Mesenchymal Stem Cell-Derived Molecules Reverse Fulminant Hepatic Failure

Modulation of the immune system may be a viable alternative in the treatment of fulminant hepatic failure (FHF) and can potentially eliminate the need for donor hepatocytes for cellular therapies. Multipotent bone marrow-derived mesenchymal stem cells (MSCs) have been shown to inhibit the function of various immune cells by undefined paracrine mediators in vitro. Yet, the therapeutic potential of MSC-derived molecules has not been tested in immunological conditions in vivo. Herein, we report that the administration of MSC-derived molecules in two clinically relevant forms-intravenous bolus of conditioned medium (MSC-CM) or extracorporeal perfusion with a bioreactor containing MSCs (MSC-EB)-can provide a significant survival benefit in rats undergoing FHF. We observed a cell mass-dependent reduction in mortality that was abolished at high cell numbers indicating a therapeutic window. Histopathological analysis of liver tissue after MSC-CM treatment showed dramatic reduction of panlobular leukocytic infiltrates, hepatocellular death and bile duct duplication. Furthermore, we demonstrate using computed tomography of adoptively transferred leukocytes that MSC-CM functionally diverts immune cells from the injured organ indicating that altered leukocyte migration by MSC-CM therapy may account for the absence of immune cells in liver tissue. Preliminary analysis of the MSC secretome using a protein array screen revealed a large fraction of chemotactic cytokines, or chemokines. When MSC-CM was fractionated based on heparin binding affinity, a known ligand for all chemokines, only the heparin-bound eluent reversed FHF indicating that the active components of MSC-CM reside in this fraction. These data provide the first experimental evidence of the medicinal use of MSC-derived molecules in the treatment of an inflammatory condition and support the role of chemokines and altered leukocyte migration as a novel therapeutic modality for FHF

The Inflammatory Response to Double Stranded DNA in Endothelial Cells Is Mediated by NFκB and TNFα

Endothelial cells represent an important barrier between the intravascular compartment and extravascular tissues, and therefore serve as key sensors, communicators, and amplifiers of danger signals in innate immunity and inflammation. Double stranded DNA (dsDNA) released from damaged host cells during injury or introduced by pathogens during infection, has emerged as a potent danger signal. While the dsDNA-mediated immune response has been extensively studied in immune cells, little is known about the direct and indirect effects of dsDNA on the vascular endothelium. In this study we show that direct dsDNA stimulation of endothelial cells induces a potent proinflammatory response as demonstrated by increased expression of ICAM1, E-selectin and VCAM1, and enhanced leukocyte adhesion. This response was dependent on the stress kinases JNK and p38 MAPK, required the activation of proinflammatory transcription factors NFκB and IRF3, and triggered the robust secretion of TNFα for sustained secondary activation of the endothelium. DNA-induced TNFα secretion proved to be essential in vivo, as mice deficient in the TNF receptor were unable to mount an acute inflammatory response to dsDNA. Our findings suggest that the endothelium plays an active role in mediating dsDNA-induced inflammatory responses, and implicate its importance in establishing an acute inflammatory response to sterile injury or systemic infection, where host or pathogen derived dsDNA may serve as a danger signal.United States. Dept. of Defense (CDMRP Predoctoral Training Award)National Institutes of Health (U.S.) (NIH BioMEMS Resource Center Grant P41 EB-002503)National Institutes of Health (U.S.) (NIH Grant RO1AI063795)Shriners Hospital for Childre

Conditions for the occurrence of large near-wall excesses of small particles during blood flow

Prior work showed that the near-wall concentration of platelet-sized latex beads (2.38 μm diam) in flowing blood suspensions can be greater than three times the concentration in the central region of the flow. Similar methods were used to explore the dependence of the near-wall excess (NWE) of beads on the channel height and suspension composition. The bead diameter, suspending fluid viscosity, and red blood cell deformability were varied; the hematocrit was fixed at 15%. Results showed that NWEs ⩾ three times the central concentration were associated with shear stress, rather than with strain rate, required red cell deformability, and occurred with bead diameters of 2.2 μm or larger. The amplitude of NWEs observed in the 30- and 50-μm channels changed sharply from small to large as the wall shear rate (WSR) was increased, while those observed in 100-μm channels exhibited a more gradual dependence on WSR

