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Cell therapy is promising to treat many conditions, including neurological and osteoarticular diseases. Encapsulation of cells within hydrogels facilitates cell delivery and can improve therapeutic effects. However, much work remains to be done to align treatment strategies with specific diseases. The development of imaging tools that enable monitoring cells and hydrogel independently is key to achieving this goal. Our objective herein is to longitudinally study an iodine-labeled hydrogel, incorporating gold-labeled stem cells, by bicolor CT imaging afterin vivoinjection in rodent brains or knees. To this aim, an injectable self-healing hyaluronic acid (HA) hydrogel with long-persistent radiopacity was formed by the covalent grafting of a clinical contrast agent on HA. The labeling conditions were tuned to achieve sufficient X-ray signal and to maintain the mechanical and self-healing properties as well as injectability of the original HA scaffold. The efficient delivery of both cells and hydrogel at the targeted sites was demonstrated by synchrotron K-edge subtraction-CT. The iodine labeling enabled to monitor the hydrogel biodistributionin vivoup to 3 days post-administration, which represents a technological first in the field of molecular CT imaging agents. This tool may foster the translation of combined cell-hydrogel therapies into the clinics.

International audience; Introduction: The extension of islet transplantation to a wider number of type 1 diabetes patients is compromised by severe adverse events related to the immunosuppressant therapy required for allogenic islet transplantation. In this context, microencapsulation offers the prospects of immunosuppressive-free therapy by physically isolating islets from the immune system. However, current biomaterials need to be optimized to: improve biocompatibility, guaranty the maintenance of graft viability and functionality, and prevent fibrosis overgrowth around the capsule in vivo. Accumulating evidence suggest that mesenchymal stem cells (MSCs) and anchor points consisting of tripeptides arg-gly-asp (RGD) have cytoprotective effects on pancreatic islets. Here, we investigated the effect of supplementing reference M-rich alginate microcapsules with MSCs and RGD-G rich alginate on bioprocessing as well as on human pancreatic islets viability and functionality.Methods: We characterized the microcapsules components, and then for the new microcapsule composite product: we analyzed the empty capsules biocompatibility and then investigated the benefits of MSCs and RGD-G rich alginate on viability and functionality on the encapsulated human pancreatic islets in vitro. We performed viability tests by confocal microscopy and glucose stimulated insulin secretion (GSIS) test in vitro to assess the functionality of naked and encapsulated islets.Results: Encapsulation in reference M-rich alginate capsules induced a reduction in viability and functionality compared to naked islets. This side-effect of encapsulation was in part counteracted by the presence of MSCs but the restoration was complete with the combination of both MSCs and the RGD-G rich alginate.Conclusions: The present findings show that bioprocessing a favorable composite environment inside the M-rich alginate capsule with both MSCs and RGD-G rich alginate improves human islets survival and functionality in vitro.

Human adipose-derived mesenchymal stromal cells (A-MSC) are promising tools for regenerative medicine, but their in vitro amplification before administration is still an issue. Microcarriers emerge as a novel approach for A-MSC expansion in bioreactors. Here, microcarriers with different shapes and functionalizations were compared according to their efficiency for A-MSC expansion. In particular, novel disc shape microcarriers were compared to the commonly used spherical microcarriers. This geometry increases their specific surface while presenting a flat surface, close to monolayer culture conditions. Several parameters were evaluated, such as cell amplification and harvesting yields, cell viability, and cell identity after culture. We observed that microcarriers shape and functionalization impact several A-MSC amplification process steps. However, GhaterDisc-3 microcarriers were the best alternative since harvesting is highly facilitated compared to other microcarriers with a yield of virtually 100 %. Furthermore, A-MSC identity was maintained, since A-MSC keep their characteristic immunophenotype and tri-lineage differentiation ability. Moreover, as these microcarriers are free from any animal derived components, they might be suitable for a use in a GMP compliant large-scale A-MSC production for biomedical applications.

Stroke is a devastating neurological disorder and one of the leading causes of mortality and disability. To understand the cellular and molecular mechanisms of stroke and to develop novel therapeutic approaches, two different in vitro human cell-based stroke models were established using oxygen-glucose deprivation (OGD) conditions. In addition, the effect of adipose stem cells (ASCs) on OGD-induced injury was studied. In the present study, SH-SY5Y human neuroblastoma cells and human induced pluripotent stem cells (hiPSCs) were differentiated into neurons, cultured under OGD conditions (1% O2) for 24 h, and subjected to a reperfusion period for 24 or 72 h. After OGD, ASCs were cocultured with neurons on inserts for 24 or 72 h to study the neuroprotective potential of ASCs. The effect of OGD and ASC coculture on the viability, apoptosis, and proliferation of and axonal damage to neuronal cells was studied. The results showed that OGD conditions induced cytotoxicity and apoptosis of SH-SY5Y- and hiPSC-derived neurons, although more severe damage was detected in SH-SY5Y-derived neurons than in hiPSC-derived neurons. Coculture with ASCs was protective for neurons, as the number of dead ASC-cocultured neurons was lower than that of control cells, and coculture increased the proliferation of both cell types. To conclude, we developed in vitro human cell-based stroke models in SH-SY5Y- and hiPSC-derived neurons. This was the first time hiPSCs were used to model stroke in vitro. Since OGD had different effects on the studied cell types, this study highlights the importance of using several cell types in in vitro studies to confirm the outcomes of the study. Here, ASCs exerted a neuroprotective effect by increasing the proliferation and decreasing the death of SH-SY5Y- and hiPSC-derived neurons after OGD. publishedVersion

