Emerging evidence suggests that both human stem cells and mature stromal cells can play an important role in the development and growth of human malignancies. In contrast to these tumor-promoting properties, we observed that in an in vivo model of Kaposi's sarcoma (KS), intravenously (i.v.) injected human mesenchymal stem cells (MSCs) home to sites of tumorigenesis and potently inhibit tumor growth. We further show that human MSCs can inhibit the in vitro activation of the Akt protein kinase within some but not all tumor and primary cell lines. The inhibition of Akt activity requires the MSCs to make direct cell–cell contact and can be inhibited by a neutralizing antibody against E-cadherin. We further demonstrate that in vivo, Akt activation within KS cells is potently down-regulated in areas adjacent to MSC infiltration. Finally, the in vivo tumor-suppressive effects of MSCs correlates with their ability to inhibit target cell Akt activity, and KS tumors engineered to express a constitutively activated Akt construct are no longer sensitive to i.v. MSC administration. These results suggest that in contrast to other stem cells or normal stromal cells, MSCs possess intrinsic antineoplastic properties and that this stem cell population might be of particular utility for treating those human malignancies characterized by dysregulated Akt.

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BACKGROUND The use of plasma-based resuscitation for trauma patients in hemorrhagic shock has been associated with a decrease in mortality. While some have proposed a beneficial effect through replacement of coagulation proteins, the putative mechanisms of protection afforded by plasma are unknown. We have previously shown in a cell culture model that plasma decreases endothelial cell permeability compared to crystalloid. The endothelial glycocalyx consists of proteoglycans and glycoproteins attached to a syndecan backbone, which together protect the underlying endothelium. We hypothesize that endothelial cell protection by plasma is due, in part, to its restoration of the endothelial glycocalyx and preservation of syndecan-1 after hemorrhagic shock. METHODS Rats were subjected to hemorrhagic shock to a mean arterial blood pressure of 30 mmHg for 90 minutes followed by resuscitation with either lactated Ringer’s solution (LR) or fresh plasma to a mean arterial blood pressure of 80 mm Hg and compared to shams or shock alone. After two hours, lungs were harvested for syndecan mRNA, immunostained with anti-syndecan-1, or stained with hematoxylin and eosin. To specifically examine the effect of plasma on the endothelium, small bowel mesentery was infused with a lanthanum-based solution, venules identified, and the glycocalyx visualized by electron microscopy. All data are presented as mean ±SEM. Results were analyzed by one-way ANOVA with Tukey post hoc tests. RESULTS Electron microscopy revealed degradation of the glycocalyx after hemorrhagic shock which was partially restored by plasma but not LR. Pulmonary syndecan-1 mRNA expression was higher in animals resuscitated with plasma (2.76 ± 0.03) compared to shock alone (1.39 ± 0.22) or LR (0.82 ± 0.03) and correlated with cell surface syndecan-1 immunostaining. Shock also resulted in significant lung injury by histopathology scoring (1.63 ± 0.26) which was mitigated by resuscitation with plasma (0.67 ± 0.17) but not LR (2.0 ± 0.25). CONCLUSION The protective effects of plasma may be due in part to its ability to restore the endothelial glycocalyx and preserve syndecan-1 after hemorrhagic shock.

BackgroundThe endothelial glycocalyx layer (EGL) is a key regulator of vascular permeability, cell adhesion, and inflammation. The EGL is primarily composed of syndecan-1, hyaluronic acid (HA), heparan sulfate (HS) and chondroitin sulfate (CS). While many studies have observed increased shedding of syndecan-1 during hemorrhagic shock, little is known about the shedding of other EGL components, and their effects on altered permeability and coagulation. We characterized shedding of all four primary components of the EGL, as well as the plasma’s effect on permeability and thrombin generation in a cohort of trauma patients.MethodsPlasma samples were collected from 5 healthy consented volunteers and 22 severely injured trauma patients upon admission to the emergency department. ELISA assays were performed to quantify shed HA, HS, CS and syndecan-1 in plasma. A colloid osmometer and Electric Cell-substrate Impedance Sensing (ECIS) system were used to measure plasma colloid osmotic pressure (COP) and cell permeability, respectively. Thrombin generation was measured using a calibrated automated thrombogram (CAT). Initial vital signs, routine laboratory values, and injury severity scores (ISS) were recorded. Non-parametric statistical tests were used to compare differences between groups.ResultsWe observed increased shedding of all four proteins in trauma patient plasma compared to healthy controls: 31.7 vs. 21.2 U/L of CS, 175.8 vs. 121.9 ng/ml of HS, 946.7 vs. 618.6 ng/ml of HA and 245.8 vs. 31.6 ng/ml of syndecan-1 (all p < 0.05). Patients with low plasma COP (≤16 mmHg) had significantly increased syndecan-1 and HA compared to those with normal COP, which corresponded to increased cell permeability via ECIS. CS and HS did not vary between COP groups. Lastly, patients with low COP displayed reduced peak thrombin generation of less than 250 nM on average (p < 0.05).ConclusionsGlycocalyx components were shed more in trauma patients compared to healthy controls in this cohort. However, only syndecan-1 and HA shedding were significantly higher in patients with reduced plasma COP. Thrombin generation was impaired in patients with low plasma COP. These data suggest that low plasma COP correlates well to glycocalyx degradation and thrombin loss following trauma, which consequently affect permeability and coagulation.

