Bone Stem cells
Stem cells found in human skeleton
New stem cells can only produce bones and cartilage
Kirill Stasevich, "Science and Life"
Our tissues and organs are constantly being updated: old cells fail, new ones come in their place. This happens in different organs at different speeds, but stem cells always serve as a resource – those that can divide for a very long time and which from time to time lose the ability to divide, acquiring some specific function. Moreover, the stem cells themselves, which are in the adult body, are not universal, they also have specialization, and those of them that renew the skin or intestinal epithelium cannot produce, for example, blood cells.
It is believed that there are no stem cells only in the heart – soon after birth they quickly fall asleep in it. However, not in all organs in which stem cells are clearly present, they were immediately detected. That's exactly what happened with the skeleton: researchers have been looking for cells for many years that would give bone, bone marrow and cartilage, and nothing more.
It should be clarified here that there are mesenchymal stem cells that turn into bone and cartilage cells, but, in addition, they also turn into adipose tissue cells, muscle cells and some more. That is, mesenchymal stem cells are cells of a fairly broad profile, and it cannot be said that they serve only the skeleton. However, in 2015, Stanford researchers found stem cells in mice that were only skeletal. The experimental mice were genetically modified so that their different stem cells fluoresced in different colors, depending on which genes they have. In this way, skeletal cells were caught.
However, to find them in humans, it was necessary to use some other method - it is (so far) impossible to make a genetically modified glowing person. Therefore, researchers began to closely study the bones of human embryos that died before birth for one reason or another. In those bone zones where the bone should grow, the authors of the work found cells in which the activity of genes was similar to the activity of the genes of skeletal stem cells of mice; and in experiments, microscopic fragments of bone, cartilage and bone marrow were actually obtained from such human cells. The same cells were subsequently found in the bones of adults (samples of adult bone tissue were obtained from patients who underwent surgery on the knee or femur). The new cells and their properties are described in detail in an article in Cell (Chan et al., Identification of the Human Skeletal Stem Cell).
Usually they talk about stem cells in connection with regenerative medicine – with their help they want to treat diseased organs, or even grow healthy organs to replace the spoiled ones. Those mesenchymal cells with a fairly broad stem specialization, which we talked about at the beginning, are not too suitable for this, although they are actively studied on this subject. That is, if we want to treat the skeleton with stem methods, we need to act on its own stem cells, which have finally been discovered.
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