Nanoformulations decrease systemic toxicity effects of antitumor agents.

The aim of this study was to characterize expression of corticogenesis-related transcription factors BCL11B and SATB2 after brain ischemic lesion in the adult mice, and to analyze their correlation to the subsequent brain recovery. Ischemic brain lesion was induced by transient middle cerebral artery occlusion followed by reperfusion, and the animals with ischemic lesion were compared to the sham controls. Progression of the brain damage and subsequent recovery was longitudinally monitored structurally, by magnetic resonance imaging, and functionally, by neurological deficit assessment. Seven days after the ischemic injury the brains were isolated and analyzed by immunohistochemistry. The results showed higher expression in the brain of both, BCL11B and SATB2 in the animals with ischemic lesion compared to the sham controls. The co-expression of both markers, BCL11B and SATB2, increased in the ischemic brains, as well as the co-expression of BCL11B with the beneficial transcriptional factor ATF3 but not its co-expression with detrimental HDAC2. BCL11B was mainly implicated in the ipsilateral and SATB2 in the contralateral brain hemisphere, and their level in these regions correlated with the functional recovery rate. The results indicate that the reactivation of corticogenesis-related transcription factors BCL11B and SATB2 is beneficial after brain ischemic lesion.

Administration of cytotoxic agents like doxorubicin (DOX) is restrained by the effects on different non-targeted/non-cancerous tissues, which instigates the development of nano-enabled drug delivery systems, among others. In this study, imaging mass spectrometry (IMS) was selected to examine the effects of DOX nanoformulations on non-targeted tissues. Chemical alterations induced by liposomal (LPS) and poly (lactic-co-glycolic acid) (PLG) nanoformulations were assessed against the ones induced by the conventional (CNV) formulation. Kidney cryosections of the treated and control Wistar rats were used as a model of the non-targeted tissue and analyzed by MALDI TOF IMS in the 200-1000 Da m/z range. Principal component analysis (PCA) and Volcano plots of the average mass spectra demonstrated a large overlap between treatments. However, the Venn diagram of significant m/z values revealed a nanoformulation-specific fingerprint consisting of 59 m/z values, which set them apart from the CNV formulation characterized by the fingerprint of 22 significant m/z values. Fingerprint m/z values that were putatively annotated by metabolome database search were linked to apoptosis, cell migration and proliferation. In CNV and PLG cases, false discovery rate adjusted ANOVA showed no differences in the spatial distribution of fingerprint m/z values between the histological substructures like glomeruli and convoluted tubules indicating their tissue-nonselective effect. LPS caused the least significant changes in m/z values and some of the LPS-specific fingerprint m/z values were primarily distributed in the glomeruli. The IMS based procedure successfully differentiated the effects of DOX formulations on the model non-targeted tissue, thus indicating the importance of IMS in effective drug development.

Silver nanoparticles (AgNPs) are among the most commercialized nanomaterials in biomedicine due to their antimicrobial and anti-inflammatory properties. Nevertheless, possible health hazards of exposure to AgNPs are yet to be understood and therefore raise public concern in regards of their safety. In this study, sex-related differences, role of steroidal hormones and influence of two different surface stabilizing agents (polymer vs. protein) on distribution and adverse effects of AgNPs were investigated in vivo. Intact and gonadectomised male and female mice were treated with seven AgNPs doses administered intraperitoneally during 21 days. After treatment, steroid hormone levels in serum, accumulation of Ag levels and oxidative stress biomarkers in liver, kidneys, brain and lungs were determined. Sex-related differences were observed in almost all tissues. Concentration of Ag was significantly higher in the liver of females compared to males. No significant difference was found for AgNP accumulation in lungs between females and males, while the lungs of intact males showed significantly higher Ag accumulation compared to gonadectomised group. Effect of surface coating was also observed, as Ag accumulation was significantly higher in kidneys and liver of intact females, as well as in kidneys and brain of intact males treated with protein-coated AgNPs compared to polymeric AgNPs. Oxidative stress response to AgNPs was the most pronounced in kidneys where protein-coated AgNPs induced stronger effects compared to polymeric AgNPs. Interestingly, proteincoated AgNPs reduced generation of reactive oxygen species in brains of females and gonadectomised males. Although there were no significant differences in levels of hormones in the AgNP-exposed animals compared to controls, sex-related differences in oxidative stress parameters were observed in all organs. Results of this study highlight the importance of including the sex-related differences and effects of protein corona in biosafety evaluation of AgNPs exposure.

