The Adult Human Brain Harbors Multipotent Perivascular Mesenchymal Stem Cells

Blood vessels and adjacent cells form perivascular stem cell niches in adult tissues. In this perivascular niche, a stem cell with mesenchymal characteristics was recently identified in some adult somatic tissues. These cells are pericytes that line the microvasculature, express mesenchymal markers and differentiate into mesodermal lineages but might even have the capacity to generate tissue-specific cell types. Here, we isolated, purified and characterized a previously unrecognized progenitor population from two different regions in the adult human brain, the ventricular wall and the neocortex. We show that these cells co-express markers for mesenchymal stem cells and pericytes in vivo and in vitro, but do not express glial, neuronal progenitor, hematopoietic, endothelial or microglial markers in their native state. Furthermore, we demonstrate at a clonal level that these progenitors have true multilineage potential towards both, the mesodermal and neuroectodermal phenotype. They can be epigenetically induced in vitro into adipocytes, chondroblasts and osteoblasts but also into glial cells and immature neurons. This progenitor population exhibits long-term proliferation, karyotype stability and retention of phenotype and multipotency following extensive propagation. Thus, we provide evidence that the vascular niche in the adult human brain harbors a novel progenitor with multilineage capacity that appears to represent mesenchymal stem cells and is different from any previously described human neural stem cell. Future studies will elucidate whether these cells may play a role for disease or may represent a reservoir that can be exploited in efforts to repair the diseased human brain

Immuno Gene Therapy of Rat Brain Tumors with interferon-gamma transfected glioma cells

Immunotherapy is a new promising approach in cancer treatment. In the future, it will hopefully offer an alternative to existing brain tumors treatments, which are unable to cure. We have established an experimental, low immunogenic, brain tumor model in the rat. We have increased tumor cell immunogenicity with mutagen treatment or transfection of IFN-g. Mutagen treated glioma cells (tum-) could cross protect for subsequent challenge of wild type tumor cells. Immunization with tum- cells pre-incubated with IFN-g could also reject wild type tumor after tumor grafting. Lymphocyte populations in draining lymph nodes after tum- immunization showed the number of CD8+ T cells to increase fastest and strongest. IFN-g and TNF-a induction was stronger (in the CD8+ T cell compartment), while IL-10 was weaker (in the CD4+ T cell compartment) after tum- immunization as compared to control immunization. Peripheral immunizations with IFN-g transfected glioma cells after tumor grafting, were able to induce total tumor rejection of 37 and 72% with the N32 and N29 glioma, respectively. B7 or IL-7 transfected tumor cells could also cure but were less effective. Analysis of tumor infiltrating leucocytes in N32-IFN-g immunized as compared to control animals, showed a significant higher infiltration density in CD8+ and CD4+ T cells, as well as NK cells. CD8+ T cells from tumors immunized with N32-IFN-g also had increased LFA-1 expression. CD25 expression was similar between immunization groups, with CD25low expression in both CD4+ and CD8+ T cells, as well as CD25high expression in a population of CD4+ T cells

Activation of purified allogeneic CD4(+) T cells by rat bone marrow-derived dendritic cells induces concurrent secretion of IFN-gamma, IL-4, and IL-10.

Dendritic cells (DCs) are highly specialized antigen-presenting cells that play a key role in the initiation and regulation of immune responses. The ability of DCs to process antigens and the outcome of their interaction with T cells are largely dependent on phenotype as well as maturation state of DCs. In this study, we generated DCs from rat bone marrow precursors. Bone marrow cells cultured in the presence of granulocyte macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-4, and Flt-3 ligand (FL) produced immature DCs that expressed intermediate levels of major histocompatibility complex (MHC) class II, low levels of CD80 and CD86 molecules and displayed a high capacity of endocytosis. Bone marrow-derived DCs (BMDCs) matured in the presence of lipopolysaccharide (LPS) upregulated expression of MHC class II, CD80 and CD86, while their phagocytic capacity was dramatically reduced. Mature BMDCs stimulated vigorous proliferation of purified allogeneic CD4(+) T cells in a primary mixed leukocyte reaction (MLR) and elicited a mixed cytokine profile in allogeneic CD4(+) T cells: DCs activated CD4(+) T cells to produce interferon (IFN)-gamma, IL-4, and IL-10. Thus, rat BMDCs effectively internalize antigens and stimulate T cell proliferation but fail to induce an unidirectional polarization of T helper (T-H) cells and in this respect differ from both human and mouse DCs. (c) 2005 Elsevier B.V. All rights reserved