The efficacy of immune checkpoint inhibitors has been shown to depend on preexisting antitumor immunity; thus, their combination with cancer vaccines is an attractive therapeutic approach. Plasmacytoid dendritic cells (PDC) are strong inducers of antitumor responses and represent promising vaccine candidates. We developed a cancer vaccine approach based on an allogeneic PDC line that functioned as a very potent antigen-presenting cell in pre-clinical studies. In this phase Ib clinical trial, nine patients with metastatic stage IV melanoma received up to 60 million irradiated PDC line cells loaded with 4 melanoma antigens, injected subcutaneously at weekly intervals. The primary endpoints were safety and tolerability. The vaccine was well tolerated and no serious vaccine-induced side effects were recorded. Strikingly, there was no allogeneic response toward the vaccine, but a significant increase in the frequency of circulating anti-tumor specific T lymphocytes was observed in two patients, accompanied by a switch from a naïve to memory phenotype, thus demonstrating priming of antigen-specific T-cells. Signs of clinical activity were observed, including four stable diseases according to IrRC and vitiligoïd lesions. Four patients were still alive at week 48. We also demonstrate the in vitro enhancement of specific T cell expansion induced by the synergistic combination of peptide-loaded PDC line with anti-PD-1, as compared to peptide-loaded PDC line alone. Taken together, these clinical observations demonstrate the ability of the PDC line based-vaccine to prime and expand antitumor CD8+ responses in cancer patients. Further trials should test the combination of this vaccine with immune checkpoint inhibitors.

Background Cell therapy is promising in experimental studies and has been assessed only in a few studies on humans. Aims To evaluate the effect of cell therapy in humans. Methods We included clinical trials with a control group that reported safety and efficacy six months following treatment. Quality was evaluated and clinical scales data were extracted. Quantitative analysis was based on the standardized means difference (SMD). Among 28 trials published from 1995 to 2016, nine studies (194 patients; 191 controls) were eligible. Publication biases were assessed with the funnel plot and pre-specified explanatory variables were tested with a group analysis and a meta-regression. Results The overall quality was moderate. Cell therapy had a positive effect on the outcome (SMD: 0.57, 95% CI: 0.22–0.92; p = 0.002). The sensitivity analysis showed an upper level of effect size of 0.81 (95% CI: 0.34–1.27; p = 0.001) and a lower level of 0.455 (95% CI: 0.04–0.87; p = 0.03). None of the pre-specified explanatory variable was significantly correlated to outcome: age, ratio infarction/hemorrhage, delay from stroke to treatment, route of administration, cell type, randomization, and blinded outcome assessment. The significant heterogeneity (p = 0.03) was not explained by publication biases (p = 0.09) and was more likely due to methodological and quality differences between the trials. Conclusions This result suggests that cell therapy is beneficial in stroke and is expected to help in the designing of stem cells controlled clinical trials (CCT) in large populations.

While motor recovery following mild stroke has been extensively studied with neuroimaging, mechanisms of recovery after moderate to severe strokes of the types that are often the focus for novel restorative therapies remain obscure. We used fMRI to: 1) characterize reorganization occurring after moderate to severe subacute stroke, 2) identify brain regions associated with motor recovery and 3) to test whether brain activity associated with passive movement measured in the subacute period could predict motor outcome six months later. Because many patients with large strokes involving sensorimotor regions cannot engage in voluntary movement, we used passive flexion-extension of the paretic wrist to compare 21 patients with subacute ischemic stroke to 24 healthy controls one month after stroke. Clinical motor outcome was assessed with Fugl-Meyer motor scores (motor-FMS) six months later. Multiple regression, with predictors including baseline (one-month) motor-FMS and sensorimotor network regional activity (ROI) measures, was used to determine optimal variable selection for motor outcome prediction. Sensorimotor network ROIs were derived from a meta-analysis of arm voluntary movement tasks. Bootstrapping with 1000 replications was used for internal model validation. During passive movement, both control and patient groups exhibited activity increases in multiple bilateral sensorimotor network regions, including the primary motor (MI), premotor and supplementary motor areas (SMA), cerebellar cortex, putamen, thalamus, insula, Brodmann area (BA) 44 and parietal operculum (OP1-OP4). Compared to controls, patients showed: 1) lower task-related activity in ipsilesional MI, SMA and contralesional cerebellum (lobules V-VI) and 2) higher activity in contralesional MI, superior temporal gyrus and OP1-OP4. Using multiple regression, we found that the combination of baseline motor-FMS, activity in ipsilesional MI (BA4a), putamen and ipsilesional OP1 predicted motor outcome measured 6 months later (adjusted-R2 = 0.85; bootstrap p, Highlights • Motor recovery after stroke can be robustly predicted using a passive task fMRI paradigm. • Sensorimotor network activity is decreased in moderate to severe stroke patients relative to healthy controls • Compensatory mechanisms in severe stroke involve both the dorsal (MI BA4a), and the ventral (OP1 and OP4) sensorimotor stream

