ABSTRACT: Following intracytoplasmic sperm injection (ICSI), in vitro culture (IVC) in ART media causes imbalance in the blastocyst's inner cell mass (ICM)with reduction of the primitive endoderm compartment compared to non-IVC blastocystsFollowing embryo transfer (ET), these imbalances do not influence birth rates, and the postnatal effects are inconspicuous. ICSI alters gene expression in mouse embryos. Choice of embryo culture media has been correlated with birth and body growth rates in human studies. No analysis has yet been made combining ICSI and IVC in the mouse. We produced mouse concepti by ICSI followed by IVC and ET so as to mimic,at least in part, the way human embryos are produced and handled in the clinical practice. Fertilized oocytes were cultured in two sets of sequential ART media, compared with an optimized mouse medium and with the mouse oviduct. Embryos were analyzed or implanted to produce newborns. In total, 3706 fertilized mouse oocytes, 1672 blastocysts and 78 newborns were examined during the course of the study. Mice of the B6C3F1, C57Bl/6 and CD1 strains were used as oocyte donors, sperm donors and embryo recipients, respectively. B6C3F1 oocytes were fertilized by intracytoplasmic C57Bl/6 sperm injection and were allowed to cleave in HTF/MultiBlast and in ISM1/ISM2 sequential culture protocols as well as in optimized mouse medium (KSOM(aa)) and in vivo in the CD1 mouse oviduct. Cleavage and blastocyst rates were analyzed by Wilcoxon / Kruskal-Wallis test and the blastocysts were split in two subgroups:one subgroup was analyzed for cell lineage allocation and for transcriptome, the other subgroup was transferred to genital tract, allowed to develop to term and characterized for birth rate, litter size, neonatal bodyweight and behavior using ANOVA F-test and t-test. The effects of ART media on blastocyst rates exceed those of ICSI. Protein and mRNA analysis reveal that IVC has a marked effect on the primitive endoderm lineage of ICSI blastocysts. In contrast to preimplantation, birth rates after ET are indistinguishable not only among ICSI but also in comparison to non-injected controls. At birth, ICSI-IVC-ET concepti are outwardly normal and weigh the same as non-ICSI controls. Confounding effects of subfertility, lifestyle and genetic heterogeneity are reduced to a minimum in the hybrid inbred mouse model compared to human patients. Confounding effects of polyspermy and parthenogenetic activation are prevented by ICSI. There is more to ART than ICSI, IVC and ET, and only a small number of ART media were examined. Preimplantation effects of ART culture media can effectively be modeled in the mouse because the in vitro environment is suboptimal for both mouse and human. However, in the optimal uterine environment of their own species, mouse and human ART blastocysts may be supported and selected for differently, depending on species-specific features such as the kinetics of implantation and the endometrium.
