Although brain scars in adults have been extensively studied, there is less data available regarding scar formation during the neonatal period, and the involvement of peripheral immune cells in this ...process remains unexplored in neonates. Using a murine model of neonatal hypoxic–ischemic encephalopathy (HIE) and confocal microscopy, we characterized the scarring process and examined the recruitment of peripheral immune cells to cortical and hippocampal scars for up to 1 year post‐insult. Regional differences in scar formation were observed, including the presence of reticular fibrotic networks in the cortex and perivascular fibrosis in the hippocampus. We identified chemokines with chronically elevated levels in both regions and demonstrated, through a parabiosis‐based strategy, the recruitment of lymphocytes, neutrophils, and monocyte‐derived macrophages to the scars several weeks after the neonatal insult. After 1 year, however, neutrophils and lymphocytes were absent from the scars. Our data indicate that peripheral immune cells are transient components of HIE‐induced brain scars, opening up new possibilities for late therapeutic interventions.
Main Points
Astrocytic and fibrotic brain scars persisted up to 1 year after neonatal hypoxia‐ischemia.
Neutrophils and lymphocytes were recruited to brain scars for several weeks.
The levels of several chemokines remained elevated in the brain after seven weeks.
Gangliosides are glycosphingolipids abundantly expressed in the vertebrate nervous system, and are classified into a‐, b‐, or c‐series according to the number of sialic acid residues. The enzyme GD3 ...synthase converts GM3 (an a‐series ganglioside) into GD3, a b‐series ganglioside highly expressed in the developing and adult retina. The present study evaluated the visual system of GD3 synthase knockout mice (GD3s–/–), morphologically and functionally. The absence of b‐ series gangliosides in the retinas of knockout animals was confirmed by mass spectrometry imaging, which also indicated an accumulation of a‐series gangliosides, such as GM3. Retinal ganglion cell (RGC) density was significantly reduced in GD3s–/– mice, with a similar reduction in the number of axons in the optic nerve. Knockout animals also showed a 15% reduction in the number of photoreceptor nuclei, but no difference in the bipolar cells. The area occupied by GFAP‐positive glial cells was smaller in GD3s–/– retinas, but the number of microglial cells/macrophages did not change. In addition to the morphological alterations, a 30% reduction in light responsiveness was detected through quantification of pS6‐expressing RGC, an indicator of neural activity. Furthermore, electroretinography (ERG) indicated a significant reduction in RGC and photoreceptor electrical activity in GD3s–/– mice, as indicated by scotopic ERG and pattern ERG (PERG) amplitudes. Finally, evaluation of the optomotor response demonstrated that GD3s–/– mice have reduced visual acuity and contrast sensitivity. These results suggest that b‐series gangliosides play a critical role in regulating the structure and function of the mouse visual system.
Gangliosides are lipid molecules important in the developing and adult nervous system. GD3 synthase enzyme is necessary to synthesize several gangliosides, denominated b‐ and c‐series. Here, we evaluated the impact of GD3 synthase deletion on the structure and function of the visual system in adult mice. GD3 knockout mice had reductions in two retinal populations, retinal ganglion cells and photoreceptors, and also showed functional visual deficits. These results suggest that b‐series gangliosides play a critical role in mouse visual system, and GD3 knockout mice are a model to investigate ganglioside functions in the nervous system during development and adulthood.
