Delivery Of Brain-derived Neurotrophic Factor Research Articles

A conductive dual-network hydrogel composed of oxidized dextran and hyaluronic-hydrazide as BDNF delivery systems for potential spinal cord injury repair

Spinal cord injury (SCI) often causes neuronal death and axonal degeneration. In this study, we report a new strategy for preparing injectable and conductive polysaccharides-based hydrogels that could sustainably deliver brain-derived neurotrophic factor (BDNF) for SCI repair. We used poly(lactic-co-glycolic acid) (PLGA) as a carrier to encapsulate BDNF. The resulting microspheres were then modified with tannic acid (TA). The polysaccharides-based hydrogel composed of oxidized dextran (Dex) and hyaluronic acid-hydrazide (HA) was mixed with TA-modified microspheres to form the ultimate BDNF@TA-PLGA/Dex-HA hydrogel.Our results showed that the hydrogel had properties similar to natural spinal cords. Specifically, the hydrogel had soft mechanical properties and high electrical conductivity. The cross-sectional morphology of the hydrogel exhibited a continuous and porous structure. The swelling and degradation behaviors of the Dex-HA hydrogel in vitro indicated the incorporation of TA into hydrogel matrix could improve the stability of the hydrogel matrix as well as extend the release time of BDNF from the matrix. Furthermore, results from immunostaining and real-time PCR demonstrated that BDNF@TA-PLGA/Dex-HA hydrogel could promote the differentiation of neural stem cells (NSCs) into neurons and inhibit astrocyte differentiation in vitro. These results show the great potential of this hydrogel as a biomimetic material in SCI regeneration.

Novel design of (PEG-ylated)PAMAM-based nanoparticles for sustained delivery of BDNF to neurotoxin-injured differentiated neuroblastoma cells

Brain-derived neurotrophic factor (BDNF) is essential for the development and function of human neurons, therefore it is a promising target for neurodegenerative disorders treatment. Here, we studied BDNF-based electrostatic complex with dendrimer nanoparticles encapsulated in polyethylene glycol (PEG) in neurotoxin-treated, differentiated neuroblastoma SH-SY5Y cells, a model of neurodegenerative mechanisms. PEG layer was adsorbed at dendrimer-protein core nanoparticles to decrease their cellular uptake and to reduce BDNF-other proteins interactions for a prolonged time. Cytotoxicity and confocal microscopy analysis revealed PEG-ylated BDNF-dendrimer nanoparticles can be used for continuous neurotrophic factor delivery to the neurotoxin-treated cells over 24 h without toxic effect. We offer a reliable electrostatic route for efficient encapsulation and controlled transport of fragile therapeutic proteins without any covalent cross-linker; this could be considered as a safe drug delivery system. Understanding the polyvalent BDNF interactions with dendrimer core nanoparticles offers new possibilities for design of well-ordered protein drug delivery systems.

Neuroprotection of Retinal Ganglion Cells with AAV2-BDNF Pretreatment Restoring Normal TrkB Receptor Protein Levels in Glaucoma.

Intravitreal delivery of brain-derived neurotrophic factor (BDNF) by injection of recombinant protein or by gene therapy can alleviate retinal ganglion cell (RGC) loss after optic nerve injury (ONI) or laser-induced ocular hypertension (OHT). In models of glaucoma, BDNF therapy can delay or halt RGCs loss, but this protection is time-limited. The decreased efficacy of BDNF supplementation has been in part attributed to BDNF TrkB receptor downregulation. However, whether BDNF overexpression causes TrkB downregulation, impairing long-term BDNF signaling in the retina, has not been conclusively proven. After ONI or OHT, when increased retinal BDNF was detected, a concomitant increase, no change or a decrease in TrkB was reported. We examined quantitatively the retinal concentrations of the TrkB protein in relation to BDNF, in a course of adeno-associated viral vector gene therapy (AAV2-BDNF), using a microbead trabecular occlusion model of glaucoma. We show that unilateral glaucoma, with intraocular pressure ( IOP) increased for five weeks, leads to a bilateral decrease of BDNF in the retina at six weeks, accompanied by up to four-fold TrkB upregulation, while a moderate BDNF overexpression in a glaucomatous eye triggers changes that restore normal TrkB concentrations, driving signaling towards long-term RGCs neuroprotection. We conclude that for glaucoma therapy, the careful selection of the appropriate BDNF concentration is the main factor securing the long-term responsiveness of RGCs and the maintenance of normal TrkB levels.

