlates with a low developmental potential of the embryos. Currently, our method of embryo assessment is tested in human embryos in a clinical setting. L5.2