The microbiota-gut-brain axis is considered a central regulator of the immune system after acute ischemic stroke (AIS), with a potential role in determining outcome. Several pathways are involved in ...the evolution of gut microbiota dysbiosis after AIS. Brain-gut and gut-brain signaling pathways involve bidirectional communication between the hypothalamic-pituitary-adrenal axis, the autonomic nervous system, the enteric nervous system, and the immune cells of the gut. Alterations in gut microbiome can be a risk factor and may also lead to AIS. Both risk factors for AIS and gut-microbiome composition are influenced by similar factors, including diabetes, hypertension, hyperlipidemia, obesity, and vascular dysfunction. Furthermore, the systemic inflammatory response after AIS may yield liver, renal, respiratory, gastrointestinal, and cardiovascular impairment, including the multiple organ dysfunction syndrome. This review focus on biochemical, immunological, and neuroanatomical modulation of gut microbiota and its possible systemic harmful effects after AIS, as well as the role of ischemic stroke on microbiota composition. Finally, we highlight the role of gut microbiota as a potential novel therapeutic target in acute ischemic stroke.The microbiota-gut-brain axis is considered a central regulator of the immune system after acute ischemic stroke (AIS), with a potential role in determining outcome. Several pathways are involved in the evolution of gut microbiota dysbiosis after AIS. Brain-gut and gut-brain signaling pathways involve bidirectional communication between the hypothalamic-pituitary-adrenal axis, the autonomic nervous system, the enteric nervous system, and the immune cells of the gut. Alterations in gut microbiome can be a risk factor and may also lead to AIS. Both risk factors for AIS and gut-microbiome composition are influenced by similar factors, including diabetes, hypertension, hyperlipidemia, obesity, and vascular dysfunction. Furthermore, the systemic inflammatory response after AIS may yield liver, renal, respiratory, gastrointestinal, and cardiovascular impairment, including the multiple organ dysfunction syndrome. This review focus on biochemical, immunological, and neuroanatomical modulation of gut microbiota and its possible systemic harmful effects after AIS, as well as the role of ischemic stroke on microbiota composition. Finally, we highlight the role of gut microbiota as a potential novel therapeutic target in acute ischemic stroke.
Stroke is the second leading cause of death and the third leading cause of disability worldwide. Approximately 16 million first-ever strokes occur each year, leading to nearly 6 million deaths. ...Nevertheless, currently, very few therapeutic options are available. Cell therapies have been applied successfully in different hematological diseases, and are currently being investigated for treating ischemic heart disease, with promising results. Recent preclinical studies have indicated that cell therapies may provide structural and functional benefits after stroke. However, the effects of these treatments are not yet fully understood and are the subject of continuing investigation. Meanwhile, different clinical trials for stroke, the majority of them small, nonrandomized, and uncontrolled, have been reported, and their results indicate that cell therapy seems safe and feasible in these conditions. In the last 2 years, the number of published and registered trials has dramatically increased. Here, we review the main findings available in the field, with emphasis on the clinical results. Moreover, we address some of the questions that have been raised to date, to improve future studies.
Mesenchymal stem cells (MSCs) have neuroprotective and immunomodulatory properties, which are partly mediated by extracellular vesicles (EVs) secretion. We aimed to evaluate the effects of human ...Wharton’s jelly-derived MSCs (WJ-MSCs) and their EVs on rat hippocampal cultures subjected to hydrogen peroxide (H
O
).
Hippocampal dissociated cultures were either co-cultured with WJ-MSCs or treated with their EVs prior to H
O
exposure and reactive oxygen species levels and cell viability were evaluated.
Coculture with WJ-MSCs or pre-incubation with EVs prior to the insult reduced reactive oxygen species after H
O
exposure. Cell viability was improved only when coculture was maintained following the insult, while EVs did not significantly improve cell viability.
WJ-MSCs have potential antioxidant and neuroprotective effects on hippocampal cultures which might be partially mediated by EVs.
Mesenchymal stem cells (MSCs) have emerged as a promising therapeutic approach for neurodegenerative diseases, yet their potential and mechanism of action have not been fully described. In this work we show that Wharton’s jelly-derived MSCs (WJ-MSCs) obtained from the human umbilical cord release vesicles that were able to reduce oxidative stress in neural cell cultures exposed to hydrogen peroxide, a potent oxidant agent. WJ-MSCs were also able to protect neural cells from hydrogen peroxide-induced cell death when they were present in the damaging environment, while treatment with WJ-MSC-derived vesicles alone did not prevent cell death at the doses used.
Intracerebral hemorrhage (ICH) has limited therapeutic options. We have shown that an intravenous injection of human umbilical cord-derived mesenchymal stromal cells (hUC-MSC) 24 h after an ICH in ...rats reduced the residual hematoma volume after a moderate hemorrhage but was inefficient in severe ICH. Here, we investigated whether a treatment in the hyperacute phase would be more effective in severe ICH.
