Chinese scientists sent into space over thousands of mouse embryos at the stage of two cells to follow their development. It turned out that the orbit of the cells of the embryo divide and differenciate worse than on Earth. Apparently, the matter of radiation: when the Earth is irradiated embryos of the same dose as in space, then they accumulate double strand DNA breaks and worse develop. Perhaps this explains why the rats still failed to multiply in space experiments. A study published in the journal National Science Review.
Scientists have repeatedly sent into space a variety of animals, including embryonic stages. Although many invertebrates and vertebrates continued to develop successfully even in zero gravity, about mammals is still unknown as possible. Attempts to force male and female rats to reproduce in orbit have so far failed. Thing is, apparently, not in the production of sex cells — at least, after his return from space, the rodents are able to become fathers. Sperm quality is also in space does not change.
A group of scientists under the leadership of Aniqua of Duan (Duan Enkui) from the Institute of Zoology, Chinese Academy of Sciences suggested that problems may arise in early embryonic development. To test this, the researchers developed an incubator for space flight. In terrestrial conditions it is possible to cultivate embryos up to the preimplantation stage (blastocyst): about one third grown in this embryo after the infusion of the females developed into full-fledged mice.
In April 2016, China launched a satellite SJ-10, and 12 hours before the start, it established an incubator with the mouse embryos at the stage of two cells. Microscope camera photographed them every 4 hours, and 64 hours them fixed to stop the development and to perform gene expression after returning to Earth.
On Earth, scientists have gathered from incubator 1184 recorded of the embryo. 856 of them developed to the morula stage (multicellular dense ball) or blastocyst (sphere with a cavity inside). However, the blastocyst in space turned out almost twice less than in the same incubator on Earth (34.3% vs 60,2). Thus, the transition from morula to blastocyst in space was violated.
When researchers began to study the quality of the resulting blastocysts, we noticed that they have less cells than in similar terrestrial embryos (average of 41.5 vs. 51.6). In addition, it was found that differs with the expression of key markers characteristic for this stage. Among the superficial cells of blastocysts that developed in space, there were twice those that are stuck in the process of differentiation: they expressed Oct4 and Cdx2 proteins characteristic of inner cell mass. This means that problems in embryos began at the level of division and differentiation of cells.
The causes of these problems, the researchers suspected cosmic radiation. To find out whether it had influence on the DNA of embryos, they measured the number of breaks of double-strand breaks in cells of blastocysts: those that flew in space, they were almost two times more.
Then the authors decided to find out what affects the development of mouse embryos is stronger: the radiation or the absence of gravity. Already on the Ground, they collected a new set of embryos and one was affected by radiation dose (which was approximately equal to that in the embryos received during the flight — 0,5-2 mgra), and the other was cultured in a rotating vessel. It turned out that in conditions of weightlessness to the blastocyst lived a little less germs than usual (65,4% as opposed to 72.9), however, under the effect of radiation the effect was stronger survived just 45.7 percent at the maximum dose. In addition, in microgravity, embryos do not have any double-strand breaks, ruptures, and under the action of radiation they have been appearing all over the blastocyst. In the end, the irradiated embryos worse stuck in the bodies of mothers: the birth rate fell to 7-21 percent (depending on dose) compared to 32.6 percent in the control group.