Andreas Svensson

Intratumoral IL-7 delivery by mesenchymal stromal cells potentiates IFNgamma-transduced tumor cell immunotherapy of experimental glioma.

The present study reports regression of pre-established experimental rat gliomas as a result of combining peripheral immunization using interferon gamma (IFNgamma) transduced autologous tumor cells with local intratumoral delivery of interleukin 7 (IL-7) by mesenchymal stromal cells. IL-7 alone significantly decreased the tumor area and this effect was enhanced with IFNgamma immunization. A higher density of intratumoral T-cells was observed in animals receiving combined therapies compared to rats receiving either cytokine alone suggesting that the therapeutic effect is dependent on a T-cell response.

Stem cell-based therapy for malignant glioma

Stem cells have been extensively investigated as tumour-tropic vectors for gene delivery to solid tumours. In this review, we discuss the potential for using stem cells as cellular vector systems in gene therapy for malignant gliomas, with a focus on neural stem cells, and multipotent mesenchymal stromal cells. Tumour cell-derived substances and factors associated with tumour-induced inflammation and tumour neovascularisation can specifically attract stem cells to invasive gliomas. Injected stem cells engineered to produce anti-tumour substances have shown strong therapeutic effects in experimental glioma models. However, the potential caveats include the immunosuppressive functions of multipotent mesenchymal stromal cells, the contribution of stem cells to the pro-tumourigenic stroma, and the malignant transformation of implanted stem cells. In addition, it is not yet known which stem cell types and therapeutic genes will be most effective for the treatment of glioma patients. Here, we highlight the possibilities and problems for translating promising experimental findings in glioma models into the clinic.

Rat Multipotent Mesenchymal Stromal Cells Lack Long-Distance Tropism to 3 Different Rat Glioma Models

BACKGROUND Viral gene therapy of malignant brain tumors has been restricted by the limited vector distribution within the tumors. Multipotent mesenchymal stromal cells (MSCs) and other precursor cells have shown tropism for gliomas, and these cells are currently being explored as potential vehicles for gene delivery in glioma gene therapy. OBJECTIVE To investigate MSC migration in detail after intratumoral and extratumoral implantation through syngeneic and orthotopic glioma models. METHODS Adult rat bone marrow-derived MSCs were transduced to express enhanced green fluorescent protein and implanted either directly into or at a distance from rat gliomas. RESULTS We found no evidence of long-distance MSC migration through the intact striatum toward syngeneic D74(RG2), N32, and N29 gliomas in the ipsilateral hemisphere or across the corpus callosum to gliomas located in the contralateral hemisphere. After intratumoral injection, MSCs migrated extensively, specifically within N32 gliomas. The MSCs did not proliferate within tumors, suggesting a low risk of malignant transformation of in vivo grafted cell vectors. Using a model for surgical glioma resection, we found that intratumorally grafted MSCs migrate efficiently within glioma remnants after partial surgical resection. CONCLUSION The findings point to limitations for the use of MSCs as vectors in glioma gene therapy, although intratumoral MSC implantation provides a dense and tumor-specific vector distribution.

Endogenous brain pericytes are widely activated and contribute to mouse glioma microvasculature.

Glioblastoma multiforme (GBM) is the most common brain tumor in adults. It presents an extremely challenging clinical problem, and treatment very frequently fails due to the infiltrative growth, facilitated by extensive angiogenesis and neovascularization. Pericytes constitute an important part of the GBM microvasculature. The contribution of endogenous brain pericytes to the tumor vasculature in GBM is, however, unclear. In this study, we determine the site of activation and the extent of contribution of endogenous brain pericytes to the GBM vasculature. GL261 mouse glioma was orthotopically implanted in mice expressing green fluorescent protein (GFP) under the pericyte marker regulator of G protein signaling 5 (RGS5). Host pericytes were not only activated within the glioma, but also in cortical areas overlying the tumor, the ipsilateral subventricular zone and within the hemisphere contralateral to the tumor. The host-derived activated pericytes that infiltrated the glioma were mainly localized to the tumor vessel wall. Infiltrating GFP positive pericytes co-expressed the pericyte markers platelet-derived growth factor receptor-β (PDGFR-β) and neuron-glial antigen 2. Interestingly, more than half of all PDGFR-β positive pericytes within the tumor were contributed by the host brain. We did not find any evidence that RGS5 positive pericytes adopt another phenotype within glioma in this paradigm. We conclude that endogenous pericytes become activated in widespread areas of the brain in response to an orthotopic mouse glioma. Host pericytes are recruited into the tumor and constitute a major part of the tumor pericyte population.

Optogenetic control of human neurons in organotypic brain cultures

Optogenetics is one of the most powerful tools in neuroscience, allowing for selective control of specific neuronal populations in the brain of experimental animals, including mammals. We report, for the first time, the application of optogenetic tools to human brain tissue providing a proof-of-concept for the use of optogenetics in neuromodulation of human cortical and hippocampal neurons as a possible tool to explore network mechanisms and develop future therapeutic strategies.

Intratumorally implanted mesenchymal stromal cells potentiate peripheral immunotherapy against malignant rat gliomas.

Bone marrow-derived mesenchymal stromal cells (MSCs) target glioma extensions and micro-satellites efficiently when implanted intratumorally. Here, we report that intratumoral implantation of MSCs and peripheral immunotherapy with interferon-gamma (IFNγ) producing tumor cells improve the survival of glioma-bearing rats (54% cure rate) compared to MSC alone (0% cure rate) or immunotherapy alone (21% cure rate) by enforcing an intratumoral CD8(+) T cell response. Further analysis revealed that the MSCs up-regulate MHC classes I and II in response to IFNγ treatment in vitro and secrete low amounts of immunosuppressive molecules prostaglandin E2 and interleukin-10.

