What are artificial seeds

Artificially produced sperm cells : Sperm from the test tube

It sounds as logical as it is trivial: a man who does not produce sperm for genetic reasons cannot father children. Biologists are now questioning the inevitability of this fate. Apparently, scientists working with Renée Reijo Pera from Stanford, California and Montana State University have succeeded for the first time in obtaining sperm precursors from the stem cells of hereditary sterile men. You report on it in the specialist magazine "Cell Reports". The technology has great potential for treating patients who are unable to produce sperm, whether for hereditary reasons or after aggressive cancer chemotherapy, Pera says. "Perhaps it will even be possible to transplant germ cells grown from stem cells directly into the testes of men who have problems with sperm production."

So far it has not been possible to grow sperm in the Petri dish

Pera's team first created stem cells from the skin cells of infertile men, which are known as induced pluripotent stem cells (ipS cells). The cells have the same genetic make-up as the patient and are therefore not rejected by the immune system during a transplant. Theoretically, all human cell types can be produced with it - including sperm and egg cells.

So far, attempts to trace the development of sperm in the Petri dish have not been very successful. Pera therefore injected the stem cells into testicular tubules obtained from mice. In both humans and mice, the maturation of the sperm takes place in these tubules under hormonal control. In fact, the sterile male's stem cells grew in the mouse testis, and they at least developed into intact sperm progenitor cells.

Are men becoming superfluous?

It is true that the tubules of the mouse testes have not yet been able to initiate the final stages of maturation so that the progenitor cells can eventually develop fertile sperm. With the help of this technique, however, the researchers can study how they have to treat stem cells in order to be able to reproduce the complete human sperm production in the Petri dish.

For this complete sperm production, among other things, substances are necessary that are provided by the male Y chromosome. "The development of sperm depends on genes on the Y chromosome, and only men have that," says George Daley, stem cell researcher at Harvard University. But it cannot be ruled out that ways will be found in the future to circumvent or replace the influence of the Y chromosome. This would make it possible to develop sperm in the Petri dish based on stem cells from women.

Only female offspring would result from such sperm, because stem cells from women do not contain the Y chromosome, which is crucial for male development. But if one day it is possible to breed both egg cells and sperm from female stem cells, then men will at least be superfluous for test-tube fertilization.

Ethically controversial way

At this point it becomes clear how far-reaching human interventions in biology could be. Be it - as in the example mentioned - the cultivation of germ cells in the Petri dish or the mixing of human and animal stem cells, the creation of human-animal chimeras for research or as an organ donor - it is an ethically controversial way that stem cell research and its experiments opened. George Daley recognized that too. The former president of the International Stem Cell Research Society ISSCR is now chairman of a “task force” that wants to “develop guidelines for responsible stem cell research and clinical implementation”.

This also applies to the question of what the egg or sperm cells produced artificially from stem cells are used for. "In order to understand the mechanisms of infertility, develop new contraceptives or improve reproductive medicine, it is necessary to research germ cell biology," says Daley. "Whether such germ cells from stem cell research are ever safe and effective enough to dare to use them for artificial insemination remains to be seen."

When the first genetic engineering methods emerged in the 1970s, researchers met in Asilomar, California, and drafted rules for the safe use of the new technology. A comparable self-reflection and commitment is still missing for stem cell research - although it becomes more urgent with every success story.

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