Michael H. Gerber

Intravenous multipotent adult progenitor cell therapy for traumatic brain injury: preserving the blood brain barrier via an interaction with splenocytes.

Recent investigation has shown an interaction between transplanted progenitor cells and resident splenocytes leading to the modulation of the immunologic response in neurological injury. We hypothesize that the intravenous injection of multipotent adult progenitor cells (MAPC) confers neurovascular protection after traumatic brain injury through an interaction with resident splenocytes, subsequently leading to preservation of the blood brain barrier. Four groups of rats underwent controlled cortical impact injury (3 groups) or sham injury (1 group). MAPC were injected via the tail vein at two doses (2*10(6) MAPC/kg or 10*10(6) MAPC/kg) 2 and 24h after injury. Blood brain barrier permeability was assessed by measuring Evans blue dye extravasation (n=6/group). Additionally, splenic mass was measured (n=12/group) followed by splenocyte characterization (n=9/group) including: cell cycle analysis (n=6/group), apoptosis index (n=6/group), cell proliferation (n=6/group), and inflammatory cytokine measurements (n=6/group). Vascular architecture was determined by immunohistochemistry (n=3/group). Traumatic brain injury results in a decrease in splenic mass and increased blood brain barrier permeability. Intravenous infusion of MAPC preserved splenic mass and returned blood brain barrier permeability towards control sham injured levels. Splenocyte characterization indicated an increase in the number and proliferative rate of CD4+ T cells as well as an increase in IL-4 and IL-10 production in stimulated splenocytes isolated from the MAPC treatment groups. Immunohistochemistry demonstrated stabilization of the vascular architecture in the peri-lesion area. Traumatic brain injury causes a reduction in splenic mass that correlates with an increase in circulating immune cells leading to increased blood brain barrier permeability. The intravenous injection of MAPC preserves splenic mass and the integrity of the blood brain barrier. Furthermore, the co-localization of transplanted MAPC and resident CD4+ splenocytes is associated with a global increase in IL-4 and IL-10 production and stabilization of the cerebral microvasculature tight junction proteins.

Bone marrow derived mesenchymal stem cells inhibit inflammation and preserve vascular endothelial integrity in the lungs after hemorrhagic shock.

Hemorrhagic shock (HS) and trauma is currently the leading cause of death in young adults worldwide. Morbidity and mortality after HS and trauma is often the result of multi-organ failure such as acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), conditions with few therapeutic options. Bone marrow derived mesenchymal stem cells (MSCs) are a multipotent stem cell population that has shown therapeutic promise in numerous pre-clinical and clinical models of disease. In this paper, in vitro studies with pulmonary endothelial cells (PECs) reveal that conditioned media (CM) from MSCs and MSC-PEC co-cultures inhibits PEC permeability by preserving adherens junctions (VE-cadherin and β-catenin). Leukocyte adhesion and adhesion molecule expression (VCAM-1 and ICAM-1) are inhibited in PECs treated with CM from MSC-PEC co-cultures. Further support for the modulatory effects of MSCs on pulmonary endothelial function and inflammation is demonstrated in our in vivo studies on HS in the rat. In a rat “fixed volume” model of mild HS, we show that MSCs administered IV potently inhibit systemic levels of inflammatory cytokines and chemokines in the serum of treated animals. In vivo MSCs also inhibit pulmonary endothelial permeability and lung edema with concurrent preservation of the vascular endothelial barrier proteins: VE-cadherin, Claudin-1, and Occludin-1. Leukocyte infiltrates (CD68 and MPO positive cells) are also decreased in lungs with MSC treatment. Taken together, these data suggest that MSCs, acting directly and through soluble factors, are potent stabilizers of the vascular endothelium and inflammation. These data are the first to demonstrate the therapeutic potential of MSCs in HS and have implications for the potential use of MSCs as a cellular therapy in HS-induced lung injury.

Human mesenchymal stem cells inhibit vascular permeability by modulating vascular endothelial cadherin/β-catenin signaling.

The barrier formed by endothelial cells (ECs) plays an important role in tissue homeostasis by restricting passage of circulating molecules and inflammatory cells. Disruption of the endothelial barrier in pathologic conditions often leads to uncontrolled inflammation and tissue damage. An important component of this barrier is adherens junctions, which restrict paracellular permeability. The transmembrane protein vascular endothelial (VE)-cadherin and its cytoplasmic binding partner β-catenin are major components of functional adherens junctions. We show that mesenchymal stem cells (MSCs) significantly reduce endothelial permeability in cocultured human umbilical vascular endothelial cells (HUVECs) and following exposure to vascular endothelial growth factor, a potent barrier permeability-enhancing agent. When grown in cocultures with HUVECs, MSCs increased VE-cadherin levels and enhanced recruitment of both VE-cadherin and β-catenin to the plasma membrane. Enhanced membrane localization of β-catenin was associated with a decrease in β-catenin-driven gene transcription. Disruption of the VE-cadherin/β-catenin interaction by overexpressing a truncated VE-cadherin lacking the β-catenin interacting domain blocked the permeability-stabilizing effect of MSCs. Interestingly, a conditioned medium from HUVEC-MSC cocultures, but not from HUVEC or MSC cells cultured alone, significantly reduced endothelial permeability. In addition, intravenous administration of MSCs to brain-injured rodents reduced injury-induced enhanced blood-brain barrier permeability. Similar to the effect on in vitro cultures, this stabilizing effect on blood-brain barrier function was associated with increased expression of VE-cadherin. Taken together, these results identify a putative mechanism by which MSCs can modulate vascular EC permeability. Further, our results suggest that the mediator(s) of these vascular protective effects is a secreted factor(s) released as a result of direct MSC-EC interaction.

