Eggs and spermatozoa from stem cells
Artificial germ cells will save from infertilityAlexey Tymoshenko, GZT.ru
Biologists have managed to obtain germ cells from embryonic stem cells for the first time.
This is an extremely important step in obtaining artificial sperm and eggs, because in the future they will be used to treat infertility.
A group of scientists from Stanford University (USA, California) published an article in the journal Nature, in which they talked about obtaining human gametes – germ cells from embryonic stem cells. It is premature to talk about their direct application in reproductive medicine, although theoretically the work of biologists can lead to a radical solution to the problem of infertility.
Infertility: the final solution to the issue?
Infertility in humans can be caused by a number of reasons. The complex and delicate process of egg and sperm formation depends on hundreds, if not thousands of factors, and currently it is not always possible to cope with its disorders.
The discovery of stem cells and the subsequent study of their properties gives some hope for solving a delicate problem. Stem cells can divide indefinitely and subsequently acquire various specializations, giving rise to a variety of tissues and organs. So why not use them to produce germ cells in the laboratory? After all, reproductive organs are formed eventually from only a few of them!
If it is possible to grow spermatozoa or an egg from stem cells in a test tube, the main thing is that the expectant mother can carry an embryo planted in the uterus. Or you can resort to surrogate motherhood: then even those couples who are faced with the most severe violations of reproductive function – the absence of the uterus, ovaries or testes will be able to have children.
However, to grow eggs and spermatozoa from cells that are not initially sexual, you just have to learn. It will also be necessary to understand how the stem cell is reprogrammed, to study possible risks, to work out many different methods – it is these problems that scientists are working on now.
Progress does not stand still
About the work in the field of artificial gametes in GZT.EN it has already been told: in the summer of 2009, scientists from the USA managed to grow an egg from an immature follicle (a vesicle inside the ovary where an egg is formed under normal conditions), and their British colleagues even went all the way from a stem cell to a sperm.
And now a new step has been taken. A California group of researchers has identified genes that have been manipulated to direct stem cells along the path of gamete formation. The genes designated as DAZ and BOULE turned out to be necessary for meiosis, a process specific to the formation of germ cells.
Ordinary cells divide by mitosis: in half and with each daughter cell receiving a double set of DNA. Germ cells are formed by meiosis – by dividing twice in a row, resulting in four cells with a single set of genetic material. When the sperm and egg merge, a cell carrying a double set of DNA is obtained again, and in the future it already begins to divide by mitosis.
Although scientists have used embryonic stem cells, progress in the field of stem cell production allows us to hope that over time it will be possible to work out sufficiently reliable methods for obtaining stem cells from conventional ones. In this case, it will be possible to take a tiny piece of skin or other tissue from the patient, isolate a group of cells from it, turn them into stem cells, then perform another manipulation – and get sperm or eggs.
The described multi-stage manipulations now seem extremely complicated. The scientists emphasize that their work is "significant in terms of further scientific research in this area," and only then add a cautious: "And potential clinical applications." There are still a lot of pitfalls on the way to solving the problem of infertility, but progress continues, and this study is a clear evidence of that.
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30.10.2009