Osteoarthritis is the most common form of arthritis. About one in 10 people will develop osteoarthritis at some point in their lifetimes. As the condition progresses, synovial membranes and cartilage break down. Osteoarthritis causes people to experience joint pain, joint stiffness, and restricted movement. Knees, hips, and hands are common sites for arthritis, though people can experience the condition in virtually every joint in the body including joints and spine. Mild osteoarthritis may be nothing more than an annoyance, but moderate and severe osteoarthritis can diminish a person’s quality of life and cause substantial suffering and disability.
Despite the commonness of osteoarthritis, there are very few effective treatment options. People may take pain medications to help cope with discomfort; however, taking these medications every day can lead to unwanted side effects. Physical therapy, braces, walking aids, and exercise may have some effect, but their benefit is unpredictable, i.e., these approaches work for some people and not others. The only definitive treatment for osteoarthritis is to replace the joint with an artificial one; however, orthopedic surgery is expensive, associated with a long recovery, and is usually only an option after patients have suffered pain and disability for a long period of time.
Ideally, osteoarthritis treatment would be focused on restoring the structure of the damaged joint itself. For a time, physicians were hopeful that glucosamine and chondroitin could do this. These two substances are diminished in osteoarthritis, so the concept was to replace them and hopefully rebuild damaged joints. While initial clinical studies seemed to suggest glucosamine and chondroitin were helpful, larger, high-quality clinical trials failed to show any benefit. Nevertheless, the goal of repairing joints damaged by osteoarthritis is still a top goal. Now, however, scientists have turned to stem cells instead of small molecules.
Stem cell researchers are particularly interested in the small sacs released by stem cells called exosomes. Exosomes contain proteins, RNA, cytokines, and other substances that are important for tissue regeneration. Exosomes are apparently responsible for most of the clinical benefit of stem cells in the first place. Moreover, it is much more convenient for doctors to use exosomes as treatment rather than stem cells themselves.
To this end, researchers have been studying the effects of stem cell exosomes. One research group recently published a report studying the effects of exosomes that were collected from synovial membrane stem cells and compared them to exosomes taken from induced pluripotent stem cells. Synovial membrane stem cells are an obvious choice for treating osteoarthritis since synovial membranes are one of the substances that break down in the disease. However, synovial membrane stem cells are difficult to obtain. It is far more practical to use induced pluripotent stem cells since there is a virtually limitless supply of them.
The researchers compared exosomes taken from these two types of stem cells in mice with experimental osteoarthritis. Not only did the scientists show that exosomes taken from pluripotent stem cells were highly effective in treating osteoarthritis, these exosomes were even more effective in treating osteoarthritis then exosomes taken from synovial membrane stem cells. Exosomes from pluripotent stem cells not only repaired synovial membranes but they also helped replace cartilage by stimulating chondrocytes (cartilage cells).
Of course, this work will need to be confirmed in humans with osteoarthritis; however, the results of this animal research are very encouraging. In short, this research suggests that exosomes taken from induced pluripotent mesenchymal stem cells may be a convenient and effective way to treat osteoarthritis in the future.
Reference: Zhu, Y. et al. (2017). Comparison of exosomes secreted by induced pluripotent stem cell-derived mesenchymal stem cells and synovial membrane-derived mesenchymal stem cells for the treatment of osteoarthritis. Stem Cell Research and Therapy. 2017 8:64.
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