Cryopreserved male testicular tissue can be reimplanted after more than 20 years and still produce viable sperm, according to a new study in rodents, published this week in PLO Biology.

however, work led by Eoin Whelan, gives University of Pennsylvania College of Veterinary Medicine (USA), notes that the long delay has a reduced fertility cost compared to tissue that is only briefly frozen.

The survival rate for childhood cancers has increased, but a serious side effect of the treatment is a decrease in future fertility.

According to Whelan, “The results may have important implications for the treatment of children with cancer, for whom chemotherapy may be preceded by the collection and freezing of tissue from your testicles for eventual reimplantation.”

The survival rate for childhood cancers has increased in recent decades, but a serious side effect of treatment is a decrease in future fertility.

One possible treatment would be to harvest, freeze and reimplant testicular tissue, which contains stem cells, a procedure recently demonstrated in a monkey model to restore fertility, at least after a short-term freezing.

But for prepubescent children with cancer, reimplantation may not be viable for a decade or more after removal, raising the question of how long the cells can remain viable. spermatogenic stem cells frozen.

Cells cryopreserved for 23 years

To explore this question, the authors thawed these mouse stem cells that had been cryopreserved in their lab for over 23 years and implanted them in so-called ‘nude’ mice, which lack a immune response that would otherwise reject the foreign tissue.

They then compared the ability of long-frozen spermatogenic stem cells to generate viable sperm with those cryopreserved for just a few months and those freshly harvested, all from a single mouse colony maintained for several decades.

They found that frozen spermatogenic stem cells were able to generate all the cell types needed to successfully produce sperm.

The authors found that frozen spermatogenic stem cells were able to colonize rodent testes and generate all the cell types needed to produce sperm successfully, but not as strongly as cells from more recently collected tissue samples.

Although the long-frozen cells exhibited similar profiles of gene expression changes compared to the other samples, they produced fewer elongated spermatids, which went on to form swimming sperm.

Good news

The results highlight the importance of testing on site viability of spermatogenic stem cells, rather than relying on biochemical or cellular biomarkers, to determine the potential of cryopreserved cells, which may not reflect the actual loss of potential of these cells over time.

The good news, says Whelan, “is that this viability is not lost during the long-term freeze, indicating that it may be possible to identify and mitigate key drivers of loss of viability to improve production rates.” reproductive options of children treated for childhood cancer.

Reference:

Whelan EC, Yang F, Avarbock MR, Sullivan MC, Beiting DP, Brinster RL. “Reestablishment of spermatogenesis after more than 20 years of mouse spermatogonial stem cell cryopreservation reveals an important impact on the ability to differentiate.” PLoS Biol (May 2022)

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