The effect of sperm DNA fragmentation on the development of embryos in assisted reproductive technologies

Recently high attention in the reproductive medicine is paid to the paternal genome failures. Assisted reproductive techniques (ART) such as conventional in vitro fertilization (IVF), and especially intracytoplasmic sperm injection (ICSI), allow couples whose sperm characteristics are impaired obtaining a pregnancy, whereas a few years ago, these couples would have had to use sperm donation in order to obtain their child. One can nevertheless wonder about the capacity of poor quality sperm samples to generate embryos having normal capacities of development. Among the factors involved in the failure of obtaining embryos and/or pregnancies, the impaired sperm genome is frequently incriminated. Sperm DNA fragmentation is rather new discussible reason of male infertility. There are contradictory data about the possible influence of sperm DNA fragmentation on the sperm fertilization ability and the process of embryo development, particularly on the process of the blastocyst formation. There are data about the correlation of the sperm DNA fragmentation level and high percentage of the spontaneous miscarriages for patients included in the IVF treatment. Sperm DNA fragmentation consists of single and double stranded DNA breaks, frequently occurring in semen of subfertile patients. Despite the origin and the mechanisms responsible for such genomic anomaly are not yet clarified, it has been proposed that sperm DNA fragmentation could be a good parameter to predict the male fertility status as an alternative or in addition to poorly predictive standard parameters presently determined in routine semen analysis. Spermatogenesis is a complicated process that includes spermatozoa development and maturation. It depends on such factors as genetics, hormonal statement, environmental conditions etc. Spermatogenesis failures could lead to the formation of aneuploid sperm or sperm with the DNA damage. The level of sperm DNA fragmentation index (DFI) and its relationship with the features of embryos' development obtained in IVF from men with reduced fertility from Eastern Ukraine and Spain were studied. The negative correlation between DFI and the blastocyst formation rates for Ukrainian men is proved (p < 0.01). A positive correlation was found between the level of sperm DNA fragmentation and the proportion of aneuploid blastocysts obtained from patients from Spain (p <0.01). The level of DNA fragmentation in men with a reduced fertility from Spain does not significantly differ from this indicator for infertile men from Eastern Ukraine. A high level of DNA fragmentation in spermatozoa can be an indication for preimplantation genetic diagnosis in IVF. In studies investigating the impact of sperm DNA fragmentation on reproduction, the prevailing idea is that sperm with damaged DNA, even if retaining the ability to fertilize the oocyte, affect the subsequent steps resulting in increased failure of embryo development and miscarriage. However, data on the relationship between DNA damage and ART outcome are very conflicting. The obtained data confirmed that DNA fragmentation could be one of the male infertility factor that affects the embryo development.