It has been estimated that 70 million adults suffer from arthritis in the US. While there are several types of arthritis, rheumatoid arthritis and osteoarthritis are the major conditions that lead to disability. The economic burden of arthritis is estimated to reach $100 billion by the year 2020.
Bone joints in our body that give us a wide range of motion have ends that are covered with cartilage. This provides a lubricating surface for frictionless movement. It is damage to this cartilage tissue that leads to rheumatoid arthritis and osteoarthritis.
Cartilage is produced inside chondrocyte cells on the ends of bones, and then deposited outside the cell. When the entire cartilage layer is damaged exposing the bone, stems cells from the bone repair and heal the damage. Often times, cartilage damage occurs such that the cartilage layer is penetrated partially. In such cases, the live cells in the bone are not exposed so that they cannot repair the damage.
Several medical strategies exist to reduce pain and swelling associated with cartilage damage. However, medical intervention is not able to restore or replace the cartilage. Clearly there is a demand for artificial cartilage, and tissue engineering is being explored to meet this demand.
Tissue engineering consists of four components:
- An active cell source
- A 3D structure or scaffold
- Bioactive factors or nutrients
- Maturation promoting mechanical environment.
Mesenchymal stem cells can generate cartilage and bone tissue and are the favored cell source for tissue engineering. They are easy to isolate from any tissue in the body. The ability for expansion by several-fold in cell culture lends another value. And lastly, mesenchymal stem cells have been demonstrated to be able to integrate into bone-cartilage lesions under experimental conditions. As previously discussed, mesenchymal stem cells are likened to duct tape for the human body.
There are several extracellular matrices (ECM) that can be used as scaffold on which to culture mesenchymal stem cells. Such scaffolding needs to be stable enough to provide a 3D structure for depositing cartilage. And yet, the scaffolding must also biodegrade once the cartilage tissue is in place. The ECM must also have the ability to promote integration of the artificial tissue into the human body.
The bioactive factors for mesenchymal stem cells must be able to promote their proliferation, differentiation, and maturation. Several protein molecules as well as hypoxic or low oxygen environment have bee identified. Researchers are evaluating different combinations of factors in order to identify the most promising candidates.
Physical force or mechanical stimulants are imperative in the maturation of mesenchymal stem cells into cartilage tissue. Cartilage in the body is subjected to compressive, tensile, and shear forces. A variety of forces have been evaluated for tissue engineering. These include electromagnetic fields, dynamic compression, shear force, sliding contact, fluid flow, hydrostatic pressure, and ultrasound.
Tissue engineering with mesenchymal stem cells to generate cartilage is a field that is actively pursued by clinicians and scientists. We at HemaCare offer high quality mesenchymal stem cells for such research endeavors.
Tamer AE and Maxwell TH. Mesenchymal stem cell-based tissue engineering strategies for repair of articular cartilage. Histology and histopathology, 2014 Jan 23 [ePub ahead of print] PMID 24452855.