Mesenchymal Stromal Cells Directly Promote Inflammation by Canonical NLRP3 and Non-canonical Caspase-11 Inflammasomes

Mesenchymal stromal cells (MSCs) based therapy is a promising approach to treat inflammatory disorders. However, therapeutic effect is not always achieved. Thus the mechanism involved in inflammation requires further elucidation. To explore the mechanisms by which MSCs respond to inflammatory stimuli, we investigated whether MSCs employed inflammasomes to participate in inflammation. Using in vitro and in vivo models, we found that canonical NLRP3 and non-canonical caspase-11 inflammasomes were activated in bone-associated MSCs (BA-MSCs) to promote the inflammatory response. The NLRP3 inflammasome was activated to mainly elicit IL-1β/18 release, whereas the caspase-11 inflammasome managed pyroptosis. Furthermore, we sought a small molecule component (66PR) to inhibit the activation of inflammasomes in BA-MSCs, which consequently improved their survival and therapeutic potential in inflammation bowel diseases. These current findings indicated that MSCs themselves could directly promote the inflammatory response by an inflammasome-dependent pathway. Our observations suggested that inhibition of the proinflammatory property may improve MSCs utilization in inflammatory disorders.