Gametogenesis failure is the inability to produce viable sex cells. It is estimated that about 15% of couples are plagued with this condition. Finding a way to create these reproductive cells has become a major focus for infertility treatment. Scientist from China have finally achieve this goal in mice, making fully functioning sperm from stem cells.
Spermatogenesis is the process that produces sperm. It begins with specificification of embryonic stem cells into primordial germ cells (PGCs). They then divide by meiosis. All other cells divide via mitosis, but sex cells only contain half the number of chromosomes as all other cells.
However, replicating meiosis outside the body has proved to be a hurdle for scientists. To fully achieve meiosis, researchers must demonstrate all stages of meiosis including synapsis and recombination which is the division and re-joining of chromosomes. Any cells that do complete the meiosis must also be able to produce viable offspring. Only then can it be considered the creation of in vitro gametes.
To achieve changing the embryonic stem cells into PGC-like cells they first surrounded them with testicular tissue that was genetically engineered for high levels of testicular retinoic acid. They then tested introducing several sex hormones. They tested testosterone, follicle-stimulating hormone and bovine pituitary extract. Only when all three were present together did meiosis take place.
Through genetic analysis they were able to determine the presence of compounds that are known to be involved in the chromosomal synapsis and recombination. Thus proving that the stages of meiosis had occurred.
To further prove the viability of the process, the produced gametes were used to fertilize mouse eggs, then implanted and developed into embryos and ultimately giving birth to healthy pups. These pups lived into adulthood and successfully produced offspring on their own validating the process.
Further research is need to understand if this process is suitable for human reproduction. The researchers are optimistic that their work gives a starting point for treating male infertility.