"There are a number of places, including at the Children's Hospital of Philadelphia," Brinster said, "that are already freezing cells for patients to use later, with the expectation that the necessary culture system and implantation techniques will be developed. A logical question for patients to ask is, How do we know that, after 10 years or more of being stored, these cells are any good? That's what our study addresses."
The techniques for extracting these cells and re-implanting them have been developed, so a critical question for researchers was whether spermatogonial stem cells could survive the decade-plus period they might need to remain frozen.
Fortunately, Brinster had a large collection of cryopreserved spermatogonial stem cells stored in the mid-'90s. The collection consisted mostly of cells taken from mice but included a small number of rat, rabbit and baboon samples. Between their age and variety, these samples represented an important resource to address questions regarding long-term cryopreservation of spermatogonial stem cells, before the technique could be used in humans.
After being thawed, the spermatogonial stem cells of rabbits and baboons were labeled with a fluorescent dye so that the researchers could track where in the testes they would eventually migrate and embed once they were implanted in mice. This was a critical step for the rabbit and baboon cells, which lacked appropriate experimental recipients; once implanted in mice, the studies showed that the cells migrated correctly and embedded in the recipient testes' basement membrane, indicating their viability.
A complete functional test could only be done for the mouse spermatogonial stem cells, as they could be implanted into mice and tested to see if they could produce sperm, and whether that sperm could lead to healthy offspr
|Contact: Evan Lerner|
University of Pennsylvania