Intranasal delivery of BDNF rescues memory deficits in AD11 mice and reduces brain microgliosis

A decrease in brain-derived neurotrophic factor (BDNF), a neurotrophin essential for synaptic function, plasticity and neuronal survival, is evident early in the progression of Alzheimer’s disease (AD), being apparent in subjects with mild cognitive impairment or mild AD, and both proBDNF and mature BDNF levels are positively correlated with cognitive measures. BDNF delivery is, therefore, considered of great interest as a potentially useful therapeutic strategy to contrast AD. Invasive BDNF administration has indeed been recently used in animal models of AD with promising results in rescuing memory deficits, synaptic density and cell loss. Here, we tested whether non-invasive intranasal administration of different BDNF concentrations after the onset of cognitive and anatomical deficits (6 months of age) could rescue neuropathological and memory deficits in AD11 mice, a model of NGF deprivation-induced neurodegeneration. In addition to AD hallmarks, we investigated BDNF effects on microglia presence in the brain of AD11 mice, since alterations in microglia activation have been associated with ageing-related cognitive decline and with the progression of neurodegenerative diseases, including AD. We found that intranasal delivery of 42 pmol BDNF (1 μM), but not PBS, was sufficient to completely rescue performance of AD11 mice both in the object recognition test and in the object context test. No further improvement was obtained with 420 pmol (10 μM) BDNF dose. The strong improvement in memory performance in BDNF-treated mice was not accompanied by an amelioration of AD-like pathology, Aβ burden, tau hyperphosphorylation and cholinergic deficit, but there was a dramatic decrease of CD11b immunoreactive brain microglia. These results reinforce the potential therapeutic uses of BDNF in AD and the non-invasive intranasal route as an effective delivery strategy of BDNF to the brain. They also strengthen the connection between neuroinflammation and neurodegenerative dementia and suggest microglia as a possible mediator of BDNF therapeutic actions in the brain.

Biomimetic surface delivery of NGF and BDNF to enhance neurite outgrowth.

Treatment for peripheral nerve injuries includes the use of autografts and nerve guide conduits (NGCs). However, outcomes are limited, and full recovery is rarely achieved. The use of nerve scaffolds as a platform to surface immobilize neurotrophic factors and deliver locally is a promising approach to support neurite and nerve outgrowth after injury. We report on a bioactive surface using functional amine groups, to which heparin binds electrostatically. X-ray photoelectron spectroscopy analysis was used to characterize the presence of nitrogen and sulfur. Nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) were bound by electrostatic interaction to heparin, and the release profile evaluated by enzyme-linked immunosorbent assay, which showed that ca. 1% of NGF was released from each of the bioactive surface within 7 days. Furthermore, each surface showed a maximum release of 97% of BDNF. Neurotrophin release on neurite outgrowth was evaluated by primary dorsal root ganglion with a maximum neurite growth response in vitro of 1,075 µm detected for surfaces immobilized with NGF at 1 ng/ml. In summary, the study reports on the design and construction of a biomimetic platform to deliver NGF and BDNF using physiologically low concentrations of neurotrophin. The platform is directly applicable and scalable for improving the regenerative ability of existing NGCs and scaffolds.

A Study of Antidepressant Effect and Mechanism on Intranasal Delivery of BDNF-HA2TAT/AAV to Rats with Post-Stroke Depression.

AimPost-stroke depression (PSD) is one of the most frequent neuropsychiatric disorders associated with stroke characterized by depression. The neuroplasticity hypothesis postulates that loss of brain-derived neurotrophic factor (BDNF) plays a major role in pathophysiology of PSD, and restoration of it may represent a critical mechanism underlying antidepressant efficacy.MethodsIn previous studies, we designed a new fusion gene, HA2TAT-BDNF, and cloned it into adenovirus associated virus (AAV) to construct the BDNF-HA2TAT/AAV for the delivery of BDNF to central nervous system (CNS) via nose-brain pathway. In this study, we used it to explore the antidepressant effects on PSD rats through behavioral and various histological methods, and try to find out its specific mechanism.ResultsCompared with the control group, the PSD+AAV group showed decreased sucrose consumption percentage in the sucrose preference test (SPT) (P < 0.001) and prolonged immobility in the forced swimming test (FST) (P=0.000). However, the nasal administration of BDNF-HA2TAT/AAV reversed results of these two behavioral tests (P>0.05, P >0.05), showing an adequate antidepressant effect. Compared with the control group, the concentrations of BDNF mRNA and protein in the hippocampus (P< 0.05, P < 0.01) and prefrontal cortex (P < 0.01, P < 0.01) of PSD rats both decreased. Increased BDNF mRNA and protein expression was observed in the prefrontal cortex (P > 0.05, P < 0.05), without notable change in the hippocampus (P < 0.05, P < 0.001) of PSD+BDNF rats.ConclusionThese results suggest that BDNF reductions in the prefrontal cortex and hippocampus are associated with the development of post-stroke depression, and that increased levels of BDNF in the prefrontal cortex could be used as a therapeutic target to treat PSD. However, the exact mechanism of BDNF action remains unclear in this regard, hindering the wider application of our method. We expect that our research could facilitate the exploration of pathogenesis and the new treatment method of PSD.

