Sperm DNA fragmentation: causes and identification

Abstract

SummarySperm DNA fragmentation is referred to as one of the main causes of male infertility. Failures in the protamination process, apoptosis and action of reactive oxygen species (ROS) are considered the most important causes of DNA fragmentation. Action of ROS or changes in sperm protamination would increase the susceptibility of sperm DNA to fragmentation. Routine semen analysis is unable to estimate sperm chromatin damage. Sperm DNA integrity influences sperm functional capability, therefore tests that measure sperm DNA fragmentation are important to assess fertility disorders. Actually, there is a considerable number of methods for assessing sperm DNA fragmentation and chromatin integrity, sperm chromatin stability assay (SCSA modified), sperm chromatin dispersion (SCD), comet assay, transferase dUTP nick end labelling (TUNEL); and protamine evaluation in sperm chromatin assay, such as toluidine blue, CMA3, protamine expression and evaluation of cysteine radicals. This review aims to describe the main causes of sperm DNA fragmentation and the tests commonly used to evaluate sperm DNA fragmentation.

Negative Impact of Elevated DNA Fragmentation and Human Papillomavirus (HPV) Presence in Sperm on the Outcome of Intra-Uterine Insemination (IUI)

“…By including sperm DNA fragmentation analysis as a parameter in the routine diagnosis of male fertility patients in combination with HPV detection, it would be possible to avoid or to postpone unnecessary and unsuccessful IUI treatments, which would prevent a large burden of physical, financial and psychological stress caused by unsuccessful IUI trials. Although detection of infectious HPV virions could explain a substantial part of subfertility in our cohort, the elevated DFI is multifactorial and not exclusive to HPV infection, and can also be caused by other factors like oxidative stress [58]. Importantly, HPV infection in sperm is temporal, leading to DFI normalization after 3-6 months, and higher success rates can be achieved by postponing IUI until HPV negativation.…”

“…The dashed line represents the calculated DFI cutoff of 26% above which no clinical pregnancies could be achieved (sensitivity of 100% and specificity of 36.3%). Real time qPCR was used to quantify following HPV types: HPV 6,11,16,18,31,33,35,39,45,51,52,53,56,58,59, 67 and 68.…”

Semen evaluation: methodological advancements in sperm quality-specific fertility assessment

“…Moreover, ROS levels can be measured indirectly by analyzing the expression levels of genes associated with DNA damage and mitochondrial ROS modulation. The methods developed include DNA fragmentation, chromatin integrity, sperm chromatin stability assay (SCSA modified), sperm chromatin dispersion (SCD), comet assay, transferase dUTP nick end labeling (TUNEL), and protamine evaluation in sperm chromatin assays, such as toluidine blue, CMA3, protamine expression, and cysteine radical evaluation [160].…”

An improved acetic acid‐urea polyacrylamide electrophoresis method to evaluate bovine sperm protamines

“…Another issue to be considered about protamines is the fact that both the total number of amino acids and the positions of arginine residues have changed considerably during mammalian evolution (Queralt et al, 1995). This feature could contribute to the fact that bovine sperm chromatin is highly compacted when compared to humans, and thus, standardized protocols used to evaluate human sperm chromatin should not be used in bovine samples (Hamilton & Assumpção, 2020). Recently, Soler-Ventura et al (2018) described a step-by-step protocol to extract and analyse mammalian sperm protamine; however, a protocol for bovine sperm protamine extraction and analysis might require confirmation and/or modification since the bovine sperm is a distinct cell as described above.…”