Zona manipulation in an assisted reproductive technologies (ART) programme.
We investigated whether the aged oocytes maintain the ability to fuse with spermatozoa when the oocyte investment is removed. In the first study, 87 two-days-old oocytes provided from IVF-ET programme were treated with pronase to dissolve the zona pellucida. The oocytes were then inseminated with 100, 10 or 1 per microliters sperm and the incidence of monospermic and polyspermic fertilization was determined. In the second study 100 one-day-old unfertilized oocytes obtained from 18 IVF patients with "zero fertilization" at initial insemination were treated in the same way to either remove or thinning of the zona pelucida. They were then re-inseminated with 10 motile sperm per microliter of the husband. The incidence of monospermic and polyspermic fertilization were 0.0% (0/13) and 61.6% (8/14), respectively, with a sperm count of 100/microliters, 7.3% (3/41) and 31.6% (13/41) with 10/microliters, and 14.2% and 11.9% (5/33) with 1/microliter. The incidence of monospermic and polyspermic fertilization with reinsemination of one day old oocytes were 12.5% (3/24) and 25.0% (6/24) after zona removal and were 18.3% (9/49) and 10.2% (5/49) after zona thinning. The incidence of fertilization by zona removal was significantly higher than the results of conventional reinsemination (p < 0.001). It appeared that human aged oocytes maintain the ability to fuse spermatozoa after even two days. A higher rate of monospermic fertilization was obtained by carefully controlling the number of spermatozoa for insemination. We concluded that zona manipulation might improve fertilization in vitro in case of severe male factor infertility.
Odawara
Y
Y
Department of Obstetrics and Gynecology, Jikei University School of Medicine, Tokyo, Japan.
Matsumoto
K
K
Shinozuka
S
S
Kusuhara
K
K
Terashima
Y
Y
D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D007248:Infertility, Male / Q000628:therapy; D008297:Male; D009865:Oocytes; D013997:Time Factors; D015044:Zona Pellucida