Ultrasound-responsive neurotrophic factor-loaded microbubble- liposome complex: Preclinical investigation for Parkinson's disease treatment

Ultrasound-targeted microbubble destruction (UTMD) in conjunction with neurotrophic factors (NFs) gene delivery has the potential to facilitate the penetration of therapeutic genes into the brain for neuroprotective therapy against neurodegenerative diseases. We previously presented a gene delivery system that conjugates gene-carrying liposomes with microbubbles (MBs) to open the blood-brain barrier (BBB) for the delivery of genes into the brain. Since both glia cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) can protect dopaminergic neurons from neurotoxicity demonstrated in Parkinson's disease (PD) animal models, the present study seeks (1) to develop a novel gene-nanocarrier MB complex carrying BDNF or GDNF gene and (2) to protect dopaminergic neurons in a mouse model of PD via the proposed UTMD system. In the experimental design, PD animals received treatment that delivered GDNF, BDNF, or combined GDNF/BDNF in conjunction with UTMD treatment, and pathological changes in dopamine neurons were histologically examined. Rotarod assay was employed to evaluate the motor behavior. Our results demonstrate that either BDNF or GDNF gene delivery via the UTMD system provides a neuroprotective effect with evidence of improvements of behavioral deficits, decreased calcium influx, GFAP and caspase 3 expression, and rescued dopaminergic neuronal loss. Simultaneously performing GDNF/BDNF gene delivery did not show additional benefits beyond individually delivering BDNF or GDNF genes, possibly due to a hampering effect of simultaneous GDNF/BDNF competing expressions, thus dampening the overall therapeutic effect. In conclusion, these results suggest that UTMD in conjunction with delivery of GDNF or BDNF gene can synergistically serve as an effective gene therapy strategy for neurodegenerative diseases.

BDNF as a Promising Therapeutic Agent in Parkinson’s Disease

Brain-derived neurotrophic factor (BDNF) promotes neuroprotection and neuroregeneration. In animal models of Parkinson’s disease (PD), BDNF enhances the survival of dopaminergic neurons, improves dopaminergic neurotransmission and motor performance. Pharmacological therapies of PD are symptom-targeting, and their effectiveness decreases with the progression of the disease; therefore, new therapeutical approaches are needed. Since, in both PD patients and animal PD models, decreased level of BDNF was found in the nigrostriatal pathway, it has been hypothesized that BDNF may serve as a therapeutic agent. Direct delivery of exogenous BDNF into the patient’s brain did not relieve the symptoms of disease, nor did attempts to enhance BDNF expression with gene therapy. Physical training was neuroprotective in animal models of PD. This effect is mediated, at least partly, by BDNF. Animal studies revealed that physical activity increases BDNF and tropomyosin receptor kinase B (TrkB) expression, leading to inhibition of neurodegeneration through induction of transcription factors and expression of genes related to neuronal proliferation, survival, and inflammatory response. This review focuses on the evidence that increasing BDNF level due to gene modulation or physical exercise has a neuroprotective effect and could be considered as adjunctive therapy in PD.

Non-invasive Brain Delivery and Efficacy of BDNF in APP/PS1 Transgenic Mice as a Model of Alzheimer's Disease.

