Human umbilical cord mesenchymal stem cells ameliorate acute liver failure by inhibiting apoptosis, inflammation and pyroptosis

BACKGROUND: Human umbilical cord mesenchymal stem cells (UC-MSCs) are multipotent progenitor cells representing an attractive therapeutic tool for tissue damage and inflammation owing to their unique immunomodulatory properties. This study was designed to determine the protective effects and underlying mechanisms of UC-MSCs on acute liver failure (ALF). METHODS: ALF was induced in mice by intraperitoneal injection of D-galactosamine (D-GalN) and lipopolysaccharide (LPS). Mice were intravenously injected with 1×10(6) UC-MSCs one hour before or six hours after D-GalN/LPS injection. Liver function was valued by serum biochemical parameters and hematoxylin-eosin staining. Inflammatory cytokine and chemokine levels were measured by real-time PCR, and inflammatory cells infiltration was observed by immunofluorescence staining. Hepatocyte apoptosis and pyroptosis related proteins were detected by western blot. Murine macrophage Raw264.7 in the presentation of LPS was treated with the UC-MSCs condition medium (UC-MSCs-CM), and then the levels of inflammatory cytokines and NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome in Raw264.7 were measured. RESULTS: UC-MSCs significantly reduced the mortality, decreased serum alanine aminotransferase and aspartate aminotransferase levels, and improved the pathological damage. Moreover, UC-MSCs inhibited inflammatory cytokine and chemokine levels, especially TNF-α, interleukins-6 (IL-6), IL-1β, monocyte chemoattractant protein (MCP-1), CC-chemokines ligand 2 (CCL2), C-X-C motif ligand 2 (CXCL2), and reduced macrophage, neutrophil and T lymphocyte infiltration into the liver tissue. UC-MSCs also attenuated hepatocyte apoptosis, as evidenced by decreased TUNEL positive cells, increased Bcl-xl/Bax protein ratio and downregulated cleaved caspase 3 levels. NLRP3 inflammasome activation, IL-1β maturation and cleaved caspase1 were suppressed by UC-MSC administration. Furthermore, the UC-MSCs-CM reduced the levels of inflammatory cytokines and the activation of NLRP3 inflammasome in Raw264.7. CONCLUSIONS: Our results demonstrated that UC-MSCs exerted therapeutic effects on ALF by inhibiting apoptosis, inflammation, and pyroptosis.