Characterization of key mechanisms involved in transmigration and invasion of mesenchymal stem cells

Stem cell therapy using human adult mesenchymal stem cells (MSCs) has emerged as a novel strategy for the treatment of a variety of damaged tissues. For a successful systemic stem cell therapy MSCs have to exit the blood circulation by transmigrating across the endothelium and invading into the target tissue. Elevating our knowledge on these core processes might help to optimize stem cell based therapies. The first part of the present study provides insights into key mechanisms involved in the transmigration and invasion of MSCs. Different model systems as well as in vivo studies revealed that MSCs quickly come into contact with the endothelium and subsequently exit the blood circulation by (1) integrating into the endothelium, (2) transmigrating across the endothelial barrier via the insertion of plasmic podia, (3) penetrating the basement membrane and subsequently invading the surrounding tissue. Additionally, it was proven that transmigration of human MSCs not only requires the interaction of very late antigen-4 (VLA-4) and its most important ligand vascular cell adhesion molecule-1 (VCAM-1), but also triggers a clustering of beta 1 integrins. Furthermore, upon invading into cardiac tissue MSCs secrete active matrix metalloproteinase (MMP)-2, but not MMP-9. This study also demonstrates that both the time course and the morphological aspects of MSC transmigration differ depending on the endothelial phenotype, thus indicating, that a variable capacity for transendothelial migration exists within the vasculature. Furthermore, addition of cytokines, mainly vascular endothelial growth factor (VEGF) and erythropoietin (EPO), accelerate the transmigration of MSCs at early stages. Moreover, nitric oxide (NO) and reactive oxygen species (ROS) are released by MSCs upon contact with endothelial cells; manipulating the NO and ROS system by donors and inhibitors resulted in alterations of the transmigratory capacity of MSCs. The second part of the study deals with two possible strategies to enhance the transmigration of MSCs and thereby their therapeutic effectiveness. First, the results demonstrate that genetic modification of MSCs using adenoviral overexpression of the chemokine receptor CXCR4 does not lead to an increase in the transmigration efficiency. Second, focussed pretreatment of the endothelium by a novel and non-invasive technique using ultrasound-mediated microbubble stimulation (UMS) induces a targeted improvement of MSC attraction, transmigration and invasion into non-ischemic as well as into ischemic myocardium. This effect was most likely due to the release of nitric oxide, cytokines and the regional activation of proteases. Thus, UMS represents a forward-looking possibility to increase the efficiency of MSC engraftment by modulating the process of transmigration in a targeted and non-invasive manner

Urokinase type plasminogen activator mediates Interleukin-17-induced peripheral blood mesenchymal stem cell motility and transendothelial migration

Mesenchymal stem cells (MSCs) have the potential to migrate toward damaged tissues increasing tissue regeneration. Interleukin-17 (IL-17) is a proinflammatory cytokine with pleiotropic effects associated with many inflammatory diseases. Although IL-17 can modulate MSC functions, its capacity to regulate MSC migration is not well elucidated so far. Here, we studied the role of IL-17 on peripheral blood (PB) derived MSC migration and transmigration across endothelial cells. IL-17 increased PB-MSC migration in a wound healing assay as well as cell mobilization from collagen gel. Concomitantly IL-17 induced the expression of urokinase type plasminogen activator (uPA) without affecting matrix metalloproteinase expression. The incremented uPA expression mediated the capacity of IL-17 to enhance PB-MSC migration in a ERK1,2 MAPK dependent way. Also, IL-17 induced PB-MSC migration alongside with changes in cell polarization and uPA localization in cell protrusions. Moreover, IL-17 increased PB-MSC adhesion to endothelial cells and transendothelial migration, as well as increased the capacity of PB-MSC adhesion to fibronectin, in an uPA-dependent fashion. Therefore, our data suggested that IL-17 may act as chemotropic factor for PB-MSCs by incrementing cell motility and uPA expression during inflammation development

Leucocyte and Platelet-rich Fibrin: A carrier of autologous multipotent cells for regenerative medicine

The wound healing is a complex process wherein inflammation, proliferation and regeneration evolve according to a spatio-temporal pattern from the activation of coagulation cascade to the formation of a plug clot including fibrin matrix, blood-borne cells and cytokines/growth factors. Creating environments conducive to tissue repair, the haemoderivatives are commonly proposed for the treatment of hard-to-heal wounds. Here, we explored in vitro the intrinsic regenerative potentialities of a leucocyte- and platelet-rich fibrin product, known as CPL-MB, defining the stemness grade of cells sprouting from the haemoderivative. Using highly concentrated serum-based medium to simulate wound conditions, we isolated fibroblast-like cells (CPL-CMCs) adhering to plastic and showing stable in vitro propagation, heterogeneous stem cell expression pattern, endothelial adhesive properties and immunomodulatory profile. Due to their blood derivation and expression of CXCR4, CPL-CMCs have been suggested to be immature cells circulating in peripheral blood at quiescent state until activation by both coagulation event and inflammatory stimuli such as stromal-derived factor 1/SDF1. Expressing integrins (CD49f, CD103), vascular adhesion molecules (CD106, CD166), endoglin (CD105) and remodelling matrix enzymes (MMP2, MMP9, MMP13), they showed a transendothelial migratory potential besides multipotency. Taken together, our data suggested that a standardized, reliable and economically feasible blood product such as CPL-MB functions as an artificial stem cell niche that, under permissive conditions, originate ex vivo immature cells that could be useful for autologous stem cell-based therapies

