Cortical neurogenesis in adult rats after ischemic brain injury: most new neurons fail to mature

Neurogenesis and Neuroplasticity in Major Depression: Its Therapeutic Implication

The neurochemical model of depression, based on monoaminergic theories, does not allow on its own to understand the mechanism of action of antidepressants. This approach does not explain the gap between the immediate biochemical modulations induced by antidepressants and the time required for their clinical action. Several hypotheses have been developed to try to explain more precisely the action of these molecules, each of them involving mechanisms of receptor regulation. At the same time, data on the neuroanatomy of depression converge toward the existence of specific lesions of this pathology. This chapter aims to provide an overview of recent advances in understanding the mechanisms of neural plasticity involved in pathophysiology depression and in its treatment.

[Apoptosis as a systemic adaptive mechanism in ischemic stroke]

This paper presents a literature review considering the role and mechanism of apoptosis in the pathogenesis of ischemic stroke (IS). The authors introduce a new concept: the functional request of the patient as a set of external (the nature and intensity of rehabilitation measures, characteristics of everyday life, diet, etc.) and internal (genetic factors, internal picture of the disease, availability of rental and other psychological facilities and etc.) attributes. This concept allows a new angle in understanding the pathogenesis of IS and creates fundamental and clinical potential for more successful approaches to therapy and rehabilitation after IS.

Functional dissection of astrocyte-secreted proteins: Implications in brain health and diseases

Astrocytes, which are homeostatic cells of the central nervous system (CNS), display remarkable heterogeneity in their morphology and function. Besides their physical and metabolic support to neurons, astrocytes modulate the blood-brain barrier, regulate CNS synaptogenesis, guide axon pathfinding, maintain brain homeostasis, affect neuronal development and plasticity, and contribute to diverse neuropathologies via secreted proteins. The identification of astrocytic proteome and secretome profiles has provided new insights into the maintenance of neuronal health and survival, the pathogenesis of brain injury, and neurodegeneration. Recent advances in proteomics research have provided an excellent catalog of astrocyte-secreted proteins. This review categorizes astrocyte-secreted proteins and discusses evidence that astrocytes play a crucial role in neuronal activity and brain function. An in-depth understanding of astrocyte-secreted proteins and their pathways is pivotal for the development of novel strategies for restoring brain homeostasis, limiting brain injury/inflammation, counteracting neurodegeneration, and obtaining functional recovery.

Specific Features of SVZ Neurogenesis After Cortical Ischemia: a Longitudinal Study

Stroke is a devastating disease with an increasing prevalence. Part of the current development in stroke therapy is focused in the chronic phase, where neurorepair mechanisms such as neurogenesis, are involved. In the adult brain, one of the regions where neurogenesis takes place is the subventricular zone (SVZ) of the lateral ventricles. Given the possibility to develop pharmacological therapies to stimulate this process, we have performed a longitudinal analysis of neurogenesis in a model of cortical ischemia in mice. Our results show an initial decrease of SVZ proliferation at 24 h, followed by a recovery leading to an increase at 14d and a second decrease 28d after stroke. Coinciding with the 24 h proliferation decrease, an increase in the eutopic neuroblast migration towards the olfactory bulb was observed. The analysis of the neuroblast ectopic migration from the SVZ toward the lesion showed an increase in this process from day 14 after the insult. Finally, our data revealed an increased number of new cortical neurons in the peri-infarct cortex 65d after the insult. In summary, we report here critical check-points about post-stroke neurogenesis after cortical infarcts, important for the pharmacological modulation of this process in stroke patients.

Mild hypothermia modulates the expression of nestin and caspase-3 in the sub-granular zone and improves neurological outcomes in rats with ischemic stroke

We assessed neurological outcomes, infarct volume, and the expression of nestin and caspase-3 in the hippocampal dentate gyrus following middle cerebral artery occlusion (MCAO) followed by reperfusion, with mild hypothermia (MH) treatment at the onset of ischemia in a MCAO rat model. Reperfusion began 2 hours after the MCAO model was set-up. MH treatment began at the onset of ischemia and was maintained for 4 hours. We evaluated neurological deficit score, brain infarct volumes, along with the immunohistochemical staining of nestin and caspase-3 in the sub-granular zone of the injured hemisphere on the 1st, 3rd, 7th, and 14th day after the onset of ischemia. Correlations between the number of nestin-positive (nestin⁺) cells, caspase-3-positive (caspase-3⁺) cells with infarct volume, as well as neurological deficit scores, were evaluated by linear regression. MH significantly promoted survival, reduced mortality, improved neurological deficit score, reduced brain infarct volume, increased the number of neural stem/progenitor cells and inhibited neuronal apoptosis in the sub-granular zone of the injured hemisphere. The number of nestin⁺ cells correlated with neurological deficit score in the normothermic group, and with infarct volume in the hypothermia group except for the first day after the onset of ischemia. The number of caspase-3⁺ cells correlated with the neurological deficit score but not infarct volume. The neuroprotective effects of MH may be mediated by modulating neural stem/progenitor cells and neuronal apoptotic cells in the sub-granular zone of the injured hemisphere during cerebral ischemia/reperfusion injury.

