Mesenchymal Stem Cell Therapy for Autoimmune Disease: Risks and Rewards.

Mesenchymal stem cells (MSC) possess a range of immunomodulatory properties which they exert through soluble mediators and through direct cell-cell contact. Due to these immune regulatory properties, the safety and clinical efficacy of MSC treatment has been tested in a number of autoimmune disorders. In this review we analyze the current data from early phase trials into Crohn's disease, systemic lupus erythematosus, and rheumatoid arthritis. In general, no adverse side effects were observed in patients treated with MSC; however, their clinical efficacy is difficult to interpret. Systemic or site-specific administration of MSC has been reported to exert potent immunomodulatory effects in 7 of the 11 trials discussed. Nonetheless, the mechanism(s) by which MSC exert their regulatory effects in vivo remain largely unknown. We discuss potential limitations or safety concerns associated with MSC therapy, including the heterogeneity of MSC and their potential contribution to disease pathogenesis, which need to be considered when designing future clinical trials, along with the need to standardize trial design. Although we are bridging the translational gap between scientific observations on MSC function and clinical applications for therapy, our understanding of basic MSC biology is still limited. Despite these issues, large, double-blinded, multicenter clinical trials are already underway. Further research into the endogenous function of MSC is required to elucidate the mechanism by which therapeutic MSC are acting.