Mesenchymal Stem Cells Exhibit Firm Adhesion, Crawling, Spreading and Transmigration across Aortic Endothelial Cells: Effects of Chemokines and Shear

Mesenchymal stem cells (MSCs) have anti-inflammatory and immunosuppressive properties and may be useful in the therapy of diseases such as arteriosclerosis. MSCs have some ability to traffic into inflamed tissues, however to exploit this therapeutically their migratory mechanisms need to be elucidated. This study examines the interaction of murine MSCs (mMSCs) with, and their migration across, murine aortic endothelial cells (MAECs), and the effects of chemokines and shear stress. The interaction of mMSCs with MAECs was examined under physiological flow conditions. mMSCs showed lack of interaction with MAECs under continuous flow. However, when the flow was stopped (for 10min) and then started, mMSCs adhered and crawled on the endothelial surface, extending fine microvillous processes (filopodia). They then spread extending pseudopodia in multiple directions. CXCL9 significantly enhanced the percentage of mMSCs adhering, crawling and spreading and shear forces markedly stimulated crawling and spreading. CXCL9, CXCL16, CCL20 and CCL25 significantly enhanced transendothelial migration across MAECs. The transmigrated mMSCs had down-regulated receptors CXCR3, CXCR6, CCR6 and CCR9. This study furthers the knowledge of MSC transendothelial migration and the effects of chemokines and shear stress which is of relevance to inflammatory diseases such as arteriosclerosis

Temporal Information Processing in Short- and Long-Term Memory of Patients with Schizophrenia

Cognitive deficits of patients with schizophrenia have been largely recognized as core symptoms of the disorder. One neglected factor that contributes to these deficits is the comprehension of time. In the present study, we assessed temporal information processing and manipulation from short- and long-term memory in 34 patients with chronic schizophrenia and 34 matched healthy controls. On the short-term memory temporal-order reconstruction task, an incidental or intentional learning strategy was deployed. Patients showed worse overall performance than healthy controls. The intentional learning strategy led to dissociable performance improvement in both groups. Whereas healthy controls improved on a performance measure (serial organization), patients improved on an error measure (inappropriate semantic clustering) when using the intentional instead of the incidental learning strategy. On the long-term memory script-generation task, routine and non-routine events of everyday activities (e.g., buying groceries) had to be generated in either chronological or inverted temporal order. Patients were slower than controls at generating events in the chronological routine condition only. They also committed more sequencing and boundary errors in the inverted conditions. The number of irrelevant events was higher in patients in the chronological, non-routine condition. These results suggest that patients with schizophrenia imprecisely access temporal information from short- and long-term memory. In short-term memory, processing of temporal information led to a reduction in errors rather than, as was the case in healthy controls, to an improvement in temporal-order recall. When accessing temporal information from long-term memory, patients were slower and committed more sequencing, boundary, and intrusion errors. Together, these results suggest that time information can be accessed and processed only imprecisely by patients who provide evidence for impaired time comprehension. This could contribute to symptomatic cognitive deficits and strategic inefficiency in schizophrenia

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The rice field cyanobacteria Anabaena azotica and Anabaena sp. CH1 express vanadium-dependent nitrogenase

Anabaena azotica FACHB-118 and Anabaena sp. CH1, heterocystous cyanobacteria isolated from Chinese and Taiwanese rice fields, expressed vanadium-containing nitrogenase when under molybdenum deficiency. This is the second direct observation of an alternative nitrogenase in cyanobacteria. The vanadium nitrogenase-specific genes vnfDG are fused and clustered in a phylogenetic tree next to the corresponding genes of Methanosarcina. The expression of vnfH in cells cultured in Mo-free medium and of nifH in Mo-grown cells was shown for the first time by sequencing cDNA derived from cultures of A. azotica and Anabaena sp. CH1. The vnfH sequences clustered with that of Anabaena variabilis. The vnf genes were strongly transcribed only in cultures grown either in Mo-free medium, or in W-containing medium, but also weakly in Mo-containing medium. NifH was transcribed in all media. On-line measurements of acetylene reduction by Mo-free A. azotica cultures demonstrated that the V-nitrogenase was active. Ethane was formed continuously at a rate of 2.1% of that of ethylene. Acetylene reduction of cultures grown either with or without Mo had a high temperature optimum of 42.5°C. The uptake hydrogenase gene hupL was expressed in Mo-free medium concomitantly with vnfDG in A. azotica, Anabaena sp. CH1, and A. variabilis

Performance on the script-generation task separately for patients with schizophrenia and healthy controls.

<p>Note. N = number of subjects; SZ = chronic schizophrenia patients; C = healthy controls; in brackets = standard errors;</p><p>* = groups differ; p = .05.</p