Neurotrophic factors such as brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) have been demonstrated for their potential as a neuroregenerative treatment of Alzheimer's disease (AD). Unfortunately, most proteins cannot be effectively delivered into the brain from the blood stream due to the presence of the blood-brain barrier (BBB). In this study, we delivered BDNF using ADTC5 as BBB modulator (BBBM) into the brains of transgenic APP/PS1 mice, a mouse model for AD. As controls, two groups of APP/PS1 mice were treated with BDNF alone and vehicle, respectively. All three groups were subjected to behavioral/cognitive assessments in Y-maze and novel object recognition (NOR) tests as well as evaluation of the brain markers activated by BDNF. The results showed that BDNF + ADTC5 group performed significantly better in both the Y-maze and NOR assessments compared to mice that received BDNF alone or vehicle. In addition, significant upregulations of NG2 receptors as well as EGR1 and ARC mRNA transcripts were observed in the brain cortex of mice treated with BDNF + ADTC5, further indicating the efficacy of delivered BDNF in the brain. There were high plaque loads in all groups of mice, suggesting no influence of BDNF on the plaque formation. In summary, ADTC5 can deliver BDNF into the brains of APP/PS1 mice and the activity of BDNF in improving cognitive function was likely due to improvement in synaptic plasticity via NG2 glia cells and not by reducing the plaque load.

Noninvasive Brain Delivery and Efficacy of BDNF to Stimulate Neuroregeneration and Suppression of Disease Relapse in EAE Mice.

The number of FDA-approved protein drugs (biologics), such as antibodies, antibody-drug conjugates, hormones, and enzymes, continues to grow at a rapid rate; most of these drugs are used to treat diseases of the peripheral body. Unfortunately, most of these biologics cannot be used to treat brain diseases such as Alzheimer's disease (AD), multiple sclerosis (MS), and brain tumors in a noninvasive manner due to their inability to permeate the blood-brain barrier (BBB). Therefore, there is a need to develop an effective method to deliver protein drugs into the brain. Here, we report a proof of concept to deliver a recombinant brain-derived neurotrophic factor (BDNF) to the brains of healthy and experimental autoimmune encephalomyelitis (EAE) mice via intravenous (iv) injections by co-administering BDNF with a BBB modulator (BBBM) peptide ADTC5. Western blot evaluations indicated that ADTC5 enhanced the brain delivery of BDNF in healthy SJL/elite mice compared to BDNF alone and triggered the phosphorylation of TrkB receptors in the brain. The EAE mice treated with BDNF + ADTC5 suppressed EAE relapse compared to those treated with BDNF alone, ADTC5 alone, or vehicle. We further demonstrated that brain delivery of BDNF induced neuroregeneration via visible activation of oligodendrocytes, remyelination, and ARC and EGR1 mRNA transcript upregulation. In summary, we have demonstrated that ADTC5 peptide modulates the BBB to permit noninvasive delivery of BDNF to exert its neuroregeneration activity in the brains of EAE mice.

Focused ultrasound enhanced intranasal delivery of brain derived neurotrophic factor produces neurorestorative effects in a Parkinson\u2019s disease mouse model

Focused ultrasound-enhanced intranasal (IN + FUS) delivery is a noninvasive approach that utilizes the olfactory pathway to administer pharmacological agents directly to the brain, allowing for a more homogenous distribution in targeted locations compared to IN delivery alone. However, whether such a strategy has therapeutic values, especially in neurodegenerative disorders such as Parkinson’s disease (PD), remains to be established. Herein, we evaluated whether the expression of tyrosine hydroxylase (TH), the rate limiting enzyme in dopamine catalysis, could be enhanced by IN + FUS delivery of brain-derived neurotrophic factor (BDNF) in a toxin-based PD mouse model. Mice were put on the subacute dosing regimen of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), producing bilateral degeneration of the nigrostriatal pathway consistent with early-stage PD. MPTP mice then received BDNF intranasally followed by multiple unilateral FUS-induced blood-brain barrier (BBB) openings in the left basal ganglia for three consecutive weeks. Subsequently, mice were survived for two months and were evaluated morphologically and behaviorally to determine the integrity of their nigrostriatal dopaminergic pathways. Mice receiving IN + FUS had significantly increased TH immunoreactivity in the treated hemisphere compared to the untreated hemisphere while mice receiving only FUS-induced BBB opening or no treatment at all did not show any differences. Additionally, behavioral changes were only observed in the IN + FUS treated mice, indicating improved motor control function in the treated hemisphere. These findings demonstrate the robustness of the method and potential of IN + FUS for the delivery of bioactive factors for treatment of neurodegenerative disorder.