Introduction Le developpement de vaccins anti-tumoraux est une approche prometteuse dans le traitement du melanome notamment en combinaison avec les inhibiteurs de points de controle immunitaire (ICI) car l’efficacite des ICI requiert une immunite anti-tumorale prealable. Les cellules dendritiques plasmocytoides representent un candidat ideal pour cette approche car elles sont capables d’induire de fortes reponses anti-tumorales. Nous avons developpe un vaccin anti-tumoral fonde sur une lignee de cellules dendritiques plasmocytoides allogeniques ayant une forte capacite de presentation antigenique et ciblant 4 antigenes de melanome, appelee GeniusVac-Mel4. Materiel et methodes Essai de phase 1b multicentrique, non randomise, en ouvert etudiant l’effet du vaccin GeniusVac-Mel4 en injections sous-cutanees en escalade de dose : 4, 20, 60 millions de cellules irradiees chargees avec 4 peptides de melanome (MLANA, MAGEA3, PMEL, TYR) a raison de 3 injections a 1 semaine d’intervalle, chez des patients HLA A*02 :01 atteints de melanome metastatique, en 2e ligne ou plus de traitement systemique. L’objectif primaire etait l’evaluation de la securite et de la tolerance, les objectifs secondaires etaient l’evaluation des reponses clinique et biologique. Resultats Entre juin 2013 et mars 2016, 9 patients atteints de melanome metastatique (5 femmes et 4 hommes, âge moyen 71,8 ans) ont ete inclus. Le vaccin etait bien tolere. Ainsi, 22 evenements indesirables severes ont ete rapportes chez 8 patients, mais aucun n’etait relie au traitement a l’etude. Concernant la reponse clinique, une stabilisation de la maladie selon les criteres IRCs etait constatee chez 4 patients avec de plus une depigmentation vitiligoide chez l’un des patients. Quatre patients etaient encore en vie a la semaine 48 parmi lesquels 2 n’avaient pas recu de nouvelle ligne de traitement. L’immuno-monitoring a montre l’absence de reponse allogenique developpee in vivo vis-a-vis du vaccin. Une augmentation significative des lymphocytes T CD8+ circulants specifiques d’antigenes tumoraux a ete mise en evidence chez 2 patients, accompagnee d’une bascule d’un phenotype de lymphocytes T naifs (CD45RA + CCR7+) vers un phenotype de lymphocytes T memoires (CD45RA-CCR7-). De plus, des experiences menees ex vivo ont montre que l’association d’un anti-PD1 en combinaison avec Genius Vac avait un effet synergique sur l’expansion de la reponse CD8+ specifique. Discussion Cette etude de phase 1b a demontre la capacite de Genius VAc mel-4 a generer une reponse lymphocytaire T CD8 + specifique chez des patients atteints de melanome avec un profil de tolerance satisfaisant (Charles et al., Oncoimmunology 2020). Nous envisageons de poursuivre cette approche en combinaison avec un anti-PD1 dans un essai clinique de phase 2.

Background Islets of Langerhans transplantation is a promising therapy for type 1 diabetes mellitus, but this technique is compromised by transplantation stresses including inflammation. In other tissues, co-transplantation with mesenchymal stem cells has been shown to reduce damage by improving anti-inflammatory and anti-oxidant defences. Therefore, we probed the protection afforded by bone marrow mesenchymal stem cells to islets under pro-inflammatory cytokine stress. Methods In order to evaluate the cytoprotective potential of mesenchymal stem cells on rat islets, co-cultures were exposed to the interleukin-1, tumour necrosis factor α and interferon γ cocktail for 24 h. Islet viability and functionality tests were performed. Reactive oxygen species and malondialdehyde were measured. Expression of stress-inducible genes acting as anti-oxidants and detoxifiers, such as superoxide dismutases 1 and 2, NAD(P)H quinone oxidoreductase 1, heme oxygenase-1 and ferritin H, was compared to non-stressed cells, and the corresponding proteins were measured. Data were analysed by a two-way ANOVA followed by a Holm-Sidak post hoc analysis. Results Exposure of rat islets to cytokines induces a reduction in islet viability and functionality concomitant with an oxidative status shift with an increase of cytosolic ROS production. Mesenchymal stem cells did not significantly increase rat islet viability under exposure to cytokines but protected islets from the loss of insulin secretion. A drastic reduction of the antioxidant factors heme oxygenase-1 and ferritin H protein levels was observed in islets exposed to the cytokine cocktail with a prevention of this effect by the presence of mesenchymal stem cells. Conclusions Our data evidenced that MSCs are able to preserve islet insulin secretion through a modulation of the oxidative imbalance mediated by heme and iron via heme oxygenase-1 and ferritin in a context of cytokine exposure. Electronic supplementary material The online version of this article (10.1186/s13287-019-1190-4) contains supplementary material, which is available to authorized users.

