Protection of hUC-MSCs against neuronal complement C3a receptor-mediated NLRP3 activation in CUMS-induced mice

Background Hyperactivation of complement C3 and inflammation-related activation of NLR family pyrin domain containing 3 (NLRP3) inflammasome are implicated in the etiology of stress-related disorders. Studies have shown that human umbilical cord mesenchymal stromal cells (hUC-MSCs) have immunomodulatory and anti-inflammatory effects; however, the mechanism remains unclear. Methods hUC-MSCs were administered to chronic unpredictable mild stress (CUMS) model mice once a week for four weeks. After the administration of hUC-MSCs, several parameters were assessed, including behavioral performance, synapse-related proteins, complement C3 receptors (C3aR) in neurons, and the NLRP3 inflammasome. Then, CUMS mice were injected with SB290157, a complement C3aR antagonist, and the behavioral index and NLRP3 inflammasome activation were tested. Results The open-field and forced swimming behavioral tests showed an improvement in depression-like behaviors in the CUMS-exposed mice after the administration of hUC-MSCs. Treatment with hUC-MSCs significantly decreased the neuronal C3aR levels and alleviated synaptic damage. Furthermore, the levels of the NLRP3 inflammasome and inflammatory factors were reduced after hUC-MSC administration. In particular, treatment with a C3aR antagonist also decreased NLRP3 inflammasome expression and inflammation, which was consistent with the observed improvements after hUC-MSC treatment. Conclusion hUC-MSCs can attenuate NLRP3 activation in CUMS-induced mice, which may be correlated with C3aR in neurons.