05 October 2012

Mice from stem cells

Japanese biologists have turned stem cells into eggs

<url>Scientists from Kyoto University have learned how to create full-fledged eggs from embryonic and induced stem cells of mice.

During fertilization and implantation of a surrogate mother, healthy mice are obtained from such eggs (photo of one of the litters – Katsuhiko Hayashi).

The work of Hayashi et al. Offspring from Oocytes Derived from in Vitro Primordial Germ Cell–Like Cells in Mice is published in the journal Science, its summary is given by NatureNews (Mouse stem cells lay eggs. Lab-made oocytes produce fertile offspring).

At first, the researchers treated the stem cells of mice with a cocktail of various signaling proteins in order to launch a program of transformation into gonocytes (primordial germ cells) in them. These cells in an ordinary embryo are the precursors of any germ cells – both eggs and spermatozoa.

Auxiliary cells were added to the obtained gonocytes from the tissue of the donor ovaries, having previously removed all the germ cells from them. After that, the authors implanted the resulting mixture into the ovaries of mice.

Inside the rodent organism, structures similar to ovaries were formed from gonocytes and donor auxiliary cells. In this state, artificial gonocytes matured and turned into eggs. Eggs were isolated and artificial insemination was performed. The resulting embryo was implanted into a surrogate mother. The "artificial" mice were born healthy, without any noticeable abnormalities.

Earlier, the same group of scientists was able to turn stem cells into male germ cells – spermatozoa. This process, as expected, turned out to be somewhat simpler – at that time, scientists did not need, for example, to use auxiliary donor tissue. Induced gonocytes could be directly injected into the testes of sterile mice.

The transformation of stem cells into sex cells has only now been possible due to the fact that the development of sexual and non-sexual (somatic) cells occurs in very different ways.

In all multicellular organisms, from the very beginning of embryo growth, germ cells are separated into a special line (germline) and do not mix with ordinary, somatic cells. In addition, germ cells divide in a special way during maturation (meiosis) – so that the original double set of chromosomes in the cell turns into a single one. The regulation of this process in mammals – how signals from surrounding tissues affect the inclusion of such a division program in germ cells is still poorly known. Reproducing this process in a test tube will help to better understand the mechanisms that control it.

Portal "Eternal youth" http://vechnayamolodost.ru05.10.2012

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