Mesenchymal stem cell-derived molecules directly modulate hepatocellular death and regeneration in vitro and in vivo

Orthotopic liver transplantation is the only proven effective treatment for fulminant hepatic failure (FHF), but its use is limited because of organ donor shortage, associated high costs, and the requirement for lifelong immunosuppression. FHF is usually accompanied by massive hepatocellular death with compensatory liver regeneration that fails to meet the cellular losses. Therefore, therapy aimed at inhibiting cell death and stimulating endogenous repair pathways could offer major benefits in the treatment of FHF. Recent studies have demonstrated that mesenchymal stem cell (MSC) therapy can prevent parenchymal cell loss and promote tissue repair in models of myocardial infarction, acute kidney failure, and stroke through the action of trophic secreted molecules. In this study, we investigated whether MSC therapy can protect the acutely injured liver and stimulate regeneration. In a D-galactosamine-induced rat model of acute liver injury, we show that systemic infusion of MSC-conditioned medium (MSC-CM) provides a significant survival benefit and prevents the release of liver injury biomarkers. Furthermore, MSC-CM therapy resulted in a 90% reduction of apoptotic hepatocellular death and a three-fold increment in the number of proliferating hepatocytes. This was accompanied by a dramatic increase in the expression levels of 10 genes known to be up-regulated during hepatocyte replication. Direct antiapoptotic and promitotic effects of MSC-CM on hepatocytes were demonstrated using in vitro assays. Conclusion: These data provide the first dear evidence that MSC-CM therapy provides trophic support to the injured liver by inhibiting hepatocellular death and stimulating regeneration, potentially creating new avenues for the treatment of FHF

dsDNA mediated TNFα secretion for sustained secondary activation of the endothelium.

<p>(a) Q-PCR for expression of TNFα in endothelial cells after stimulation with dsDNA (.5 or 4 µg/ml) or mock transfected with Lipofectamine for 12 hours. (b) ELISA for TNFα in culture supernatant of endothelial cells stimulated with dsDNA (.5 or 4 µg/ml) or mock transfected with Lipofectamine for 24 hours. (c) ELISA for TNFα in supernatants of wildtype MEFs (WT), TBK1/IKKε DKO MEFs (TBK1/IKKε DKO), and IKKα/IKKβ DKO MEFs (IKKα/IKKβ DKO) stimulated with 4 µg/mL of dsDNA for 24 hours. (d) ELISA for TNFα in supernatants of endothelial cells after stimulation with dsDNA (4 µg/ml) for 24 hours in the presence or absence of PDTC (PD), SB202190 (SB) or SP600125 (SP) which are inhibitors of NFκB, p38 MAPK and JNK pathways, respectively. (e) Q-PCR for expression of VCAM1 in endothelial cells stimulated with dsDNA (1 µg/ml) for 4 or 12 hours, in the presence or absence of TNFα neutralizing antibody (+Anti-TNFa) or cycloheximide (+CHX). (*P<0.05 compared to control, #P<0.05 compared to dsDNA alone.)</p

dsDNA activates NFκB and MAPK pathways, which modulate adhesion molecule expression in endothelium.

<p>(a) Fluorescence histogram of NFκB reporter clone of endothelial cells treated with Lipofectamine alone (control) or dsDNA (2 µg/ml) for 16 hours. (b) ELISA for NFκB activity in endothelial cells stimulated with a dose of dsDNA (0 to 4 µg/ml) for 6 hours. (c) Phosphorylated protein levels in endothelial cells stimulated with dsDNA (2 µg/ml) for 6 hours. (d) Q-PCR for expression of ICAM-1, VCAM-1, and E-Selectin in RHMECs after stimulation with dsDNA (2 µg/ml) for 4 hours in the presence or absence of PDTC (PD), SP600125 (SP), or SB202190 (SB), which are inhibitors of NFκB, JNK, and p38 MAPK pathways, respectively. (*P<0.05 compared to control, #P<0.05 and ##P<0.01 compared to dsDNA alone.)</p