AIM:To propose potential mechanisms of action of electromagnetic fields (EMF) on astrocytes and microglia and to elucidate the role of heat shock proteins (HSP), adenosine triphosphate (ATP), calcium ions (Ca2+), and hypoxia-inducible factor 1α (HIF1α) in neurorestoration following the application of EMF.METHODS:We reviewed the existing studies within the public domain and cross-evaluated their results in order to conclude on the molecular mechanisms of microglia-astrocyte crosstalk at work during EMF treatment.RESULTS:The existing studies suggest that EMF induces the increase of HSP70 expression and inhibition of HIF1α, thus decreasing inflammation and allowing the microglia-astrocyte crosstalk to initiate the formation of a glial scar within the central nervous system. Furthermore, by potentially up-regulating A2A and A3 adenosine receptors, EMF increases cAMP accumulation from astrocytes and reduces the expression of inflammatory cytokines TNF α and IL-8, thus initiating neurorestoration.CONCLUSION:The microglia-astrocyte crosstalk during EMF treatment is crucial for the initiation of neurorestoration. Elucidating the exact mechanisms of EMF actions upon microglia and astrocytes, and its role in neurorestoration could be a key step in further research of the therapeutic potential of EMFs in various neurological disorders.

The aim of this study was to apply multimodal in vivo imaging to assess the influence of altered innate immunity on brain repair after ischemic lesion. Tlr2-deficient mice were compared to wild type controls, as they lack Tlr2-mediated pro-inflammatory signaling triggered by postischemic necrosis. The ischemic lesion was induced by transient middle cerebral artery occlusion for 60 min, followed by brain imaging and analysis at four time points until 28 days after ischemia. Multimodal in vivo imaging involved a combination of 3 modalities: (1) magnetic resonance imaging by T2-weighted scans to assess brain lesion size, (2) bioluminescence imaging of Gap43-luc/gfp transgenic mice to visualize the axonal remodeling, and (3) caged-luciferin bioluminescence imaging of DEVD-luciferin allowing for visualization of caspase 3 and 7 activity in Gap43-luc/gfp mice. This enabled innovative correlation of the MRI-determined lesion size to photon fluxes obtained by bioluminescence imaging. Our data revealed that following ischemia, Tlr2-deficient mice had higher Gap43 expression and higher levels of caspases 3 and 7 activity, which was accompanied by enhanced levels of synaptic plasticity markers DLG4 and synaptophysin when compared to wild type controls. Altered inflammation in Tlr2-deficient mice was accompanied by enhanced elements of post-stroke repair, in particular during the chronic phase of recovery, but also with delayed final consolidation of the brain lesion.

A reliable method of cell tracing is essential in evaluating potential therapeutic procedures based on stem cell transplantation. Here we present data collected using neural stem cells isolated from a transgenic mouse line Thy1-YFP. When transplanted into a stroke affected brain these cells give rise to neurons that express a fluorescent signal which can be used for their detection and tracing. Observed processes were compared with those taking place during normal embryonic neurogenesis as well as during in vitro differentiation. Since the same neurogenic patterns were observed, we confirm that neural stem cell transplantation fits well into the paradigm of neuronal birth and differentiation.

