When it comes to infertility treatment, you may have a strong image of it being something that women take the lead in. However, according to a survey by the World Health Organization (WHO), approximately half of the causes of infertility are on the male side, so it is not at all uncommon.
Among the various types of male infertility, including spermatogenic dysfunction, sexual dysfunction, and sperm duct obstruction, spermatogenic dysfunction, which is an inability to produce sperm properly, has been considered particularly difficult to treat.
In this article, we will take a closer look at some surprising research findings that may dramatically change the future of male infertility treatment.
Source: Agency for Children and Families | Three causes of male infertility
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Aging and male fertility
Here we explain fertility and how aging affects the causes of male infertility.
What is Fertility?
Fertility is the ability to become pregnant, and it may be easier to understand if you think of it as almost synonymous with reproductive function. Medically, it refers to the organs of each man and woman necessary for conception, gametes such as sperm and eggs, and the overall function of these organs.
| [Fertility in men and women] | male | woman |
|---|---|---|
| organs | testes | Uterus and ovaries |
| gametes | sperm | egg |
| Function (narrow sense) | Erection, ejaculation, etc. | Ovulation, implantation, etc. |
Pregnancy is only possible when both men and women cooperate, and men have important roles to play in producing high-quality sperm (spermatogenesis) and delivering sperm into the woman's body (sexual function).
Source: Japan Society of Obstetrics and Gynecology | Decline in Fertility
Causes of male infertility
The causes of male infertility can be broadly divided into three categories:
| Causes of infertility | Content |
|---|---|
| Spermatogenesis dysfunction | A condition in which the sperm in the ejaculate are low in number, have reduced motility, or both. |
| Sexual dysfunction | Inability to achieve an erection and therefore unable to penetrate, or erection but inability to ejaculate, or both. |
| Sperm duct obstruction | Although sperm are produced, the sperm passage (spermatic duct) is blocked, so there are no sperm in the semen. |
Although men's functions are not as rapidly affected as women's, they are certainly affected by aging. For example, regarding sperm quality, one report found that when comparing men in their 30s and 50s, semen volume in men in their 50s decreases by 3-22%, the percentage of sperm that swim vigorously (sperm motility rate) decreases by 3-37%, and the percentage of sperm that are well-formed (normal sperm morphology rate) decreases by 4-18%.
Furthermore, the man's age is important for maintaining a pregnancy: fathers over 45 years of age are reported to be twice as likely to have a miscarriage than fathers under 25 years of age.
Source: Japan Society for Reproductive Medicine | Q4. What are the causes of infertility?
Source: Japan Society for Reproductive Medicine | Q25. How does aging affect infertility and miscarriage in men?
How are sperm produced? Spermatogonia (stem cells) hold the key
Understanding the mechanisms by which sperm are produced is key to understanding new treatments.
The place where sperm are produced is the seminiferous tubules, which are very thin tubes in the testicles. Imagine this as a sperm factory.
The most important entity here is the spermatogonium, which is the source of all sperm. These spermatogonium are special stem cells that have the ability to continue to supply sperm throughout life.
- Maintaining numbers by copying itself (self-replication ability)
- Produce cells that transform into sperm (differentiation potential)
In other words, while producing their own offspring, they also send out the cells that will become sperm. Sperm cells divide repeatedly with the help of Sertoli cells, and over the course of 42 to 76 days, they mature into tadpole-shaped sperm.
The foundation of male fertility is based on the health and normal functioning of spermatogonia (stem cells), which are the beginning of everything.
Source: Japan Society of Cancer and Reproductive Medicine | Fertility/Fertility Preservation "For Men: Male Reproductive Function"
[Latest research status] Surprising report that stem cell administration improves spermatogenesis
A treatment that involves transplanting stem cells to restore spermatogenesis is attracting attention for male infertility, which occurs when spermatogonia (stem cells), the cells that produce sperm, stop functioning.
There are two main approaches:
- Transplanting spermatogonia themselves
- Injecting other stem cells to improve the testicular environment and support the function of spermatogonia
Although still in the research stage, transplantation of spermatogonial stem cells (PSCs), the source of sperm, is a particularly promising technique for restoring spermatogenesis, and animal experiments have reported surprising results.
For example, one study showed that administering other types of stem cells to rats that had become azoospermic due to drugs completely restored spermatogenesis and even restored fertility. It was also confirmed that transplanting spermatogonia (SSCs) into dogs and monkeys that had lost the ability to produce sperm due to radiation partially restored sperm production.
These studies strongly suggest that stem cell therapy may be an effective option for male infertility, which has been extremely difficult to treat. Currently, research aimed at clinical application in humans is being conducted with safety as the top priority, and great expectations are being placed on this therapy as a future treatment.
Source: Cellular Therapy via Spermatogonial Stem Cells for Treating Impaired Spermatogenesis, Non-Obstructive Azoospermia
summary
Male infertility treatment using stem cells has not yet been established as a standard treatment that anyone can receive. However, it is no longer a dream of the distant future. For those with spermatogenic dysfunction, which has been considered extremely difficult to treat until now, stem cell therapy has the potential to open the door to great hope.
If you have concerns about your fertility or would like to know more about the possibilities of cutting-edge medical treatment, please do not suffer alone; please consult a specialized clinic. Thinking about your future together with a doctor with the latest knowledge is the first step towards hope.
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Supervisor: Dr. Nobuhito Ueda (Surgery Specialist)