Clozapine reduces chemokine-mediated migration of lymphocytes by targeting NF-κB and AKT phosphorylation.

Multiple sclerosis is a disease characterised by demyelination of axons in the central nervous system. The atypical antipsychotic drug clozapine has been shown to attenuate disease severity in experimental autoimmune encephalomyelitis (EAE), a mouse model that is useful for the study of multiple sclerosis. However, the mechanism of action by which clozapine reduces disease in EAE is poorly understood. To better understand how clozapine exerts its protective effects, we investigated the underlying signalling pathways by which clozapine may reduce immune cell migration by evaluating chemokine and dopamine receptor-associated signalling pathways. We found that clozapine inhibits migration of immune cells by reducing chemokine production in microglia cells by targeting NF-κB phosphorylation and promoting an anti-inflammatory milieu. Furthermore, clozapine directly targets immune cell migration by changing Ca2+ levels within immune cells and reduces the phosphorylation of signalling protein AKT. Linking these pathways to the antagonising effect of clozapine on dopamine and serotonin receptors, we provide insight into how clozapine alters immune cells migration by directly targeting the underlying migration-associated pathways.

Development of agarose-gelatin bioinks for extrusion-based bioprinting and cell encapsulation.

Three-dimensional bioprinting continues to advance as an attractive biofabrication technique to employ cell-laden hydrogel scaffolds in the creation of precise, user-defined constructs that can recapitulate the native tissue environment. Development and characterisation of new bioinks to expand the existing library helps to open avenues that can support a diversity of tissue engineering purposes and fulfil requirements in terms of both printability and supporting cell attachment. In this paper, we report the development and characterisation of agarose-gelatin (AG-Gel) hydrogel blends as a bioink for extrusion-based bioprinting. Four different AG-Gel hydrogel blend formulations with varying gelatin concentration were systematically characterised to evaluate suitability as a potential bioink for extrusion-based bioprinting. Additionally, autoclave and filter sterilisation methods were compared to evaluate their effect on bioink properties. Finally, the ability of the AG-Gel bioink to support cell viability and culture after printing was evaluated using SH-SY5Y cells encapsulated in bioprinted droplets of the AG-Gel. All bioink formulations demonstrate rheological, mechanical and swelling properties suitable for bioprinting and cell encapsulation. Autoclave sterilisation significantly affected the rheological properties of the AG-Gel bioinks compared to filter sterilisation. SH-SY5Y cells printed and differentiated into neuronal-like cells using the developed AG-Gel bioinks demonstrated high viability (>90%) after 23 d in culture. This study demonstrates the properties of AG-Gel as a printable and biocompatible material applicable for use as a bioink.

Cell Replacement Therapy for Huntington's Disease.

Huntington's disease (HD) is an inherited neurodegenerative disorder which is characterised by a triad of highly debilitating motor, cognitive, and psychiatric symptoms. While cell death occurs in many brain regions, GABAergic medium spiny neurons (MSNs) in the striatum experience preferential and extensive degeneration. Unlike most neurodegenerative disorders, HD is caused by a single genetic mutation resulting in a CAG repeat expansion and the production of a mutant Huntingtin protein (mHTT). Despite identifying the mutation causative of HD in 1993, there are currently no disease-modifying treatments for HD. One potential strategy for the treatment of HD is the development of cell-based therapies. Cell-based therapies aim to restore neuronal circuitry and function by replacing lost neurons, as well as providing neurotropic support to prevent further degeneration. In order to successfully restore basal ganglia functioning in HD, cell-based therapies would need to reconstitute the complex signalling network disrupted by extensive MSN degeneration. This chapter will discuss the potential use of foetal tissue grafts, pluripotent stem cells, neural stem cells, and somatic cell reprogramming to develop cell-based therapies for treating HD.

Clozapine reduces infiltration into the CNS by targeting migration in experimental autoimmune encephalomyelitis.

