In Vitro Mouse Fertilization as an Experimental Model for the Monitoring of Adverse Effects on Gametes and Gamete Fusion
In vitro fertilization of mice gametes is frequently used to assess different factors that disturb human in vitro fertilization, as almost identical conditions prevail for both species. The mouse in vitro fertilization technique was considered to be a suitable model to evaluate chemically induced effects on male and female gametes. Optimal results were obtained with gametes of the C57B1/6J and B6C3F1 mouse inbred strains cultured in Toyoda’s modified medium. The spermatozoa were preincubated for 90 min prior to being added to the oocytes; the sperm concentration was 1 × 106/ml medium. This system’s response to the heavy metal cadmium chloride (CdCl2), present in the environment worldwide, was investigated. In vivo tests of this chemical’s effects on the reproductive systems have resulted in controversial findings.
0.4, 0.8, and 1.6 μM of CdCl2 were added, together with the spermatozoa, to the medium. Spermatozoa, oocytes and CdCl2 were then incubated for 6 h, after which the oocytes were washed several times and cultured for another 18 h, up to the 2-cell stage. 0.4 and 0.8 μM of CdCl2 had no effects on sperm motility, whereas 1.6 μM affected sperm motility slightly. Nevertheless, cleaveage rates were unaffected in all groups, thus indicating that CdCl2 had no direct effect on the processes of gamete fusion, such as sperm-ovum binding, penetration of the oocyte by the spermatozoon, syngamy fusion of the male and female pronuclei, and cleavage.