Stem cell therapy is considered to be the future of modern medicine. Our knowledge of how these cells can repair and regenerate damaged tissue is developing rapidly. As new therapies and applications are now readily available, stem cells therapies are no longer a vision of the future.
Regenerative medicine involves the repair of injured or diseased tissue using stem cells to restore or establish normal function. There are many different types of stem cells and not all stem cells are the same. The body contains over 250 different cell types, each customised to a particular function. All cells in the body are derived from stem cells. Stem cells are special because they have the ability to renew themselves through mitotic cell division but also have the ability to differentiate into specialised cell types (Figure 1).
Figure 1. Stem cells are defined by their ability to self-renew through cell division and differentiate into specialised cell types
Mesenchymal stem cells are non-tissue specific stem cells with powerful regeneration capabilities across many indications. As a result, mesenchymal stem cells are the most widely therapeutically administered stem cell type.
Mesenchymal stem cells use multiple biological mechanisms to promote the natural healing of injured or diseased tissue. It is important to note that although stem cells are defined by their ability to self-renew and differentiate into different cell types, stem cells regenerate damaged tissues through multiple different mechanisms. In fact, scientific data does not support the purported ‘cell replacement theory’ which proposes that stem cells directly replace injured cells with new cells. Furthermore, stem cells have been shown to exert their regenerative potency through: 1) immunomodulation; 2) host-tissue Regeneration through paracrine signal; and, 3) chemoattraction that tracks stem cells to the injury site (as shown in Figure 2). (Ref 1, 2)
Mesenchymal stem cells respond to the injured or diseased environment through the release of factors that are anti-inflammatory. Mesenchymal stem cells have been shown to exert potent immunosuppressive properties that reduce tissue damage resulting from inflammation. Fundamentally, it is impossible for damaged tissue to repair in the presence of acute inflammation. In fact, inflammation often leads to further tissue destruction. The administration of stem cells can attenuate inflammation; thereby enabling the natural healing process to begin.
Mesenchymal stem cells promote tissue regeneration with reduced scar formation. In simple terms, mesenchymal stem cells promote the body’s natural ability to heal damaged tissue. Stem cells have been shown to promote angiogenesis; the formation of blood vessels, which promotes healing of injured tissue. Furthermore, host tissue specific resident stem cells are mobilised to repair the damaged tissue that may otherwise be dormant.
Stem cells have the natural ability to locate the injury site through chemoattraction by soluble factors. Mesenchymal stem cells have been shown to track to the injury site where they promote natural healing of the injured or diseased tissue.
Figure 2. Illustrates multiple mechanisms by which stem cell therapy has been shown to repair and regenerate damaged tissue. A standardised stem cell dose may be administered either by direct injection into the injured tissue or by intravenous infusion. Stem cells at the site of tissue damage are activated by the injury. In response to the injury, stem cells secrete paracrine factors that conduct three main functions: 1) Modulate immune cells to reduce inflammation; 2) Rebuild and remodel tissue, stimulate blood vessel formation and reduce scar formation; and 3) recruit stem cells to the injury site to promote healing of the injured tissue. These biological functions of mesenchymal stem cells taken in concert lead to host tissue regeneration and restoration of tissue to normal function.
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- Markoski, M.M., Advances in the Use of Stem Cells in Veterinary Medicine: From Basic Research to Clinical Practice. Scientifica (Cairo), 2016. 2016: p. 4516920.