Intracytoplasmic sperm injection (ICSI) is an in vitro fertilization procedure in which a single sperm is injected directly into an egg; this procedure is most commonly used to overcome male infertility problems. With conventional IVF, one can expect approximately 75% of the oocytes (eggs) to fertilize if they are healthy and the sperm parameters are not severely abnormal.
However, when there are severe sperm defects in count, motility or morphology, prolonged unexplained infertility, or abnormalities of the oocyte membrane , there may be severely reduced fertilization or none at all.
Fertilization involves a complex series of physical and biochemical events, which take place between the egg and sperm. Conventional IVF overcomes the need for the sperm to swim long distances to reach the egg. However, the sperm must still be able to secrete enzymes to enable it to move through the cumulus mass, which surrounds the egg, be able to attach to and drill through the protein coat (zona pellucida) which protects the egg, and to attach to the egg membrane. The egg must be able to engulf the sperm and to cause the sperm head to swell and become a male pronucleus. This will then combine with the female pronucleus to complete the process of fertilization. Failure of any of these steps will result in no fertilization.
Intracytoplasmic Sperm Injection (ICSI) is used to treat severe male infertility. Male infertility is a lowering of a male’s sperm count or sperm quality sufficient to reduce a patient’s chance of pregnancy. Male infertility is often classified as mild, moderate or severe based on the number of motile sperm and the number of normally-shaped sperm in a man’s semen. Men with fewer than five million sperm or fewer than 10 percent normally-shaped sperm are classified as having severe male infertility.
During IVF, patients who do not have male infertility have their eggs inseminated by a standard insemination procedure that involves placing a small volume of specially prepared motile sperm with the eggs in a dish. The process of fertilization is complex and requires sperm to function normally. The sperm from men with male infertility often do not possess normal sperm functions. Therefore, when sperm and eggs are simply placed together in a dish, as is done in the standard insemination procedure, the eggs often do not fertilize.
The ICSI technique was developed to assist the fertilization process in patients with severe male infertility. ICSI is a highly successful procedure that involves injecting one sperm directly into the egg using a microscope equipped with specialized micromanipulation equipment. The first step in ICSI involves selecting a normal-appearing sperm for injection into the egg. The sperm is then inserted into the egg using a micropipet.
The ICSI procedure can be used successfully to treat a wide array of male infertility disorders, such as low sperm counts, low sperm motility, or abnormally-shaped sperm. ICSI may also be used to treat a condition called azoospermia, which is the complete absence of sperm in the man’s ejaculate. When no sperm are present in the ejaculate, the sperm aspiration techniques, Epididymal sperm aspiration and Testicular Sperm Extraction (TESE) may be used to obtain sperm from the male’s reproductive tract. These sperm may then be used in conjunction with IVF and ICSI, donor egg IVF and ICSI, surrogacy.
Posted by : Goral Gandhi, MSc,
Rotunda – Center for Human Reproduction (Pvt) Ltd