Matthias Schilling

Microglial activation precedes and predominates over macrophage infiltration in transient focal cerebral ischemia: a study in green fluorescent protein transgenic bone marrow chimeric mice.

Resident microglia and hematogenous macrophages play crucial roles in the pathogenetic cascade following cerebral ischemia but may functionally differ regarding neuroprotective and cytotoxic properties. Distinction between these cells has not been possible due to a lack of discriminating cellular markers. We generated bone marrow chimeric mice by transplanting bone marrow from green fluorescent protein (GFP) transgenic mice into irradiated wild-type recipients. Transient focal cerebral ischemia was induced by transient middle cerebral artery occlusion (MCAO) for 30 min. Resident microglia and infiltrating macrophages were identified by immunohistochemistry and GFP fluorescence after 1-28 days. The first blood-derived cells infiltrating the infarct area were seen on Day 1 and identified as granulocytes. Hematogenous GFP(+) macrophages were rarely observed on Day 2, reached peak numbers on Day 7, and decreased thereafter. In contrast, resident GFP(-) microglial cells rapidly became activated already on Day 1 after MCAO. Even on Days 4 and 7, most macrophage-like cells remained GFP(-), indicating their derivation from resident microglia. Hematogenous macrophages were able to acquire a ramified morphology indistinguishable from resident microglia while microglial cells could develop into a phagocytic phenotype indistinguishable from infiltrating macrophages. The vast majority of macrophages in the infarct area are derived from local microglia, revealing a remarkable predominance of local defense mechanisms over immune cells arriving from the blood. GFP bone marrow chimeric mice are a powerful tool to further differentiate the function of resident microglia and hematogenous macrophages following cerebral ischemia.

Predominant phagocytic activity of resident microglia over hematogenous macrophages following transient focal cerebral ischemia: An investigation using green fluorescent protein transgenic bone marrow chimeric mice

Activated microglia and hematogenous macrophages are known to be involved in infarct development after cerebral ischemia. Traditionally, hematogenic macrophages are thought to be the primary cells to remove the ischemic cell debris. However, phagocytosis is a well known property also of activated microglia. Due to a lack of discriminating cellular markers, the cellular origin of phagocytes and the temporal course of phagocytosis by these two cell types are largely unknown. In this study, we used green fluorescent protein (GFP) transgenic bone marrow chimeric mice and semithin serial sections after methyl methacrylate embedding of the brains to dissect in detail the proportion of identified activated resident microglial cells and infiltrating hematogenous macrophages in phagocytosing neuronal cell debris after 30 min of transient focal cerebral ischemia. Already at day one after reperfusion, we found a rapid decrease of neurons in the ischemic tissue reaching minimum numbers at day seven. Resident GFP-negative microglial cells rapidly became activated at day one and started to phagocytose neuronal material. By contrast, hematogenous macrophages incorporating neuronal cell debris were observed in the ischemic area not earlier than on day four. Quantitative analysis showed maximum numbers of phagocytes of local origin within 2 days and of blood-borne macrophages on day four. The majority of phagocytes in the infarct area were derived from local microglia, preceding and predominating over phagocytes of hematogenous origin. This recruitment reveals a remarkable predominance of local defense mechanisms for tissue clearance over immune cells arriving from the blood after ischemic damage.

Pneumonia in acute stroke patients fed by nasogastric tube

Background: Aspiration pneumonia is the most important acute complication of stroke related dysphagia. Tube feeding is usually recommended as an effective and safe way to supply nutrition in dysphagic stroke patients. Objective: To estimate the frequency of pneumonia in acute stroke patients fed by nasogastric tube, to determine risk factors for this complication, and to examine whether the occurrence of pneumonia is related to outcome. Methods: Over an 18 month period a prospective study was done on 100 consecutive patients with acute stroke who were given tube feeding because of dysphagia. Intermediate outcomes were pneumonia and artificial ventilation. Functional outcome was assessed at three months. Logistic regression and multivariate regression analyses were used, respectvely, to identify variables significantly associated with the occurrence of pneumonia and those related to a poor outcome. Results: Pneumonia was diagnosed in 44% of the tube fed patients. Most patients acquired pneumonia on the second or third day after stroke onset. Patients with pneumonia more often required endotracheal intubation and mechanical ventilation than those without pneumonia. Independent predictors for the occurrence of pneumonia were a decreased level of consciousness and severe facial palsy. The NIH stroke scale score on admission was the only independent predictor of a poor outcome. Conclusions: Nasogastric tubes offer only limited protection against aspiration pneumonia in patients with dysphagia from acute stroke. Pneumonia occurs mainly in the first days of the illness and patients with decreased consciousness and a severe facial palsy are especially endangered.

