Abstract
Biologic drug therapies are effective treatments for autoimmune diseases such as rheumatoid arthritis (RA) but may cause significant unwanted adverse effects, as they are administered continuously at high doses that can suppress the immune system. As the severity of RA fluctuates over time, targeted strategies that can dynamically sense and respond to changing levels of endogenous inflammatory mediators may achieve similar therapeutic efficacy while reducing risks of adverse effects. Using CRISPR-Cas9 genome editing, we engineered stem cells that harbor a synthetic gene circuit expressing biologic drugs to antagonize interleukin-1 (IL-1) or tumor necrosis factor α (TNF-α) in an autoregulated, feedback-controlled manner in response to activation of the endogenous chemokine (C-C) motif ligand 2 (Ccl2) promoter. To examine the in vivo therapeutic potential of this approach, cells were tissue-engineered to form a stable cartilaginous scaffold, which was implanted subcutaneously in mice with inflammatory arthritis. These bioengineered anti-cytokine implants mitigated arthritis severity as measured by joint pain, structural damage, and systemic and local inflammation. The coupling of synthetic biology with tissue engineering promises a wide range of potential applications for treating chronic diseases by generating custom-designed cells that regulate the expression of therapeutic transgenes in direct response to dynamically changing pathologic signals in the body.