Identification of two distinct mesenchymal stromal cell populations in human malignant glioma.

Gene profiling has revealed that malignant gliomas can be divided into four distinct molecular subtypes, where tumors with a mesenchymal gene expression are correlated with short survival. The present investigation was undertaken to clarify whether human malignant gliomas contain endogenous mesenchymal stromal cells (MSC), fulfilling consensus criteria defined by The International Society for Cellular Therapy, recruited from the host. We found that MSC-like cells can be isolated from primary human malignant gliomas. Two distinct MSC-like cell populations, differing in their expression of the CD90 surface marker, were discovered after cell sorting. RNA sequencing revealed further genetic differences between these two cell populations and MSC-like cells lacking CD90 produced higher amounts of VEGF and PGE2 compared to cells with the true MSC phenotype, implying that the CD90− MSC-like cells most probably are more active in tumor vascularization and immunosuppression than their CD90+ counterpart. The results highlight the CD90− subpopulation as an important tumor component, however, its functional effects in glioma remains to be resolved. Using the protocols presented here, it will be possible to isolate, characterize and analyze brain tumor-derived MSC-like cells in more detail and to further test their functions in vitro and in in vivo xenograft models of glioma.

Sequestering of damage-associated molecular patterns (DAMPs): a possible mechanism affecting the immune-stimulating properties of aluminium adjuvants

Aluminium-based adjuvants (ABAs) have been used in human and veterinary vaccines for decades, and for a long time, the adjuvant properties were believed to be mediated by an antigen depot at the injection site, prolonging antigen exposure to the immune system. The depot hypothesis is today more or less abandoned, and instead replaced by the assumption that ABAs induce an inflammation at the injection site. Induction of an inflammatory response is consistent with immune activation initiated by recognition of molecular patterns associated with danger or damage (DAMPs), and the latter are derived from endogenous molecules that normally reside intracellularly. When extracellularly expressed, because of damage, stress or cell death, a sterile inflammation is induced. In this paper, we report the induction of DAMP release by viable cells after phagocytosis of aluminium-based adjuvants. Two of the most commonly used ABAs in pharmaceutical vaccine formulations, aluminium oxyhydroxide and aluminium hydroxyphosphate, induced a vigorous extracellular expression of the two DAMP molecules calreticulin and HMGB1. Concomitantly, extracellular adjuvant particles adsorbed the DAMP molecules released by the cells whereas IL-1β, a previously reported inflammatory mediator induced by ABAs, was not absorbed by the adjuvants. Induction of extracellular expression of the two DAMP molecules was more prominent using aluminium hydroxyphosphate compared to aluminium oxyhydroxide, whereas the extracellular adsorption of the DAMP molecules was more pronounced with the latter. Furthermore, it is hypothesised how induction of DAMP expression by ABAs and their concomitant adsorption by extracellular adjuvants may affect the inflammatory properties of ABAs.

Tracing Aluminium-based Adjuvants: Their Interactions with Immune Competent Cells and their Effect on Mitochondrial Activity

Results: No or minor change of zeta potential and average particle size of lumogallion labelled aluminium oxyhydroxide, AlO(OH) and aluminium hydroxyphosphate, Al(OH)x(PO4)y. Both phagocytosing and non-phagocytosing leukocytes became associated with ABAs at concentrations expected after in vivo administration of a vaccine. The ABAs were relatively toxic, affecting both lymphocytes and monocytes, and Al(OH)x(PO4)y was more toxic than AlO(OH). Endocytosed aluminium adjuvant particles were not secreted from the cells and remained intracellular throughout several cell divisions. The presence of ABAs increased the mitochondrial activity of the monocytic cell line THP-1 and peripheral monocytes, as based on the transformation of tetrazolium into formazan.

Periostin is Secreted by Glioblastoma CD90-positive Stromal Cells and Acts as a Pericyte Chemoattractant

Glioblastoma (GBM) stroma is composed of multiple cell types including vascular elements, immune cells and mesenchymal stromal cells (MSCs). Periostin (POSTN) is a secreted extracellular matrix protein which plays a crucial role in the progression of this aggressive and highly vascularized tumor. However, the cellular distribution of gliomaderived POSTN and whether POSTN can act as a chemoattractant for tumor vasculogenic cells is not known. The aim of the present study was to identify the specific cellular distribution of POSTN within GBM and to explore the possibility of POSTN acting as an attractant for tumor pericytes. Here we show that POSTN expression by large is restricted to the stromal compartment of GL261 mouse GBM. Within the stroma, POSTN is mainly localized to CD90+, most likely mesenchymal stromal cells (MSCs), and to pericytes recruited into the tumor. High POSTN protein levels were found to be produced by CD90+ MSCs acutely isolated from human GBM. Both mouse and human CD90+ MSCs co-expressed POSTN and Integrin β1, permitting autocrine interaction between ligand and receptor. Pericytes expressing Integrin β1 and CD90+ perivascular cells expressing POSTN are adjacently localized within the mouse GL261 stroma. A large fraction of human brain pericytes were found to express Integrin β1 and showed Integrin β1- dependent migration in response to POSTN. In summary, our findings tie the expression and action of POSTN to the stromal compartment of GBM and support a role for POSTN in GBM angioproliferation.