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The development of 1-cell mouse embryos in explanted oviducts, on mouse and bovine oviduct epithelial cells and on two established cell line supports is compared. The best rates of blastocyst formation were obtained using explanted oviducts; mouse and to a lesser extent, bovine oviduct epithelial cells allow good embryonic development, associated with high viability after transfer of the blastocysts obtained in co-culture. MDBK (from bovine kidney) and Vero (from Green monkey kidney) have been tested. MDBK allows high rates of blastocyst formation (67%) and the blastocysts obtained are viable. Vero does not allow the 2-cell block to be overcome. Maintenance of cell polarity for all the feeder layers did not improve embryo development. A preliminary study on the metabolic modifications induced by the feeder layers showed no modifications at all related to a decrease in glucose, an increase in lactate and early embryonic development. On the other hand, for the free amino acids, cellular supports with high embryotrophic activity seem to mimic tubal secretions, especially with a high level of glycine. Neither a genital tract origin, nor a hormonal contribution are strictly necessary for embryo co-culture, as already demonstrated by co-culture with trophoblastic tissue. Established cell lines, which are easy to handle and control, could be useful tools in embryo biotechnology.

SummaryThe impact of sperm DNA fragmentation on assisted reproductive technology (ART) successes, in terms of outcome, is now established. High levels of DNA strand breaks severely affect the probability of pregnancy. The importance of sperm nucleus condensation in early embryogenesis and, subsequently, on the quality of the conceptus is now emerging. In this article we have compared in situ analyses with terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labelling (TUNEL) (for DNA fragmentation) with aniline blue (AB) (for nucleus decondensation), versus flow cytometry (FC) after acridine orange staining, in a double-blinded analysis. In our hands, TUNEL and acridine orange give perfectly comparable results. For decondensation the results are also comparable, but the double-stranded green fluorescence obtained with acridine orange seems to slightly underestimate the decondensation status obtained with AB.

In this study 874 mouse embryos were allocated to six groups including a control, co-culture, and four groups that underwent partial zona dissection (PZD): at the 2-cell (PZD-2) and morula stages (PZD-M) both with and without co-culture. Rates of complete blastocyst hatching on day 5 increased in the following order: control, co-culture alone, PZD-2 alone, PZD-M alone, PZD-2 with co-culture and PZD-M with co-culture (P < 0.00001). PZD-M led to significantly higher rates of complete blastocyst hatching compared to PZD-2 (P < 0.03). This study showed also that co-culture apparently compensates for any minor damage incurred during the PZD technique at the 2-cell and morula stages, (P < 0.01 and P < 0.01) respectively. Therefore PZD and co-culture seem mutually beneficial techniques that promote early blastocyst hatching in the mouse.