Frozen testicles can produce sperm 20 years later

Frozen testicles can produce sperm 20 years later
  • Male testicular tissue that is cryopreserved can be reimplanted after more than 20 years and will produce viable sperm, according to a new study in rats.
  • The findings have implications for childhood cancer survivors, the researchers say.
  • While long-frozen testicular tissue could produce sperm, the long delay took a toll in reducing sperm production.

The male testicular tissue that is cryopreserved can be reimplanted after more than 20 years and will produce viable sperm, according to a new study in rats.

The findings have implications for childhood cancer survivors, the researchers say.

The survival rate for childhood cancers has increased dramatically in recent decades, but a serious side effect of treatment is decreased fertility later in life.

One possible treatment for boys facing cancer treatment would be to collect, freeze and, after the cancer is cured, reimplant their testicular tissue, which contains stem cells that could give rise to sperm.

However, it’s not clear what happens to that tissue when it’s subjected to the long-term freezing that might be necessary.

The researchers report that while long-frozen testicular tissue could produce spermthe long delay came at a cost in reduced sperm production compared to tissue that is only briefly frozen.

The new results may have Important implications for the treatment of prepubertal children with cancerfor whom chemotherapy may be preceded by the extraction and freezing of testicular tissue for eventual reimplantation.

“The glass-half-empty way to look at this is that the stem cells appear to be compromised in their ability to regenerate sperm after a long time of freezing,” says Eoin C. Whelan, a principal investigator at the University of Pennsylvania and first author. of the study in PLOS Biology.

“But the good news is that sperm can be produced, and they appear to be transcriptionally normal when we examine their RNA.”

The researchers conducted the study in the lab of Ralph L. Brinster, a professor of reproductive physiology at Penn Vet.

“The findings are critical when considering the transplantation of stem cells from testicular biopsies obtained from prepubertal boys undergoing cancer treatment for later use in reestablishing spermatogenesis after recovery,” says Brinster.

“Early transplantation of these cells is clearly better than waiting a long time before reintroducing the cells into the testicles.”


If a child receives treatment for cancer at a young age, it can take a decade or more between testicular tissue being removed and reimplantation, raising the question of how long tests can remain viable. mother cells frozen spermatogenic (SSC).

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To find an answer the researchers thawed rat SSCs that had been cryopreserved in their lab for more than 23 years and implanted them into so-called nude mice, which lack an immune response that would otherwise reject foreign tissue. They compared the ability of long-frozen SSCs to generate sperm with SSCs frozen for only a few months and freshly harvested SSCs, all from a single rat colony maintained for several decades.

They found that long-frozen SSCs could colonize mouse testes and generate all cell types necessary for successful sperm production, but not as robustly as SSCs from any of the more recently collected tissue samples. While the long-frozen SSCs had similar profiles of gene expression changes compared to the other samples, they produced fewer elongated spermatids, which then form swimming sperm.

“When we looked at the cells immediately after thawing, they looked the same as cells that had been frozen for a short period of time,” says Whelan. “It was only after we transplanted the testicular tissue that we started to see a difference in the efficiency of sperm production.”


These results have several important implications. First, they point out the importance of testing the feasibility of SSCs by directly monitoring the results after reimplantation to determine the potential of cryopreserved cells. Relying on biochemical or cellular biomarkers may not reflect the true loss of stem cell potential over time.

Second, while there are currently no protocols that can expand human SSCs for reimplantation, a requirement to translate this treatment to clinical use, such protocols may need to consider time-dependent degradation of viability, assuming that SSCs humans mimic those of rats.

In third place, the findings underscore that sperm can be produced from long-preserved testicular tissue. Additional research to identify and potentially mitigate key drivers of viability loss could improve the reproductive options of children whose childhood cancers are successfully treated.

“An important follow-up question is ‘What is causing this? What’s the mechanism of operation?’” says Whelan. Ongoing work is investigating some of the genes that the team’s analysis showed to be altered by long-term freezing.

The findings may also hold important clues to preserving other types of stem cells, which are increasingly being investigated in a variety of therapeutic applications.

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