Submitted by Dr. Hesham Al-Inany, M.D. Lecturer, Gynaecology & Obstetrics dept. Kasr El-Aini hospital, Cairo University, Egypt.
Transmission electron microscopy (TEM) after SUZI
Sathananthan et al,(1989) , studied the ultrasrtucural features of
spermatozoa-oocyte incorporation after sperm transfer Of 100 spermatozoa
examined by TEM in the PVS of 16 oocytes after transfer of 5-10 spermatozoa
from oligozoospermic men , 76% had intact acrosomes and 33% of intact
spermatozoa were morphologically abnormal . Nuclear, acrosomal, midpiece
and tail defect were entered in these abnormal sperm forms.
Ng et al, (1990), also studied the spermatozoa undergoing sperm head decondensation and formation of a pronucleus. Between 10-30 sperm were transferred into 11 donated human embryos between pronuclear and 16-cell stages. After culture for 24 hours, the embryos were fixed TEM.
Both acrosome-intact and acrosome-reacted sperm were located in the PVS and between blastomeres. Sperm-blastomere membrane fusion was not observed. The study clearly showed that sperm heads are incapable of expanding their chromatin to form typical male pronuclei following SUZI into early human embryos.
Intracytoplasmic sperm injection
Assisted-fertilization methods e.g., partial zona dissection and subzonal
insemination have been successful in some couples with severe male-factor
infertility who could not be helped by IVF. Pregnancies and births have
been reported, but despite use of these methods some women still do not
Intracytoplasmic sperm injection (ICSI) is a promising assisted-fertilization technique. It is the direct injection of spermatozoon into the ooplasm of the oocyte. It is indicated in situations where the spermatozoal count so low that SUZI is not possible and possibly when there is a structural abnormality preventing gamete fusion e.g round -headed acrosomeless spermatozoa (Lalonde et al , 1988) .
With recent advances of technology and lab tools, TEM studies show that a spermatozoon could be injected with minimal injury to the ooplasm and possible sperm-oocyte membrane fusion could occur in the ooplasm (Sathananthan et al, 1989).
Lanzendorf et al, (1988) showed that human oocytes are capable of surviving the mechanical insertion of spermatozoon directly into ooplasm. However, mechanical damage to the oocyte may still occur, the likelihood of which may be influenced by characteristics of the injection pipette or of the micromanipulation technique.
In rabbits and cattle , embryos obtained by such injections have been transferred to recipient mothers and live offspring have resulted (Iritani , 1991) .
It needs using very fine micropipettes handling gametes very gently by highly experienced person to avoid oocyte injury which is the major side effects of this technique (Markert et al, 1983).
The outer and inner diameters of the holding and injection pipettes are, respectively, 60 and 20 um and 7 and 5um. The injection pipette has a bevel angle of 50 and a sharp spike to assist penetration through the oolemma . An immotile sperm is aspirated tail-first into the tip of the microinjection pipette .
Then the micropipette is pushed through the zona pellucida and into the ooplasm. The injection pipette is withdrawn gently and the oocyte is released from the holding pipette.
Palermo et al ,(1992) described successful intracytoplasmic injection
into 47 metaphase-II oocytes of single spermatozoa from men severely impaired
spermatozoa characteristics after IVF and SUZI had failed. 38 oocytes
remained intact after injection, 31 become fertilized, and 15 embryos
were replaced in utero .
Four pregnancies occurred after eight treatment cycles-two singleton and one twin pregnancy, and a preclinical abortion. Two healthy boys have been delivered from the singleton pregnancies and a healthy boy and girl from the twin pregnancy.
ICSI bypasses many steps in the fertilization process i.e., the spermatozoon's binding to penetration into ZP and its fusion with the oolemma. ICSI may allow fertilization by spermatozoa with deficient kinetic properties or anomalies of the acrosome. However, further studies are necessary to confirm the high survival and fertilization rates obtained after ICSI.
Are you a Doctor, Pharmacist, PA or a Nurse?
Join the Doctors Lounge online medical community
Editorial activities: Publish, peer review, edit online articles.
Ask a Doctor Teams: Respond to patient questions and discuss challenging presentations with other members.