Prolonged and intense neuroinflammation after severe traumatic brain injury assessed by cerebral microdialysis with 300 kDa membranes

Background: A neuroinflammatory response that may lead to edema and secondary brain damage is elicited in severe traumatic brain injury (TBI). Previous studies using microdialysis (MD) membranes with 100 k Dalton (kDa) cut-off found a transient intracerebral release of cytokines and chemokines without significant correlations to clinical course, intracranial pressure (ICP) or metabolites. In this study, a (300 kDa) MD probe was used to measure the levels of cytokines and chemokines in relation to ICP and metabolites. Methods: Seven patients with severe TBI received 2 MD catheters. In four patients sufficient dialysate could be retrieved for analysis from both catheters. MD samples were analyzed bedside, then frozen and analyzed for chemokines and cytokines using a multiplex assay (Mesoscale Discovery). Results: MD sampling was performed from 9 to 350 h. In total, 17 chemokines and cytokines were detected. Of these, IL-6, IL-8, IP-10, MCP-1 and MIP-1β were consistently elevated, and investigated further in relation to metabolites, and ICP. Levels of chemokines and cytokines were higher than previously reported from TBI patients, and partially higher than those reported in patients with cytokine release syndrome. There were no significant differences between the two catheters regarding cytokine/chemokine concentrations, except for IL-6 which was higher in the peri-contusional area. No correlation with metabolites and ICP was observed. No significant increase or decline of chemokine or cytokine secretion was observed during the study period. Conclusion: Our data suggest that cytokine and chemokine levels reflect a perpetual, potent and pan-cerebebral inflammatory response that persists beyond 15 days following TBI

The MAP kinases are differently utilized by CD28 and CD2 adhesion pathways in superantigen-activated Jurkat T cells

To mimic the two-signal requirements for T cell activation mediated by ligands, we exposed the superantigens SEA or SEE (signal 1) to T cells incubated with HLA-DR/LFA-3 or HLA-DR/137-1-CHO transfected cells (signal 2). LFA-3 costimulation was able to induce T cell proliferation as well as IFN-gamma and IL-4 production at similar levels as in cells induced by B7-1. Analysis of the CD28RE of the IL-2 promoter showed specific transcription factor recruitment at the CD28RE element upon induction by B7-1/SEE. Further functional Studies with an IL-2 enhancer-promoter carrying either wild type or mutated versions of the CD28RE site revealed that this element is necessary for full activation upon B7-1 costimulation. While both CD28/B7-1 and CD2/LFA-3 costimulation resulted in the up-regulation of IL-4 and IFN-gamma promoters, IL-2 promoter activity and production of IL-2 were only seen after B7-1 costimulation. However, contrary to what has been previously proposed, we show that costimulation with either B7-1 or LFA-3 further enhanced the ERK-2 activity and strongly activated the p38 MAPK pathway, but only B7-1 costiniulation induced high levels of JNK-1 activity. These data Suggest that the differential effect of CD28 vs. CD2 can be related to the difference in the ability of the two pathways to induce JNK-1 activity

ANALYSIS OF CLUSTER OF DIFFERENTIATION (CD) MARKERS IN PEDIATRIC BRAIN TUMORS CAN BE USED AS A DIAGNOSTIC AND PROGNOSTIC TOOL

BACKGROUND: Malignant pediatric brain tumors constitute a heterogeneic group of central nervous system tumors, and general markers of diagnosis and prognosis are not available. Recently, a panel of CD markers (CD15, CD24, CD29) was used to define increasing neural differentiation of embryonic stem cells. Although these CD markers have been associated with worse prognosis due to presence of tumor propagating cells, alterations in adhesion and migration in various cancer types, no studies of multiple CD markers in pediatric brain tumors have been performed. METHODS: We have collected tumors, including medulloblastomas (MB), ependymomas (EP) and juvenile astrocytomas, from >20 pediatric brain tumor patients. Frozen tumor sections and cultured tumor cells were stained for CD15, CD24 and CD29 and analyzed using fluorescence microscopy or flowcytometry. RESULTS: MB contained a mixture of cells with strong CD15 labeling inside vessels and cells with diffuse CD15 staining in the parenchyma of the tumor tissue. Cells strongly labeled with CD15 were also positive for the leukocyte marker CD45. The previously proposed association between CD15 expression and prognosis in MB could instead of reflecting abundance of tumor propagating cells depend on infiltrating immune cells. In low-grade pediatric tumors and EP, larger areas stained weakly for CD15 while few cells displayed strong staining. CD24 was expressed on the vast majority of cells in pediatric brain tumors, despite grade of malignancy. MB, however, displayed an intense and aberrant staining for CD24. Computerized image analysis of frozen tumor sections showed that proliferation of cells and the expression of CD29 correlated in a sub-group of MB. CONCLUSIONS: Our preliminary data show that CD15, CD24 and CD29 are differentially expressed in high- and low-malignant pediatric brain tumors in vivo. By defining the patterns of CD antigen expression in different pediatric tumors their relationship to biological behavior and thus prognosis can be established

