Today, approximately 1 in 3 of couples experiencing infertility suffer from male-induced infertility. Sperm DNA damage is an important health problem detected in a significant portion of patients investigated for male infertility.
However, it is a measure that cannot be analyzed by the fertility tests currently used in the clinic. Sperm DNA damage may indirectly lead to a decrease in the potential success of adjunctive treatments such as in vitro fertilization or ICSI.
In the classical sperm test applied today, sperm DNA damage cannot be detected. Just because a man’s sperm test results are normal does not indicate that there is no sperm DNA damage. Different methods are used to detect sperm DNA damage.
Sperm DNA damage occurs due to different reasons. Many factors such as smoking and alcohol use, choosing overly tight underwear (as it causes increased heat in the genital area), varicocele, exposure of the testicles to heat and radiation, or obesity can lead to sperm DNA damage.
However, eliminating the factor that causes damage can have a positive effect on DNA damage. In other words, sperm DNA damage is a treatable and reversible disorder. Changes in daily habits, weight loss or, if any, can reduce DNA damage after varicocele treatment.
For this, first the underlying cause of sperm DNA damage must be correctly diagnosed
What is Sperm?
Sperm can basically be defined as the male reproductive cell or gamete. Gamete is also considered as half of a complete cell. When the sperm comes together with the female gamete or egg cell, it forms the human embryo.
The sperm cell is divided into three main parts: head, middle part and tail. The head of the sperm contains chromatin, which is the DNA material that forms chromosomes. Generally, both sperm and egg cells carry 23 chromosomes. When the sperm cell and the egg come together, the embryo has 46 chromosomes.
There is a section called the acrosome at the head of the sperm. There are proteins inside the acrosome that break down the outer membrane of the egg and allow the sperm to enter. In the middle part of the sperm, there are mitochondria that produce energy.
These special structures produce the energy that enables the movement of the sperm cell. Finally, the sperm tail, also known as the flagellum, also provides movement. The tail enables the sperm cell to move forward and reach the egg cell. In this way, the sperm swims and reaches the egg cell and fertilization occurs.
How Is Sperm Formed?
Sperm is produced in the testicles, the male reproductive organ. The testicles also produce the hormone testosterone, known as the male hormone. The process of producing sperm cells is called spermatogenesis. This process begins in the sperm ducts in the testicles. Sperm cells called spermatocytes are produced in the ducts.
Spermocyte cells go through several divisions to become cells called spermatids. The spermatids then grow and mature until they become adult sperm. On average, it takes 74 days for the male body to produce new sperm cells. However, this process may vary from person to person.
What is Sperm DNA?
Chromatin in mammalian sperm differs from other somatic cells in terms of structure and organization. Sperm chromatin structure protects the genetic structure during the transfer of the paternal genome from the male reproductive system to the female reproductive system.
Sperm DNA is enclosed in an almost crystalline state with special, small and simple proteins. This structure is almost six times denser than mitotic chromosomes.
What is Sperm DNA Damage?
To understand sperm DNA damage, it is first necessary to understand the structure of DNA. DNA has a long and spiral structure called a double helix. The helix is made up of chemicals called nucleotides. The unique sequence of these nucleotides reveals each organism’s unique genetic sequence.
These nucleotides are linked to each other via sugar and phosphate. Normal sperm carries the genetic material necessary for successful fertilization, embryo development and birth. Sperm DNA is half of the baby’s genomic material, and abnormalities in DNA also affect the reproductive process.
Sperm chromatin or DNA may be damaged due to environmental conditions, genetic mutations or chromosomal disorders. It may occur due to sperm DNA packaging disorders, oxidative stress or premature cell division.
What Causes Sperm DNA Damage?
Sperm DNA damage can occur during or as a result of DNA packaging during spermiogenesis. Additionally, sperm DNA damage may occur due to reactive oxygen species known as free radicals or premature division.
Despite many studies conducted to date, it is still not known exactly what causes sperm DNA damage. However, the variable sperm chromatin structure in a single ejaculate is attributed to the protamine content.
Therefore, abnormalities in the proteolytic cleavage of protamine precursors lead to heterogeneity of human sperm DNA and may be an additional source of potential infertility.
How to Detect Sperm DNA Damage?
There are multiple tests to detect sperm DNA damage. Most of these tests are extremely important for planning assisted reproductive treatments such as in vitro fertilization. There are direct and indirect assessments to understand sperm DNA damage.
Common direct methods include Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-nick-end labeling method, briefly called TUNEL, and Comet analysis. The most commonly performed indirect method is sperm chromatin structure analysis, briefly known as SCSA. Although there are many other methods other than these, the frequency of preference of other methods is quite low.