Rationale: Sepsis refers to the clinical syndrome of severe systemic inflammation precipitated by infection. Despite appropriate antimicrobial therapy, sepsis-related morbidity and mortality remain intractable problems in critically ill patients. Moreover, there is no specific treatment strategy for the syndrome of sepsis-induced multiple organ dysfunction. Objectives: We hypothesized that mesenchymal stem cells (MSCs), which have been shown to have immunomodulatory properties, would reduce sepsis-induced inflammation and improve survival in a polymicrobial model of sepsis. Methods: Sepsis was induced in C57Bl/6J mice by cecal ligation and puncture (CLP), followed 6 hours later by an intravenous injection of MSCs or saline. Twenty-eight hours after CLP, plasma, bronchoalveolar lavage fluid and tissues were collected for analyses. Longer-term studies were performed with antibiotic coadministration to assess the effect of MSCs on survival. Measurements and Main Results: MSC treatment significantly reduced mortality in septic mice receiving appropriate antimicrobial therapy. MSCs alone reduced systemic and pulmonary cytokine levels in mice with CLP-induced sepsis, preventing acute lung injury and organ dysfunction, despite the low levels of cell persistence. Microarray data highlighted an overall down-regulation of inflammation and inflammation-related genes (such as IL-10, IL-6) and a shift toward up-regulation of genes involved in promoting phagocytosis and bacterial killing. Finally, bacterial clearance was significantly greater in MSC-treated mice, in part due to enhanced phagocytotic activity of the host immune cells. Conclusions: These data demonstrate that MSCs have beneficial effects on experimental sepsis, possibly by paracrine mechanisms, and suggest that immunomodulatory cell therapy may be an effective adjunctive treatment to reduce sepsis-related morbidity and mortality.

Rationale: The acute respiratory distress syndrome is a significant cause of morbidity and mortality in critically ill patients. Angiopoietin-1 (Ang-1), a ligand for the endothelial Tie2 receptor, is an endothelial survival and vascular stabilization factor that reduces endothelial permeability and inhibits leukocyte–endothelium interactions. Objectives: We hypothesized that Ang-1 counteracts vascular inflammation and pulmonary vascular leak in experimental acute lung injury. Methods: We used cell-based gene therapy in a rat model of ALI. Transgenic mice overexpressing Ang-1 or deficient in the Tie2 receptor were also studied to better elucidate the mechanisms of protection. Measurements and Main Results: The present report provides data that support a strong protective role for the Ang-1/Tie2 system in two experimental models of LPS-induced acute lung injury. In a rat model, cell-based Ang-1 gene transfer improved morphological, biochemical, and molecular indices of lung injury and inflammation. These findings were confirmed in a gain-of-function conditional, targeted transgenic mouse model, in which Ang-1 reduced endothelial cell activation and the expression of adhesion molecules, associated with a marked improvement in airspace inflammation and intraalveolar septal thickening. Moreover, heterozygous Tie2-deficient mice demonstrated enhanced evidence of lung injury and increased early mortality. Conclusions: These results support a critical role for the Ang-1/Tie2 axis in modulating the pulmonary vascular response to lung injury and suggest that Ang-1 therapy may represent a potential new strategy for the treatment and/or prevention of acute respiratory distress syndrome in critically ill patients.

Background—: Resistant ventricular fibrillation, refibrillation. and diminished myocardial contractility are important factors leading to poor survival after cardiac arrest. We hypothesized that dantrolene improves survival after ventricular fibrillation (VF) by rectifying the calcium dysregulation caused by VF. Methods and Results—: VF was induced in 26 Yorkshire pigs for 4 minutes. Cardiopulmonary resuscitation was then commenced for 3 minutes, and dantrolene or isotonic saline was infused at the onset of cardiopulmonary resuscitation. Animals were defibrillated and observed for 30 minutes. To study the effect of VF on calcium handling and its modulation by dantrolene, hearts from 14 New Zealand rabbits were Langendorff-perfused. The inducibility of VF after dantrolene administration was documented. Optical mapping was performed to evaluate diastolic spontaneous calcium elevations as a measure of cytosolic calcium leak. The sustained return of spontaneous circulation (systolic blood pressure ≥60 mm Hg) was achieved in 85% of the dantrolene group in comparison with 39% of controls ( P =0.02). return of spontaneous circulation was achieved earlier in dantrolene-treated pigs after successful defibrillation (21±6 s versus 181±57 s in controls, P =0.005). The median number of refibrillation episodes was lower in the dantrolene group (0 versus 1, P =0.04). In isolated rabbit hearts, the successful induction of VF was achieved in 83% of attempts in controls versus 41% in dantrolene-treated hearts ( P =0.007). VF caused diastolic calcium leaks in the form of spontaneous calcium elevations. Administration of 20 μmol/L dantrolene significantly decreased spontaneous calcium elevation amplitude versus controls. (0.024±0.013 versus 0.12±0.02 arbitrary unit [200-ms cycle length], P =0.001). Conclusions—: Dantrolene infusion during cardiopulmonary resuscitation facilitates successful defibrillation, improves hemodynamics postdefibrillation, decreases refibrillation, and thus improves survival after cardiac arrest. The effects are mediated through normalizing VF-induced dysfunctional calcium cycling.

