Scientists have discovered a method of reprogramming embryonic stem cells in lab mice to mimic the abilities of fertilized eggs. The new stem cells then exhibit characteristics of cell types whose job it is to deliver nutrients from mother to embryo. Researchers at the University of California are using these stem cells to understand what the first decisions are made by cells in an early embryo. The insights of this research could broaden the understanding of a number of body tissues that stem cells can generate and ultimately lead to new stem cell therapy and regenerative medicine. The report was published in the journal Science.
Research Sheds New Light on Embryonic Development
Stem cells that come from embryos are considered pluripotent because they can turn into any cell type. Induced pluripotent stem cells are taken from the skin or blood and modified genetically to mimic an embryonic stem cell. These cells are pluripotent, giving them the ability to turn into any adult cell type. Stem cell research has given scientists a new way of studying embryonic development, which has given them a method of detecting molecular pathways that decide the embryonic cells fate.
New research is concentrating on a cell type called a zygote, which is created immediately after sperm and egg merge, but it has become a difficult task to analyze due to the limits of the current technology. The new study has revealed a mechanism that regulates cell totipotency, or ability to divide and create new cell types.
New Stem Cells May Re-Grow Damaged Tissue
Scientists have harvested mouse embryos for lab research in the quest to discover the genetic switches that tell the embryonic cells what tissue to develop as the embryo grows into a fetus. These genetic switches are giving scientists insight into early stage diseases, because stem cells have the ability to re-grow body tissue damaged from heart failure or diabetes.
An alternative to using embryionic stem cells is the expanding field of artificially derived stem cell research. These adult stem cells are almost as flexible as the embryonic stem cells, but neither are as flexible as the cells of the fertilized egg at the beginning of conception which can produce extra-embryonic tissues. Cells harvested from embryos have already begun to commit to different cell types.
Removing MicroRNAs Enables Stem Cell Development
The researchers found small molecules called MicroRNAs which appeared to be a braking mechanism preventing embryonic and adult stem cells from generating extra-embryonic tissues. When this molecule was genetically removed, about 20 percent of both types of stem cells were able to greatly expand the potential to develop into other cell types. The stem cells were able to survive up to a month in a cell culture.
One final discovery in lab mice was a class of ancient DNA which makes up a small fraction of the overall DNA of the mammal genome. For decades scientists regarded this as ancient junk DNA that served no purpose in the growth of embryos. But this study has suggested that ancient DNA may be closely linked to the decision-making process of embryonic cells. According to the co-author of this study Todd MacFanlan, it remains an open question as to whether this “junk DNA” are the real drivers of cell fate decisions in early embryonic development.