Controlled Delivery of Brain Derived Neurotrophic Factor and Gold-Nanoparticles from Chitosan/TPP Nanoparticles for Tissue Engineering Applications

Brain derived neurotrophic factor (BDNF) is highly effective in the treatment of various diseases, and selected for growth factor delivery system. Also, gold-nanoparticles (AuNPs) plays the paramount role in diagnosis and treatment of diseases. The aim of this study is to encapsulate BDNF and AuNPs in chitosan nanoparticles and its effect on human adipose derived stem cells (h-ADSCs) proliferation was evaluated. The ratio of 1:3 chitosan/TPP was determined as the optimum ratio, BDNF or AuNPs were added to 0.1% chitosan solution for preparation of nanoparticles. The release rate of BDNF and AuNPs were assessed by Bradford test and inductive coupled plasma optical emission spectrometry technique, respectively. In this study, BDNF and AuNPs loading efficiency were 89.46 ± 2.77 (%) and 93.8 ± 2.12 (%), respectively. The kinetic release of BDNF is 83.28 ± 2.22 (%) and AuNPs release rate was 48.4 ± 0.108(%), during the 7 days. MTT findings demonstrated h-ADSCs viability in the presence encapsulated BDNF and AuNPs is significantly more than control group on 3 and 7 days (p < 0.05). These findings indicate the controlled release of encapsulated BDNF and AuNPs, and synergist effects of nanoparticles on h-ADSCs viability; it suggests an efficient delivery of BDNF and AuNPs, for tissue engineering.

BDNF-producing, amyloid β-specific CD4 T cells as targeted drug-delivery vehicles in Alzheimer's disease.

BackgroundThe delivery of therapeutic proteins to selected sites within the central nervous system (CNS) parenchyma is a major challenge in the treatment of various neurodegenerative disorders. As brain-derived neurotrophic factor (BDNF) is reduced in the brain of people with Alzheimer's disease (AD) and its administration has shown promising therapeutic effects in mouse model of the disease, we generated a novel platform for T cell-based BDNF delivery into the brain parenchyma.MethodsWe generated amyloid beta-protein (Aβ)-specific CD4 T cells (Aβ-T cells), genetically engineered to express BDNF, and injected them intracerebroventricularly into the 5XFAD mouse model of AD.FindingsThe BDNF-secreting Aβ-T cells migrated efficiently to amyloid plaques, where they significantly increased the levels of BDNF, its receptor TrkB, and various synaptic proteins known to be reduced in AD. Furthermore, the injected mice demonstrated reduced levels of beta-secretase 1 (BACE1)—a protease essential in the cleavage process of the amyloid precursor protein—and ameliorated amyloid pathology and inflammation within the brain parenchyma.InterpretationA T cell-based delivery of proteins into the brain can serve as a platform to modulate neurotoxic inflammation and to promote neuronal repair in neurodegenerative diseases.

Graphene oxide-PLGA hybrid nanofibres for the local delivery of IGF-1 and BDNF in spinal cord repair

Spinal cord injury (SCI) can lead to permanent and severe functional impairment below the lesion level and is still one of the most challenging clinical problems. The treatment of SCI has progressed with the development of tissue engineering techniques. Insulin-like growth factor 1 (IGF-1) and brain-derived neurotrophic factor (BDNF) are growth factors closely related to nerve regeneration. In this study, IGF-1 and BDNF were successfully immobilized on biodegradable graphene oxide (GO)-incorporated PLGA (PLGA/GO) electrospun nanofibres. The effect of PLGA/GO nanofibres with immobilized IGF-1 and BDNF on neurogenesis was investigated in vitro and in vivo utilizing MTT assays, immunofluorescence, motor function detection and histology observations. We demonstrated that PLGA/GO nanofibres loaded with IGF-1 and BDNF not only protected NSCs from oxidative stress induced by H2O2 but also enhanced NSC proliferation and neuronal differentiation in vitro. The in vivo study of an SCI animal model demonstrated that local delivery of IGF-1 and BDNF immobilized to PLGA/GO nanofibres significantly improved functional locomotor recovery, reduced cavity formation and increased the number of neurons at the injury site. Our study indicated that PLGA/GO is an effective carrier for IGF-1 and BDNF delivery and that immobilization of IGF-1 and BDNF onto PLGA/GO nanofibres has a great potential as a nerve implant for spinal cord injury applications.