The early use of fresh frozen plasma as a resuscitative agent after hemorrhagic shock has been associated with improved survival, but the mechanism of protection is unknown. Hemorrhagic shock causes endothelial cell dysfunction and we hypothesized that fresh frozen plasma would restore endothelial integrity and reduce syndecan-1 shedding after hemorrhagic shock. A prospective, observational study in severely injured patients in hemorrhagic shock demonstrated significantly elevated levels of syndecan-1 (554±93 ng/ml) after injury, which decreased with resuscitation (187±36 ng/ml) but was elevated compared to normal donors (27±1 ng/ml). Three pro-inflammatory cytokines, interferon-γ, fractalkine, and interleukin-1β, negatively correlated while one anti-inflammatory cytokine, IL-10, positively correlated with shed syndecan-1. These cytokines all play an important role in maintaining endothelial integrity. An in vitro model of endothelial injury then specifically examined endothelial permeability after treatment with fresh frozen plasma orlactated Ringers. Shock or endothelial injury disrupted junctional integrity and increased permeability, which was improved with fresh frozen plasma, but not lactated Ringers. Changes in endothelial cell permeability correlated with syndecan-1 shedding. These data suggest that plasma based resuscitation preserved endothelial syndecan-1 and maintained endothelial integrity, and may help to explain the protective effects of fresh frozen plasma after hemorrhagic shock.

BACKGROUND We have recently demonstrated that injured patients in hemorrhagic shock shed syndecan-1 and that the early use of fresh frozen plasma (FFP) in these patients is correlated with improved clinical outcomes. As the lungs are frequently injured after trauma, we hypothesized that hemorrhagic shock-induced shedding of syndecan-1 exposes the underlying pulmonary vascular endothelium to injury resulting in inflammation and hyperpermeability, and that these effects would be mitigated by FFP. METHODS In vitro, pulmonary endothelial permeability, endothelial monolayer flux, transendothelial electrical resistance (TER), and leukocyte-endothelial binding were measured in pulmonary endothelial cells after incubation with equal volumes of FFP or lactated Ringers (LR). In vivo, using a coagulopathic mouse model of trauma and hemorrhagic shock, pulmonary hyperpermeability, neutrophil infiltration, and syndecan-1 expression and systemic shedding were assessed after three hours of resuscitation with either 1XFFP or 3XLR and compared to shock alone and shams. RESULTS In vitro, endothelial permeability and flux were decreased, TER was increased, and leukocyte-endothelial binding was inhibited by FFP compared to LR treated endothelial cells. In vivo, hemorrhagic shock was associated with systemic shedding of syndecan-1 which correlated with decreased pulmonary sydnecan-1 and increased pulmonary vascular hyperpermeability and inflammation. FFP resuscitation, compared to LR resuscitation, abrogated these injurious effects. CONCLUSIONS After hemorrhagic shock, FFP resuscitation inhibits endothelial cell hyperpermeability and inflammation and restores pulmonary syndecan-1 expression. Modulation of pulmonary syndecan-1 expression may mechanistically contribute to the beneficial effects FFP.

Background Clinical studies have shown that resuscitation with fresh frozen plasma (FFP) is associated with improved outcome after severe hemorrhagic shock (HS). We hypothesized that in addition to its effects on hemostasis, FFP has protective and stabilizing effects on the endothelium that translate into diminished endothelial cell (EC) permeability and improved resuscitation in vivo after HS. We further hypothesized that the beneficial effects of FFP would diminish over 5 days of routine storage at 4°C. Methods EC permeability was induced by hypoxia and assessed by the passage of 70-kDa Dextran between monolayers. Thrombin generation time and coagulation factor levels or activity were assessed in FFP. An in vivo rat model of HS and resuscitation was used to determine the effects of FFP on hemodynamic stability. Results Thawed FFP inhibits EC permeability in vitro by 10.2-fold. Protective effects diminish (to 2.5-fold) by day 5. Thrombin generation time is increased in plasma that has been stored between days 0 and 5. In vivo data show that day 0 FFP is superior to day 5 FFP in maintaining mean arterial pressure in rats undergoing HS with resuscitation. Conclusion Both in vitro and in vivo studies show that FFP has beneficial effects on endothelial permeability, vascular stability, and resuscitation in rats after HS. The benefits are independent of hemostasis and diminish between days 0 and 5 of storage.

Sunitinib malate is a multi-targeted receptor tyrosine kinase inhibitor used in the treatment of human malignancies. A substantial number of sunitinib-treated patients develop cardiac dysfunction, but the mechanism of sunitinib-induced cardiotoxicity is poorly understood. We show that mice treated with sunitinib develop cardiac and coronary microvascular dysfunction and exhibit an impaired cardiac response to stress. The physiological changes caused by treatment with sunitinib are accompanied by a substantial depletion of coronary microvascular pericytes. Pericytes are a cell type that is dependent on intact PDGFR signaling but whose role in the heart is poorly defined. Sunitinib-induced pericyte depletion and coronary microvascular dysfunction are recapitulated by CP-673451, a structurally distinct PDGFR inhibitor, confirming the role of PDGFR in pericyte survival. Thalidomide, an anti-cancer agent that is known to exert beneficial effects on pericyte survival and function, prevents sunitinib-induced pericyte cell death in vitro and prevents sunitinib-induced cardiotoxicity in vivo in a mouse model. Our findings suggest that pericytes are the primary cellular target of sunitinib-induced cardiotoxicity and reveal the pericyte as a cell type of concern in the regulation of coronary microvascular function. Furthermore, our data provide preliminary evidence that thalidomide may prevent cardiotoxicity in sunitinib-treated cancer patients.