Anyone who has closely followed the Nobel Prize Awards in 2012 should not have missed the fact that the Nobel Prize in Medicine was awarded for discoveries in the area of stem cells. Strictly speaking, for the development of so-called induced pluripotent stem cells (iPS) .
Stem cells are cells of an organism that have the following two properties: self-renewal and differentiation. Self-renewal means nothing other than that a cell divides and these daughter cells again have the same properties as before the division. In turn, differentiation means for a cell to specialize, for example in a skin, liver, or blood cell.
On the one hand, stem cells ensure that they do not die out, at the same time they ultimately form every different type of cell during the development of an organism.
The somewhat wooden term "induced pluripotent stem cells" now describes a class of stem cells that can surprisingly be obtained synthetically from already differentiated body cells.
"Pluripotency" describes the ability of such cells to specialize in almost any tissue. Until now, this property was reserved for the so-called embryonic stem cells, i.e. cells that could previously only be obtained by destroying an early embryo. These (if of human origin) ethically highly problematic cells have long been the only way to enable cell replacement therapies.
Against this background, it is very gratifying that the Japanese Shinya Yamanaka managed to transfer the properties of the embryonic cells to cells that are ethically much less harmful. The latter can be obtained from patient skin samples, for example, and also offer the advantage that they are inherent to the body. That in turn could make problematic rejection reactions less likely.
294/5000 But how can it be that fully differentiated cells, which once stem from a stem cell, but otherwise do not usually have the slightest tendency in the body to change into other cells, suddenly show capabilities that are otherwise only found in cells in the embryo?
The key to understanding lies at the level of gene regulation. It has to be made clear that the variety of cells in a human body, for example the cells of the skin, blood cells, nerve or liver cells, does not simply result from the sequence of their genes. The latter is virtually identical in all cells. So you couldn't just look at the DNA of a cell to see what type of cell it is.
Rather, a cell is what it is because its genes are in a certain state. This condition could mean being on or off. In fact, one can compare this gene regulation with a dimmer than with a simple switch, because numerous states can occur on the scale from "off" to "maximum on".
The totality of all these states determines, if not completely, what a cell is phenotypically, that is, externally.
If one could now specifically change the regulation of genes in a cell, it should be possible to simulate the conditions of an embryonic cell in a skin cell, for example.
Exactly this has apparently been achieved with the induced pluripotent stem cells, because Yamanaka was able, by injecting some biological tools from the outside into already specialized cells, whose state changed by changing the gene regulation in such a way that they resembled embryonic cells in numerous properties. In this way, cells of the skin can be de-differentiated and re-programmed into other cells, for example in nerve cells.
The tremendous chances of such an approach are obvious:
Wherever one can expect healing success by introducing healthy, new cells, such patient's own cells could be used. Parkinson's, Alzheimer's, heart attacks, diabetes, to name just a few, would be candidates for therapy.
So far, however, mainly because certain concerns regarding the safety risks of the iPS cells have not yet been resolved, no human study has shown that the induced pluripotent stem cells can actually deliver on this promise, although experiments with mice have already done so look promising.
It is also interesting to see which therapeutic promises and molecular biological findings stem cell research will publish in the near future.