Wistar rats were randomly selected to receive an intravenous injection of hUC-MSC or the vehicle 1 h after a severe ICH.
The hyperacute treatment with hUC-MSC did not affect the 22-day survival rate, the motor function or the residual hematoma volume.
These results indicate the need for optimization of hUC-MSC-based therapies for severe ICH.
Hemorrhagic stroke, caused by the leakage of blood from blood vessels to the brain, is a life-threatening condition that reduces the quality of life of a large number of patients worldwide without effective treatments. Here, we induced a severe hemorrhagic stroke in rats to study the effects of a treatment using mesenchymal stromal cells, stem cells obtained from the umbilical cord tissue capable of producing protective molecules for the brain. The treatment; however, did not improve some aspects of the disease, such as the motor ability and the size of the brain lesion, indicating that further studies are still necessary.
After an ischemic stroke, mononuclear phagocytic cells such as microglia, macrophages, and monocytes migrate to the lesion site and coordinate an immune response. Monocytes, which are recruited from ...the bloodstream after ischemic brain injury, can be categorized into two subsets in mice: inflammatory and patrolling monocytes. Although inflammatory monocytes (Ly6Chi) seem to have a protective role in stroke progression, the impact of patrolling monocytes (Ly6Clow) is unknown. To address the role of Ly6Clow monocytes in stroke, we generated bone marrow chimeric mice in which their hematopoietic system was replaced by Nr4a1−/− cells, allowing the complete and permanent ablation of Ly6Clow monocytes without affecting the Ly6Chi subset. We then subjected adult mice to cerebral hypoxia-ischemia using the Levine/Vannucci model. Functional outcomes after stroke such as body weight change, neurologic score, motor functions and spatial learning were not affected. Moreover, depletion in Ly6Clow monocytes did not change significantly the total infarct size, cell loss, atrophy, the number, or the activation state of microglia/macrophages at the lesion site. These data suggest that Ly6Clow patrolling monocytes are redundant in the progression and recovery of ischemic stroke.
Bone marrow-derived mesenchymal stromal cells (BM-MSCs) are dynamic cells that can sense the environment, adapting their regulatory functions to different conditions. Accordingly, the therapeutic ...potential of BM-MSCs can be modulated by preconditioning strategies aimed at modifying their paracrine action. Although rat BM-MSCs (rBM-MSCs) have been widely tested in preclinical research, most preconditioning studies have employed human and mouse BM-MSCs. Herein, we investigated whether rBM-MSCs modify their phenotype and paracrine functions in response to Toll-like receptor (TLR) agonists. The data showed that rBM-MSCs expressed TLR3, TLR4, and MDA5 mRNA and were able to internalize polyinosinic-polycytidylic acid (Poly(I:C)), a TLR3/MDA5 agonist. rBM-MSCs were then stimulated with Poly(I:C) or with lipopolysaccharide (LPS, a TLR4 agonist) for 1 h and were grown under normal culture conditions. LPS or Poly(I:C) stimulation did not affect the viability or the morphology of rBM-MSCs and did not modify the expression pattern of key cell surface markers. Poly(I:C) did not induce statistically significant changes in the release of several inflammatory mediators and VEGF by rBM-MSCs, although it tended to increase IL-6 and MCP-1 secretion, whereas LPS increased the release of IL-6, MCP-1, and VEGF, three factors that were constitutively secreted by unstimulated cells. The neurotrophic activity of the conditioned medium from unstimulated and LPS-preconditioned rBM-MSCs was investigated using dorsal root ganglion explants, showing that soluble factors produced by unstimulated and LPS-preconditioned rBM-MSCs can stimulate neurite outgrowth similarly, in a VEGF-dependent manner. LPS-preconditioned cells, however, were slightly more efficient in increasing the number of regrowing axons in a model of sciatic nerve transection in rats. In conclusion, LPS preconditioning boosted the production of constitutively secreted factors by rBM-MSCs, without changing their mesenchymal identity, an effect that requires further investigation in exploratory preclinical studies.
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