Children before puberty who become infertile due to cancer treatment may be able to produce sperm after re-implantation of frozen testicular tissue if animal studies are performed on humans.


May 10, 2022

Germ cells and rat semen after implantation in a mouse testicle

Eoin Whelan, Whelan et al., 2022, PLOS Biology, CC-BY 4.0

Rat testicle cells, which had been frozen for 23 years, produced sperm after implantation in mice.

The findings suggest that children who have frozen testicular tissue before cancer treatment may be able to re-implant the tissue so that they can one day have their own biological children through in vitro fertilization (IVF), he said. Eoin Whelan at the University of Pennsylvania in Philadelphia.

Chemotherapy to treat cancer can kill the stem cells in the testicles that produce sperm. Adults may have frozen sperm samples before this treatment, but this is not an option for children who are about to go through puberty.

In such cases, some clinics remove and freeze small samples of immature tissue from children’s testicles in the hope that if they are re-implanted as adults, they will mature and begin to produce sperm. At least one clinic located in Belgium has been approved to start such reimplantation surgery.

The study of Whelan and his colleagues gives some reason for optimism. They took advantage of rat stem cells that were isolated and frozen 23 years ago by thawing and implanting them in the testicles of mice.

The mice were treated with a drug that killed their own sperm-producing cells – which is too toxic for use in rats – and had a defective immune system so they could not reject the transplant. In comparison, the same procedure was performed in other mice using rat cells that had been removed and implanted immediately, as well as in rat cells that had been frozen several months ago.

When the testicles of the mice were examined, the 23-year-old stem cells survived and developed into groups of sperm-producing cells, although they formed about 20 times fewer groups of cells than fresh tissue or recently frozen tissue. The cell groups of the 23-year-old implants produced mature sperm, but each produced about a third more than those obtained from implants of fresh or recently frozen cells.

However, if the same results occur in humans, participants may produce less semen, even if the numbers are low, Whelan said. “You really only need one viable sperm to succeed.”

It is unclear whether the results will be translated for humans, as there are some differences between the team’s methods and those currently used by fertility clinics, he said. Rod Mitchell at the University of Edinburgh, UK.

Researchers froze isolated stem cells from testicles while clinics froze entire tissue samples. They also took cells from adult rats, while clinics had to take tissues from children who had not yet passed puberty. “There are a lot of unknowns,” Mitchell said.

Reference in the magazine: PLoS biology, DOI: 10.1371 / journal.pbio.3001618

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