Effects of Glucose on Development of ICR Mouse Embryos in vitro

To study the effects of glucose on the development of ICR mouse embryos in vitro. Experiment 1: ICR female mice (6－8 weeks of age) were super-ovulated with i.p. injections of PMSG and hCG, and mated overnight with males. One-cell embryos were collected at 22－26 hrs after hCG and cultured in CZB supplemented with 0, 0.5, 1.0, 3.0, 5.0 or 10 mmol/L glucose respectively. Experiment 2: One-cell embryos were collected from the oviducts of ICR female mice, super-ovulated and cultured in glucose-free CZB. The embryos，respectively at one-cell, two-cell, four-cell or morula stage，were removed from glucose-free CZB medium and placed in CZB medium supplemented with 3.0 mmol/L glucose (optimal concentration) and removed to glucose-free CZB 24 h later (except the morula stage embryo). The embryos in another group were cultured in CZB supplemented with 3.0 mmol/L glucose during the entire culture time. The embryos in the control group were continuously cultured in glucose-free CZB. Embryos were cultured for 120 h at 37°C under 5% CO2 in sealed culture chambers and observed every 24 h under a Nikon inverted microscope. The culture efficiency was evaluated by determining the proportion of embryos reaching the four-cell (48 h), blastocyst (96 h), or hatched blastocyst (120 h) stage. The total cell numbers were counted in the blastocyst and hatched blastocyst embryos. The experiment results were: 1) There were no significant differences in the rates of four-cell embryos between every glucose-containing group and the glucose-free group. 2)The blastocyst rates of glucose-containing groups were significantly higher than that of the control. 3)The total cell numbers in the concentration group containing 3.0 mmol/L glucose were significantly higher than one another. 4)Addition of glucose from the two-cell to four-cell stage or from the four-cell to morula stage, significantly increased the blastocyst rates compared with the control. In contrast, addition of glucose from one-cell to two-cell, at morula or after morula, did not increase the blastocyst rates compared with the control. It indicates that addition of glucose to CZB does not result in two-cell block of the embryo development, and addition of glucose to CZB in a concentration as high as 10 mmol/L does not inhibit the development of ICR mouse one-cell to hatched blastocyst development. The optimal concentration of glucose added in CZB could be 3.0 mmol/L in the culture of ICR mouse embryos in vitro. Exposure of embryos to glucose, beginning at the two-cell and extending to the four-cell stage or beginning at the four-cell and extending to the morula stage, is necessary for the development of ICR mouse embryos in vitro.