Scientists have found a new way to reprogram mouse stem cells so that they exhibit developmental characteristics similar to the ones of fertilized eggs, or zygotes. These types of factotum stem cells have the capacity to create both all the cell types inside of a developing embryo and also the ones that help the process of nutrient exchange between the embryo and the mother.
The new type of stem cells will allow scientists to have a better understanding of the first molecular decisions in the early embryo, which will then help them increase the variety of tissues which can be generated from stem cells. This ultimate procedure will significantly affect regenerative medicine and therapy using this type of cells.
Embryo Research Underlines Stem Cells' Potential
The research, published Jan. 12 in the online version of the journal Science, as a pre-print article, could revolutionize the way stem cells are employed in various medical processes, as well as broaden the applications of these cells due to their regenerative proprieties.
As part of the research, the scientists also observed a connection between miR-34a and a class of mouse retrotransposons, which are bits of ancient foreign DNA with an important function in mammals. The miR-34a was perceived for a long time as "junk DNA," but this new research ties it to the embryo's decision in the first part of the developmental process.
"Embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) efficiently generate all embryonic cell lineages, but rarely generate extra-embryonic cell types. We show that microRNA miR-34a deficiency expands the developmental potential of mouse pluripotent stem cells to yield both embryonic and extra-embryonic lineages and strongly induce MuERV-L (MERVL) endogenous retroviruses, similar to what is seen with totipotent 2-cell blastomeres," noted the research.
Fertilized eggs are believed to have a full developmental potential, including the capacity to generate all the necessary cell types for embryo gestation, from the developing embryo to the extra tissues sustaining its life. Only seen in placental mammals, the placenta and the yolk sac are of outmost importance for the nutrition and waste exchange between the fetus and the mother carrying the pregnancy.
Totipotent Stem Cells, A Technique Of The Future
On the other hand, the majority of embryonic and inducted pluripotent stem cells have less developmental potential, as they can only generate embryonic cell types, but not the extra-embryonic tissues. The egg's capacity to create both these cell types is often referred to as "totipotency," which is the ultimate state in which a stem cell can be found, happening only during the first stages of the development.
However, little was known about the specific developmental potential of a zygote, which forms immediately after the sperm and the egg come in contact. The zygote is highly difficult to study, as there are very few materials and there is no cell-culture experimental system to allow it yet, which would make this research an important foundation stone in studying the characteristics of this very early developmental process.
"Altogether, our studies reveal a complex molecular network that defines and restricts pluripotent developmental potential, raising the tantalizing possibility of culturing bi-potential ESCs to explore the molecular basis for totipotency," concluded the study.