Local Delivery of Brain-Derived Neurotrophic Factor Enables Behavioral Recovery and Tissue Repair in Stroke-Injured Rats.

We developed a biocomposite that can be mixed with brain-derived neurotrophic factor (BDNF) and dispensed onto the surface of the brain to provide sustained, local release of the protein using a procedure that avoids additional damage to neural tissue. The composite is simple to fabricate, and provides sustained release without nanoparticle encapsulation of BDNF, preserving material and protein bioactivity. We demonstrate that when delivered epicortically to a rat model of stroke, this composite allows BDNF to diffuse into the brain, resulting in enhanced behavioral recovery and synaptic plasticity in the contralesional hemisphere.

Conditional BDNF Delivery from Astrocytes Rescues Memory Deficits, Spine Density, and Synaptic Properties in the 5xFAD Mouse Model of Alzheimer Disease.

It has been well documented that neurotrophins, including brain-derived neurotrophic factor (BDNF), are severely affected in Alzheimer's disease (AD), but their administration faces a myriad of technical challenges. Here we took advantage of the early astrogliosis observed in an amyloid mouse model of AD (5xFAD) and used it as an internal sensor to administer BDNF conditionally and locally. We first demonstrate the relevance of BDNF release from astrocytes by evaluating the effects of coculturing WT neurons and BDNF-deficient astrocytes. Next, we crossed 5xFAD mice with pGFAP:BDNF mice (only males were used) to create 5xFAD mice that overexpress BDNF when and where astrogliosis is initiated (5xF:pGB mice). We evaluated the behavioral phenotype of these mice. We first found that BDNF from astrocytes is crucial for dendrite outgrowth and spine number in cultured WT neurons. Double-mutant 5xF:pGB mice displayed improvements in cognitive tasks compared with 5xFAD littermates. In these mice, there was a rescue of BDNF/TrkB downstream signaling activity associated with an improvement of dendritic spine density and morphology. Clusters of synaptic markers, PSD-95 and synaptophysin, were also recovered in 5xF:pGB compared with 5xFAD mice as well as the number of presynaptic vesicles at excitatory synapses. Additionally, experimentally evoked LTP in vivo was increased in 5xF:pGB mice. The beneficial effects of conditional BDNF production and local delivery at the location of active neuropathology highlight the potential to use endogenous biomarkers with early onset, such as astrogliosis, as regulators of neurotrophic therapy in AD.SIGNIFICANCE STATEMENT Recent evidence places astrocytes as pivotal players during synaptic plasticity and memory processes. In the present work, we first provide evidence that astrocytes are essential for neuronal morphology via BDNF release. We then crossed transgenic mice (5xFAD mice) with the transgenic pGFAP-BDNF mice, which express BDNF under the GFAP promoter. The resultant double-mutant mice 5xF:pGB mice displayed a full rescue of hippocampal BDNF loss and related signaling compared with 5xFAD mice and a significant and specific improvement in all the evaluated cognitive tasks. These improvements did not correlate with amelioration of β amyloid load or hippocampal adult neurogenesis rate but were accompanied by a dramatic recovery of structural and functional synaptic plasticity.

Brain Derived Neurotrophic Factor (BDNF) Delays Onset of Pathogenesis in Transgenic Mouse Model of Spinocerebellar Ataxia Type 1 (SCA1).

Spinocerebellar ataxia type 1 (SCA1) is a fatal neurodegenerative disease caused by an abnormal expansion of CAG repeats in the Ataxin-1 (ATXN1) gene and characterized by motor deficits and cerebellar neurodegeneration. Even though mutant ATXN1 is expressed from an early age, disease onset usually occurs in patient’s mid-thirties, indicating the presence of compensatory factors that limit the toxic effects of mutant ATXN1 early in disease. Brain derived neurotrophic factor (BDNF) is a growth factor known to be important for the survival and function of cerebellar neurons. Using gene expression analysis, we observed altered BDNF expression in the cerebella of Purkinje neuron specific transgenic mouse model of SCA1, ATXN1[82Q] mice, with increased expression during the early stage and decreased expression in the late stage of disease. We therefore investigated the potentially protective role of BDNF in early stage SCA1 through intraventricular delivery of BDNF via ALZET osmotic pumps. Extrinsic BDNF delivery delayed onset of motor deficits and Purkinje neuron pathology in ATXN1[82Q] mice supporting its use as a novel therapeutic for SCA1.