The role of CC chemokine receptor 2 on microglia activation and blood-borne cell recruitment after transient focal cerebral ischemia in mice

The chemokine receptor 2 (CCR2) is involved in inflammatory reactions following cerebral ischemia. Monocyte chemoattractant protein-1 (MCP-1) binds with high affinity to CCR2. MCP-1 is necessary for recruiting blood-borne cells to the injury site whereas it does not affect microglia activation and migration. MCP-1-deficient mice develop smaller infarcts and show a better functional outcome. CCR2-deficient mice also develop smaller infarcts and have a reduced expression of inflammatory cytokines during reperfusion. In the present study we investigated the differential role of inflammatory cells in CCR2-deficient mice, using green fluorescent protein (GFP)-transgenic bone marrow chimeras. After 30 min of transient middle cerebral artery occlusion (MCAO), activation of local microglia was similar in CCR2-deficient animals and their littermate controls over the study period, whereas an influx of GFP-positive cells was diminished in CCR2-deficient mice. Infiltrating macrophages were significantly reduced at day seven in the deficient animals (26.04+/-25.19 cells/mm(2)) compared to control mice (86.83+/-44.41 cells/mm(2), p<0.001). Neutrophils were also significantly reduced in CCR2-deficient mice (83% on day 2, 76% on day 4 and 89% on day 7, p<0.001). A significant reduction of infarct volume in CCR2-deficient animals could not be detected. In this study a clear differentiation of local and blood-borne inflammatory cell reaction after cerebral ischemia could be shown, demonstrating that CCR2-deficiency attenuates hematogenous cell recruitment to the injury site whereas microglia activation and migration is not affected.

Effects of Neural Progenitor Cells on Sensorimotor Recovery and Endogenous Repair Mechanisms After Photothrombotic Stroke

Background and Purpose— Intravenous neural progenitor cell (NPC) treatment was shown to improve functional recovery after experimental stroke. The underlying mechanisms, however, are not completely understood so far. Here, we investigated the effects of systemic NPC transplantation on endogenous neurogenesis and dendritic plasticity of host neurons. Methods— Twenty-four hours after photothrombotic ischemia, adult rats received either 5 million NPC or placebo intravenously. Behavioral tests were performed weekly up to 4 weeks after ischemia. Endogenous neurogenesis, dendritic length, and dendritic branching of cortical pyramid cells and microglial activation were quantified. Results— NPC treatment led to a significantly improved sensorimotor function measured by the adhesive removal test. The dendritic length and the amount of branch points were significantly increased after NPC transplantation, whereas endogenous neurogenesis was decreased compared to placebo therapy. Decreased endogenous neurogenesis was associated with an increased number of activated microglial cells. Conclusions— Our findings suggest that an increased dendritic plasticity might be the structural basis of NPC-induced functional recovery. The decreased endogenous neurogenesis after NPC treatment seems to be mediated by microglial activation.

Endogenous brain protection by granulocyte-colony stimulating factor after ischemic stroke.

Several lines of evidence have demonstrated beneficial effects of the hematopoietic factor G-CSF in experimental stroke. A conclusive demonstration of this effect in G-CSF deficient mice is, however, lacking. We therefore investigated the effect of G-CSF deficiency on infarct volumes, functional recovery, mRNA and protein expression of the matrix metalloproteinase 9 (MMP-9) after stroke. Furthermore we tested the efficacy of G-CSF substitution in G-CSF deficient animals to prevent the potential consequences of G-CSF deficiency. In the present study experimental stroke was induced in female non-treated wildtype (wt), G-CSF deficient mice and G-CSF substituted G-CSF deficient mice followed by assessment of infarct volumes, neurological outcome and sensorimotor function. In addition, immunohistochemistry and real-time PCR of the peri-ischemic area were performed. G-CSF deficient mice showed increased infarct volumes, whereas G-CSF substituted mice had a remarkable reduction in lesion size compared to wt mice. These findings are accompanied by an improvement in neurological and sensorimotor function. G-CSF deficiency resulted in an upregulation of MMP-9 in the direct peri-ischemic tissue. Treatment with G-CSF suppressed the upregulation of MMP-9. Taken together, G-CSF deficiency clearly resulted in enlarged infarct volumes, and worsened neurological outcome. G-CSF substitution abolished these negative effects, led to significant reduced lesion volumes, and improved neurological outcome. G-CSF mediated suppression of MMP-9 further demonstrates that endogenous G-CSF plays a significant role in brain protective mechanisms. We have shown for the first time that endogenous G-CSF is required for brain recovery mechanisms after stroke.