BACKGROUND: Atypical antipsychotic agents, such as clozapine, are used to treat schizophrenia and other psychiatric disorders by a mechanism that is believed to involve modulating the immune system. Multiple sclerosis is an immune-mediated neurological disease, and recently, clozapine was shown to reduce disease severity in an animal model of MS, experimental autoimmune encephalomyelitis (EAE). However, the mode of action by which clozapine reduces disease in this model is poorly understood. METHODS: Because the mode of action by which clozapine reduces neuroinflammation is poorly understood, we used the EAE model to elucidate the in vivo and in vitro effects of clozapine. RESULTS: In this study, we report that clozapine treatment reduced the infiltration of peripheral immune cells into the central nervous system (CNS) and that this correlated with reduced expression of the chemokines CCL2 and CCL5 transcripts in the brain and spinal cord. We assessed to what extent immune cell populations were affected by clozapine treatment and we found that clozapine targets the expression of chemokines by macrophages and primary microglia. Furthermore, in addition to decreasing CNS infiltration by reducing chemokine expression, we found that clozapine directly inhibits chemokine-induced migration of immune cells. This direct target on the immune cells was not mediated by a change in receptor expression on the immune cell surface but by decreasing downstream signaling via these receptors leading to a reduced migration. CONCLUSIONS: Taken together, our study indicates that clozapine protects against EAE by two different mechanisms; first, by reducing the chemoattractant proteins in the CNS; and second, by direct targeting the migration potential of peripheral immune cells.

Concise Review: The Use of Stem Cells for Understanding and Treating Huntington's Disease.

Two decades ago, researchers identified that a CAG expansion mutation in the huntingtin (HTT) gene was involved in the pathogenesis of Huntington's disease (HD). However, since the identification of the HTT gene, there has been no advance in the development of therapeutic strategies to prevent or reduce the progression of HD. With the recent advances in stem cell biology and human cell reprogramming technologies, several novel and exciting pathways have emerged allowing researchers to enhance their understanding of the pathogenesis of HD, to identify and screen potential drug targets, and to explore alternative donor cell sources for cell replacement therapy. This review will discuss the role of compensatory neurogenesis in the HD brain, the use of stem cell-based therapies for HD to replace or prevent cell loss, and the recent advance of cell reprogramming to model and/or treat HD. These new technologies, coupled with advances in genome editing herald a promising new era for HD research with the potential to identify a therapeutic strategy to alleviate this debilitating disorder. Stem Cells 2018;36:146-160.

Understanding Parkinson's Disease through the Use of Cell Reprogramming.

Recent progress in the field of somatic cell reprogramming offers exciting new possibilities for the study and treatment of Parkinson's disease (PD). Reprogramming technology offers the ability to untangle the diverse contributing risk factors for PD, such as ageing, genetics and environmental toxins. In order to gain novel insights into such a complex disease, cell-based models of PD should represent, as closely as possible, aged human dopaminergic neurons of the substantia nigra. However, the generation of high yields of functionally mature, authentic ventral midbrain dopamine (vmDA) neurons has not been easy to achieve. Furthermore, ensuring cells represent aged rather than embryonic neurons has presented a significant challenge. To date, induced pluripotent stem (iPS) cells have received much attention for modelling PD. Nonetheless, direct reprogramming strategies (either to a neuronal or neural stem/progenitor fate) represent a valid alternative that are yet to be extensively explored. Direct reprogramming is faster and more efficient than iPS cell reprogramming, and appears to conserve age-related markers. At present, however, protocols aiming to derive authentic, mature vmDA neurons by direct reprogramming of adult human somatic cells are sorely lacking. This review will discuss the strategies that have been employed to generate vmDA neurons and their potential for the study and treatment of PD.

Treatment with the antipsychotic agent, risperidone, reduces disease severity in experimental autoimmune encephalomyelitis.

