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Structural damage to nuclear DNA in mammalian spermatozoa: its evaluation techniques and relationship with male infertility.

Diagnosis of the fertilizing ability of a semen sample is important for consistently high reproductive efficiency. Disturbances in the organization of the genomic material in sperm nuclei can have a serious impact on the growth of the offspring, therefore a stable nuclear matrix is crucial for participation in embryonic development. Routine semen analysis investigates parameters such as sperm motility and morphology, but does not examine the nuclear DNA integrity of spermatozoa. It has been suggested that altered nuclear chromatin structure or damaged DNA in spermatozoa is implicated as a possible cause of increased infertility in males. Therefore, it is crucial to develop and use accurate and diagnostic tests, which may provide better prognostic capabilities than the standard sperm assessments. This article reviews and discusses some of the current techniques employed for evaluating chromatin structure or DNA damage in spermatozoa. These different techniques include the comet assay, sperm chromatin structure assay (SCSA), acridine orange test (AOT), tritium-labelled 3H-actinomycin D (3H-AMD) incorporation assay, terminal TdT-mediated dUTP-nick-end labelling (TUNEL) assay, in-situ nick translation (ISNT) assay, DNA breakage detection-fluorescence in-situ hybridizations (DBD-FISH) assay and sperm chromatin dispersion (SCD) test. The aforementioned assays, which are considered independent measure of sperm quality, may help to detect subtle defects in the chromatin structure or DNA integrity, and thereby assist in semen quality assessment. The relationship between DNA damage and male infertility is also addressed.