Event Abstract Back to Event Transplantation of fluorescent neural stem cells in healthy and stroke-affected mice Roland Pochet1*, Ivan Alic2, Nina Kosi2, Katarine Kapuralin3, Dunja Gorup2, Srecko Gajovic3 and Dinko Mitrecic2 1 Université Libre de Bruxelles, Faculté de Médecine, Belgium 2 Zagreb University School of Medicine, Croatian Institute for Brain Research, Croatia 3 Zagreb University School of Medicine, Croatian Institute for Brain Research, Croatia Transgenic mouse line Thy1-YFP selectively expressing fluorescent proteins in neurons has been developed to study many aspects of neuronal structure and connectivity. Taking advantage of the long term expression and repeated expression of Yellow Fluorescent Protein (YFP) labeled cells being minimally toxic and providing robust fluorescent signal (Feng et al.) we used YFP labeled stem cells. Neural stem cells were purified from the THY1 YFP-16 transgenic mouse line to study the birth and fate of transplanted YFP labelled neuronal stem cells in the healthy and stroke-affected mouse brain. During embryonic development THY1 – YFP positive cells were first observed at E12.5 and they were followed during differentiation of the nervous tissue. Thy1-positive cells were mostly present in prosencephalon, rombencephalon the spinal cord and in peripheral nerves of the embryo. Number of THY1 – YFP positive cells was 22% of the total cells and remained constant along the differentiation. Analysis on both RT-PCR and immunocytochemical level revealed that Thy1 positive cells during embryonic and in vitro differentiation were first nestin/SOX2 positive, which was gradually replaced by expression of MAP2, β3-tubulin and NeuN. Neural stem cells isolated from THY1 – YFP mouse strain transplanted in the striatum of the healthy and stroke affected mouse brain differentiated into mature neurons and were detectable even after 14 weeks, the end point of our experiment. Stroke region attracted transplanted cells but did not affect signal of Thy1. This study revealed that neural stem cells during in vitro differentiation and after transplantation in the brain followed the same pattern observed during development of embryo. SHORT COMMENT: En français: Il est aujourd'hui possible de transplanter des cellules souches et leurs dérivés (i.e. des cellules souches neurales). Cette nouvelle approche thérapeutique ouvre la voie vers le remplacement de neurones défectueux ou morts présents dans les maladies neurodégénératives. Ce concept doit être validé par la parfaite connaissance du devenir de ces cellules transplantées. Notre travail décrit le devenir de cellules souches neurales de souris une fois transplantées dans le cerveau de souris normales ou ayant subis un accident vasculaire cérébral. Le suivi de ces cellules a pu être réalisé grâce au marquage préalable de ces cellules par un marqueur fluorescent. Samenvatting in het Nederlands: Het is tegenwoordig mogelijk om stamcellen of de daarvan afgeleide cellen (bv. stamcellen van het zenuwstelsel) te transplanteren. Deze therapeutische benadering effent de weg naar het vervangen van gebrekkige of dode hersencellen bij degeneratieve hersenaandoeningen. Dit concept dient gevalideerd te worden door een gedegen kennis van het lot van zulke getransplanteerde cellen. Ons werk beschrijft het lot van neurale muizestamcellen na transplantatie in de hersenen van normale muizen of in de hersenen van muizen die een beroerte hebben opgelopen. Het opvolgen van deze cellen wordt mogelijk gemaakt door een voorafgaande markering met een fluorescerende merker. Figure 1 Acknowledgements This work has been supported by projects of the Croatian National Foundation (02.05/40), Foundation Adris and YoungBrain (EU-ESF) awarded to D.M., and FP7 Glowbrain project awarded to S.G. References Feng G1, Mellor RH, Bernstein M, Keller-Peck C, Nguyen QT, Wallace M, Nerbonne JM, Lichtman JW, Sanes JR. Neuron. 2000 Oct;28(1):41-51. Imaging neuronal subsets in transgenic mice expressing multiple spectral variants of GFP. Keywords: Neural Stem Cells, Yellow fluorescent protein, Transgenic mice, Stem Cell Transplantation, Stroke Conference: 6th Belgian Brain Congress, MONS, Belgium, 8 Oct - 8 Oct, 2016. Presentation Type: Poster Presentation Topic: Brain and brain diseases: between heredity and environment Citation: Pochet R, Alic I, Kosi N, Kapuralin K, Gorup D, Gajovic S and Mitrecic D (2016). Transplantation of fluorescent neural stem cells in healthy and stroke-affected mice. Conference Abstract: 6th Belgian Brain Congress. doi: 10.3389/conf.fnagi.2016.03.00002 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 14 Jun 2016; Published Online: 21 Jun 2016. * Correspondence: Prof. Roland Pochet, Université Libre de Bruxelles, Faculté de Médecine, Bruxelles, 1070, Belgium, rpochet@ulb.ac.be Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Roland Pochet Ivan Alic Nina Kosi Katarine Kapuralin Dunja Gorup Srecko Gajovic Dinko Mitrecic Google Roland Pochet Ivan Alic Nina Kosi Katarine Kapuralin Dunja Gorup Srecko Gajovic Dinko Mitrecic Google Scholar Roland Pochet Ivan Alic Nina Kosi Katarine Kapuralin Dunja Gorup Srecko Gajovic Dinko Mitrecic PubMed Roland Pochet Ivan Alic Nina Kosi Katarine Kapuralin Dunja Gorup Srecko Gajovic Dinko Mitrecic Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Postischemic neuroinflammation depends on innate immunity that is predominantly relying on the TLR signaling. To determine the role of TLR2 on the functional recovery and reactive synaptogenesis, research was conducted inducing ischemic brain lesions (MCAO) in mice lacking the Tlr2 gene investigating postischemic events at the level of mRNA and protein expression, angiogenesis, neuronal network and neurological symptoms. Functional deficits had later and more mild onset in Tlr2-/- mice and also displayed a prolonged chronic phase of recovery compared to wild type (WT). qRT-PCR revealed an increase in the mRNA expression of several components of the TLR2 signalling: MyD88, FADD and CASP8. Western blot of synaptic markers (DLG4, synaptophysin) and a marker of axonogenesis (GAP43) revealed their changed profile in the acute phase and a significant increase in their expression 1 month after ischemia in Tlr2-/- mice compared to their WT controls. Neuronal network density was lower in Tlr2-/- mice and they showed slower maturation of the microvascular network with lesser bifurcations, compared to the WT mice. TLR2 was shown to influence the dynamics of postischemic recovery indicating a therapeutic potential of timed modulation of the TLR2 response. The therapeutic window can be determined using colocalisation of CASP3 and GAP43.