Protective Effect of Antioxidants on Neuronal Dysfunction and Plasticity in Huntington's Disease

Huntington's disease (HD) is characterised by movement disorders, cognitive impairments, and psychiatric problems. The abnormal generation of reactive oxygen species and the resulting oxidative stress-induced mitochondrial damage in neurons upon CAG mutations in the HTT gene have been hypothesized as the contributing factors of neurodegeneration in HD. The potential use of antioxidants against free radical toxicity has been an emerging field in the management of ageing and many neurodegenerative disorders. Neural stem cells derived adult neurogenesis represents the regenerative capacity of the adult brain. The process of adult neurogenesis has been implicated in the cognitive functions of the brain and is highly modulated positively by different factors including antioxidants. The supportive role of antioxidants to reduce the severity of HD via promoting the functional neurogenesis and neuroprotection in the pathological adult brain has great promise. This review comprehends the recent studies describing the therapeutic roles of antioxidants in HD and other neurologic disorders and highlights the scope of using antioxidants to promote adult neurogenesis in HD. It also advocates a new line of research to delineate the mechanisms by which antioxidants promote adult neurogenesis in HD.

In Vitro Differentiation of Bone Marrow Mesenchymal Stem Cells into Neuron-Like Cells by Cerebrospinal Fluid Improves Motor Function of Middle Cerebral Artery Occlusion Rats

Bone marrow mesenchymal stem cells (BMSCs) represent a promising tool for stem cell-based therapies. However, the majority of BMSC transplants only allow for limited recovery of the lost functions. We previously found that human cerebrospinal fluid (hCSF) is more potent than growth factors in differentiating human BMSCs into neuron-like cells in vitro. In this study, we studied the effect of transplantation of rat BMSC-derived neuron-like cells (BMSC-Ns) induced by hCSF into rat brain with middle cerebral artery occlusion (MCAO). The survival and differentiation of the transplanted cells were determined using immunofluorescence staining of bromodeoxyuridine. The recovery of neurological function were observed by the modified neurological severity score (modified NSS) at 4, 15, and 32 days after cell transplantation, HE staining for determination of the infarct volume at day 32 after cell transplantation. Transplantation of BMSC-Ns or BMSCs significantly improved indexes of neurological function and reduced infarct size in rats previously subjected to MCAO compared with those in the control group. Remarkably, 32 days after transplantation, rats treated with BMSC-Ns presented a smaller infarct size, higher number of neuron-specific, enolase-positive, and BrdU-positive cells, and improved neurological function compared with BMSC group. Our results demonstrate that transplantation of hCSF-treated BMSC-Ns significantly improves neurological function and reduces infarct size in rats subjected to MCAO. This study may pave a new avenue for the treatment of MCAO.

Induced cortical neurogenesis after focal cerebral ischemia--Three active components from Huang-Lian-Jie-Du Decoction

ETHNOPHARMACOLOGICAL RELEVANCE

Huang-Lian-Jie-Du-Decoction (HLJDD) is a Traditional Chinese Medicine (TCM) clinical prescription noted for its neuroprotective effects. The total alkaloids, flavonoids, and iridoids are the main active components of HLJDD. In the present study we explored the possible effects of the total alkaloids, flavonoids, and iridoids from HLJDD on behavioral recovery and cortical neurogenesis after stroke.

METHODS

The stroke model was induced by permanent middle cerebral artery occlusion (pMACO). The total alkaloids (44 mg/kg), flavonoids (50 mg/kg), and iridoids (80 mg/kg) from HLJDD were orally administered for 2h after stroke and daily thereafter. Neurological function was assessed and then rats were sacrificed 7 days after pMACO. Following repeated intraperitoneal injections of the cell proliferation - specific marker 5-bromodeoxyuridine (BrdU) after stroke induction, precursor cell proliferation and differentiation was monitored by immunofluorescent staining. The levels of relevant proteins were determined by western blotting and the mRNA expressions were assessed by quantitative real time-polymerase chain reaction (qRT-PCR).

RESULTS

Total alkaloids, flavonoids and iridoids from HLJDD showed improved functional outcome after brain ischemia. The total alkaloids and iridoids increased number of BrdU-positive cells and enhanced neuronal differentiation in the cortex. Alkaloids-enhanced neurogenesis might be associated with increased VEGF, Ang-1, and Ang-2 protein expression. And the neuroproliferative effect of alkaloids was partially correlated with increased phosphorylation of AKT, and GSK-3β. Flavonoids treatment was found to promote differentiation of cortical precursor cells into neuronal but not glial cells, which may be at least attributable to the regulation of AKT, GSK-3β mRNA and Ang-1 protein levels.

CONCLUSIONS

Total alkaloids, iridoids and flavonoids from HLJDD promoted functional recovery likely via enhancing cortical neurogenesis and thus have potential as a treatment for ischemic brain injury.

Chitosan-collagen porous scaffold and bone marrow mesenchymal stem cell transplantation for ischemic stroke

In this study, we successfully constructed a composite of bone marrow mesenchymal stem cells and a chitosan-collagen scaffold in vitro, transplanted either the composite or bone marrow mesenchymal stem cells alone into the ischemic area in animal models, and compared their effects. At 14 days after co-transplantation of bone marrow mesenchymal stem cells and the hitosan-collagen scaffold, neurological function recovered noticeably. Vascular endothelial growth factor expression and nestin-labeled neural precursor cells were detected in the ischemic area, surrounding tissue, hippocampal dentate gyrus and subventricular zone. Simultaneously, a high level of expression of glial fibrillary acidic protein and a low level of expression of neuron-specific enolase were visible in BrdU-labeled bone marrow mesenchymal stem cells. These findings suggest that transplantation of a composite of bone marrow mesenchymal stem cells and a chitosan-collagen scaffold has a neuroprotective effect following ischemic stroke.