Fertilization of human oocytes in capillary tubes using very low number of spermatozoa. A new treatment of severe oligozoospermia?

In this study a culture system was developed in which successful fertilization was performed in capillary tubes (75 x 0.9 mm) using very low numbers of spermatozoa. Oocytes were fertilized in 5-10 microliters medium containing 500-4,000 sperms (0.1-0.4 Mill. sperms/ml). In 10 IVF-patients with normozoospermia a total of 64 oocytes were cultured in capillaries and in tissue culture tubes (1 ml medium, 0.1 Mill. sperms/ml). The fertilization rate in tubes was 78% (25/32) and in capillaries using 4,000, 2,000, 1,000 and 500 sperms/oocyte: 71% (5/7), 86% (6/7), 60% (6/10) and 50% (4/8), respectively. The fertilization rate of mature oocytes was higher compared to immature oocytes (tubes: 83% vs 63%) capillaries: 74% vs 44%). Fertilization in capillaries using a volume of 10 microliters compared to 5 microliters seems to provide better culture conditions (fertilization rate: 75% vs 62.5%) cleavage rate: 91% vs 60%). The capillary technique may also provide a new treatment of severe oligozoospermia or in cases of poor sperm recovery after sperm preparation for IVF since in 3 patients with poor quality semen (total motile sperm/ejaculate: 0.2-1.4 Mill.) fertilization, cleavage and 1 pregnancy resulted. These preliminary results indicate the usefulness of capillary technique if standard IVF systems fail or before semen donation or sperm microinjection are anticipated.