Imeglimin (IME) is a novel glucose-lowering agent improving insulin secretion in response to glucose and insulin sensitivity by targeting mitochondrial bioenergetics. IME is currently in phase 3 in Japan. The toxicity of high glucose or fructose concentrations in INS-1 cells was linked to the opening of the permeability transition pore (PTP), a mitochondrial channel involved in cell death. IME has been shown to prevent PTP opening in human endothelial cells under oxidative stress. This study investigated whether IME could also prevent PTP opening and cell death induced by high glucose or fructose concentrations in INS-1 cells and human pancreatic islets. PTP status in intact cells was assessed by confocal microscopy by measuring mitochondrial membrane potential (TMRM) and NAD(P)H (autofluorescence). Cell viability was measured by flow cytometry. In INS-1 cells and human islets, 30 mM Glucose or 2.5 mM Fructose for 24h led to PTP opening (increase in the NAD(P)H/TMRM ratio), this phenomenon being prevented by 100µM IME. Compared to normal glucose concentration (100%), cell viability significantly decreased (p Disclosure S. Lablanche: Other Relationship; Self; Poxel SA. E. Tubbs: None. C. Cottet-Rousselle: None. F. Lamarche: None. A. Moisan: None. V. Persoons: None. P.Y. Benhamou: Consultant; Self; Abbott, Sanofi, Novo Nordisk Inc.. Other Relationship; Self; Eli Lilly and Company, Roche Diabetes Care Health and Digital Solutions. Advisory Panel; Self; Diabeloop S.A.. S. Hallakou-Bozec: None. E. Fontaine: Other Relationship; Self; Poxel SA.

L’ischemia cerebrale (IC) rappresenta l’80% degli accidenti vascolari cerebrali (AVC), seconda causa di mortalita nel mondo. Essa fa seguito all’interruzione del flusso ematico in un’arteria cerebrale. Si definisce come una riduzione della pressione di perfusione cerebrale sotto la soglia di autoregolazione fisiologica del flusso ematico cerebrale, che conduce a un insufficiente apporto in ossigeno e in energia. Si tratta di un fenomeno che evolve molto rapidamente nel tempo e nello spazio, andando dal «silenzio elettrofisiologico» di neuroni ancora vitali (penombra) alla necrosi irreversibile (infarto). La risonanza magnetica o la TC di perfusione permettono di visualizzare in urgenza queste zone di IC. I meccanismi che inducono la morte cellulare (omeostasi di Ca2+, Na+/Cl–, K+ ed eccitotossicita, depolarizzazione peri-infartuale, stress ossidativo, infiammazione, ecc.) non sono limitati ai neuroni. Essi coinvolgono l’insieme dell’unita neurovascolare, gli oligodendrociti e la microglia. Inoltre, l’immunodepressione sistemica causata dall’AVC e responsabile di infezioni che peggiorano la prognosi funzionale. E necessaria una migliore comprensione integrativa «al di la del neurone» di questi fenomeni per sviluppare dei trattamenti limitati, a tutt’oggi, alla gestione specializzata delle AVC, alla riperfusione per trombolisi e all’emicraniectomia decompressiva per gli infarti estesi. Parallelamente ai meccanismi deleteri, esistono una neuroprotezione endogena iniziale e, poi, un recupero che dura diversi mesi. Questo recupero, facilitato dalla rieducazione, e legato a un compenso dei deficit e alla plasticita cerebrale: riorganizzazione dei circuiti danneggiati e neurosinaptogenesi in relazione con la glia e i microvasi all’interno di «nicchie neuro-oligo-vascolari» perilesionali. L’ottimizzazione di questa plasticita multicellulare e, oggi, l’obiettivo di trattamenti promettenti di medicina rigenerativa basati sull’utilizzo di fattori di crescita e di cellule staminali o differenziate (terapia cellulare).

International audience; Background Islet transplantation is indicated for patients with type 1 diabetes with severe hypoglycaemia or after kidney transplantation. We did a randomised trial to assess the efficacy and safety of islet transplantation compared with insulin therapy in these patients. Methods In this multicentre, open-label, randomised controlled trial, we randomly assigned (1:1) patients with type 1 diabetes at 15 university hospitals to receive immediate islet transplantation or intensive insulin therapy (followed by delayed islet transplantation). Eligible patients were aged 18-65 years and had severe hypoglycaemia or hypoglycaemia unawareness, or kidney grafts with poor glycaemic control. We used computer-generated randomisation, stratified by centre and type of patient. Islet recipients were scheduled to receive 11000 islet equivalents per kg bodyweight in one to three infusions. The primary outcome was proportion of patients with a modified (beta-score (in which an overall score of 0 was not allocated when stimulated C-peptide was negative) of 6 or higher at 6 months after first islet infusion in the immediate transplantation group or 6 months after randomisation in the insulin group. The primary analysis included all patients who received the allocated intervention; safety was assessed in all patients who received islet infusions. This trial is registered with ClinicalTrials.gov, number NCT01148680, and is completed. Findings Between July 8, 2010, and July 29, 2013, 50 patients were randomly assigned to immediate islet transplantation (n=26) or insulin treatment (n=24), of whom three (one in the immediate islet transplantation group and two in the insulin therapy group) did not receive the allocated intervention. Median follow-up was 184 days (IQR 181-186) in the immediate transplantation group and 185 days (172-201) in the insulin therapy group. At 6 months, 16 (64% [95% CI 43-82]) of 25 patients in the immediate islet transplantation group had a modified (beta-score of 6 or higher versus none (0% [0-15]) of the 22 patients in the insulin group (p\textless0.0001). At 12 months after first infusion, bleeding complications had occurred in four (7% [2-18]) of 55 infusions, and a decrease in median glomerular filtration rate from 90-5 mL/min (IQR 76-6-94-0) to 71-8 mL/min (59-0-89-0) was observed in islet recipients who had not previously received a kidney graft and from 63 .0 mL/min (55.0-71-0) to 57. 0 mL/min (45-5-65 . 1) in islet recipients who had previously received a kidney graft. Interpretation For the indications assessed in this study, islet transplantation effectively improves metabolic outcomes. Although studies with longer-term follow-up are needed, islet transplantation seems to be a valid option for patients with severe, unstable type 1 diabetes who are not responding to intensive medical treatments. However, immunosuppression can affect kidney function, necessitating careful selection of patients. Copyright (C) 2018 Elsevier Ltd. All rights reserved.

