An improved, efficient method for analyzing human sperm chromosomes using zona-free hamster ova

Abstract

We have developed an improved method for analyzing human sperm chromosome, using zona-free hamster ova. Our main improvements of methodology are as follows: (1) Fertilization rate of hamster oocytes by human spermatozoa was markedly raised by successive treatments of the spermatozoa with 5-15 microM ionophore A23187 solutions and a capacitation medium (BWW medium) containing 3.5% HSA. The HSA most effective in inducing capacitation was selected from several kinds of HSA products commercially available. (2) Monospermic fertilization was ensured by inseminating oocytes with highly capacitated spermatozoa at a low concentration for a short time. (3) TC medium 199 was used for postinsemination culture of the eggs. (4) A medium containing podophyllotoxin and vinblastine (0.04 micrograms/ml each) was used to block karyogamy and first-cleavage spindle formation. (5) Chromosome slides were prepared with our gradual fixation-air-dry method instead of Tarkowski's method. Ninety-two to 177 spermatozoa corresponding in number to 43%-79% (mean: 62%) of the inseminated oocytes were successfully karyotyped in each experiment. In spite of above-mentioned quantitative improvements, quality of Q-banding was not necessarily satisfactory in our slides. Improvement of banding technique is an important problem to be solved in our method. Spontaneous incidence of chromosome aberrations was studied in a total of 1,091 spermatozoa obtained from nine semen samples from four donors. Incidences of aneuploidy and structural anomaly were 0.9% (hyperhaploidy, 0.45%; hypohaploidy, 0.45%) and 13.0%, respectively. Structural aberrations included breaks (45.1%), fragments (32.4%), exchanges (21.8%), and deletions (0.7%). Ratio of X-sperm to Y-sperm was 53% to 47%. These results were discussed in comparison with those reported previously.