Bone marrow-derived MOs/MPs recruited via CCR2 and acting via TGF-β1 are essential for maintaining integrity of the neurovascular unit following brain ischemia. Future therapies should be aimed at enhancing physiological repair functions of CCR2(+) MOs/MPs rather than blocking their hematogenous recruitment.

The cerebellar cortex consists of a small set of neuronal cell types interconnected in a highly stereotyped way. While the development of cerebellar cortical projection neurons, i.e. Purkinje cells, and that of granule cells has been elucidated in considerable detail, that of cerebellar cortical inhibitory interneurons is still rather fragmentarily understood. Here, we use mice expressing green fluorescent protein (GFP) from the Pax2 locus to analyse the ontogenesis of these cells. Numbers of Pax2-positive inhibitory interneuronal precursors increase following a classical sigmoidal growth curve to yield a total of some 905.000 +/- 77.000 cells. Maximal cell increase occurs at about postnatal day (P)5.4, and some 75% of all inhibitory interneurons are generated prior to P7. Conjoint analysis of the developmental accruement of Pax2-GFP-positive cells and their cell cycle distribution reveals that, at least at P0 and P3, the numerical increase of these cells results primarily from proliferation of a Pax2-negative precursor population and suggests that Pax2 expression begins at or around the final mitosis. Following their terminal mitosis, inhibitory cerebellar cortical interneurons go through a protracted quiescent phase in which they maintain expression of the cell cycle marker Ki-67. During this phase, they translocate into the nascent molecular layer, where they stall next to premigratory granule cell precursors without penetrating this population of cells. These observations provide a quantitative description of cerebellar cortical inhibitory interneuron genesis and early differentiation, and define Pax2 as a marker expressed in basket and stellate cells, from around their final mitosis to their incipient histogenetic integration.

Infarcted regions of the brain after stroke are segregated from the intact brain by scar tissue comprising both fibrous and glial components. The extent and quality of scarring is influenced by inflammation. The matricellular glycoprotein osteopontin (OPN) is strongly induced in myeloid cells after stroke and may contribute to repair of ischemic brain lesions. To elucidate the role of OPN in scar formation, we induced photothrombotic brain infarction, characterized by circumscribed cortical infarctions with a well-defined border zone toward the intact brain parenchyma. The cellular source and functional role of OPN was addressed by studies in OPN null (OPN(-/-) ) mice, wild-type mice depleted of hematogenous monocytes/macrophages by clodronate-filled liposome treatment, and CCR2(-/-) bone marrow chimeric mice characterized by impaired hematogenous macrophage influx into the infarctions. OPN was mainly produced by hematogenous macrophages infiltrating into the inner border zone of the infarcts whereas astrocyte activation occurred in the outer border zone. In OPN(-/-) as well as macrophage-depleted mice, reactive astrocytes failed to properly extend processes from the periphery toward the center of the infarctions. This was associated with incomplete coverage of neovessels by astrocytic endfeet and persistent leakiness of the damaged blood brain barrier. In conclusion, OPN produced by hematogenous macrophages induces astrocyte process extension toward the infarct border zone, which may contribute to repair of the ischemic neurovascular unit.

Introduction: Multiple sclerosis (MS) is a chronic demyelinating disorder of the central nervous system (CNS) leading to progressive neurological disability. Interferon β (IFNβ) represents a standard treatment for relapsing-remitting MS and exogenous administration of IFNβ exhibits protective effects in experimentally induced CNS autoimmunity. Also, genetic deletion of IFNβ in mice leads to an aggravation of disease symptoms in the MS model of experimental autoimmune encephalomyelitis (EAE). However, neither the underlying mechanisms mediating the beneficial effects nor the cellular source of IFNβ have been fully elucidated. Results: In this report, a subpopulation of activated microglia was identified as the major producers of IFNβ in the CNS at the peak of EAE using an IFNβ-fluorescence reporter mouse model. These IFNβ expressing microglia specifically localized to active CNS lesions and were associated with myelin debris in demyelinated cerebellar organotypic slice cultures (OSCs). In response to IFNβ microglia showed an enhanced capacity to phagocytose myelin in vitro and up-regulated the expression of phagocytosis-associated genes. IFNβ treatment was further sufficient to stimulate association of microglia with myelin debris in OSCs. Moreover, IFNβ-producing microglia mediated an enhanced removal of myelin debris when co-transplanted onto demyelinated OSCs as compared to IFNβ non-producing microglia.

