Friday, April 5, 2013

What Are Mesenchymal Stem Cells and Why Are They So Important in Osteoarthritis?

Mesenchymal stem cells are progenitor cells, meaning they are cells that can differentiate and become other cells. And in fact, they are the cells from each all other cells are derived.

They are found in a number of adult tissues including the bone marrow, fat, synovium (joint lining), teeth, skin bone, and cartilage.

What makes these cells unique is that when they're cultured outside the body, they multiply quickly but don't differentiate into anything specific until a unique stimulus is applied. What that means is that by culturing these cells, a large number of them can be grown in a relatively short period of time. The therapeutic potential is obvious.

Given the ability to expansively grow a large number of these cells, it has been a dream for a number of investigators to harness this potential for various tissue engineering endeavors.

The area of most excitement in our specialty or rheumatology is osteoarthritis.

Osteoarthritis is the most common form of arthritis, affecting more than 20 million Americans. It is a disease of articular cartilage, the gristle that caps the ends of long bones within a joint. Cartilage consists of cells, called chondrocytes, that manufacture a matrix, in which they reside.

Picture grapes sitting in a gelatin mold. The grapes are the chondrocytes and the gelatin is the matrix.

Under normal conditions, the matrix has an ideal balance of protein building blocks and water. When osteoarthritis develops, the ratio of water to proteins becomes unbalanced. In addition, the chondrocytes begin to manufacture destructive enzymes and inflammation causing chemicals, called cytokines. Also, the chondrocytes stimulate the environment around the joint, including the synovium, to manufacture destructive enzymes and cytokines. The end result is damage to the cartilage and the premature wearing away of this substance.

Once thought to be an entirely "wear and tear" disease, it is now firmly known that osteoarthritis damage occurs within an environment characterized by inflammation as well as other immunological disturbances.

Attention to the use of mesenchymal stem cells to act as repair cells is driven not only by their ability to proliferate and differentiate into different tissue types but also by their potential to engage in the anti-inflammatory and immunoregulatory battle taking place in osteoarthritis.

Also, according to recent research, it is now known that mesenchymal stem cells can produce factors that affect the local environment and protect the regenerative processes that have been started.

According to Chen and Tuan, (Arthritis Res Ther. 2008; 10(5): 223) " these properties make mesenchymal stem cells an ideal candidate cell type as building blocks for tissue engineering efforts to regenerate replacement tissues and repair damaged structures as encountered in various arthritic conditions."

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