This study was supported by EU FP7 grant GlowBrain (REGPOT–2012–CT2012– 316120) to S.G. and by a University of Trento Startup Grant and the Cassa di Risparmio di Trento e Rovereto Grant n. 2011.0251 to S.C. Since the central nervous system shows very little capability for self-repair following ischemic injury, regenerative medicine approaches are increasingly interested in the use of neural stem cells (NSCs) for cell replacement strategies. Labelling NSCs with maghemite (γ-Fe2O3) nanoparticles allows direct in vivo tracking and imaging of NSCs during brain repair using medical imaging techniques such as magnetic resonance imaging. In addition, application of biomaterials, such as alginate, represents an interesting tool to carry out cell replacement therapies. We reported in vitro NSCs viability and initial differentiation in alginate hydrogels. Furthermore, we investigated in vivo the potential of alginate hydrogels as support system for NSCs injection in the brain. Our preliminary in vivo results demonstrate the possibility to obtain injectable alginate hydrogels that crosslink once injected in the brain tissue. Inflammation profiles, obtained using TLR2-luc mouse reporter line after alginate injection, suggest that alginate presence is not harmful for the brain tissue. Taken together these findings show that alginate could be used as an efficient support for NSCs transplantation in the nervous system, able to increase cell survival and integration in an injury-affected brain. Moreover, using GlowBrain platform we reported that coating γ-Fe2O3 nanoparticles with either poly(L-lysine) or D-mannose improves their biocompatibi-

Occlusion of cerebral arteries leads to ischemic stroke accompanied by subsequent brain edema. Bradykinin (BK) is involved in the formation of cerebral edema, and natriuretic peptides (NPs) potentially have beneficial effects on brain edema formation via a still unknown mechanism. The aim of this study was clarifying the mechanisms of action of NPs on BK signaling, and their interactive effects after ischemic brain injury. We used a mouse model for stroke, the middle cerebral artery (MCA) occlusion. Brain lesion and edema were measured by microcomputerized tomography volumetric measurements. To determine the effects of NPs on the BK signaling pathway in the MCAs we measured changes in vessel diameter and membrane potentials in endothelial cells. To determine the effects of NPs on BK signaling pathway in isolated astrocytes and neurons, membrane potentials and intercellular Ca2+ concentrations were measured. Urodilatin inhibited and when applied together with BK, reduced the formation of the ischemic lesion via activation of G-Protein-Signaling Protein Type 4 at the cellular (atrocities, neurons) and blood vessel (endothelial cells and isolated MCA) level as well as in in vivo experiments. The results of this study show the existence of a natural antagonist of BK in the brain, and the possible use of NPs in the treatment of stroke.

