According to a new study of rodents, frozen male testicular tissue can be transplanted again after more than 20 years and will continue to produce viable sperm The study by Eoin Whelan of the University of Pennsylvania School of veterinary medicine and colleagues was published in [PLoS Biology] on May 10( https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3001618 ) 》In open journals. However, compared with tissues that are only temporarily frozen, the cost of long-term delay is the reduction of fertility. This finding may have a profound impact on the treatment of young male cancer patients. For them, testicular tissue can be frozen before chemotherapy in order to finally re implant into the body.
In recent decades, the survival rate of childhood cancer has been greatly improved, but a serious side effect of treatment is the decline of fertility in the future. One potential treatment is freezing and re implanting testicular tissue, which contains stem cells, a procedure that has recently been shown to restore the fertility of macaque models, at least after short-term freezing.
However, for pre adolescent boys with cancer, re implantation may not be feasible for ten years or more after harvest, which raises the question of how long frozen spermatogonial stem cells (SSCs) can be maintained. To explore this problem, the authors thawed rat hematopoietic stem cells that had been frozen in their laboratory for more than 23 years and implanted them into so-called nude mice, which lacked immune response or would reject foreign tissues. They compared the ability of long-term frozen hematopoietic stem cells to produce viable sperm with hematopoietic stem cells frozen for only a few months and freshly harvested hematopoietic stem cells from a rat population that has been maintained for decades.
The researchers found that long-term frozen hematopoietic stem cells can colonize the rat testis and produce all the necessary cell types to successfully produce sperm, but they are not as powerful as hematopoietic stem cells from recently harvested tissue samples. Although the gene expression changes of long-term frozen SSCs are similar to those of other samples, they produce less elongated sperm, and these sperm will continue to form swimming sperm.
These results have several important implications. First, they pointed out the importance of testing SSC viability in situ rather than relying on biochemical or cellular biomarkers to determine the potential of cryopreserved cells, which may not reflect the actual loss of stem cell potential over time. Second, although there is currently no agreement to expand human hematopoietic stem cells for re implantation - a requirement for the clinical development of this treatment. However, assuming that human hematopoietic stem cells mimic rat hematopoietic stem cells, this protocol may need to consider the degradation of viability over time. Finally, this is good news that survivability will never be lost during long-term cryopreservation, which indicates that it is possible to identify and reduce the key factors of survivability loss in order to improve the reproductive choice of boys with successful treatment of childhood cancer.
Whelan added: "our study shows that rat spermatogonial stem cells can be successfully frozen for more than 20 years, transplanted into infertile recipient animals and regenerate the ability to produce sperm, albeit at a reduced rate. This can provide a way to recover the loss of fertility of pre adolescent boys treated for cancer."