In Vivo Interleukin-13-Primed Macrophages Contribute to Reduced Alloantigen-Specific T Cell Activation and Prolong Immunological Survival of Allogeneic Mesenchymal Stem Cell Implants

Monoclonal antibody-mediated immunosuppression enables long-term survival of transplanted human neural stem cells in mouse brain

BACKGROUND

As the field of stem cell therapy advances, it is important to develop reliable methods to overcome host immune responses in animal models. This ensures survival of transplanted human stem cell grafts and enables predictive efficacy testing. Immunosuppressive drugs derived from clinical protocols are frequently used but are often inconsistent and associated with toxic side effects. Here, using a molecular imaging approach, we show that immunosuppression targeting costimulatory molecules CD4 and CD40L enables robust survival of human xenografts in mouse brain, as compared to conventional tacrolimus and mycophenolate mofetil.

METHODS

Human neural stem cells were modified to express green fluorescent protein and firefly luciferase. Cells were implanted in the fimbria fornix of the hippocampus and viability assessed by non-invasive bioluminescent imaging. Cell survival was assessed using traditional pharmacologic immunosuppression as compared to monoclonal antibodies directed against CD4 and CD40L. This paradigm was also implemented in a transgenic Alzheimer's disease mouse model.

RESULTS

Graft rejection occurs within 7 days in non-immunosuppressed mice and within 14 days in mice on a traditional regimen. The addition of dual monoclonal antibody immunosuppression extends graft survival past 7 weeks (p < .001) on initial studies. We confirm dual monoclonal antibody treatment is superior to either antibody alone (p < .001). Finally, we demonstrate robust xenograft survival at multiple cell doses up to 6 months in both C57BL/6J mice and a transgenic Alzheimer's disease model (p < .001). The dual monoclonal antibody protocol demonstrated no significant adverse effects, as determined by complete blood counts and toxicity screen.

CONCLUSIONS

This study demonstrates an effective immunosuppression protocol for preclinical testing of stem cell therapies. A transition towards antibody-based strategies may be advantageous by enabling stem cell survival in preclinical studies that could inform future clinical trials.

Immune recognition of syngeneic, allogeneic and xenogeneic stromal cell transplants in healthy retinas

Background

Advanced therapies using adult mesenchymal stromal cells (MSCs) for neurodegenerative diseases are not effectively translated into the clinic. The cross talk between the transplanted cells and the host tissue is something that, despite its importance, is not being systematically investigated.

Methods

We have compared the response of the mouse healthy retina to the intravitreal transplantation of MSCs derived from the bone marrow in four modalities: syngeneic, allogeneic, xenogeneic and allogeneic with immunosuppression using functional analysis in vivo and histology, cytometry and protein measurement post-mortem. Data were considered significant (p < 0.05) after nonparametric suitable statistical tests.

Results

Transplanted cells remain in the vitreous and are cleared by microglial cells a process that is quicker in allotransplants regardless of immunosuppression. All transplants cause anatomical remodelling which is more severe after xenotransplants. Xeno- and allotransplants with or without immunosuppression cause macro- and microglial activation and retinal functional impairment, being xenotransplants the most detrimental and the only ones that recruit CD45⁺Iba1⁻cells. The profile of proinflammatory cytokines changes in all transplantation settings. However, none of these changes affect the retinal ganglion cell population.

Conclusions

We show here a specific functional and anatomical retinal response depending on the MSC transplantation modality, an aspect that should be taken into consideration when conducting preclinical studies if we intend a more realistic translation into clinical practice.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03129-y.

Comparison of the Cytokine Profile in Mesenchymal Stem Cells from Human Adipose, Umbilical Cord, and Placental Tissues