Hematogenous recruitment of monocytes and macrophages has traditionally been viewed as a harmful process causing exacerbation of brain injury after stroke. However, emerging findings suggest equally important protective features. Inflammatory monocytes are rapidly recruited to ischemic brain via a CCR2-dependent pathway and undergo secondary differentiation in the target tissue towards non-inflammatory macrophages, mediating neuroprotection and repair of the ischemic neurovascular unit. In contrast, independent recruitment of non-inflammatory monocytes via CX3CR1 does not occur. Thus, protective features of hematogenous macrophages mainly depend on initial CCR2-dependent cell recruitment. Under therapeutic considerations, specific modulation of monocyte-derived macrophages will therefore be more appropriate than non-selectively blocking their hematogenous recruitment. This article is part of a Special Issue entitled: Neuro Inflammation edited by Helga E. de Vries and Markus Schwaninger.

The endoplasmic reticulum (ER) serves as the major intracellular Ca 2+ store and has a role in the synthesis and folding of proteins. BAX (BCL2-associated X protein) inhibitor-1 (BI-1) is a Ca 2+ leak channel also implicated in the response against protein misfolding, thereby connecting the Ca 2+ store and protein-folding functions of the ER. We found that BI-1-deficient mice suffer from leukopenia and erythrocytosis, have an increased number of splenic marginal zone B cells and higher abundance and nuclear translocation of NF-κB (nuclear factor-κ light-chain enhancer of activated B cells) proteins, correlating with increased cytosolic and ER Ca 2+ levels. When put into culture, purified knockout T cells and even more so B cells die spontaneously. This is preceded by increased activity of the mitochondrial initiator caspase-9 and correlated with a significant surge in mitochondrial Ca 2+ levels, suggesting an exhausted mitochondrial Ca 2+ buffer capacity as the underlying cause for cell death in vitro. In vivo, T-cell-dependent experimental autoimmune encephalomyelitis and B-cell-dependent antibody production are attenuated, corroborating the ex vivo results. These results suggest that BI-1 has a major role in the functioning of the adaptive immune system by regulating intracellular Ca 2+ homeostasis in lymphocytes. Cell Death and Differentiation (2016) 23, 358-368; doi:10.1038/cdd.2015; published online 16 October 2015The endoplasmic reticulum (ER) serves as the major intracellular calcium (Ca 2+ ) store, the release of which controls a vast array of cellular functions from short-term responses such as contraction and secretion to long-term regulation of cell growth and proliferation. 1 Dysregulated release of ER Ca 2+ , in contrast, initiates programmed cell death by several mechanisms including mitochondrial Ca 2+ overload, depolarization, ATP loss and cytochrome c release. 2 Besides this, the ER also has a key role in the synthesis, folding and sorting of proteins destined for the secretory pathway. The deleterious consequences of an increase in unfolded proteins is called ER stress and can be antagonized by the unfolded protein response (UPR), a mechanism that coordinates a simultaneous increase in the ER folding capacity and a decrease in folding load. In the case of insufficient adaptation to ER stress, cells undergo apoptosis. 3 BAX (BCL2-associated X protein) inhibitor-1 (BI-1) is an evolutionarily conserved protein that bridges both the Ca 2+ homeostasis and UPR functions of the ER. 4 BI-1 was first identified in a screen for human proteins capable of inhibiting BAX-mediated cell death in yeast. 5 In mammalian cells, BI-1's antiapoptotic function is most pronounced in paradigms of ER stress 6 and involves changes in the amount of Ca 2+ that can be released from intracellular stores. 6,7 BI-1 is a highly hydrophobic protein that forms a Ca 2+ pore responsible for its Ca 2+ leak properties 8 and is the founding member of a family of six proteins with similar properties. 9 The increase in the ER Ca 2+ lea...

