Human Umbilical Cord Mesenchymal Stem Cell-Derived Exosomes Modulate the NLRP3 Inflammasome/Caspase-1 Pathway to Repress Pyroptosis Induced by Hypoxia/Reoxygenation in Cardiac Microvascular Endothelial Cells

Human umbilical cord mesenchymal stem cell-derived exosomes (hUCMSC-Exos) have the ability to treat cardiovascular diseases (CVDs). We explored their mechanism on pyroptosis modulation in cardiac microvascular endothelial cells (CMECs).Exosomes were extracted from hUCMSCs using a differential high-speed centrifugation method, and then identified by transmission electron microscopy, nanoparticle tracking analysis, and Western blot analysis. Later, the CMECs were induced by hypoxia/reoxygenation (H/R) in vitro and processed with hUCMSC-Exos or the NLRP3 inflammasome inhibitor CY-09 and the NLRP3 inflammasome activator Nigerian sodium sulfate (NSS). A rat model of ischemia/reperfusion (I/R) injury was established in vivo, followed by hUCMSC-Exo injection. Cell viability and death, and myocardial injury were assessed by CCK-8 and LDH assays and H&E staining. Levels of GSDMD-N, NLRP3, cleaved Caspase-1, IL-1β and IL-18 proteins, and inflammatory factors (IL-1β, IL-18) were determined by Western blot analysis and ELISA.H/R-induced CMECs represented attenuated cell viability and increased cell death, as well as up-regulated levels of pyroptosis proteins (cleaved Caspase-1, GSDMD-N, IL-18, IL-1β), inflammasome key protein (NLRP3) and cell supernatant inflammatory factors (IL-18, IL-1β), while hUCMSC-Exos amplified H/R-induced CMEC viability and lowered cell death, and diminished levels of NLRP3, cleaved Caspase-1, GSDMD-N, IL-18 and IL-1β proteins, and cell supernatant inflammatory factors IL-1β and IL-18. Activating the NLRP3 inflammasome/Caspase-1 pathway partially reversed the inhibitory effect of hUCMSC-Exos on CMEC pyroptosis. hUCMSC-Exos alleviated myocardial injury in I/R rats by modulating the NLRP3 inflammasome/Caspase-1 pathway.hUCMSC-Exos weakened CMEC pyroptosis by inactivating the NLRP3 inflammasome/Caspase-1 pathway.