Human mesenchymal stem cells (MSCs) can be isolated from various tissues. However, the cytokine profile in different MSC types remains unclear. In this study, MSCs were extracted from adipose, umbilical cord, and placental tissues. The surface marker expression, multilineage differentiation potential, and cytokine secretion of these cells were compared. The isolated MSCs exhibited similar morphology and surface marker expression. However, they differed with regard to their differentiation potential. Adipose-MSCs (A-MSCs) exhibited a higher potential for adipogenesis and osteogenic differentiation compared with umbilical cord-MSCs (UC-MSCs) and placental-MSCs (P-MSCs). The expression levels of 80 cytokines were detected, and the data demonstrated that the three MSC types abundantly secreted insulin-like growth factor-binding protein (IGFBP)-4, IGFBP-3, tissue inhibitor of metalloproteinase (TIMP)-1, TIMP-2, IGFBP-6, monocyte chemoattractant protein-1, and granulocyte colony-stimulating factor. However, the expression levels of vascular endothelial growth factor, tumor necrosis factor alpha, interleukin (IL)-6 receptor, and IL-13 in A-MSCs were higher compared with those of UC-MSCs and P-MSCs. Moreover, the expression levels of intercellular adhesion molecule-1 and growth differentiation factor 15 were lower in A-MSCs. Kyoto Encyclopedia of Genes and Genomes analysis indicated that the "adipocytokine" and the "PI3K/Akt pathways" were enriched in A-MSCs. Taken together, the results demonstrated that MSCs from different sources exhibited differences in the secretion of specific factors. A-MSCs were associated with the expression of several proangiogenic factors and may be an improved source for angiogenesis and tissue regeneration.

Transplantation of mesenchymal stem cells causes long-term alleviation of schizophrenia-like behaviour coupled with increased neurogenesis

Schizophrenia is a neurodevelopmental disease with a mixed genetic and environmental aetiology. Impaired adult hippocampal neurogenesis was suggested both as a pathophysiological mechanism and as a target for therapy. In the present study, we utilized intracerebroventricular transplantation of bone marrow-derived mesenchymal stem cells (MSC) as a means to enhance hippocampal neurogenesis in the ketamine-induced neurodevelopmental murine model for schizophrenia. Syngeneic MSC have successfully engrafted and survived for up to 3 months following transplantation. Improvement in social novelty preference and prepulse inhibition was noted after transplantation. In parallel to behavioural improvement, increased hippocampal neurogenesis as reflected in the numbers of doublecortin expressing neurons in the dentate gyrus and gene expression was noted both 2 weeks following transplantation as well as 3 months later compared with nontreated animals. An independent aging effect was observed for both behaviour and neurogenesis, which was attenuated by MSC treatment. As opposed to MSC treatment, short-term treatment with clozapine was efficient only during treatment and diminished 3 months later. Interestingly, while shortly after transplantation (2 weeks) behavioural improvement was correlated mainly to FGF2 gene expression, 3 months later it was mainly correlated to the expression of the notch ligand DLL1. This suggests that long-term effect during ageing may depend on neural stem cell self-renewal. We conclude that a single intracerebroventricular injection of bone marrow-derived MSC can suffice for long-term reversal of changes in adult hippocampal neurogenesis and improve schizophrenia-like behavioural phenotype inflicted by developmental exposure to ketamine in mice.

Mesenchymal Stem Cell Transplantation for Ischemic Diseases: Mechanisms and Challenges

Ischemic diseases are conditions associated with the restriction or blockage of blood supply to specific tissues. These conditions can cause moderate to severe complications in patients, and can lead to permanent disabilities. Since they are blood vessel-related diseases, ischemic diseases are usually treated with endothelial cells or endothelial progenitor cells that can regenerate new blood vessels. However, in recent years, mesenchymal stem cells (MSCs) have shown potent bioeffects on angiogenesis, thus playing a role in blood regeneration. Indeed, MSCs can trigger angiogenesis at ischemic sites by several mechanisms related to their trans-differentiation potential. These mechanisms include inhibition of apoptosis, stimulation of angiogenesis via angiogenic growth factors, and regulation of immune responses, as well as regulation of scarring to suppress blood vessel regeneration when needed. However, preclinical and clinical trials of MSC transplantation in ischemic diseases have shown some limitations in terms of treatment efficacy. Such studies have emphasized the current challenges of MSC-based therapies. Treatment efficacy could be enhanced if the limitations were better understood and potentially resolved. This review will summarize some of the strategies by which MSCs have been utilized for ischemic disease treatment, and will highlight some challenges of those applications as well as suggesting some strategies to improve treatment efficacy.

Engraftment potential of maternal adipose-derived stem cells for fetal transplantation