Recent studies have demonstrated that atypical antipsychotic agents, which are known to antagonize dopamine D2 and serotonin 5-HT2a receptors, have immunomodulatory properties. Given the potential of these drugs to modulate the immune system both peripherally and within the central nervous system, we investigated the ability of the atypical anti-psychotic agent, risperidone, to modify disease in the animal model of multiple sclerosis (MS)4, experimental autoimune encephalomyelitis (EAE). We found that chronic oral administration of risperidone dose-dependently reduced the severity of disease and decreased both the size and number of spinal cord lesions. Furthermore, risperidone treatment substantially reduced antigen-specific interleukin (IL)-17a, IL-2, and IL-4 but not interferon (IFN)-γ production by splenocytes at peak disease and using an in vitro model, we show that treatment of macrophages with risperidone alters their ability to bias naïve T cells. Another atypical antipsychotic agent, clozapine, showed a similar ability to modify macrophages in vitro and to reduce disease in the EAE model but this effect was not due to antagonism of the type 1 or type 2 dopamine receptors alone. Finally, we found that while risperidone treatment had little effect on the in vivo activation of splenic macrophages during EAE, it significantly reduced the activation of microglia and macrophages in the central nervous system. Together these studies indicate that atypical antipsychotic agents like risperidone are effective immunomodulatory agents with the potential to treat immune-mediated diseases such as MS.

Efficacy against subcutaneous or intracranial murine GL261 gliomas in relation to the concentration of the vascular-disrupting agent, 5,6-dimethylxanthenone-4-acetic acid (DMXAA), in the brain and plasma.

PURPOSE: Glioblastomas are amongst the most highly vascularised tumours, and the pursuit of anti-angiogenic approaches such as bevacizumab has provided short-term benefits. The purpose of this study was to determine whether the vascular-disrupting agent, dimethylxanthenone-4-acetic acid (DMXAA), could provide longer-lasting therapeutic benefits in a murine model of glioblastoma. METHODS: Luciferase-expressing murine GL261 glioma cells were inoculated subcutaneously or intracranially into C57Bl/6 mice. Mice with tumours were administered DMXAA, and tumours measured using callipers or by optical imager. Concentrations of DMXAA in plasma and brain were measured by LC-MS/MS. RESULTS: DMXAA (25 mg/kg) caused widespread necrosis at 24 h, a 9-day growth delay and complete regressions in 50 % of the mice with subcutaneous GL261 tumours. Co-administered lenalidomide (100 mg/kg) increased the growth delay to 20 days and the percentage of cures to 83 %. The same dose of DMXAA with or without lenalidomide had minimal effects on intracranial GL261 tumours. Concentrations of DMXAA extracted from brain tissue were approximately 25-fold lower than those measured in plasma 15 min to 4 h after DMXAA administration. The presence of intracranial GL261 tumours did not alter the concentrations of DMXAA entering the brain. CONCLUSIONS: DMXAA does not appear to cross the blood-brain barrier efficiently. Thus, whilst excellent activity was obtained against subcutaneous GL261 gliomas, minimal effects were observed against intracranial GL261 tumours. These results emphasise the need to use appropriate orthotopic models for the evaluation of new approaches for the treatment of brain cancers.

Concise review: the involvement of SOX2 in direct reprogramming of induced neural stem/precursor cells.

Since induced pluripotent stem cells were first generated from mouse embryonic fibroblasts in 2006, somatic cell reprogramming has become a powerful and valuable tool in many fields of biomedical research, with the potential to lead to the development of in vitro disease models, cell-based drug screening platforms, and ultimately novel cell therapies. Recent research has now demonstrated the direct conversion of fibroblasts into stem, precursor, or mature cell types that are committed in their fate within a specific lineage, such as hematopoietic precursors or mature neurons. This has been achieved by ectopic expression of defined, tissue-specific transcription factors. Several studies have demonstrated direct reprogramming of mouse and human fibroblasts into immature neural stem or precursor cells, either by transient expression of the four pluripotency genes OCT3/4, KLF4, SOX2, and C-MYC or by application of different combinations of up to 11 neural transcription factors. Interestingly, in all of these studies SOX2 was introduced alone or in combination with other transcription factors. In this review we discuss the different combinations of ectopic transcription factors used to generate neural stem/precursor cells from somatic cells, with particular emphasis on SOX2 and its potential to act as a master regulator for reprogramming to a neural precursor state.

