We often hear about stem cells and how they are widely used in the research world. In fact, these represent great hope in the field of regenerative medicine, but what are they really? How they are generated?
Stem cells are undifferentiated cells capable of unlimited dividing and differentiating into other cell types: nervous, bone, of the heart, of the skin, liver and pancreas. They can be taken from the embryo, from the fetus or adult and depending on the potential of the stem cells, are classified in: totipotenti, if they give rise to a whole organism; pluripotent, if they generate many types of tissues but not a complete and multipotent organism, if they only differentiate into tissue cells from which they are taken. Therefore, embryonic stem cells (ESC) they are distinguished from the adult ones because the former are totipotent while the latter are multipotent. However, ESCs cannot be taken from human embryos for both ethical and legal reasons, therefore such cells are made pluripotent.
The transformation of embryonic stem cells into induced pluripotent stem cells (IPSC) takes place through a reprogramming process that introduces within the ESCs, the essential factors that induce pluripotency. They are called “Yamanaka factors” from the name of the scientist who discovered them or even “OSKM”, acronym of the initials of the four factors: Oct4 , Sox2, Klf4, Myc. These genes reprogram the genome returning the cell to a primordial state, capable of generating all cell types of the embryo except extra-embryonic tissues, that is, those tissues that form the embryonic appendages allowing the fetus to implant and survive in the maternal uterus.
In 2006 a group of Japanese scientists, guidato da Shinya Yamanaka, managed to obtain iPSCs from dermal cells called fibroblasts, both mouse and human the following year. They have been collected 24 initial genes that could induce pluripotency and each was introduced into mouse fibroblasts. These cells were transplanted into nude mice, who have an inhibited immune system, in order to observe the different combinations of 24 genes and identify the four essential transcription factors.
Further discoveries showed that iPSCs can also be created with different gene combinations, not just from human mouse fibroblasts, but also from cells of the gastric mucosa and liver. However, the reprogramming process needs to be improved in order to make these cells more efficient, which represent a great promise for the treatment of numerous diseases that are currently incurable, such as Parkinson's disease, Alzheimer's disease or multiple sclerosis.
Ebrahimi. Reprogramming barriers and enhancers: strategies to enhance the efficiency and kinetics of induced pluripotency. Cell regeneration. (2015) 4:10 DOI 10.1186 / s13619-015-0024-9
Kejin Hu. All roads lead to induced pluripotent stem cells: the technologies of iPSC generation. Stem cells And development. Volume 23, number 12, 2014. DOI: 10.1089/scd.2013.0620