Twenty years ago, theoretical developments were initiated to model the behavior of the NMR transverse relaxation rates in presence of vessels. These developments enabled the MRI-based mapping of mean vessel diameter, microvascular density, and vessel size index with comparable results to those obtained by a pathologist. The transfer of these techniques to routine clinical use has been hindered by the unavailability of the required sequences, namely fast gradient-echo spin-echo sequences. Based on the increasing accessibility of such sequences on MRI scanners over recent years, we review the principles governing microvascular MRI, the validation studies, and the applications that have been tested worldwide by several teams. We also provide some recommendations on how to measure microvessel caliber and density with MRI.

Stroke is the leading cause of disability in adults. After the very narrow time frame during which treatment by thrombolysis and mechanical thrombectomy is possible, cell therapy has huge potential for enhancing stroke recovery. Accurate analysis of the response to new therapy using imaging biomarkers is needed to assess therapeutic efficacy. The aim of this study was to compare 2 analysis techniques: the parametric response map (PRM), a voxel-based technique, and the standard whole-lesion approach. These 2 analyses were performed on data collected at 4 time points in a transient middle cerebral artery occlusion (MCAo) model, which was treated with human mesenchymal stem cells (hMSCs). The apparent diffusion coefficient (ADC), cerebral blood volume (CBV), and vessel size index (VSI) were mapped using magnetic resonance imaging (MRI). Two groups of rats received an intravenous injection of either 1 mL phosphate-buffered saline (PBS)-glutamine (MCAo-PBS, n = 10) or 3 million hMSCs (MCAo-hMSC, n = 10). One sham group was given PBS-glutamine (sham, n = 12). Each MRI parameter was analyzed by both the PRM and the whole-lesion approach. At day 9, 1 d after grafting, PRM revealed that hMSCs had reduced the fraction of decreased ADC (PRMADC−: MCAo-PBS 6.7% ± 1.7% vs. MCAo-hMSC 3.3% ± 2.4%), abolished the fraction of increased CBV (PRMCBV+: MCAo-PBS 16.1% ± 3.7% vs. MCAo-hMSC 6.4% ± 2.6%), and delayed the fraction of increased VSI (PRMVSI+: MCAo-PBS 17.5% ± 6.3% vs. MCAo-hMSC 5.4% ± 2.6%). The whole-lesion approach was, however, insensitive to these early modifications. PRM thus appears to be a promising technique for the detection of early brain changes following treatments such as cell therapy.

Stroke is the leading cause of disability in adults. Many current clinical trials use intravenous (IV) administration of human bone marrow-derived mesenchymal stem cells (BM-MSCs). This autologous graft requires a delay for ex vivo expansion of cells. We followed microvascular effects and mechanisms of action involved after an IV injection of human BM-MSCs (hBM-MSCs) at a subacute phase of stroke. Rats underwent a transient middle cerebral artery occlusion (MCAo) or a surgery without occlusion (sham) at day 0 (D0). At D8, rats received an IV injection of 3 million hBM-MSCs or PBS-glutamine. In a longitudinal behavioral follow-up, we showed delayed somatosensory and cognitive benefits 4 to 7 weeks after hBM-MSC injection. In a separate longitudinal in vivo magnetic resonance imaging (MRI) study, we observed an enhanced vascular density in the ischemic area 2 and 3 weeks after hBM-MSC injection. Histology and quantitative polymerase chain reaction (qPCR) revealed an overexpression of angiogenic factors such as Ang1 and transforming growth factor-β1 (TGF-β1) at D16 in hBM-MSC-treated MCAo rats compared to PBS-treated MCAo rats. Altogether, delayed IV injection of hBM-MSCs provides functional benefits and increases cerebral angiogenesis in the stroke lesion via a release of endogenous angiogenic factors enhancing the stabilization of newborn vessels. Enhanced angiogenesis could therefore be a means of improving functional recovery after stroke.