Stem cell-based therapy for Huntington's disease.

Huntington's disease (HD) is a late-onset neurodegenerative disease characterized by a progressive loss of medium spiny neurons in the basal ganglia. The development of stem cell-based therapies for HD aims to replace lost neurons and/or to prevent cell death. This review will discuss pre-clinical studies which have utilized stem or progenitor cells for transplantation therapy using HD animal models. In several studies, neural stem and progenitor cells used as allotransplants and xenografts have been shown to be capable of surviving transplantation and differentiating into mature GABAergic neurons, resulting in behavioral improvements. Beneficial effects have also been reported for transplantation of stem cells derived from non-neural tissue, for example, mesenchymal- and adipose-derived stem cells, which have mainly been attributed to their secretion of growth and neurotrophic factors. Finally, we review studies using stem cells genetically engineered to over-express defined neurotrophic factors. While these studies prove the potential of stem cells for transplantation therapy in HD, it also becomes clear that technical and ethical issues regarding the availability of stem cells must be solved before human trials can be conducted.

Differential fate and functional outcome of lithium chloride primed adult neural progenitor cell transplants in a rat model of Huntington disease.

INTRODUCTION: The ability to predetermine the fate of transplanted neural progenitor cells (NPCs) and specifically to direct their maturation has the potential to enhance the efficiency of cell-transplantation therapy for neurodegenerative disease. We previously demonstrated that transient exposure of subventricular zone (SVZ)-derived adult NPCs to lithium chloride during in vitro proliferation alters differential fate in vitro and increases the proportion of cells expressing neuronal markers while reducing glial progeny. To extend these findings, we examined whether in vitro priming of adult SVZ-derived NPCs with lithium chloride before transplantation into the quinolinic acid (QA) lesion rat model of Huntington disease altered in vivo neuronal differentiation and sensorimotor function compared with nonprimed NPC transplants. METHODS: NPCs were isolated from the SVZ of the adult rat brain and cultured for 2 weeks. Four days before transplantation into the QA-lesioned rat striatum, the cells were labeled with BrdU and primed with lithium chloride. The rats underwent regular evaluation of forelimb use and sensorimotor neglect to establish functional effects of NPC transplantation. Twelve weeks after transplantation, the brains were analyzed with immunohistochemistry to compare the differential fate of primed and nonprimed NPCs. RESULTS: We observed that in vitro priming of adult NPCs with lithium chloride reduced gliogenesis and enhanced the occurrence of DARPP-32-positive neurons when compared with nonprimed cells 12 weeks after transplantation into the QA-lesioned striatum. Lithium chloride priming also augmented the formation of efferent projections from newly formed neurons in the damaged host striatum to the globus pallidus. This was associated with acceleration of sensorimotor function recovery in rats receiving transplants of lithium chloride-primed adult NPCs compared with nonprimed transplants. CONCLUSIONS: These initial findings indicate that in vitro priming of adult NPCs with lithium chloride may augment transplant efficiency and accelerate sensorimotor function outcome in vivo.

Comparison of transplant efficiency between spontaneously derived and noggin-primed human embryonic stem cell neural precursors in the quinolinic acid rat model of Huntington's disease.