Advances in prenatal molecular testing have made it possible to diagnose most genetic disorders early in gestation. In utero mesenchymal stem cell (MSC) therapy can be a powerful tool to cure the incurable. With this in mind, this method could ameliorate potential physical and functional damage. However, the presence of maternal T cells trafficking in the fetus during pregnancy is thought to be the major barrier to achieving the engraftment into the fetus. We investigated the possibility of using maternal adipose-derived stem cells (ADSCs) for in utero transplantation to improve engraftment, thus lowering the risk of graft rejection. Herein, fetal brain engraftment using congenic and maternal ADSC grafts was examined via in utero stem cell transplantation in a mouse model. ADSCs were purified using the mesenchymal stem cell markers, PDGFRα, and Sca-1 via fluorescence-activated cell sorting. The PDGFRα⁺Sca-1⁺ ADSCs were transplanted into the fetal intracerebroventricular (ICV) at E14.5. The transplanted grafts grew for at least 28 days after in utero transplantation with PDGFRα⁺Sca-1⁺ ADSC, and mature neuronal markers were also detected in the grafts. Furthermore, using the maternal sorted ADSCs suppressed the innate immune response, preventing the infiltration of CD8 T cells into the graft. Thus, in utero transplantation into the fetal ICV with the maternal PDGFRα⁺Sca-1⁺ ADSCs may be beneficial for the treatment of congenital neurological diseases because of the ability to reduce the responses after in utero stem cell transplantation and differentiate into neuronal lineages.

Heparin-based, injectable microcarriers for controlled delivery of interleukin-13 to the brain

The anti-inflammatory cytokine IL-13 can be loaded and released from heparin-based cryogel biomaterials for sustained delivery to the brain.

Interleukin-13 Gene Modification Enhances Grafted Mesenchymal Stem Cells Survival After Subretinal Transplantation

Mesenchymal stem cells (MSCs) hold great potential for cell- and gene-based therapies for retinal degeneration. Limited survival is the main obstacle in achieving successful subretinal transplantation of MSCs. The present study sought to evaluate the effect of interleukin-13 (IL-13) gene modification on the phenotypic alteration of retinal microglia (RMG) and the survival of MSCs following subretinal grafting. In this study, LPS-activated RMG were cocultured with MSCs or IL-13-expressing MSCs (IL-13-MSCs) for 24 h, and activated phenotypes were detected in vitro. Western blotting was performed to quantify cytokine secretion by light-injured retinas following subretinal transplantation. The numbers of activated RMG and surviving grafted cells were analysed, and the integrity of the blood-retinal barrier (BRB) was examined in vivo. We found that, compared with normal MSCs, cocultured IL-13-MSCs suppressed the expression of pro-inflammatory factors and major histocompatibility complex II, promoted the expression of anti-inflammatory cytokines by activated RMG and simultaneously inhibited the proliferation of and phagocytosis by RMG. The subretinal transplantation of IL-13-MSCs increased the expression of neurotrophic factors, IL-13 and tight junction proteins in the host retina, decreased the number of phagocytic RMG and improved the survival of grafted cells. Furthermore, IL-13-MSCs alleviated BRB breakdown induced by subretinal injection. Our results demonstrate that IL-13-MSCs can polarize activated RMG to the neuroprotective M2 phenotype and enhance the survival of grafted MSCs against the damage stress induced by subretinal transplantation.

Murine iPSC-derived microglia and macrophage cell culture models recapitulate distinct phenotypical and functional properties of classical and alternative neuro-immune polarisation

The establishment and validation of reliable induced pluripotent stem cell (iPSC)-derived in vitro models to study microglia and monocyte/macrophage immune function holds great potential for fundamental and translational neuro-immunology research. In this study, we first demonstrate that ramified CX₃CR1⁺ iPSC-microglia (cultured within a neural environment) and round-shaped CX₃CR1^- iPSC-macrophages can easily be differentiated from newly established murine CX₃CR1^eGFP/+CCR2^RFP/+ iPSC lines. Furthermore, we show that obtained murine iPSC-microglia and iPSC-macrophages are distinct cell populations, even though iPSC-macrophages may upregulate CX₃CR1 expression when cultured within a neural environment. Next, we characterized the phenotypical and functional properties of murine iPSC-microglia and iPSC-macrophages following classical and alternative immune polarisation. While iPSC-macrophages could easily be triggered to adopt a classically-activated or alternatively-activated phenotype following, respectively, lipopolysaccharide + interferon γ or interleukin 13 (IL13) stimulation, iPSC-microglia and iPSC-macrophages cultured within a neural environment displayed a more moderate activation profile as characterised by the absence of MHCII expression upon classical immune polarisation and the absence of Ym1 expression upon alternative immune polarisation. Finally, extending our preceding in vivo studies, this striking phenotypical divergence was also observed for resident microglia and infiltrating monocytes within highly inflammatory cortical lesions in CX₃CR1^eGFP/+CCR2^RFP/+ mice subjected to middle cerebral arterial occlusion (MCAO) stroke and following IL13-mediated therapeutic intervention thereon. In conclusion, our study demonstrates that the applied murine iPSC-microglia and iPSC-macrophage culture models are able to recapitulate in vivo microglia and monocyte/macrophage ontogeny and corresponding phenotypical/functional properties upon classical and alternative immune polarisation, and therefore represent a valuable in vitro platform to further study and modulate microglia and (infiltrating) monocyte immune responses under neuro-inflammatory conditions within a neural environment.