Mesenchymal Stem Cells Regulate Blood-Brain Barrier Integrity Through TIMP3 Release After Traumatic Brain Injury

The matrix metalloproteinase inhibitor TIMP3 mediates the beneficial effects of mesenchymal stem cells on the blood-brain barrier of the injured mouse brain. Mesenchymal Stem Cells Spill Their Secrets Traumatic brain injury (TBI) is the leading cause of death and disability in children and young adults worldwide and is considered a “silent epidemic” in the United States in both civilian and military populations. Pathological cerebral edema and blood-brain barrier (BBB) permeability are the leading causes of death acutely after TBI with very few therapeutic options. It has been established in animal models that intravenously administered adult bone marrow–derived mesenchymal stem cells (MSCs) are able to ameliorate BBB permeability in mice after TBI. In new work, Menge et al. identify the mechanism responsible for this beneficial effect and identify the mediator as a soluble factor produced by MSCs called TIMP3. In a mouse model of TBI, Menge et al. show that down-regulation of TIMP3 expression in intravenously administered human MSCs abrogates their protective effects on the BBB and endothelial cell stability after TBI. Furthermore, the authors demonstrate that administering intravenous recombinant human TIMP3 alone to mice after TBI can fully recapitulate the protective effects of MSCs on vascular stability and BBB integrity, indicating that TIMP3 may be a key factor regulating integrity of the BBB. Although much more work needs to be done, TIMP3 could be a useful cell-free therapeutic for treating the breakdown of BBB integrity and cerebral edema that occurs after TBI. Mesenchymal stem cells (MSCs) may be useful for treating a variety of disease states associated with vascular instability including traumatic brain injury (TBI). A soluble factor, tissue inhibitor of matrix metalloproteinase-3 (TIMP3), produced by MSCs is shown to recapitulate the beneficial effects of MSCs on endothelial function and to ameliorate the effects of a compromised blood-brain barrier (BBB) due to TBI. Intravenous administration of recombinant TIMP3 inhibited BBB permeability caused by TBI, whereas attenuation of TIMP3 expression in intravenously administered MSCs blocked the beneficial effects of the MSCs on BBB permeability and stability. MSCs increased circulating concentrations of soluble TIMP3, which blocked vascular endothelial growth factor-A–induced breakdown of endothelial cell adherens junctions in vitro and in vivo. These findings elucidate a potential molecular mechanism for the beneficial effects of MSCs on the BBB after TBI and demonstrate a role for TIMP3 in the regulation of BBB integrity.

Human mesenchymal stem cells inhibit endothelial proliferation and angiogenesis via cell-cell contact through modulation of the VE-Cadherin/β-catenin signaling pathway.

Over the past 10 years, a great deal has been learned about the fundamental biology and therapeutic application of bone marrow-derived human mesenchymal stem cells (MSCs). Intravenous administration of these cells is the preferred route for therapeutic delivery of MSCs. Vascular endothelial cells (ECs) are the first cell type that MSCs encounter following IV administration. However, little is known about the biological consequences of interactions between MSCs and ECs, and if any therapeutic benefit results from this interaction. We show that MSCs exert potent stabilizing effects on ECs using an in vitro coculture system. Such effects include decreased EC proliferation and the reduction of EC vascular network formation in matrigel. Interestingly, these effects appear to require EC-MSC contact and result in enhanced colocalization of VE-Cadherin and β-catenin at the cell membrane. Disruption of the VE-Cadherin/β-catenin interaction abrogates the observed effects. As a functional in vivo correlate, we show that intravenously administered MSCs strongly inhibit angiogenesis in a matrigel plug assay. Taken together, these results identify a novel mechanism of action of MSCs that involves a contact-dependent EC interaction. These findings are relevant to intravenous use of MSCs and provide insight into further optimizing therapeutic strategies involving MSCs.