To analyse events following transplantation of stem cells in the brain robust tools for tracing stem cells are required. Here we took advantage of the mouse strain B6.Cg-Tg(Thy1-YFP)16Jrs/J (Thy1 YFP-16), where yellow fluorescent protein (YFP) is under control of the promoter of Thy1 gene. This allows visualising whole neurons, i.e. their cell body, axons and dendrites. In this work fluorescent cells were followed during embryonic development, in vitro differentiation, and after transplantation in the healthy and stroke-affected mouse brain. During embryonic development Thy1-YFP positive cells were first observed on E12.5 and subsequently located in the prosencephalon, rhombencephalon, spinal cord and peripheral nerves. Quantitative analysis by RT-PCR and immunocytochemistry revealed that Thy1-YFP positive cells during embryo development and in vitro differentiation were expressing nestin and SOX2 then MAP2, β3-tubulin and NeuN. Thy1-YFP positive cells isolated from E14.5 represented 21.88±053% (SD) of the cultivated neurons and this remained constant along in vitro differentiation. On the other hand, proportion of Thy1-YFP positive cells reached 50% of neurons in perinatal and one month old mouse brain. Neural stem cells isolated from Thy1 YFP-16 mouse strain transplanted near hippocampus of the healthy and stroke-affected brain were distinguishable by YFP fluorescence. They differentiated into mature neurons and were detectable even 14 weeks after transplantation, the end point of our experiment. In conclusion, stem cells originating from Thy1 YFP-16 mice represent an outstanding tool to monitor neurogenesis enabling morphological analyses of new neurons and their projections, in particular after transplantation in the brain.

GAP43 is a protein involved in neurite outgrowth during development and axon regeneration reflecting its presynaptic localization in developing neurons. Recently, it has been demonstrated that GAP43 is a ligand of CASP3 involved in receptor endocytosis and is also localized post-synaptically. In this study, by using a transgenic mouse strain carrying a bioluminescent reporter for GAP43 combined with an in vivo bioluminescence assay for CASP3, we demonstrated that one day after brain ischemic lesion and, even more pronounced, four days after stroke, expression of both CASP3 and Gap43 in neurons increased more than 40 times. The in vivo approach of CASP3 and GAP43 colocalization imaging was further validated and quantified by immunofluorescence. Importantly, in 82% of GAP43 positive cells, colocalization with CASP3 was present. These findings suggested that one and four days after stroke CASP3 expression, not necessarily associated with neuronal death, increased and suggested that CASP3 and GAP43 might be part of a common molecular pathway involved in early response to ischemic events occurring after onset of stroke.

Background Ischemic stroke is characterized by a rapid loss of brain function due to disturbance in blood supply to a part of the brain. Due to fixed intracranial space, any increase in intracranial fluid volume, or progressive brain oedema formation, contributes to further deterioration of the already impaired brain function. Bradykinin (BK), which levels increase during ischemic stroke, promotes blood– brain barrier permeability and raises intracranial capillary blood pressure, leading to brain oedema formation. Furthermore, BK induces glutamate release from neurons and astrocytes via activation of BK receptor type 2. suggesting involvement of BK in glutamate neurotoxicity. It has been recently shown that humans without functional natriuretic peptides (NPs) suffer from massive stokes [1,2]. NPs can reduce brain oedema and have a neuroprotective role in acute ischemic stroke as well as during recovery after stroke. Although mechanisms are still not clear, it appears that NPs enhance angiogenesis, neurogenesis and oligodenrogenesis [3,4]. One of the possible beneficiary effects of NPs during the stroke could be an inhibition of BK pathological function. Materials and methods Aim of our study is to determine beneficial effects of the NPs in stroke development in murine model (middle cerebral artery occlusion – MCAO). The symptoms of the stroke are determined by behavioural studies. The sizes of the lesion and brain oedema are established by μCT. Furthermore, we determined the effects of NPs on the BK signalling pathway in primary culture of neurons and astrocytes using whole cell patch clamp experiments to measure membrane potential and measurements of intracellular Ca 2+ concentration.

Aim To explore the possibility of brain imaging by microcomputed tomography (microCT) using x-ray contrasting methods to visualize mouse brain ischemic lesions after middle cerebral artery occlusion (MCAO).Methods Isolated brains were immersed in ionic or nonionic radio contrast agent (RCA) for 5 days and subsequently scanned using microCT scanner. To verify whether ex-vivo microCT brain images can be used to characterize ischemic lesions, they were compared to Nissl stained serial histological sections of the same brains. To verify if brains immersed in RCA may be used afterwards for other methods, subsequent immunofluorescent labeling with anti-NeuN was performed.Results Nonionic RCA showed better gray to white matter contrast in the brain, and therefore was selected for further studies. MicroCT measurement of ischemic lesion size and cerebral edema significantly correlated with the values determined by Nissl staining (ischemic lesion size: P=0.0005; cerebral edema: P=0.0002). Brain immersion in nonionic RCA did not affect subsequent immunofluorescent analysis and NeuN immunoreactivity.Conclusion MicroCT method was proven to be suitable for delineation of the ischemic lesion from the non-infarcted tissue, and quantification of lesion volume and cerebral edema.

