Background Mesenchymal stem cells (MSCs), including adipose-derived mesenchymal stem cells (ADSCs), have been shown to attenuate organ damage in acute respiratory distress syndrome (ARDS) and sepsis; however, the underlying mechanisms are not fully understood. In this study, we aimed to explore the potential roles and molecular mechanisms of action of ADSCs in histone-induced endothelial damage. Methods Male C57BL/6 N mice were intravenously injected with ADSCs, followed by histones or a vehicle. The mice in each group were assessed for survival, pulmonary vascular permeability, and histological changes. A co-culture model with primary human umbilical vein endothelial cells (HUVECs) exposed to histones was used to clarify the paracrine effect of ADSCs. Overexpression and inhibition of miR-126 ADSCs were also examined as causative factors for endothelial protection. Results The administration of ADSCs markedly improved survival, inhibited histone-mediated lung hemorrhage and edema, and attenuated vascular hyper-permeability in mice. ADSCs were engrafted in the injured lung and attenuated histone-induced endothelial cell apoptosis. ADSCs showed endothelial protection (via a paracrine effect) and Akt phosphorylation in the histone-exposed HUVECs. Notably, increased Akt phosphorylation by ADSCs was mostly mediated by exosomes in histone-induced cytotoxicity and lung damage. Moreover, the expression of miR-126 was increased in exosomes from histone-exposed ADSCs. Remarkably, the inhibition of miR-126 in ADSCs failed to increase Akt phosphorylation in histone-exposed HUVECs. Conclusion ADSC-derived exosomes may exert protective effects on endothelial cells via activation of the PI3K/Akt pathway.

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BackgroundMesenchymal stem cells (MSCs), including adipose-derived mesenchymal stem cells (ADSCs), have been shown to attenuate organ damage in acute respiratory distress syndrome (ARDS) and sepsis; however, the underlying mechanisms have not been fully understood. In this study, we aimed to explore the potential roles and molecular mechanisms of action of ADSCs in histone-induced endothelial damage. MethodsMale C57BL/6N mice were intravenously injected with ADSCs, followed by histones or a vehicle. The mice in each group were assessed for survival, pulmonary vascular permeability, and histological changes. A co-culture model with primary human umbilical vein endothelial cells (HUVECs) exposed to histones was used to clarify the paracrine effect of ADSCs. Overexpression and inhibition of miR-126 ADSCs were also examined as causative factors for endothelial protection.ResultsThe administration of ADSCs markedly improved survival, inhibited histone-mediated lung hemorrhage and edema, and attenuated vascular hyper-permeability in mice. ADSCs were engrafted in the injured lung and attenuated histone-induced endothelial cell apoptosis. ADSCs showed endothelial protection (via a paracrine effect) and Akt phosphorylation in the histone-exposed HUVECs. Notably, increased Akt phosphorylation by ADSCs was mostly mediated by exosomes in histone-induced cytotoxicity and lung damage. Moreover, inhibition of miR-126, which is known to be present in exosomes, in ADSCs did not increase Akt phosphorylation in histone-exposed HUVECs. ConclusionADSC-derived exosomes may exert protective effects on endothelial cells via activation of the PI3K/Akt pathway.

Hepatic ischemia/reperfusion injury (IRI) is a major complication of liver surgery and transplantation, especially in patients with nonalcoholic steatohepatitis (NASH). The mechanism of NASH susceptibility to IRI has not been fully clarified. We investigated the role of liver‐produced histidine‐rich glycoprotein (HRG) in NASH IRI. A NASH mouse model was established using C57BL/6J mice fed a methionine‐choline–deficient diet (MCDD) for 6 weeks. The MCDD and standard diet groups were exposed to 60 minutes of partial hepatic ischemia/reperfusion (I/R). We further evaluated the impact of HRG in this context using HRG knockdown (KD) mice. IRI increased HRG expression in the standard diet group, but not in the MCDD group after I/R. HRG expression was inversely correlated with neutrophil infiltration and the formation of neutrophil extracellular traps (NETs). HRG KD mice showed severe liver injury with neutrophil infiltration and the formation of NETs. Pretreatment with supplementary HRG protected against I/R with the inhibition of neutrophil infiltration and the formation of NETs. In vitro, hepatocytes showed that the expression of HRG was upregulated under hypoxia/reoxygenation conditions, but not in response to oleic acid–treated hepatocytes. The decrease in HRG expression in fatty hepatocytes was accompanied by decreased farnesoid X receptor and hypoxia inducible factor 2 alpha subunit expression. HRG is a hepatoprotective factor during hepatic IRI because it decreases neutrophil infiltration and the formation of NETs. The decrease in HRG is a cause of susceptibility to IRI in steatotic livers. Therefore, HRG is a new therapeutic target for minimizing liver damage in patients with NASH.

Doxorubicin (DOX) induces dose-dependent cardiotoxicity via oxidative stress and abnormal mitochondrial function in the myocardium. Therefore, a noninvasive in vivo imaging procedure for monitoring the redox status of the heart may aid in monitoring diseases and developing treatments. However, an appropriate technique has yet to be developed. In this study, we demonstrate a technique for detecting and visualizing the redox status of the heart using in vivo dynamic nuclear polarization–magnetic resonance imaging (DNP–MRI) with 3-carbamoyl-PROXYL (CmP) as a molecular imaging probe. Male C57BL/6N mice were administered DOX (20 mg/kg) or saline. DNP–MRI clearly showed a slower DNP signal reduction in the DOX group than in the control group. Importantly, the difference in the DNP signal reduction rate between the two groups occurred earlier than that detected by physiological examination or clinical symptoms. In an in vitro experiment, KCN (an inhibitor of complex IV in the mitochondrial electron transport chain) and DOX inhibited the electron paramagnetic resonance change in H9c2 cardiomyocytes, suggesting that the redox metabolism of CmP in the myocardium is mitochondrion-dependent. Therefore, this molecular imaging technique has the potential to monitor the dynamics of redox metabolic changes in DOX-induced cardiomyopathy and facilitate an early diagnosis of this condition.