Male primates who become sterile due to side effects of cancer drugs can regain fertility by injecting banked sperm-producing stem cells, researchers say.
In the animal study by researchers at the University Of Pittsburgh School Of Medicine And Magee-Womens Research Institute, previously frozen stem cells restored production of sperm that successfully fertilized eggs to produce early embryos.
Some cancer drugs work by destroying rapidly dividing cells. As it is not possible to discriminate between cancer cells and other rapidly dividing cells in the body, the precursor cells involved in making sperm can be inadvertently wiped out leaving the patient infertile, said senior investigator Kyle Orwig from Magee-Womens Research Institute.
"Men can bank sperm before they have cancer treatment if they hope to have biological children later in their lives," Orwig said.
"But that is not an option for young boys who haven't gone through puberty, can't provide a sperm sample, and are many years away from thinking about having babies," he said.
Even very young boys, though, have spermatogonial stem cells in their testicular tissue that are poised to begin producing sperm during puberty.
To see whether it was possible to restore fertility using these cells, Dr. Orwig and his team biopsied the testes of prepubertal and adult male macaque monkeys and cryopreserved the cells from the small samples. The monkeys were then treated with chemotherapy agents known to impair fertility.
A few months after chemotherapy treatment, the team re-introduced each monkey's own spermatogonial stem cells back in to his testes using an ultrasound-guided technique. Sperm production was established from transplanted cells in nine out of 12 adult animals and three out of five prepubertal animals after they reached maturity.
In another test, spermatogonial stem cells from other unrelated monkeys were transplanted into infertile animals, which created sperm with the DNA fingerprint of the donor to allow easy tracking of their origin.
In lab tests, sperm from transplant recipients successfully fertilized 81 eggs, leading to embryos that developed to the morula and blastocyst stages, which are the stages that normally precede implantion in the mother's uterus. Donor parentage was confirmed in seven of the embryos.
"This study demonstrates that spermatogonial stem cells from higher primates can be frozen and thawed without losing their activity, and that they can be transplanted to produce functional sperm that are able to fertilize eggs and give rise to early embryos," Orwig added.
The study has been recently published I the journal Cell Stem Cell.