The Immunomodulatory Properties of Amniotic Cells: The Two Sides of the Coin

Among the many cell types useful in developing therapeutic treatments, human amniotic cells from placenta have been proposed as valid candidates. Both human amniotic epithelial and mesenchymal stromal cells, and the conditioned medium generated from their culture, exert multiple immunosuppressive activities. Indeed, they inhibit T and B cell proliferation, suppress inflammatory properties of monocytes, macrophages, dendritic cells, neutrophils, and natural killer cells, while promoting induction of cells with regulatory functions such as regulatory T cells and anti-inflammatory M2 macrophages. These properties have laid the foundation for their use for the treatment of inflammatory-based diseases, and encouraging results have been obtained in different preclinical disease models where exacerbated inflammation is present. Moreover, an immune-privileged status of amniotic cells has been often highlighted. However, even if long-term engraftment of amniotic cells has been reported into immunocompetent animals, only few cells survive after infusion. Furthermore, amniotic cells have been shown to be able to induce immune responses in vivo and, under specific culture conditions, they can stimulate T cell proliferation in vitro. Although immunosuppressive properties are a widely recognized characteristic of amniotic cells, immunogenic and stimulatory activities appear to be less reported, sporadic events. In order to improve therapeutic outcome, the mechanisms responsible for the suppressive versus stimulatory activity need to be carefully addressed. In this review, both the immunosuppressive and immunostimulatory activity of amniotic cells will be discussed.

Targeted intracerebral delivery of the anti-inflammatory cytokine IL13 promotes alternative activation of both microglia and macrophages after stroke

Background

Subtle adjustment of the activation status of CNS resident microglia and peripheral macrophages, to promote their neuroprotective and neuroregenerative functions, may facilitate research towards curing neurodegenerative disorders. In the present study, we investigated whether targeted intracerebral delivery of the anti-inflammatory cytokine interleukin (IL)13, by means of transplanting IL13-expressing mesenchymal stem cells (IL13-MSCs), can promote a phenotypic switch in both microglia and macrophages during the pro-inflammatory phase in a mouse model of ischemic stroke.

Methods

We used the CX₃CR1^eGFP/+ CCR2^RFP/+ transgenic mouse model to separately recognize brain-resident microglia from infiltrated macrophages. Quantitative immunohistochemical analyses were applied to characterize polarization phenotypes of both cell types.

Results

Distinct behaviors of both cell populations were noted dependent on the anatomical site of the lesion. Immunohistochemistry revealed that mice grafted with IL13-MSCs, in contrast to non-grafted and MSC-grafted control mice, were able to drive recruited microglia and macrophages into an alternative activation state, as visualized by a significant increase of Arg-1 and a noticeable decrease of MHC-II expression at day 14 after ischemic stroke. Interestingly, both Arg-1 and MHC-II were expressed more abundantly in macrophages than in microglia, further confirming the distinct behavior of both cell populations.

Conclusions

The current data highlight the importance of controlled and localized delivery of the anti-inflammatory cytokine IL13 for modulation of both microglia and macrophage responses after ischemic stroke, thereby providing pre-clinical rationale for the application of L13-MSCs in future investigations of neurodegenerative disorders.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1212-7) contains supplementary material, which is available to authorized users.

The differentiation of mesenchymal stem cells to vascular cells regulated by the HMGB1/RAGE axis: its application in cell therapy for transplant arteriosclerosis

BACKGROUND

Mesenchymal stem cell (MSC) transplantation shows promise for treating transplant arteriosclerosis, at least partly via promoting endothelial regeneration. However, the efficacy and safety are still under investigation especially regarding recent findings that neointimal smooth muscle cells are derived from MSC-like cells. The high mobility group box 1 (HMGB1)/receptor for advanced glycation end-product (RAGE) axis is involved in regulating proliferation, migration, and differentiation of MSCs, and therefore it can be presumably applied to improve the outcome of cell therapy. The aim of the current study was to investigate this hypothesis.

