Sperm DNA Fragmentation : Understanding the basics

Understanding sperm DNA fragmentation

DNA damage in sperm can come from many different outside sources, like

·?????UV and ionising radiation and genotoxic chemicals,

·?????as well as from inside the body, like reactive oxygen species (ROS) and DNA polymerase mistakes.

There are many different kinds of damage that can be caused by these insults, and different agents tend to cause different kinds of DNA damage.

. Most damage to spermatozoa is caused by three things:

·?????bad chromatin condensation during spermiogenesis,

·?????failed apoptosis, and

·?????oxidative stress.

Chromatin remodelling during spermiogenesis causes chromatin condensation defects. The goal of this process is to pack the DNA into the smallest possible shape, which changes the size of the sperm head into the best shape for movement.

Endonucleases (like caspases) are responsible for breaking down DNA, but they are unable to access the nucleus in sperm because the mitochondria and nucleus are located in different parts of the cell. Thus, mitochondrial ROS are the primary trigger of apoptosis in sperm.

What Happens with Apoptotic sperm?

Apoptotic spermatozoa are less mobile and have reduced fertility, but they can still fertilise an egg. This can cause problems during embryo development or even result in a miscarriage if sperm contains DNA damage..

What can change DNA FRAGMENTATION?

Diet, exercise, and smoking all affect reactive oxygen species (ROS) levels, which in turn affects male fertility. Sperm quality can decline with age. The DNA in sperm from older men is more fragmented, making them less mobile than sperm from younger men.

What is the impact of DNA fragmentation on embryo development ?

Sperm DNA damage can be detrimental to embryo development. The risk of infertility, spontaneous abortion, or a low-quality embryo is correlated with the severity of the damage.

Zygotes fertilised by damaged sperm still have a chance of blastulating and developing into a pregnancy, but the success rate is lower.

This is probably due to the low level of transcriptional activity in spermatozoa.

Extremely high levels of genotoxic insults, however, render sperm cells incapable of fertilising oocytes. The plasma membrane of the sperm is being harmed by peroxides, which is why this is happening. Human oocytes' resistance to damage is less well understood than that of spermatozoa.

DNA ASSESMENT TESTS : how many tests are there ?

In the comet assay, DNA damage is detected by running single cells through an electrophoresis machine. Sperm and embryos can be tested for DNA damage with this method.

The terminal deoxynucleotidyl transferase (TUNEL) assay is a test for detecting DNA damage in cells by using an enzyme that has been fluorescently labelled.

The sperm chromatin structure assay (SCSA) detects DNA damage by measuring the sensitivity of sperm chromatin to acid.

The DNA fragmentation index (DFI) measures the percentage of fragmented sperm DNA through the use of flow cytometry.

DNA damage in embryos can be detected by a test that counts the number of copies of mitochondrial DNA.

The development of an embryo can be tracked over time with the help of time-lapse photography. Issues with cell division and other aspects of development may be indicated.

When deciding which embryos to transfer in assisted reproductive technologies, we can learn a lot about their DNA using these non-invasive methods.

Views from

DNA damage in preimplantation embryos and gametes: specification, clinical relevance and repair strategies".