The scientists used human blood cells, which they reprogrammed into induced pluripotent stem cells. Then, using a previously developed method, they transformed them into germ cell precursors. The next step was to create an environment in which these cells could continue to develop.
To do this, the scientists mixed human cells with non-reproductive cells from the testes of developing mice. These cells provide structural support and create the conditions necessary for the maturation of male reproductive cells. In previous preclinical experiments, this system only allowed for the earliest stages of development, and the process stopped there. Now, the researchers have gone further. Nature reports their findings.
The resulting cell mixture was transplanted into a special pocket created on the surface of a living mouse kidney, which is well suited for the engraftment and development of transplanted tissue. Following transplantation, the cells spontaneously organized into tubular structures resembling the seminiferous tubules in which sperm are normally produced. A month after the transplant, tissue resembling testicular tissue had formed.
After six months, the human cells reached the spermatogonia stage. These are precursor cells that later develop into mature sperm. However, development stopped at this stage, so it was not possible to obtain fully developed sperm.
According to the authors, the work marks an important step towards growing human sperm in the laboratory, but practical applications are still a long way off.
The developed system can already be useful for studying the early stages of male germ cell formation and identifying the causes of infertility. According to statistics, approximately 40% of male infertility cases still have no identified cause.
The technology has potential for treating infertility in the future, but healthy offspring need to be produced in preclinical models to prove it.
Previously, stem cells helped grow retinal cells to restore vision.