Human neural precursors (hNP) derived from embryonic stem cells (hESC) may provide a viable cellular source for transplantation therapy for Huntington's disease (HD). However, developing effective transplantation therapy for the central nervous system (CNS) using hESC relies on optimizing the in vitro production of hNP to control appropriate in vivo posttransplantation neuronal differentiation. The current study provides the first direct in vivo comparison of the transplant efficiency and posttransplantation characteristics of spontaneously derived and noggin-primed hNP following transplantation into the quinolinic acid (QA) rat model of HD. We show that spontaneously derived and noggin-primed hNP both survived robustly up to 8 weeks after transplantation into the QA-lesioned striatum of the adult rat. Transplanted hNP underwent extensive migration and large-scale differentiation towards a predominantly neuronal fate by 8 weeks posttransplantation. Furthermore, in vitro noggin priming of hNP specifically increased the extent of neuronal differentiation at both 4 and 8 weeks posttransplantation when compared to spontaneously derived hNP grafts. The results of this study suggest that in vitro noggin priming provides an effective mechanism by which to enhance hNP transplant efficiency for the treatment of HD.

Oxaliplatin-induced loss of phosphorylated heavy neurofilament subunit neuronal immunoreactivity in rat DRG tissue.

BACKGROUND: Oxaliplatin and related chemotherapeutic drugs cause painful chronic peripheral neuropathies in cancer patients. We investigated changes in neuronal size profiles and neurofilament immunoreactivity in L5 dorsal root ganglion (DRG) tissue of adult female Wistar rats after multiple-dose treatment with oxaliplatin, cisplatin, carboplatin or paclitaxel. RESULTS: After treatment with oxaliplatin, phosphorylated neurofilament heavy subunit (pNF-H) immunoreactivity was reduced in neuronal cell bodies, but unchanged in nerve fibres, of the L5 DRG. Morphometric analysis confirmed significant changes in the number (-75%; P < 0.0002) and size (-45%; P < 0.0001) of pNF-H-immunoreactive neurons after oxaliplatin treatment. pNF-H-immunoreactive neurons had overlapping size profiles and co-localisation with neurons displaying cell body immunoreactivity for parvalbumin, non-phospho-specific neurofilament medium subunit (NF-M) and non-phospho-specific neurofilament heavy subunit (NF-H), in control DRG. However, there were no significant changes in the numbers of neurons with immunoreactivity for parvalbumin (4.6%, P = 0.82), NF-M (-1%, P = 0.96) or NF-H (0%; P = 0.93) after oxaliplatin treatment, although the sizes of parvalbumin (-29%, P = 0.047), NF-M (-11%, P = 0.038) and NF-H (-28%; P = 0.0033) immunoreactive neurons were reduced. In an independent comparison of different chemotherapeutic agents, the number of pNF-H-immunoreactive neurons was significantly altered by oxaliplatin (-77.2%; P < 0.0001) and cisplatin (-35.2%; P = 0.03) but not by carboplatin or paclitaxel, and their mean cell body area was significantly changed by oxaliplatin (-31.1%; P = 0.008) but not by cisplatin, carboplatin or paclitaxel. CONCLUSION: This study has demonstrated a specific pattern of loss of pNF-H immunoreactivity in rat DRG tissue that corresponds with the relative neurotoxicity of oxaliplatin, cisplatin and carboplatin. Loss of pNF-H may be mechanistically linked to oxaliplatin-induced neuronal atrophy, and serves as a readily measureable endpoint of its neurotoxicity in the rat model.

Chemokines direct neural progenitor cell migration following striatal cell loss.

In this study we demonstrate the chemokines MCP-1, MIP-1alpha and GRO-alpha play a role in directing adult subventricular zone (SVZ)-derived progenitor cell migration following striatal cell death. MCP-1, MIP-1alpha and GRO-alpha were significantly upregulated in the striatum 2-3 days following QA-induced lesioning, correlating with maximum SVZ-derived progenitor cell recruitment into the lesioned striatum. We established that SVZ-derived progenitor cells express receptors for each chemokine, and demonstrated MCP-1, MIP-1alpha and GRO-alpha to be potent chemoattractants for SVZ-derived progenitor cells in vitro. Immunofluorescence revealed MCP-1, MIP-1alpha and GRO-alpha are predominantly expressed in the striatum by NG2-positive cells that appear to infiltrate from the bloodstream 6 h following QA lesioning. These results indicate that upregulation of MCP-1, MIP-1alpha and GRO-alpha following striatal cell death leads to chemoattraction of SVZ-derived progenitor cells into the damaged striatum and raises a potential role for blood-derived cells in directing the recruitment of SVZ-derived progenitors following brain injury.

