Potential use of stem cell therapies for treating osteoarthritis and rheumatoid arthritis.

Arthritis, defined as a chronic inflammation often accompanied by swelling of one or more joints, encompasses more than 100 conditions that affect the joints, tissues around them as well as other connective tissues. This condition causes severe discomfort compromising the quality of life drastically, and thereby inflicts severe financial and social impact on the people affected. The incidence rate of arthritis is increasing all around the globe including the United States every year. In general, osteoarthritis (OA) affects more people in comparison to rheumatoid arthritis (RA). In the USA itself, more than 14 million people are affected by OA in comparison to 1.4 million people suffering from RA. In both conditions, elevated levels of proinflammatory cytokines have been recorded, this incidence generally precedes the cartilage degradation observed in the patients. The use of mesenchymal stem cells (MSCs) has proven to be a safe and efficient therapeutic option for treating many inflammation-rooted pathological conditions. Evidence suggests that MSCs down-regulate the effects of proinflammatory cytokines including tumor necrosis factor (TNF)-α, interferon (IFN)-γ, interleukin (IL)-1B, IL-2, and IL-17, and help restore the functions of immune cells. In addition, these cells promote the polarization of M2 phenotype macrophages, thus contributing to the suppression of the inflammatory process and consequentially to cartilage regeneration. Preclinical and clinical trials have proven the safety and effectiveness of this therapy, supported by the fact that these do not provoke any host immune response, and their influence on the cytokine profiles. An attempt to survey the results of stem cell therapy for treating arthritis has been carried out in this review.