Correspondence
Viable Embryos from Injection of Round Spermatids into Oocytes
N Engl J Med 1995; 333:525August 24, 1995
- Article
To the Editor:
By injecting sperm into the cytoplasm of an oocyte1 it is now possible to achieve fertilization and pregnancy in cases of obstructive azoospermia or severe oligozoospermia and asthenospermia after obtaining sperm directly from the epididymis or testis.2 Still, many patients with nonobstructive azoospermia cannot benefit from these techniques. The recently reported birth of normal mice after the electrofusion of oocytes with round spermatids, the youngest male germ cells to have a set of haploid chromosomes,3 has suggested a new approach to the treatment of this condition.
In our sperm-injection program, we have seen 12 men with unexplained azoospermia. In the ejaculates from these men, round spermatids were found. In seven cases oocytes had already been recovered from the patient's partner, and it was decided to try to fertilize them by injecting round spermatids.
The injections were performed with the same basic techniques and equipment that are used to inject sperm.4 The azoospermic semen samples were layered onto a discontinuous Percoll gradient (whose layers contained 40 percent, 60 percent, 70 percent, 80 percent, and 100 percent colloidal suspensions) and centrifuged at 330× g for 20 minutes. Cells from the 70 percent Percoll fraction were washed and resuspended in a 10 percent povidone solution in sperm-preparation medium. For each oocyte in the second stage of metaphase, one round spermatid was selected from the preparation, aspirated into a microinjection needle, and injected deep into the ooplasm. Oocyte activation was boosted by a vigorous ooplasmic aspiration at the time of the injection.
Normal fertilization (as shown by the presence of two pronuclei on the day after the injection) occurred in 14 of 39 oocytes (36 percent). All these zygotes had cleaved to at least the two-cell stage 44 hours after the injection and were transferred to the patient's uterus. At least one embryo was implanted in each of the seven women. Clinical pregnancies were established in two women. One healthy boy (3500 g) was delivered by cesarean section at 39 weeks' gestation. The other birth is anticipated in September 1995; the fetus has a normal karyotype and morphology.
These results show that normal human embryos can be obtained by the injection of round spermatids. Because the normal activation of human oocytes requires a factor released from the sperm cell,4 the results also show that this oocyte-activating factor is present in round spermatids. Moreover, the detection of round spermatids in all the azoospermic ejaculates examined suggests that many patients with defective spermiogenesis that is believed to be untreatable can benefit from this novel technique of assisted fertilization without needing a urologic intervention.
4 ReferencesJan Tesarik, M.D., Ph.D.
American Hospital of Paris, 92202 Neuilly-sur-Seine, FranceCarmen Mendoza, Ph.D.
University of Granada, 18071 Granada, SpainJacques Testart, Ph.D.
INSERM, Unité 355, 92140 Clamart, France1
Palermo G ,Joris H ,Devroey P ,Van Steirteghem AC . Pregnancies after intracytoplasmic injection of single spermatozoon into an oocyte. Lancet 1992;340:17-18
CrossRef | Web of Science | Medline2
Silber SJ. The use of epididymal sperm in assisted reproduction. In: Tesarik J, ed. Male factor in human infertility. Rome: Ares-Serono Symposia, 1994:335-68.
3
Ogura A ,Matsuda J ,Yanagimachi R . Birth of normal young after electrofusion of mouse oocytes with round spermatids. Proc Natl Acad Sci U S A 1994;91:7460-7462
CrossRef | Web of Science | Medline4
Tesarik J ,Sousa M ,Testart J . Human oocyte activation after intracytoplasmic sperm injection. Hum Reprod 1994;9:511-518
Web of Science | Medline
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