Rationale:: Ventricular fibrillation (VF) leads to global ischemia. The modulation of ischemia-dependent pathways may alter the electrophysiological evolution of VF.Objective:: We addressed the hypotheses that there is regional disease-related expression of K_ATPchannels in human cardiomyopathic hearts and that K_ATPchannel blockade promotes spontaneous VF termination by attenuating spatiotemporal dispersion of refractoriness.Methods and Results:: In a human Langendorff model, electric mapping of 6 control and 9 treatment (10 μmol/L glibenclamide) isolated cardiomyopathic hearts was performed. Spontaneous defibrillation was studied and mean VF cycle length was compared regionally at VF onset and after 180 seconds between control and treatment groups. K_ATPsubunit gene expression was compared between LV endocardium versus epicardium in myopathic hearts. Spontaneous VF termination occurred in 1 of 6 control hearts and 7 of 8 glibenclamide-treated hearts (P=0.026). After 180 seconds of ischemia, a transmural dispersion in VF cycle length was observed between epicardium and endocardium (P=0.001), which was attenuated by glibenclamide. There was greater gene expression of all K_ATPsubunit on the endocardium compared with the epicardium (P<0.02). In an ischemic rat heart model, transmural dispersion of refractoriness (ΔERP_Transmural=ERP_Epicardium−ERP_Endocardium) was verified with pacing protocols. ΔERP_Transmuralin control was 5±2 ms and increased to 36±5 ms with ischemia. This effect was greatly attenuated by glibenclamide (ΔERP_Transmuralfor glibenclamide+ischemia=4.9±4 ms,P=0.019 versus control ischemia).Conclusions:: K_ATPchannel subunit gene expression is heterogeneously altered in the cardiomyopathic human heart. Blockade of K_ATPchannels promotes spontaneous defibrillation in cardiomyopathic human hearts by attenuating the ischemia-dependent spatiotemporal heterogeneity of refractoriness during early VF.

Background—: The therapeutic potential of renal denervation (RDN) for arrhythmias has not been fully explored. Detailed mechanistic evaluation is in order. The objective of the present study was to determine the antiarrhythmic potential of RDN in a postinfarct animal model and to determine whether any benefits relate to RDN-induced reduction of sympathetic effectors on the myocardium. Methods and Results—: Pigs implanted with single-chamber implantable cardioverter defibrillators to record ventricular arrhythmias (VAs) were subjected to percutaneous coronary occlusion to induce myocardial infarction. Two weeks later, a sham or real RDN treatment was performed bilaterally using the St Jude EnligHTN basket catheter. Parameters of ventricular remodeling and modulation of cardio–renal sympathetic axis were monitored for 3 weeks after myocardial infarction. Histological analysis of renal arteries yielded a mean neurofilament score of healthy nerves that was significantly lower in the real RDN group than in sham controls; damaged nerves were found only in the real RDN group. There was a 100% reduction in the rate of spontaneous VAs after real RDN and a 75% increase in the rate of spontaneous VAs after sham RDN ( P =0.03). In the infarcted myocardium, presence of sympathetic nerves and tissue abundance of neuropeptide-Y, an indicator of sympathetic nerve activities, were significantly lower in the RDN group. Peak and mean sinus tachycardia rates were significantly reduced after RDN. Conclusions—: RDN in the infarcted pig model leads to reduction of postinfarction VAs and myocardial sympathetic effectors. This may form the basis for a potential therapeutic role of RDN in postinfarct VAs.