It is now recognized that, among others, genetic and epigenetic factors affect the ‘quality’ of sperm and lead to male infertility. For example, an increased sperm aneuploidy rate is found with a relatively high frequency in infertile men, particularly those with non-obstructive azoospermia, while an increased percentage of sperm apoptosis (programmed cell death) leads to a sperm population with a low fertilization potential and inability to maintain the developing fetus in the early stages.
Sperm analysis by flow cytometry
The commonly employed laboratory technique of FISH for sperm aneuploidy testing and for the study of sperm apoptosis have significant limitations, such as high reagent costs, a long processing time, failure to study a large number of sperm cells, etc..
Therefore, the laboratory investigation of the above parameters to date remains largely subjective and incomplete. Application of the technique of flow cytometry as it has developed today, is considered the reference method ( ‘state of the art’) in the study of sperm parameters.
Sperm analysis by multi-parametric flow cytometry permits, for example, simultaneous, objective and accurate:
Measurement of the sperm ploidy index
Calculation of the percentage of sperm bearing numerical chromosomal abnormalities (aneuploidies) which would result in chromosomally abnormal embryos.
Measurement of the percentage of apoptotic sperm
Apoptosis is the process of programmed cell death, which constitutes a natural phenomenon. The assay calculates the percentage of apoptotic spermatozoa, an increase in which leads to low fertilization rates.
Measurement of the DNA fragmentation index (DFI)
‘Breaking’ of the DNA strands (DNA fragmentation) occurs in the final stages of cell death. The assay calculates the percentage of sperm that bear ‘breaks’ in their DNA (and are therefore necrotic) and which will not lead to a successful pregnancy.
Measurement of the number of lymphocytes in the sperm sample
The assay measures the number of leukocytes in the sperm sample, which when elevated indicates, among other things, the possible presence of inflammation.
Measurement of acrosome integrity
The acrosome is part of the sperm and is essential for the successful penetration of the oocyte and fertilization. This assay measures the percentage of sperm that bear abnormalities in the structure of the acrosome and therefore are not able to fertilize successfully the oocyte.