Mesenchymal stem cells

Mesenchymal stem cells (MSCs), are multipotent stem cells with the capacity to differentiate into a variety of somatic cells, mainly the ones of the skeletal tissue. MSCs have long thin cell bodies with a large and round nucleus. Their are multipotent in nature and are thus categorised as adult stem cells. They are also known as multipotent mesenchymal stromal cells

They were first described in 1924 by Alexander Maximow, a Russian-American scientist who identified a precursor cell in the mesenchyme that differentiates into many blood cell types.


Picture of a mesenchymal stem cell
A Mesenchymal Stem Cell

MSCs Differentiation
As mentioned before mesenchymal stem cells have the capacity to differentiate into somatic cells of the skeletal tissue. This includes:
  • Adipocytes (cells found in fat)
  • Chondrocytes (cells found in cartilage)
  • Myocytes (muscle cells)
  • Neuron
  • Osteoblasts (cells found in bones)
It should mentioned that it is currently unclear whether MSC-derived neurons function properly or not.


Chondrocyte cells
Chondrocyte cells

Where are MSCs found?
MSCs were first extracted from bone marrow which also contains hematopoietic stem cells. Only a  0.001-0.01% of all the different bone marrow stem cells are mesenchymal stem cells. As of today scientists have successfully extracted mesenchymal stem cells from the following tissues:
  • Adipose Tissue (fat)
  • Bone marrow
  • Muscles
  • Umbilical cord blood

Image of Human mesenchymal stem cells
Human Mesenchymal Stem Cells Derived from bone marrow


MSCs research and clinical applications
It is safe to say that mesenchymal stem cell research is still in its infancy. Currently there isn't any clinically approved treatment involving MSCs available. It should be mentioned that although there are many stem cell clinics offering treatments based on mesenchymal stem cells,  none of these treatments are tested by the FDA (or other similar organizations)  These clinics offer stem cell treatments on the ground that since the cells used are autologous (coming from the patient himself) they don't need approval for safety. Indeed, most doctors agree that autologous stem cell transplants are safe, but whether or not they actually work is highly questionable.

Many researchers believe that MSCs are promising candidates in the following fields:

Bone cartilage repair and regeneration
MSCs mainly differentiate into osteoblasts and chondrocytes, so the first obvious application is the treatment of skeletal and chondral (cartilage) defects. This is especially true for cartilage defects which are one of the most difficult problems doctors have yet to solve. Even a small and asymptomatic cartilage defect has the potential to lead into debilitating arthritis. Some major breakthroughs in this field are:
  • The study,  Repair of articular cartilage defects in the patello-femoral joint with autologous bone marrow mesenchymal cell transplantation: three case reports involving nine defects in five knees, by Wakitani et al showed that MSCs have great potential for treating cartilage defects
  • A 5 case study where it was shown that  a combination of microfracture and mesencymal stem cells can lead to the creation of true hyaline cartilage. You can read more about this study here
  • A clinical trial on Cartistem was announced during January 2013. Cartistem is already approved by the Korean FDA for treating localised cartilage defects.
  • A clinical trial on Mesoblast, a mesenchymal stem cell product for treating Rheumatoid arthritis

Heart and blood vessel repair
Some mice studies suggest that mesenchymal stem cells may have the capacity to promote the formation and growth of new vessels. Although they don't create blood vessel cells themselves, MSCs have been shown to release proteins that in return stimulate the growth of endothelial precursors. Endothelial precursors are cells that form the inner layer of blood vessels (tunica intima). These findings have made many scientists believe that mesenchymal stem cells can potentially be a viable option for treating patients with damaged heart tissue, resulting from either a heart attack or a disease like Acute limb Ischaemia. A clinical trial is currently running on SB623, a mesenchymal stem cell therapy for treating damages induced after an ischemic stroke.


Inflammatory and autoimmune diseases
Some studies indicate that mesenchymal stem cells can't be detected by the immune system. This means that a MSCs transplantion wouldn't need to be followed by anti-rejection drug therapy. On the other hand other studies have disconfirmed this finding, so whether or not they are detectable remains unclear..

MSCs had also shown some early success for  inflammatory diseases (e.g. inflammatory bowel disease), but later findings revealed that other methods like the ones that increase the local concentration of cells are better alternatives.

Other
A clinical trial on Astrostem, for the treatment of cerebral palsy, was announced in 2013. Astrostem is a mesenchymal stem cell-based treatment by RNL BIO CO.


Video about mesenchymal stem cells and their potential applications


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