Stroke, the leading cause of disability, lacks treatment beyond thrombolysis. The acute injection of human mesenchymal stem cells (hMSCs) provides a benefit which could be mediated by an enhancement of angiogenesis. A clinical autologous graft requires an hMSC culture delay incompatible with an acute administration. This study evaluates the cerebral microvascular changes after a delayed injection of hMSCs. At day 8 after middle cerebral artery occlusion (MCAo), two groups of rats received an intracerebral injection in the damaged brain of either 10 μL of cell suspension medium (MCAo-PBS, n = 4) or 4 × 10(5) hMSCs (MCAo-hMSC, n = 5). Two control groups of healthy rats underwent the same injection procedures in the right hemisphere (control-PBS, n = 6; control-hMSC, n = 5). The effect of hMSCs on the microvasculature was assessed by MRI using three parameters: apparent diffusion coefficient (ADC), cerebral blood volume (CBV) and vessel size index (VSI). At day 9, eight additional rats were euthanised for a histological study of the microvascular parameters (CBV, VSI and vascular fraction). No ADC difference was observed between MCAo groups. One day after intracerebral injection, hMSCs abolished the CBV increase observed in the lesion (MCAo-hMSC: 1.7 ± 0.1% versus MCAo-PBS: 2.2 ± 0.2%) and delayed the VSI increase (vasodilation) secondary to cerebral ischaemia. Histological analysis at day 9 confirmed that hMSCs modified the microvascular parameters (CBV, VSI and vascular fraction) in the lesion. No ADC, CBV or VSI differences were observed between control groups. At the stroke post-acute phase, hMSC intracerebral injection rapidly and transiently modifies the cerebral microvasculature. This microvascular effect can be monitored in vivo by MRI. Copyright © 2012 John Wiley & Sons, Ltd.

Stroke is an important health issue corresponding to the second cause of mortality and first cause of severe disability with no effective treatments after the first hours of onset. Regenerative approaches such as cell therapy provide an increase in endogenous brain structural plasticity but they are not enough to promote a complete recovery. Tissue engineering has recently aroused a major interesting development of biomaterials for use into the central nervous system. Many biomaterials have been engineered based on natural compounds, synthetic compounds, or a mix of both with the aim of providing polymers with specific properties. The mechanical properties of biomaterials can be exquisitely regulated forming polymers with different stiffness, modifiable physical state that polymerizesin situ,or small particles encapsulating cells or growth factors. The choice of biomaterial compounds should be adapted for the different applications, structure target, and delay of administration. Biocompatibilities with embedded cells and with the host tissue and biodegradation rate must be considerate. In this paper, we review the different applications of biomaterials combined with cell therapy in ischemic stroke and we explore specific features such as choice of biomaterial compounds and physical and mechanical properties concerning the recent studies in experimental stroke.

Recent advances in MRI methodology, such as microvascular and brain oxygenation (StO2) imaging, may prove useful in obtaining information about the severity of the acute stroke. We assessed the potential of StO2 to detect the ischaemic core in the acute phase compared to apparent diffusion coefficient and to predict the final necrosis. Sprague-Dawley rats (n = 38) were imaged during acute stroke (D0) and 21 days after (D21). A multiparametric MRI protocol was performed at 4.7T to characterize brain damage within three region of interest: ‘LesionD0’ (diffusion), ‘Mismatch’ representing penumbra (perfusion/diffusion) and ‘Hypoxia’ (voxels 2 within the region of interest LesionD0). Voxel-based analysis of stroke revealed heterogeneity of the region of interest LesionD0, which included voxels with different degrees of oxygenation decrease. This finding was supported by a dramatic decrease of vascular and perfusion parameters within the region of interest hypoxia. This zone presented the lowest values of almost all parameters analysed, indicating a higher severity. Our study demonstrates the potential of StO2 magnetic resonance imaging to more accurately detect the ischaemic core without the inclusion of any reversible ischaemic damage. Our follow-up study indicates that apparent diffusion coefficient imaging overestimated the final necrosis while StO2 imaging did not.

A quantitative estimate of cerebral blood oxygen saturation is of critical importance in the investigation of cerebrovascular disease. While positron emission tomography can map in vivo the oxygen level in blood, it has limited availability and requires ionizing radiation. Magnetic resonance imaging (MRI) offers an alternative through the blood oxygen level-dependent contrast. Here, we describe an in vivo and non-invasive approach to map brain tissue oxygen saturation ( StO2) with high spatial resolution. StO2 obtained with MRI correlated well with results from blood gas analyses for various oxygen and hematocrit challenges. In a stroke model, the hypoxic areas delineated in vivo by MRI spatially matched those observed ex vivo by pimonidazole staining. In a model of diffuse traumatic brain injury, MRI was able to detect even a reduction in StO2 that was too small to be detected by histology. In a F98 glioma model, MRI was able to map oxygenation heterogeneity. Thus, the MRI technique may improve our understanding of the pathophysiology of several brain diseases involving impaired oxygenation.