Prediction of Malignant Middle Cerebral Artery Infarction Using Computed Tomography-Based Intracranial Volume Reserve Measurements

Background and Purpose— Early decompressive surgery in patients with malignant middle cerebral artery (MCA) infarction improves outcome. Elevation of intracranial pressure depends on both the space occupying brain edema and the intracranial volume reserve (cerebrospinal fluid [CSF]). However, CSF volume was not investigated as a predictor of malignant infarction so far. We hypothesize that assessment of CSF volume in addition to admission infarct size improves early prediction of malignant MCA infarction. Methods— Stroke patients with carotid-T or MCA main stem occlusion and ischemic lesion (reduced cerebral blood volume [CBV]) on perfusion CT were considered for the analysis. The end point malignant MCA infarction was defined by clinical signs of herniation. Volumes of CSF and CBV lesion were determined on admission. Receiver-operator characteristics analysis was used to calculate predictive values for radiological and clinical measurements. Results— Of 52 patients included, 26 (50%) developed malignant MCA infarction. Age, a decreased level of consciousness on admission, CBV lesion volume, CSF volume, and the ratio of CBV lesion volume to CSF volume were significantly different between malignant and nonmalignant groups. The best predictor of a malignant course was the ratio of CBV lesion volume to CSF volume with a cut-off value of 0.92 (96.2% sensitivity, 96.2% specificity, 96.2% positive predictive value, and 96.2% negative predictive value). Conclusions— Based on admission native CT and perfusion CT measurements, the ratio of ischemic lesion volume to CSF volume predicts the development of malignant MCA infarction with higher accuracy than other known predictors, including ischemic lesion volume or clinical characteristics.

Continuous Positive Airway Pressure Ventilation for Acute Ischemic Stroke A Randomized Feasibility Study

Background and Purpose— Sleep-related breathing disorders occur frequently after stroke. We assessed the feasibility of continuous positive airway pressure (CPAP) treatment initiated in the first night after stroke. Methods— In this open-label, parallel-group trial, 50 patients were randomly assigned to the CPAP therapy or to the control group. All patients underwent polysomnography in the fourth night. Intervention patients received CPAP therapy for 3 nights starting the first night after stroke onset and for an additional 4 nights when polysomnography revealed an apnea–hypopnea index >10/hour. The primary end point was feasibility defined as apnea–hypopnea index reduction under CPAP treatment, nursing workload, and CPAP adherence. Results— The apnea–hypopnea index under CPAP treatment was significantly reduced (32.2±25.3–9.8±6.6, P=0.0001). Nursing workload did not significantly differ between the CPAP (n=25) and the control group (n=25; P=0.741). Ten patients (40.0%) had excellent CPAP use, 14 patients (56.0%) had some use, and 1 patient (4.0%) had no use. There was a trend toward greater National Institutes of Health Stroke Scale score improvement until Day 8 in patients on CPAP (2.00 versus 1.40, P=0.092) and a significantly greater National Institutes of Health Stroke Scale score improvement in patients with excellent CPAP use when compared with control patients (2.30 versus 1.40, P=0.022). Conclusions— CPAP therapy initiated in the first night after stroke seems to be feasible and was not associated with neurological deterioration. Clinical Trial Registration— URL: www.clinicaltrials.gov. Unique identifier: NCT00151177.

Neuroleptic-induced dysphagia: case report and literature review.

Neuroleptic medication may cause extrapyramidal symptoms (EPS) that can affect swallowing as well. This report describes a case of drug-induced dysphagia in a 53-year-old man receiving haloperidol for treatment of schizophrenia. The diagnosis was established by fiberoptic endoscopic evaluation of swallowing. After changing medication to fluphenazin, dysphagic symptoms resolved. The literature on EPS-related dysphagia, its demographic features, typical symptoms, diagnostic modalities, clinical course, and treatment options is reviewed.

Monocyte Chemoattractant Protein-1-Deficiency Impairs the Expression of IL-6, IL-1β and G-CSF after Transient Focal Ischemia in Mice

Monocyte chemoattractant protein-1 (MCP-1), a chemokine secreted by neurons and astrocytes following stroke is known to aggravate ischemia-related damage. Previous studies revealed that MCP-1-deficient mice develop smaller infarcts and have an improved neurological outcome, whereas mice overexpressing MCP-1 show worsened brain damage and impaired neurological function. The aim of the present study was to elucidate the molecular background of the enhanced recovery in MCP-1-deficient mice after stroke. For this purpose, we (1) performed expression analyses on crucial post-stroke related inflammatory genes in MCP-1-deficient mice compared to wildtype controls, (2) analyzed a possible impact of MCP-1 on astrocyte activation (3) investigated the cellular origin of respective inflammatory cytokines and (4) analyzed the impact of MCP-1 secretion on the migration of both neutrophil granulocytes and T-cells. Here we report that MCP-1-deficiency leads to a shift towards a less inflammatory state following experimental occlusion of the middle cerebral artery including an impaired induction of interleukin-6, interleukin-1β and granulocyte-colony stimulating factor expression as well as a subsequent diminished influx of hematogenous cells. Additionally, MCP-1-deficient mice developed smaller infarcts 36 hours after experimental stroke. Investigations revealed no differences in transcription of tumor necrosis factor-α and astrogliosis 12 and 36 hours after onset of ischemia. These novel results help to understand post ischemic, inflammatory mechanisms and might give further arguments towards therapeutical interventions by modulation of MCP-1 expression in post stroke inflammation.