The cellular composition and morphological organization of the rostral migratory stream in the adult human brain.

The rostral migratory stream (RMS) is the major pathway by which progenitor cells migrate from the subventricular zone (SVZ) to the olfactory bulb (OB) in rodents, rabbits and primates. However, the existence of an RMS within the adult human brain has been elusive. Immunohistochemical studies utilising cell-type specific markers for early progenitor cells (CD133), proliferating cells (PCNA), astrocytes and type B cells (GFAP) and migrating neuroblasts (PSA-NCAM), reveal that the adult human RMS is organized into layers containing glial cells, proliferating cells and neuroblasts. In addition, the RMS is arranged around a remnant of the ventricular cavity that extends from the SVZ to the OB as seen by immunohistological staining analysis and electron microscopy, showing the presence of basal bodies and a typical 9+2 arrangement of tubulin in tufts of cilia from all levels of the RMS. Overall, these findings suggest that a pathway of migratory progenitor cells similar to that seen in other mammals is present within the adult human brain and that this pathway could provide for neurogenesis in the human forebrain. These findings contribute to the scientific understanding of adult neurogenesis and establish the detailed cytoarchitecture of this novel neurogenic niche in the human brain.

In vitro priming to direct neuronal fate in adult neural progenitor cells.

We have previously reported methods that allow for the routine isolation, culture and transplantation of multipotent neural progenitor cells (NPCs) derived from the adult rat sub-ventricular zone (SVZ). In order to expand these techniques, the aim of the current study was to develop an in vitro strategy which can "prime" proliferating adult NPCs towards a neuronal fate during their subsequent differentiation under standard conditions. Our results show that transient exposure to lithium chloride during in vitro proliferation of adult SVZ-derived NPCs has the ability to alter differential fate in vitro and increase the proportion of cells expressing neuronal markers while at the same time causing a reduction in glial progeny. Treatment of adult NPCs with lithium chloride may therefore provide a novel mechanism by which adult NPCs can be primed towards a specific neuronal fate for cell replacement therapy.

AAV-mediated expression of Bcl-xL or XIAP fails to induce neuronal resistance against quinolinic acid-induced striatal lesioning.

Apoptotic mechanisms have been proposed to contribute to the selective loss of medium spiny striatal projection neurons in Huntington's disease (HD). This raises the question as to whether enhancing the expression of anti-apoptotic factors in vulnerable striatal projection neurons can reduce their susceptibility to neurotoxic processes occurring in the HD brain. In this study AAV 1/2 vectors encoding either the anti-apoptotic factor Bcl-xL or XIAP were used to transduce striatal neurons prior to an intrastriatal injection of the excitotoxic glutamate analogue quinolinic acid (QA). AAV 1/2 vector treated rats were observed in behavioural tests undertaken to assess whether anti-apoptotic factor expression provided amelioration of motor function impairment following unilateral QA-induced striatal lesioning. AAV-XIAP treated rats displayed complete amelioration of an ipsilateral forelimb use bias relative to control animals. However, neither AAV-XIAP nor AAV-Bcl-xL treated rats demonstrated an improvement in sensorimotor neglect compared to control animals. Furthermore, we did not observe a significant reduction of QA-induced pathology in assessed neuronal populations of the basal ganglia. These results indicate that sole enhancement of XIAP or Bcl-xL is not sufficient to counteract QA-induced excitotoxic insult of striatal neurons.

Neural progenitor cells derived from the adult rat subventricular zone: characterization and transplantation.