METHODS

Rat MSCs were treated with HMGB1 or modified with HMGB1 vectors to activate the HMGB1/RAGE axis. RAGE was targeted and inhibited by specific short hairpin RNA vectors. We assessed the capacity for cell proliferation, migration, and differentiation after vector transfection in vitro and in a rat model of transplant arteriosclerosis. The expression of CD31 and α-smooth muscle actin (αSMA) was determined to evaluate the differentiation of MSCs to endothelial cells and smooth muscle cells.

RESULTS

Exogenous HMGB1 treatment and transfection with HMGB1 vectors promoted MSC migration and vascular endothelial growth factor (VEGF)-induced differentiation to CD31+ cells while inhibiting their proliferation and platelet-derived growth factor (PDGF)-induced differentiation to αSMA+ cells. Such an effect was blocked by RAGE knockdown. HMGB1-modified cells preferably migrated to graft neointima and differentiated to CD31+ cells along with significant relief of transplant arteriosclerosis and inhibition of HMGB1 and RAGE expression in graft vessels. RAGE knockdown inhibited cell migration to graft vessels.

CONCLUSIONS

HMGB1 stimulated MSCs to migrate and differentiate to endothelial cells via RAGE signaling, which we translated to successful application in cell therapy for transplant arteriosclerosis.

Cell-Based Delivery of Interleukin-13 Directs Alternative Activation of Macrophages Resulting in Improved Functional Outcome after Spinal Cord Injury

The therapeutic effects of mesenchymal stem cell (MSC) transplantation following spinal cord injury (SCI) to date have been limited. Therefore, we aimed to enhance the immunomodulatory properties of MSCs via continuous secretion of the anti-inflammatory cytokine interleukin-13 (IL-13). By using MSCs as carriers of IL-13 (MSC/IL-13), we investigated their therapeutic potential, compared with non-engineered MSCs, in a mouse model of SCI. We show that transplanted MSC/IL-13 significantly improve functional recovery following SCI, and also decrease lesion size and demyelinated area by more than 40%. Further histological analyses in CX₃CR1^EGFP/+ CCR2^RFP/+ transgenic mice indicated that MSC/IL-13 significantly decrease the number of resident microglia and increase the number of alternatively activated macrophages. In addition, the number of macrophage-axon contacts in MSC/IL-13-treated mice was decreased by 50%, suggesting a reduction in axonal dieback. Our data provide evidence that transplantation of MSC/IL-13 leads to improved functional and histopathological recovery in a mouse model of SCI.

Concise Review: Innate and Adaptive Immune Recognition of Allogeneic and Xenogeneic Cell Transplants in the Central Nervous System

Over the last 30 years, numerous allogeneic and xenogeneic cell grafts have been transplanted into the central nervous system (CNS) of mice and men in an attempt to cure neurological diseases. In the early studies, human or porcine embryonic neural cells were grafted in the striatum of animals or patients in an attempt to replace lost neurons. Although the immune-privileged status of the brain as a recipient organ was widely accepted, it rapidly became evident that CNS-grafted allogeneic and xenogeneic cells could be recognized and rejected by the immune system, resulting in poor neural graft survival and limited functional recovery. Since then, the CNS transplantation field has witnessed a sharp rise in the number of studies in which allogeneic and xenogeneic neural or mesenchymal stem cells (NSCs or MSCs, respectively) are transplanted, predominantly aiming at providing trophic stimulation and promoting endogenous repair of the brain. Interestingly, in many recent NSC and MSC-based publications functional improvement was used as the principal measure to evaluate the success of cell transplantation, while the fate of transplanted cells remained largely unreported. In this review, we first attempt to understand why primary neural cell isolates were largely substituted for NSCs and MSCs in cell grafting studies. Next, we review the current knowledge on the immune mechanisms involved in the recognition and rejection of allogeneic and xenogeneic cellular grafts in the CNS. Finally, we propose strategies to reduce graft immunogenicity and to improve graft survival in order to design improved cell-based CNS therapies. Stem Cells Translational Medicine 2017;6:1434-1441.

Intracerebral transplantation of interleukin 13-producing mesenchymal stem cells limits microgliosis, oligodendrocyte loss and demyelination in the cuprizone mouse model

Background

Promoting the neuroprotective and repair-inducing effector functions of microglia and macrophages, by means of M2 polarisation or alternative activation, is expected to become a new therapeutic approach for central nervous system (CNS) disorders in which detrimental pro-inflammatory microglia and/or macrophages display a major contribution to the neuropathology. In this study, we present a novel in vivo approach using intracerebral grafting of mesenchymal stem cells (MSC) genetically engineered to secrete interleukin 13 (IL13-MSC).

