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. 2013 Nov 1;6(6):e26631.
doi: 10.4161/cib.26631. Epub 2013 Sep 27.

Stem Cell Therapy Without the Cells

Free PMC article

Stem Cell Therapy Without the Cells

Greg Maguire. Commun Integr Biol. .
Free PMC article


As an example of the burgeoning importance of stem cell therapy, this past month the California Institute for Regenerative Medicine (CIRM) has approved $70 million to create a new network of stem cell clinical trial centers. Much work in the last decade has been devoted to developing the use of autologous and allogeneic adult stem cell transplants to treat a number of conditions, including heart attack, dementia, wounds, and immune system-related diseases. The standard model teaches us that adult stem cells exists throughout most of the body and provide a means to regenerate and repair most tissues through replication and differentiation. Although we have often witnessed the medical cart placed in front of the scientific horse in the development of stem cell therapies outside of academic circles, great strides have been made, such as the use of purified stem cells(1) instead of whole bone marrow transplants in cancer patients, where physicians avoid re-injecting the patients with their own cancer cells.(2) We most often think of stem cell therapy acting to regenerate tissue through replication and then differentiation, but recent studies point to the dramatic effects adult stem cells exert in the repair of various tissues through the release of paracrine and autocrine substances, and not simply through differentiation. Indeed, up to 80% of the therapeutic effect of adult stem cells has been shown to be through paracrine mediated actions.(3) That is, the collected types of molecules released by the stem cells, called the secretome, or stem cell released molecules (SRM), number in the 100s, including proteins, microRNA, growth factors, antioxidants, proteasomes, and exosomes, and target a multitude of biological pathways through paracrine actions. The composition of the different molecule types in SRM is state dependent, and varies with cell type and conditions such as age and environment.

Keywords: SRM; antimicrobial; growth factors; paracrine; stem cells; systems therapeutic; transplants.


Figure 1. Molecules do the work. A model shows the injection of SRM (molecules) directly to the injured tissue, vs. the injection of cells that then indirectly release the SRM (molecules) to the injured tissue. Direct injection of the SRM to the tissue allows for a precise dosing schedule in space and time, whereas injection of cells into the tissue is highly variable.

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