The link between stem cells and regeneration is currently one of the most intensively researched fields. Understanding it promises solutions that can overcome some diseases that have been considered incurable, and therefore receive more and more attention.
Most therapies today that utilize the regenerative capacity of stem cells apply exogenously formed stem cells (taken from blood and grown outside of the body) e.g. for diseases associated with chronic inflammation. The exogenous methods are expensive and cannot be considered completely safe, because keeping the cells in a culture outside of the body holds the potential of stem cell mutations, and ingested in the body, unwanted immune responses, or differentiation (different as planned) may occur.
Another trend is to increase the body's ability to regenerate by stimulating and mobilizing (endogenously formed) stem cells within the body without having to isolate and maintain the stem cells under laboratory conditions, making it safer to use.
What are stem cells?
Stem cells can be divided into 2 main types: 1) embryonic stem cells, which have high pluripotency, so they can transform (differentiate) into almost any cell, and 2) adult or somatic stem cells, which have a lower pluripotency and are generally considered to be progenitor cells of that tissue they can be found. In terms of function, adult stem cells are responsible for the maintenance and regeneration of specific tissues, and for the replenishment of damaged and dead cells.
Stem cells are actually everywhere in our body to ensure rapid and efficient tissue regeneration. There are types of stem cells that stay in the tissues throughout, while other stem cells circulate in the body. The latter are located most of the time in the bone marrow, some of which enters the bloodstream and then either return to the bone marrow or enter to the tissues from the circulation, where they can typically return after a few days to the bloodstream through the lymphatics. They can also get back to the bone marrow from the blood, or back to the tissues, and the cycle starts all over again.
This intra-organizational circulation is mostly the characteristic of hematopoietic stem cells (stem cells giving rise to elements of the blood and immune system), but mesenchymal stem cells (MSC, especially cartilage, fat, bone-type differentiation, but can differentiate to muscle and even neuronal direction) and endothelial progenitor cells (vascular progenitor cells) may also circulate in the blood.
Stem cells circulating in the body can enter the tissues with stimuli that remain in place and differentiate into target cells. This can happen e.g. at the site of an infection where hematopoietic stem cells are often converted to immune cells to take up the fight against pathogens. Because only a small portion of stem cells circulate normally in the bloodstream, certain stimulus may increase the number of stem cells entering the bloodstream from the bone marrow. This occurs when the body is exposed to an effect where tissue damage (may) occurs and the regenerative potential of stem cells is required.
Due to the aging process, adverse environmental effects, and unfavorable eating and lifestyle habits, the number of circulating stem cells can decrease over time, which negatively affects our body’s regeneration abilities. In such cases, the so-called stem cell mobilizers are necessary.