Bradykinin is involved in the formation of cerebral edema after ischemic brain injury increasing the size of brain. Furthmore, it is known that natriuretic peptides are involved in decreasing cerebral edema via still unknown mechanisms. First, we examined the effects of natriuretic peptides and bradykinin in vitro in HEK-293 cells, primary isolated neurons and astrocytes using the whole cell patch clamp technique and by measuring the intracellular calcium concentration. In a mouse model of ischemic brain injury, we measured the size of the ischemic lesion and edema using microCT. In HEK- 293 cells, ligands of GC-A, but not GC-B, inhibit the bradykinin signaling pathway by activating RGS protein which is responsible for inactivation of G coupled protein. Our preliminary results show that the same inhibition exists in primary isolated mouse neurons. In in vivo experiments, when urodilatin, agonist of GC-A was applied, no brain lesion was detected by microCT scanning. When only bradykinin was applied, brain damage increased. Applying a combination of natriuretic peptides with bradykinin the size of the lesion and the brain edema decreased. The results indicated the existence of an endogenous antagonist of the bradykinin signaling pathway and a possible protective role of natriuretic peptides during stroke.

Toll-like receptor 2 (TLR2) is involved in innate immunity in the brain and in the cascade of events after ischemic stroke. The aim of this study was to get an insight into the expression of genes related to TLR2 signaling pathway and associated with inflammation and apoptosis in the later stages of brain response after ischemic injury. Middle cerebral artery occlusion was performed on both wild-type and TLR2(-/-) mice followed by real-time PCR to measure the relative expression of selected genes. In TLR2(-/-) mice expression of genes involved in proinflammatory response was decreased after cerebral ischemia. Tnf was the most prominent cytokine active in the late phase of recovery. Contrary to proinflammatory genes, the expression of Casp8, as a hallmark of apoptosis, was increased in TLR2(-/-) mice, in particular in the late phase of recovery. (C) 2013 IBRO. Published by Elsevier Ltd. All rights reserved.

Abstract Background Using a live imaging approach, we have previously shown that microglia activation after stroke is characterized by marked and long-term induction of the Toll-like receptor (TLR) 2 biophotonic signals. However, the role of TLR2 (and potentially other TLRs) beyond the acute innate immune response and as early neuroprotection against ischemic injury is not well understood. Methods TLR2−/− mice were subjected to transient middle cerebral artery occlusion followed by different reperfusion times. Analyses assessing microglial activation profile/innate immune response were performed using in situ hybridization, immunohistochemistry analysis, flow cytometry and inflammatory cytokine array. The effects of the TLR2 deficiency on the evolution of ischemic brain injury were analyzed using a cresyl violet staining of brain sections with appropriate lesion size estimation. Results Here we report that TLR2 deficiency markedly affects post-stroke immune response resulting in delayed exacerbation of the ischemic injury. The temporal analysis of the microglia/macrophage activation profiles in TLR2−/− mice and age-matched controls revealed reduced microglia/macrophage activation after stroke, reduced capacity of resident microglia to proliferate as well as decreased levels of monocyte chemotactic protein-1 (MCP-1) and consequently lower levels of CD45high/CD11b+ expressing cells as shown by flow cytometry analysis. Importantly, although acute ischemic lesions (24 to 72 h) were smaller in TLR2−/− mice, the observed alterations in innate immune response were more pronounced at later time points (at day 7) after initial stroke, which finally resulted in delayed exacerbation of ischemic lesion leading to larger chronic infarctions as compared with wild-type mice. Moreover, our results revealed that TLR2 deficiency is associated with significant decrease in the levels of neurotrophic/anti-apoptotic factor Insulin-like growth factor-1 (IGF-1), expressed by microglia in the areas both in and around ischemic lesion. Conclusion Our results clearly suggest that optimal and timely microglial activation/innate immune response is needed to limit neuronal damage after stroke.