Male infertility
The fertilizing potential of sperm depends on the shape of spermatozoa, their motility, their ability to perform the functions necessary for fertilizing an egg and finally, the transfer of an intact genetic material (DNA) to the egg at the time of fertilization. It is well known that 35-50% of all infertility problems are due to sperm abnormalities arising during the production of sperm or due to functional problems or in combination with other factors.
If a pregnancy does not occur naturally, then the only way to see if fertilization actually occurs is to take the eggs and sperm out of the body and put them together in the laboratory [in-vitro fertilization - IVF]. Before we get to the ultimate test of IVF we look at the sperm in great detail and perform quantitative and functional tests in order to note any possible deficiencies in the sperm profile.
Semen Analysis
A semen sample is analyzed for its volume, its concentration in sperm, its percentage of actively moving as well as normal shaped sperm. An abnormality of one or more of these parameters suggests a problem with the sperm. The greater the abnormality detected in the semen analysis, the greater the likelihood that sperm is an important factor of the couple's infertility problems.
Strict Criteria [Kruger] Criteria Morphology
Analysis based on specific strict criteria: Very detailed microscopic analysis of sperm morphology such as the measurement of sperm tail and head size. Even in fertile men around 90% of sperm in an ejaculate will be abnormal using these strict criteria.
Swim -up test
We allow the sperm to swim for a specific period of time over a certain distance (in a testing vial). The number of sperm that swim to the upper layer of the testing vial correlates with ability of the sperm to fertilize an egg in the laboratory.
Anti-sperm Antibody detection
If sperm comes in contact with the blood circulation after injury or surgery, the body can identify sperm as a foreign agent and therefore, produce antibodies against it. Antibody proteins attach to sperm and can prevent fertilization.
Chromosomal abnormalities in sperm
Many sperm disorders are due to chromosomal abnormalities, either numerical or structural. Numerical chromosomal abnormalities refer to the situation where the sperm carries more or less than the normal number of 23 chromosomes (aneuploidy). Structural chromosomal abnormalities describe the case where the man has (carrier) a balanced chromosomal rearrangement. The carrier of a balanced structural chromosomal rearrangement produces normal as well as genetically unbalanced gametes (sperm). If an unbalanced gamete manages to fertilize an egg, a chromosomally abnormal embryo with excesses and/or losses of genetic material will develop.
Both numerical and structural chromosomal abnormalities may result in an genetically unbalanced embryo which
can cause embryo death, miscarriage, or the live birth of an infant with extensive medical problems.
Aneuploidy screening of cromosomes in sperm
It is performed with Fluorescence In Situ Hybridization (FISH) technique. Small pieces of DNA (probes), are specifically bind (hybridize) to certain regions of the chromosomes being analyzed. Each probe is labelled with a different fluorescent dye. These fluorescent probes are applied to the sperm smear and are expected to attach to the specific chromosomes. Using a fluorescent microscope the geneticist can visualize the fluorescent colour signals for each different chromosome present (one, two or more). A single fluorescent signal represents a monosomy (normal), two a disomy and three a trisomy of the specific chromosome. In this way, diagnosis of aneuploidy of specific chromosomes is performed. A minimum of 500 sperm are evaluated for each chromosome studied in order to determine the percentage of aneuploidy. Normal fertile men have an aneuploidy rate of 2-4% in their sperm where as severe infertile men have above 27%. Any increase in sperm aneuploidy contributes to infertility.
DNA Fragmentation in sperm (Apoptosis)
Apoptosis is a natural procedureprog of programmed cell death. The procedure of apoptosis has various steps that include chromatin condensation, nuclear DNA fragmentation, cell shrinkage and finally fragmentation of the entire cell. Sometimes sperm with DNA damage, that is not eliminated by apoptosis, do manage to fertilize an egg, especially when intra cytoplasmic sperm injection (ICSI) is performed. All data indicate that increased levels of sperm apoptosis during in vitro fertilization (IVF) correlate to impaired embryo morphology at early cleavage stages, failure to progress to the blastocyst stage in culture and decreased pregnancy rates.
It is well known that infertile men have a higher level of apoptotic spermatozoa than the fertile men population. When the apoptotic index is >40% there is a decreased probability of intra uterus insemination (IUI) pregnancy, increased probability of spontaneous miscarriage, and in case of in vitro fertilization (IVF) or intra cytoplasmic sperm injection (ICSI), fertilization failure, early embryo arrest and pregnancy failure.
Application of transferase-mediated dUTP nick-end labelling (TUNEL method) detects apoptosis in spermatozoa by labelling any DNA strand breaks with a fluorescent molecule which can then be visualized using fluorescence microscopy. A minimum of 500 sperm are evaluated to determine the percentage of apoptotic spermatozoa.
Generally, conventional semen quality analysis, although it gives considerable is very informative, can not predict possible numerical chromosomal aberrations or the quality of spermatozoa genetic material in general and . Thus, can not be the sole attribute in the semen selection for assisted reproduction. Determining apoptosis and chromosomal aneuploidy rates in spermatozoa can improve selection criteria so that semen suitable for potential fertility is chosen.
Sperm Aspiration Procedure
Many men without sperm in the ejaculate will have sperm available in the testicles or stored in an area next to the testicles called the epididymis. Sperm may not be present in the ejaculate for several reasons:
- There may be blockage in the system so that although sperm are being produced they cannot reach the outside world to fertilize an egg this is known as obstructive azoospermia.
- There may be very few sperm that are being produced in the tests; this is known as non -obstructive azoospermia.
- In case of obstructive azoospermia sperm can often be retrieved from the epididymis using a minor surgical procedure known as Micro -Epididymal Sperm Aspiration [MESA]. If the urologist performing the procedure does not retrieve sperm from the epididymis then during the same procedure he can attempt to find sperm in the testicle. This procedure is called Testicular Sperm Extraction [TESE].
- Men who have non-obstructive azoospermia will require a TESE procedure. Sperm obtained by surgical means is always poorer quality than ejaculated sperm; therefore patients who undergo MESA or TESE will require more advanced technologies such as ICSI to help them to achieve fertilization.