Background: Microvasculature plays a key role in stroke pathophysiology both during initial damage and extended neural repair. Moreover, angiogenesis processes seem to be a promising target for future neurorestorative therapies. However, dynamic changes of microvessels after stroke still remain unclear, and MRI follow-up could be interesting as an in vivo biomarker of these. Methods: The aim of this study is to characterize the microvascular plasticity 25 days after ischemic stroke using both in vivo microvascular 7T-MRI (vascular permeability, cerebral blood volume (CBV), vessel size index (VSI), vascular density) and quantification of angiogenic factor expressions by RT-qPCR in a transient middle cerebral artery occlusion rat model. CBV and VSI (perfused vessel caliber) imaging was performed using a steady-state approach with a multi gradient-echo spin-echo sequence before and 2 min after intravenous (IV) injection of ultrasmall superparamagnetic iron particles. Vascular density (per mm2) was derived from the ratio [ΔR2/(ΔR2*)2/3]. Blood brain barrier leakage was assessed using T1W images before and after IV injection of Gd-DOTA. Additionally, microvessel immunohistology was done. Results: 3 successive stages were observed: 1) ‘Acute stage' from day 1 to day 3 post-stroke (D1-D3) characterized by high levels of angiopoietin-2 (Ang2), vascular endothelial growth factor receptor-2 (VEGFR-2) and endothelial NO synthase (eNOS) that may be associated with deleterious vascular permeability and vasodilation; 2) ‘Transition stage' (D3-D7) that involves transforming the growth factors β1 (TGFβ1), Ang1, and tyrosine kinase with immunoglobulin-like and endothelial growth factor-like domains 1 (Tie1), stromal-derived factor-1 (SDF-1), chemokine receptor type 4 (CXCR-4); and 3) ‘Subacute stage' (D7-D25) with high levels of Ang1, Ang2, VEGF, VEGFR-1 and TGFβ1 leading to favorable stabilization and maturation of microvessels. In vivo MRI appeared in line with the angiogenic factors changes with a delay of at least 1 day. All MRI parameters varied over time, revealing the different aspects of the post-stroke microvascular plasticity. At D25, despite a normal CBV, MRI revealed a limited microvessel density, which is insufficient to support a good neural repair. Conclusions: Microvasculature MRI can provide imaging of different states of functional (perfused) microvessels after stroke. These results highlight that multiparametric MRI is useful to assess post-stroke angiogenesis, and could be used as a biomarker notably for neurorestorative therapy studies. Additionally, we identified that endogenous vessel maturation and stabilization occur during the ‘subacute stage'. Thus, pro-angiogenic treatments, such as cell-based therapy, would be relevant during this subacute phase of stroke.

Twenty years ago, theoretical developments were initiated to model the behavior of the NMR transverse relaxation rates in presence of vessels. These developments enabled the MRI-based mapping of mean vessel diameter, microvascular density, and vessel size index with comparable results to those obtained by a pathologist. The transfer of these techniques to routine clinical use has been hindered by the unavailability of the required sequences, namely fast gradient-echo spin-echo sequences. Based on the increasing accessibility of such sequences on MRI scanners over recent years, we review the principles governing microvascular MRI, the validation studies, and the applications that have been tested worldwide by several teams. We also provide some recommendations on how to measure microvessel caliber and density with MRI.

Stroke is the second leading cause of death worldwide and the most common cause of severe disability. Neuroprotection and repair mechanisms supporting endogenous brain plasticity are often insufficient to allow complete recovery. While numerous neuroprotective drugs trials have failed to demonstrate benefits for patients, they have provided interesting translational research lessons related to neurorestorative therapy mechanisms in stroke. Stroke damage is not limited to neurons but involve all brain cell type including the extracellular matrix in a "glio-neurovascular niche". Targeting a range of host brain cells, biotherapies such as growth factors and therapeutic cells, currently hold great promise as a regenerative medical strategy for stroke. These techniques can promote both neuroprotection and delayed neural repair through neuro-synaptogenesis, angiogenesis, oligodendrogliogenesis, axonal sprouting and immunomodulatory effects. Their complex mechanisms of action are interdependent and vary according to the particular growth factor or grafted cell type. For example, while "peripheral" stem or stromal cells can provide paracrine trophic support, neural stem/progenitor cells (NSC) or mature neurons can act as more direct neural replacements. With a wide therapeutic time window after stroke, biotherapies could be used to treat many patients. However, guidelines for selecting the optimal time window, and the best delivery routes and doses are still debated and the answers may depend on the chosen product and its expected mechanism including early neuroprotection, delayed neural repair, trophic systemic transient effects or graft survival and integration. Currently, the great variety of growth factors, cell sources and cell therapy products form a therapeutic arsenal that is available for stroke treatment. Their effective clinical use will require prior careful considerations regarding safety (e.g. tumorgenicity, immunogenicity), potential efficacy, cell characterization, delivery route and in vivo biodistribution. Bone marrow-derived cell populations such as mesenchymal stromal/stem cells (MSC) or mononuclear cells (MNC), umbilical cord stem cells and NSC are most investigated notably in clinical trials. Finally, we discuss perspectives concerning potential novel biotherapies such as combinatorial approaches (growth factor combined with cell therapy, in vitro optimization of cell products, or co-transplantation) and the development of biomaterials, which could be used as injectable hydrogel scaffold matrices that could protect a cell graft or selectively deliver drugs and growth factors into the post-stroke cavity at chronic stages. Considering the remaining questions about the best procedure and the safety cautions, we can hope that future translational research about biotherapies will bring more efficient treatments that will decrease post-stroke disability for many patients.

