Osteoarthritis is the most common form of arthritis affecting more than 20 million Americans. It is a disease due to disordered cartilage.
Normal cartilage in the young healthy adult consists of a matrix constructed of a mixture of proteins and sugars (proteoglycans), water, as well as collagen. Within this matrix sit chondrocytes, cells that actually manufacture the matrix they sit in. Picture a bowl of gelatin with grapes sitting inside the gelatin and that is what cartilage looks like.
Under normal situation, cartilage is capable of withstanding both compressive forces as well as shear forces. It deforms when loads are placed on it and then rapidly expands to its normal contour once the load has been removed.
When cartilage is damaged as a result of trauma, injury, or other means, a change occurs in the normal functioning of cartilage. Chondrocytes begin to elaborate destructive enzymes; the underlying bone begins to deform, and the lining of the joint, the synovium, begins to produce cytokines, protein messengers that stimulate inflammation.
The end result is the gradual wearing away of cartilage accompanied by chronic inflammation, and deformity related to abnormal mechanics of the joint.
To date, the treatment of osteoarthritis has been palliative only. Symptomatic relief with non-steroidal anti-inflammatory drugs (NSAIDS), physical therapy, and joint injections of either corticosteroid or hyaluronic acid have been among the measures employed.
The rapid development of stem cell science has provided a glimmer of hope that the treatment of osteoarthritis will also include the ability to restore cartilage integrity.
A caveat: The proper application of stem cells is not merely injecting stem cells into a joint and hoping for the best.
Multiple attempts by various laboratories have searched for a method of introducing stem cells along with a scaffold to enable stem cell propagation in an organized fashion that will best stimulate cartilage regeneration. A whole new branch of basic science, termed "tissue engineering" has been used to describe these ventures.
An excellent review of the current state of the science was published by the Harvard Stem Cell Institute.
(Willerth SM, Sakiyama-Elbert SE. Combining stem cells and biomaterial scaffolds for constructing tissues and cell delivery.)
The authors reviewed the literature regarding types of scaffold materials that had been studied.
These included natural biomaterials such as collagen, fibrin, silk, sugars, algae cell walls, hyaluronan, and chitin as well as synthetic platforms such as various polymers, peptides, and ceramics.
These scaffolds are generally "seeded" with growth factors that stimulate stem cell multiplication and division while protecting the stem cells in an undeniably hostile environment, the arthritic joint.
Currently, the use of autologous stem cells in clinical medicine requires the use of fat as a matrix scaffold. When combined with growth factors from blood components, the environment simulates the biomaterial scaffold models described above.
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