Lower total cell numbers in mouse preimplantation embryos cultured in human assisted reproductive technique (ART) media are not induced by apoptosis.

A common feature of assisted reproductive techniques such as IVF or intracytoplasmic sperm injection is the IVC of oocytes or preimplantation embryos in artificial culture media. The IVC conditions are selected to mimic the environment of the female genital tract. We have shown that murine preimplantation embryos respond to different culture media with changes in developmental rates, cellular lineage composition, and gene expression patterns. In this study, we explored whether apoptosis is responsible for cell loss in mouse preimplantation embryos after exposure to different human culture media. We examined total embryonic cell count as well as the pattern of protein expression for caspase-9 (intrinsic pathway), caspase-8 (extrinsic pathway), and the executioner caspase-3 via immunohistochemical staining. Total cell counts decline in embryos cultured either in innovative sequential medium 1 and Blast Assist (Origio) or human tubal fluid and MultiBlast (Irvine Scientific) when compared to KSOM(aa). Few cells were caspase-9 and -3 positive in all experimental groups. Staining for caspase-8 was almost undetectable. We conclude that embryonic cell loss is not associated with higher rates of intrinsic apoptotic cell loss. Our results suggest that the culture medium-dependent decline in total cell count and the developmental restriction in embryos cultured in innovative sequential medium 1/Blast Assist and human tubal fluid/MultiBlast are related to processes affecting cell proliferation.