International audience; PURPOSE: Synchrotron microbeam radiation therapy (MRT) is an innovative irradiation modality based on spatial fractionation of a high-dose X-ray beam into lattices of microbeams. The increase in lifespan of brain tumor-bearing rats is associated with vascular damage but the physiological consequences of MRT on blood vessels have not been described. In this manuscript, we evaluate the oxygenation changes induced by MRT in an intracerebral 9L gliosarcoma model. METHODS: Tissue responses to MRT (two orthogonal arrays (2×400Gy)) were studied using magnetic resonance-based measurements of local blood oxygen saturation (MR_SO2) and quantitative immunohistology of RECA-1, Type-IV collagen and GLUT-1, marker of hypoxia. RESULTS: In tumors, MR_SO2 decreased by a factor of 2 in tumor between day 8 and day 45 after MRT. This correlated with tumor vascular remodeling, i.e. decrease in vessel density, increases in half-vessel distances (×5) and GLUT-1 immunoreactivity. Conversely, MRT did not change normal brain MR_SO2, although vessel inter-distances increased slightly. CONCLUSION: We provide new evidence for the differential effect of MRT on tumor vasculature, an effect that leads to tumor hypoxia. As hypothesized formerly, the vasculature of the normal brain exposed to MRT remains sufficiently perfused to prevent any hypoxia.

Understanding the multiple biological functions played by human mesenchymal stem cells (hMSCs) as well as their development as therapeutics in regenerative medicine or in cancer treatment are major fields of research. Indeed, it has been established that hMSCs play a central role in the pathogenesis and progression of tumours, but their impact on tumour growth remains controversial. In this study, we investigated the influence of hMSCs on the growth of pre-established tumours. We engrafted nude mice with luciferase-positive mouse adenocarcinoma cells (TSA-Luc+) to obtain subcutaneous or lung tumours. When tumour presence was confirmed by non-invasive bioluminescence imaging, hMSCs were injected into the periphery of the SC tumours or delivered by systemic intravenous injection in mice bearing either SC tumours or lung metastasis. Regardless of the tumour model and mode of hMSC injection, hMSC administration was always associated with decreased tumour growth due to an inhibition of tumour cell proliferation, likely resulting from deep modifications of the tumour angiogenesis. Indeed, we established that although hMSCs can induce the formation of new blood vessels in a non-tumoural cellulose sponge model in mice, they do not modify the overall amount of haemoglobin delivered into the SC tumours or lung metastasis. We observed that these tumour vessels were reduced in number but were longer. Our results suggest that hMSCs injection decreased solid tumour growth in mice and modified tumour vasculature, which confirms hMSCs could be interesting to use for the treatment of pre-established tumours.

Human mesenchymal stem cells (hMSCs) have strong potential for cell therapy after stroke. Tracking stem cells in vivo following a graft can provide insight into many issues regarding optimal route and/or dosing. hMSCs were labeled for magnetic resonance imaging (MRI) and histology with micrometer-sized superparamagnetic iron oxides (M-SPIOs) that contained a fluorophore. We assessed whether M-SPIO labeling obtained without the use of a transfection agent induced any cell damage in clinical-grade hMSCs and whether it may be useful for in vivo MRI studies after stroke. M-SPIOs provided efficient intracellular hMSC labeling and did not modify cell viability, phenotype, or in vitro differentiation capacity. Following grafting in a rat model of stroke, labeled hMSCs could be detected using both in vivo MRI and fluorescent microscopy until 4 weeks following transplantation. However, whereas good label stability and unaffected hMSC viability were observed in vitro, grafted hMSCs may die and release iron particles in vivo.

Human mesenchymal stem cells (hMSC) are a promising source for cell therapy after stroke. To deliver these cells, an IV injection appears safer than a local graft. We aimed to assess the whole-body biodistribution of IV-injected 99mTc-HMPAO-labeled hMSC in normal rats ( n = 9) and following a right middle cerebral artery occlusion (MCAo, n = 9). Whole-body nuclear imaging, isolated organ counting (at 2 and 20 h after injection) and histology were performed. A higher activity was observed in the right damaged hemisphere of the MCAo group [6.5 ± 0.9 × 10−3 % of injected dose (ID)/g] than in the control group (3.6 ± 1.2 × 10−3 %ID/g), 20 h after injection. In MCAo rats, right hemisphere activity was higher than that observed in the contralateral hemisphere at 2 h after injection (11.6 ± 2.8 vs. 9.8 ± 1.7 × 10−3 %ID/g). Following an initial hMSC lung accumulation, there was a decrease in pulmonary activity from 2 to 20 h after injection in both groups. The spleen was the only organ in which activity increased between 2 and 20 h. The presence of hMSC was documented in the spleen, liver, lung, and brain following histology. IV-injected hMSC are transiently trapped in the lungs, can be sequestered in the spleen, and are predominantly eliminated by kidneys. After 20 h, more hMSC are found in the ischemic lesion than into the undamaged cerebral tissue. IV delivery of hMSC could be the initial route for a clinical trial of tolerance.