BackgroundIn a proportion of stroke patients with acute large vessel occlusion permanent stent implantation is mandatory to achieve successful recanalization. The optimum platelet inhibition strategy after such emergency stenting is unknown. We therefore analyzed the outcome of early glycoprotein (gp) IIb/IIIa inhibitor treatment after emergency stenting in acute stroke.MethodsSixty patients with emergency stenting were identified in our stroke unit registry from 12/2010-06/2014 and analyzed retrospectively. All patients were bridged intravenously with the gpIIb/IIIa antagonist tirofiban immediately after the acute procedure until switching to oral aspirin and clopidogrel was performed. For comparison we studied 135 patients with M1 occlusion undergoing thrombectomy without stent implantation or tirofiban treatment in a propensity score-adjusted analysis.ResultsIn the acute stenting group receiving tirofiban complications with 6 deaths during the hospital stay (10%), 2 reinfarctions (3%), 12 intracerebral hemorrhages (ICH; 20%) and 5 symptomatic ICH (8%) occurred. Thirty-seven patients (62%) reached a moderate outcome of mRS 0–3 after 90 days. In the thrombectomy group without tirofiban administration the rate of deaths within hospital stay, the rate of ICH and outcome at day 90 were not different.ConclusionIn our retrospective study acute stenting with subsequent gpIIb/IIIa inhibition was not associated with an increased risk of ICH or in-hospital death.

IMPORTANCEAlthough endovascular thrombectomy (EVT) in acute ischemic stroke is recommended by guidelines to improve functional recovery, thus far there are insufficient data on its association with mortality.OBJECTIVE To identify guideline-relevant trials of EVT vs medical therapy reporting 90-day mortality and perform a meta-analysis.DATA SOURCES All randomized clinical trials cited for recommendations on EVT vs medical therapy in the latest 2018 American Stroke Association/American Heart Association guidelines.STUDY SELECTION Ten American Stroke Association/American Heart Association guideline-relevant randomized clinical trials of EVT vs medical therapy were selected for inclusion. Two EVT trials were excluded owing to infrequent use of EVT.DATA EXTRACTION AND SYNTHESIS Data were abstracted by 2 independent investigators and double-checked by 4 others. Singular study data were integrated using the Cochran-Mantel-Haenszel method and a random-effects model to compute summary statistics of risk ratios (RR) with 95% CIs.MAIN OUTCOMES AND MEASURES Risk of 90-day mortality and 90-day intracranial hemorrhage was analyzed; sensitivity analyses were performed in early-window EVT trials (which included patients from the onset of symptoms onward) vs late-window EVT trials (which included patients from 6 hours after onset of symptoms onward). RESULTSIn 10 trials with 2313 patients, EVT significantly reduced the risk for 90-day mortality by 3.7% compared with medical therapy (15.0% vs 18.7%; RR, 0.81; 95% CI, 0.68-0.98; P = .03). Trends were similar in early-window (RR, 0.83; 95% CI, 0.67-1.01; P = .06) and late-window trials only (RR, 0.76; 95% CI, 0.41-1.40; P = .38). There was no difference in the risk for intracranial hemorrhage in EVT vs medical therapy (4.2% vs 4.0%; RR, 1.11; 95% CI, 0.71-1.72; P = .65). Limitations of the studies include trial protocol heterogeneity and bias originating from prematurely terminated trials.CONCLUSIONS AND RELEVANCE This meta-analysis of all evidence on EVT cited in the 2018 American Stroke Association/American Heart Association guidelines shows significant benefits for survival during the first 90 days after acute ischemic stroke compared with medical therapy alone.