Intracerebral Delivery of Brain-Derived Neurotrophic Factor Using HyStem®-C Hydrogel Implants Improves Functional Recovery and Reduces Neuroinflammation in a Rat Model of Ischemic Stroke.

Ischemic stroke is a leading cause of death and disability worldwide. Potential therapeutics aimed at neural repair and functional recovery are limited in their blood-brain barrier permeability and may exert systemic or off-target effects. We examined the effects of brain-derived neurotrophic factor (BDNF), delivered via an extended release HyStem®-C hydrogel implant or vehicle, on sensorimotor function, infarct volume, and neuroinflammation, following permanent distal middle cerebral artery occlusion (dMCAo) in rats. Eight days following dMCAo or sham surgery, treatments were implanted directly into the infarction site. Rats received either vehicle, BDNF-only (0.167 µg/µL), hydrogel-only, hydrogel impregnated with 0.057 µg/µL of BDNF (hydrogel + BDNFLOW), or hydrogel impregnated with 0.167 µg/µL of BDNF (hydrogel + BDNFHIGH). The adhesive removal test (ART) and 28-point Neuroscore (28-PN) were used to evaluate sensorimotor function up to two months post-ischemia. The hydrogel + BDNFHIGH group showed significant improvements on the ART six to eight weeks following treatment and their behavioral performance was consistently greater on the 28-PN. Infarct volume was reduced in rats treated with hydrogel + BDNFHIGH as were levels of microglial, phagocyte, and astrocyte marker immunoexpression in the corpus striatum. These data suggest that targeted intracerebral delivery of BDNF using hydrogels may mitigate ischemic brain injury and restore functional deficits by reducing neuroinflammation.

Brain-derived neurotrophic factor in peripheral blood mononuclear cells and stroke outcome.

There are a great number of arguments suggesting that BDNF could be involved in stroke recovery dependent of neuroplasticity. Methods that can enhance BDNF levels in the ischemic brain could therefore have great clinical value. Peripheral blood mononuclear cells (PBMC) that contain BDNF and infiltrate early and sustainably the ischemic brain might be used as a cellular vector to deliver BDNF to the ischemic brain and consequently promote recovery. This work is important in this field to show if this BDNF derived from BDNF could exert a positive action on stroke recovery. Our main results showed that a high BDNF level at day 3 after hospital admission was associated with a 12.4 fold increase in favorable outcome after adjusting for still recognized prognostic markers. The new information in this field is this finding identifies PBMC as an attractive cellular vector to deliver BDNF to the ischemic brain.

Neuroprotection of retinal ganglion cells by a novel gene therapy construct that achieves sustained enhancement of brain-derived neurotrophic factor/tropomyosin-related kinase receptor-B signaling

Previous studies have demonstrated that intravitreal delivery of brain-derived neurotrophic factor (BDNF) by injection of recombinant protein or by gene therapy can alleviate retinal ganglion cell (RGC) loss after optic nerve injury. BDNF gene therapy can improve RGC survival in experimental models of glaucoma, the leading cause of irreversible blindness worldwide. However, the therapeutic efficacy of BDNF supplementation alone is time limited at least in part due to BDNF receptor downregulation. Tropomyosin-related receptor kinase-B (TrkB) downregulation has been reported in many neurological diseases including glaucoma, potentially limiting the effect of sustained or repeated BDNF delivery.Here, we characterize a novel adeno-associated virus (AAV) gene therapy (AAV2 TrkB-2A-mBDNF) that not only increases BDNF production but also improves long-term neuroprotective signaling by increasing expression of the BDNF receptor (TrkB) within the inner retina. This approach leads to significant and sustained elevation of survival signaling pathways ERK and AKT within RGCs over 6 months and avoids the receptor downregulation which we observe with treatment with AAV2 BDNF alone. We validate the neuroprotective efficacy of AAV2 TrkB-2A-mBDNF in a mouse model of optic nerve injury, where it outperforms conventional AAV2 BDNF or AAV2 TrkB therapy, before showing powerful proof of concept neuroprotection of RGCs and axons in a rat model of chronic intraocular pressure (IOP) elevation. We also show that there are no adverse effects of the vector on retinal structure or function as assessed by histology and electroretinography in young or aged animals. Further studies are underway to explore the potential of this vector as a candidate for progression into clinical studies to protect RGCs in patients with glaucoma and progressive visual loss despite conventional IOP-lowering treatment.