Methods

In the first experimental setup, control MSC and IL13-MSC were grafted in the CNS of eGFP⁺ bone marrow chimaeric C57BL/6 mice to histologically evaluate IL13-mediated expression of several markers associated with alternative activation, including arginase1 and Ym1, on MSC graft-recognising microglia and MSC graft-infiltrating macrophages. In the second experimental setup, IL13-MSC were grafted on the right side (or on both the right and left sides) of the splenium of the corpus callosum in wild-type C57BL/6 mice and in C57BL/6 CX₃CR1^eGFP/+CCR2^RFP/+ transgenic mice. Next, CNS inflammation and demyelination was induced by means of a cuprizone-supplemented diet. The influence of IL13-MSC grafting on neuropathological alterations was monitored by non-invasive T₂-weighted magnetic resonance imaging (MRI) and quantitative histological analyses, as compared to cuprizone-treated mice with control MSC grafts and/or cuprizone-treated mice without MSC injection.

Results

In the first part of this study, we demonstrate that MSC graft-associated microglia and MSC graft-infiltrating macrophages are forced into alternative activation upon grafting of IL13-MSC, but not upon grafting of control MSC. In the second part of this study, we demonstrate that grafting of IL13-MSC, in addition to the recruitment of M2 polarised macrophages, limits cuprizone-induced microgliosis, oligodendrocyte death and demyelination. Furthermore, we here demonstrate that injection of IL13-MSC at both sides of the splenium leads to a superior protective effect as compared to a single injection at one side of the splenium.

Conclusions

Controlled and localised production of IL13 by means of intracerebral MSC grafting has the potential to modulate cell graft- and pathology-associated microglial/macrophage responses, and to interfere with oligodendrocyte death and demyelinating events in the cuprizone mouse model.

Interleukin-13 immune gene therapy prevents CNS inflammation and demyelination via alternative activation of microglia and macrophages

Detrimental inflammatory responses in the central nervous system are a hallmark of various brain injuries and diseases. With this study we provide evidence that lentiviral vector-mediated expression of the immune-modulating cytokine interleukin 13 (IL-13) induces an alternative activation program in both microglia and macrophages conferring protection against severe oligodendrocyte loss and demyelination in the cuprizone mouse model for multiple sclerosis (MS). First, IL-13 mediated modulation of cuprizone induced lesions was monitored using T₂ -weighted magnetic resonance imaging and magnetization transfer imaging, and further correlated with quantitative histological analyses for inflammatory cell influx, oligodendrocyte death, and demyelination. Second, following IL-13 immune gene therapy in cuprizone-treated eGFP⁺ bone marrow chimeric mice, we provide evidence that IL-13 directs the polarization of both brain-resident microglia and infiltrating macrophages towards an alternatively activated phenotype, thereby promoting the conversion of a pro-inflammatory environment toward an anti-inflammatory environment, as further evidenced by gene expression analyses. Finally, we show that IL-13 immune gene therapy is also able to limit lesion severity in a pre-existing inflammatory environment. In conclusion, these results highlight the potential of IL-13 to modulate microglia/macrophage responses and to improve disease outcome in a mouse model for MS. GLIA 2016;64:2181-2200.

Tweaking Mesenchymal Stem/Progenitor Cell Immunomodulatory Properties with Viral Vectors Delivering Cytokines

Mesenchymal Stem Cells (MSCs) can be found in various body sites. Their main role is to differentiate into cartilage, bone, muscle, and fat cells to allow tissue maintenance and repair. During inflammation, MSCs exhibit important immunomodulatory properties that are not constitutive, but require activation, upon which they may exert immunosuppressive functions. MSCs are defined as "sensors of inflammation" since they modulate their ability of interfering with the immune system both in vitro and in vivo upon interaction with different factors. MSCs may influence immune responses through different mechanisms, such as direct cell-to-cell contact, release of soluble factors, and through the induction of anergy and apoptosis. Human MSCs are defined as plastic-adherent cells expressing specific surface molecules. Lack of MHC class II antigens makes them appealing as allogeneic tools for the therapy of both autoimmune diseases and cancer. MSC therapeutic potential could be highly enhanced by the expression of exogenous cytokines provided by transduction with viral vectors. In this review, we attempt to summarize the results of a great number of in vitro and in vivo studies aimed at improving the ability of MSCs as immunomodulators in the therapy of autoimmune, degenerative diseases and cancer. We will also compare results obtained with different vectors to deliver heterologous genes to these cells.