Rodent-avoidance, topography and forest structure shape territory selection of a forest bird

BackgroundUnderstanding the factors underlying habitat selection is important in ecological and evolutionary contexts, and crucial for developing targeted conservation action in threatened species. However, the key factors associated to habitat selection often remain poorly known. We evaluated hypotheses related to abiotic and biotic factors thought to affect territory selection of the wood warbler Phylloscopus sibilatrix, a passerine living in an unpredictable environment owing to irregular rodent outbreaks and showing long-term declines particularly in Western Europe.ResultsComparing breeding territories to unoccupied areas located close-by revealed that territory occupancy in north-western Switzerland was positively related to slope steepness (topographic hypothesis supported) as well as to numbers of tussocks and trees, respectively, while it showed a unimodal relationship to cover of herb layer (forest structure hypothesis supported). Furthermore, a strong negative correlation between breeding territory occupancy and rodent numbers was found, suggesting that wood warblers avoid areas with high rodent densities (rodent-avoidance hypothesis supported). Comparing breeding territories to abandoned territories showed that breeding territories were located on steeper slopes (topography hypothesis supported), at larger distance from the forest edge (anthropogenic disturbance hypothesis supported) and harboured more trees (forest structure hypothesis supported) than abandoned territories.ConclusionsAside from structural and topographic features of the habitat, wood warblers are affected by rodent numbers when settling, making habitat selection unpredictable from year to year. Forestry practices promoting relatively high tree densities, few bushes and an intermediate low-growing ground vegetation cover would enhance habitat quality for this declining passerine. In contrast, forestry practices aiming at increasing light in forests (selective thinning, group-felling) or keeping forest stands permanently covered with shrubs, bushes and trees of various sizes (continuous cover forestry) do not benefit the wood warbler.

Fresh frozen plasma increases adhesion molecule expression on human pulmonary endothelial cells.

BACKGROUND Current blood banking practices allow fresh frozen plasma (FFP) to be thawed and then stored for 5 d between 1 and 6 °C. We hypothesized that aged plasma (d 5 FFP) would be pro-inflammatory to the endothelium compared with fresh plasma (d 0 FFP). MATERIALS AND METHODS Human pulmonary endothelial cells (PECs) were treated with (1) media, (2) media + lipopolysaccharide (LPS), (3) lactated Ringers (LR), (4) LR + LPS, (5) d 0 FFP, (6) d 0 FFP + LPS, (7) d 5 FFP, and (8) d 5 FFP + LPS. After a 24 h incubation, the PECs were stained with antibodies for I-CAM, V-CAM, P-selectin, and E-selectin. The cells were subsequently analyzed by flow cytometry. RESULTS In both PEC groups treated with FFP and stimulated with LPS, I-CAM, V-CAM, P-selectin, and E-selectin were significantly up-regulated compared with LR when stimulated by LPS. CONCLUSION FFP at both ages significantly increased expression of four different adhesion molecules compared with LR in PECs. This may represent a possible mechanism for increased leukocyte binding on the endothelium as a result of FFP transfusion.

Traumatic brain injury: Mesenchymal stem cells regulate blood-brain barrier integrity through TIMP3 release after traumatic brain injury

The matrix metalloproteinase inhibitor TIMP3 mediates the beneficial effects of mesenchymal stem cells on the blood-brain barrier of the injured mouse brain. Mesenchymal Stem Cells Spill Their Secrets Traumatic brain injury (TBI) is the leading cause of death and disability in children and young adults worldwide and is considered a “silent epidemic” in the United States in both civilian and military populations. Pathological cerebral edema and blood-brain barrier (BBB) permeability are the leading causes of death acutely after TBI with very few therapeutic options. It has been established in animal models that intravenously administered adult bone marrow–derived mesenchymal stem cells (MSCs) are able to ameliorate BBB permeability in mice after TBI. In new work, Menge et al. identify the mechanism responsible for this beneficial effect and identify the mediator as a soluble factor produced by MSCs called TIMP3. In a mouse model of TBI, Menge et al. show that down-regulation of TIMP3 expression in intravenously administered human MSCs abrogates their protective effects on the BBB and endothelial cell stability after TBI. Furthermore, the authors demonstrate that administering intravenous recombinant human TIMP3 alone to mice after TBI can fully recapitulate the protective effects of MSCs on vascular stability and BBB integrity, indicating that TIMP3 may be a key factor regulating integrity of the BBB. Although much more work needs to be done, TIMP3 could be a useful cell-free therapeutic for treating the breakdown of BBB integrity and cerebral edema that occurs after TBI. Mesenchymal stem cells (MSCs) may be useful for treating a variety of disease states associated with vascular instability including traumatic brain injury (TBI). A soluble factor, tissue inhibitor of matrix metalloproteinase-3 (TIMP3), produced by MSCs is shown to recapitulate the beneficial effects of MSCs on endothelial function and to ameliorate the effects of a compromised blood-brain barrier (BBB) due to TBI. Intravenous administration of recombinant TIMP3 inhibited BBB permeability caused by TBI, whereas attenuation of TIMP3 expression in intravenously administered MSCs blocked the beneficial effects of the MSCs on BBB permeability and stability. MSCs increased circulating concentrations of soluble TIMP3, which blocked vascular endothelial growth factor-A–induced breakdown of endothelial cell adherens junctions in vitro and in vivo. These findings elucidate a potential molecular mechanism for the beneficial effects of MSCs on the BBB after TBI and demonstrate a role for TIMP3 in the regulation of BBB integrity.