Amount of maternal body fat significantly affected the quality of isolated mouse preimplantation embryos and slowed down their development.

The aim of our study was to investigate the effect of maternal obesity on the quality and developmental capabilities of in vivo-derived preimplantation embryos. A two-generation dietary model, based on mice overfeeding during intrauterine and early postnatal development, was used to produce four types of female animals: with physiological (7%-8%), slightly elevated (8%-11%), highly elevated (>11%), and low (<7%) amounts of body fat. Spontaneously ovulating females (5-6 weeks old) were mated with male animals and subjected to embryo isolation at Day 4. Stereomicroscopical evaluation of collected embryos showed that the amount of maternal body fat did not affect the average number of collected embryos per dam. However, significant differences were found in the stage-distribution of isolated embryos: dams with highly elevated body fat and dams with low fat delivered decreased numbers of blastocysts and increased numbers of lower-stage or degenerated embryos compared with dams with physiological or slightly elevated fat value. Fluorescence staining showed that blastocysts isolated from dams with high and low percentage of body fat contained significantly higher numbers of dead cells. Most of such dead cells were of apoptotic origin. In contrast, the amount of maternal body fat did not affect blastocyst growth-the average numbers of cells per blastocyst were comparable in all groups. In conclusion, highly elevated or decreased amount of maternal body fat slowed down the development and negatively affected the quality of naturally in vivo-derived preimplantation embryos. No negative effect of slightly elevated fat was observed.