Toxicology
Human
The SCSA , or Sperm Chromatin Structure Assay, quickly identifies men whose sperm have damaged DNA thereby reducing the probability of achieving a successful pregnancy.
There are five major populations of sperm identified by the SCSA® test:
- Non-detectable - DNA Fragmentation Index (DFI): percentage of mature sperm with non-detectable levels of nuclear DNA fragmentation.
- Moderate DFI: percentage of sperm with moderate levels of DNA fragmentation identified by their moderate susceptibility to acid-induced denaturation.
- High DFI: percentage of sperm with high levels of DNA fragmentation identified by their high susceptibility to DNA denaturation.
- DNA Fragmentation Index (DFI): the percentage of sperm with moderate and high levels of DNA fragmentation (% Moderate DFI + % High DFI).
- High DNA Stainability (HDS): the percentage of sperm with immature chromatin. HDS sperm have less chromatin condensation, which leads to increased DNA stainability. These sperm are compromised for lower efficiency of routine IVF fertilization, however, the DNA integrity appears normal and can be used for ICSI.
DNA fragmentation can be attributed to various pathological conditions including cryptorchidism, cancer, varicocele, fever, age, infection, and leukocytospermia among others. Many environmental conditions can also affect DNA fragmentation such as chemotherapy, radiation, prescription Rx, air pollution, smoking, pesticides, chemicals, and heat and ART preparation protocols. Current thoughts regarding the etiology of DNA fragmentation include both apoptotic events or damage due to reactive oxygen species (ROS); however, Henkel et al. (2004) showed no correlation with fertilization rates, pregnancy, DNA integrity or DNA fragmentation using early markers of apoptosis (Annexin V binding and Fas expression). Given, the clear relationship of high DNA fragmentation and lower pregnancy rates it seems plausible that much of DNA damage may be due to ROS.