19 Sep

Today, I am going to talk about a nice discovery that will help scientists to fight male infertility. Indeed, a French start–up just achieved to produce fully formed human spermatozoa. We are talking about something that researchers have been trying for 15 years. How did they manage to do that? We first need to know how spermatozoa are produced. Everything begins with male primordial germ cells. These cells will then go through different pathways called mitosis and meiosis. These initial cells are called spermatogonia.

As I said, there are different steps for spermatogonia to become spermatozoa; these steps are illustrated on the following scheme.


Spermatogonia will divide by mitosis to give 2 primary spermatocytes. These spermatocytes will then undergo two steps of meiosis in which 2 primary spermatocytes give 2 secondary spermatocytes and then these 2 secondary spermatocytes will give 2 spermatids each. These cells will give rise to spermatozoa. This is the basic pathway to get spermatozoa. This pathway lasts 72 days and is one of the most complicated mechanisms in the human body. Now, how did this company to obtain the same result in vitro?

In the 90’s they were already able to go through the meiotic step in vitro with rat cells, but they also had a problem. Indeed, only 80% of the process was doable and the spermatozoa were blocked in the final step. To solve the problem, they decided to use hydrogels. These gels are made out of more than 90% of water. Thus, these gels are perfect for cell culture.

copyright CNRS Photothèque

They performed biopsies on patients’ testicles containing spermatogonia only and they put them on the biomaterial. The gel is immersed into a culture medium, which allows cells to grow, and the mechanism to be done. They first tested their system on rat cells and when they noticed that everything was working fine, they decided to try on testicles biopsies. They used biopsies from transsexuals because these men are undergoing a hormonal treatment that makes them the closest model from infertile men. After 72 days, they were able to obtain spermatozoa from these biopsies. Their goal was reached!

This discovery is a huge advantage for young men who had chemotherapy, which can block the spermatogenesis afterwards. They can also treat every kind of infertility coming from men having at least spermatogonia. The company, Kallistem® is now raising funds to pursue their research!

I leave you with these pictures of their success!



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« Discovery of a new hominid species »


PhD Student in Biophysics

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