A standardized and reproducible protocol for serum-free monolayer culturing of primary paediatric brain tumours to be utilized for therapeutic assays.

In vitro cultured brain tumour cells are indispensable tools for drug screening and therapeutic development. Serum-free culture conditions tentatively preserve the features of the original tumour, but commonly comprise neurosphere propagation, which is a technically challenging procedure. Here, we define a simple, non-expensive and reproducible serum-free cell culture protocol for establishment and propagation of primary paediatric brain tumour cultures as adherent monolayers. The success rates for establishment of primary cultures (including medulloblastomas, atypical rhabdoid tumour, ependymomas and astrocytomas) were 65% (11/17) and 78% (14/18) for sphere cultures and monolayers respectively. Monolayer culturing was particularly feasible for less aggressive tumour subsets, where neurosphere cultures could not be generated. We show by immunofluorescent labelling that monolayers display phenotypic similarities with corresponding sphere cultures and primary tumours, and secrete clinically relevant inflammatory factors, including PGE2, VEGF, IL-6, IL-8 and IL-15. Moreover, secretion of PGE2 was considerably reduced by treatment with the COX-2 inhibitor Valdecoxib, demonstrating the functional utility of our newly established monolayer for preclinical therapeutic assays. Our findings suggest that this culture method could increase the availability and comparability of clinically representative in vitro models of paediatric brain tumours, and encourages further molecular evaluation of serum-free monolayer cultures

Convection-enhanced delivery of temozolomide and whole cell tumor immunizations in GL261 and KR158 experimental mouse gliomas

BACKGROUND: Glioblastomas (GBM) are therapy-resistant tumors with a profoundly immunosuppressive tumor microenvironment. Chemotherapy has shown limited efficacy against GBM. Systemic delivery of chemotherapeutic drugs is hampered by the difficulty of achieving intratumoral levels as systemic toxicity is a dose-limiting factor. Although some of its effects might be mediated by immune reactivity, systemic chemotherapy can also inhibit induced or spontaneous antitumor immune reactivity. Convection-enhanced delivery of temozolomide (CED-TMZ) can tentatively increase intratumoral drug concentration while reducing systemic side effects. The objective of this study was to evaluate the therapeutic effect of intratumorally delivered temozolomide in combination with immunotherapy and whether such therapy can generate a cellular antitumor immune response. METHODS: Single bolus intratumoral injection and 3-day mini-osmotic pumps (Alzet®) were used to deliver intratumoral TMZ in C57BL6 mice bearing orthotopic gliomas. Immunotherapy consisted of subcutaneous injections of irradiated GL261 or KR158 glioma cells. Tumor size and intratumoral immune cell populations were analyzed by immunohistochemistry. RESULTS: Combined CED-TMZ and immunotherapy had a synergistic antitumor effect in the GL261 model, compared to CED-TMZ or immunotherapy as monotherapies. In the KR158 model, immunization cured a small proportion of the mice whereas addition of CED-TMZ did not have a synergistic effect. However, CED-TMZ as monotherapy prolonged the median survival. Moreover, TMZ bolus injection in the GL261 model induced neurotoxicity and lower cure rate than its equivalent dose delivered by CED. In addition, we found that T-cells were the predominant cells responsible for the TMZ antitumor effect in the GL261 model. Finally, CED-TMZ combined with immunotherapy significantly reduced tumor volume and increased the intratumoral influx of T-cells in both models. CONCLUSIONS: We show that immunotherapy synergized with CED-TMZ in the GL261 model and cured animals in the KR158 model. Single bolus administration of TMZ was effective with a narrower therapeutic window than CED-TMZ. Combined CED-TMZ and immunotherapy led to an increase in the intratumoral influx of T-cells. These results form part of the basis for the translation of the therapy to patients with GBM but the dosing and timing of delivery will have to be explored in depth both experimentally and clinically