In order to fully characterize and determine the therapeutic potential of adult neural progenitor cells (NPCs), it is important to be able to isolate and study NPCs from animals such as rats, in which there are existing models of brain injury and disease. The focus of this study was to characterize the cultivation, differentiation, and transplantation of adult rat NPCs isolated from the subventricular zone of the lateral ventricles. We examined strategies for cell purification using a Percoll density gradient, and cell expansion using a range of maintenance medium and plating densities. Purification by Percoll gradient enriched a population of cells expressing nestin and SOX2, but resulted in a significant reduction in neurosphere generation. Culturing adult rat NPCs in Neurobasal-A media and plating at 200,000 cell/ml resulted in a higher percentage of cells surviving to generate neurospheres compared to culture in DMEM/F12 or NS-A media. On induction of differentiation, adult rat NPCs were capable of generating neurons, astrocytes, and oligodendrocytes in vitro that survived for up to 8 weeks, demonstrating multipotentiality of these cells. In addition, a population of cells continued to proliferate during the initial phase of differentiation, suggesting the presence of two populations of NPCs during differentiation. Cultured adult rat NPCs also survived and differentiated into astrocytes 6 weeks after transplantation into the striatum of the normal adult rat brain. In conclusion, we have optimized techniques that allow for the routine isolation, culture, and transplantation of multipotent NPCs derived from the adult rat SVZ.

Creating a neurogenic environment: the role of BDNF and FGF2.

Regional environmental cues present in the adult brain determine the fate of adult neural progenitor cells. To determine whether the growth factors BDNF or FGF2 can create a neurogenic environment outside the SVZ, we used AAV(1/2)-mediated gene transfer to produce ectopic BDNF or FGF2 expression in the normal adult rat striatum and transplanted SVZ-derived progenitor cells into this region. We observed that ectopic expression of BDNF in the striatum promoted neuronal differentiation of transplanted adult neural progenitor cells, while FGF2 expression supported the survival and proliferation of transplanted progenitor cells in the adult striatum. However, region-specific neuronal differentiation of transplanted progenitor cells was not observed in the adult striatum, suggesting ectopic BDNF or FGF2 expression was insufficient for the generation of mature neuronal phenotypes. This study provides direct in vivo evidence that ectopic striatal expression of either BDNF or FGF2 can induce neurogenesis in non-neurogenic regions of the adult brain.

AAV-mediated delivery of BDNF augments neurogenesis in the normal and quinolinic acid-lesioned adult rat brain.

Brain-derived neurotrophic factor (BDNF) plays a major role in regulating the survival and fate of progenitor cells in the adult brain. In order to extend previous observations in the normal adult brain and advance our knowledge regarding the effect of BDNF on neurogenesis in the injured brain, this study directly compared the effect of BDNF on basal and injury-induced neurogenesis in relation to progenitor cell distribution and levels of neuronal differentiation and survival. BDNF was overexpressed in the subventricular zone (SVZ) via recombinant adeno-associated virus (AAV(1/2)) delivery, and newly generated cells were identified using bromodeoxyuridine (BrdU) labelling. Selective striatal cell loss was induced in a subgroup of rats by unilateral striatal injection of quinolinic acid (QA) 21 days after AAV(1/2) injection. In the normal brain, BDNF overexpression significantly increased BrdU-positive cell numbers in the rostral migratory stream, indicating enhanced progenitor cell migration. Following QA lesioning, we observed a reduction in BrdU immunoreactivity in the SVZ. Overexpression of BDNF restored BrdU-positive cell numbers in the QA-lesioned SVZ to that observed in the normal brain. Most significantly, BDNF enhanced the recruitment of progenitor cells to the QA-lesioned striatum and promoted neuronal differentiation in both the normal and QA-lesioned striatum. Our findings indicate that BDNF augments the recruitment, neuronal differentiation and survival of progenitor cells in both neurogenic and non-neurogenic regions of the normal or QA-lesioned brain. Enhanced expression of BDNF may therefore be a viable strategy for augmenting neurogenesis from endogenous progenitor cells.