Neuroprotection and Neurorestoration in the MPTP Model for Parkinson s Disease

Parkinson ist die häufigste neurodegenerative Erkrankung der Basal Ganglien und ist charakterisiert durch den progressiven Verlust dopaminerger Neurone in der substantia nigra pars compacta (SNpc). Der glial cell line-derived neurotrophic factor (GDNF) ist in präklinischen Studien als wichtiger Differenzierungs- und Überlebensfaktor für dopaminerge Neurone des Mittelhirnes identifiziert worden, jedoch hat seine Anwendung in klinischen Studien inkonistente Wirkung gezeigt. Aktuelle gentherapeutische Ansätze, in denen neurotrophe Faktoren neuronal exprimiert werden, könnten essentielle Sicherheitskriterien für zukünftige Strategien unter Verwendung höherer Dosierungen an jüngeren Patienten nicht erfüllen. Da neurotrophe Faktoren potente Modulatoren neuronaler Physiologie sind und daher, falls vorhanden in Hirnregionen, die nicht durch Parkinson betroffen sind, unerwünschte Nebeneffekte hervorrufen, scheint es vorteilhaft ihren Einfluss auf den unmittelbaren Bereich der betroffenen Hirnareale zu begrenzen. In der vorliegenden Studie wurde untersucht, ob adeno-associated virus (AAV)-5 Vektoren, injiziert ins Striatum von C57Bl/6-J Mäusen in hoher und niedriger Titerkonzentration, neuronale oder astrozytäre Produktion von GDNF hervorrufend, unterschiedliche Einflüsse auf die protektive und neurorestaurierende Wirkung von GDNF im 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridin (MPTP) Maus Modell der Parkinson Erkrankung zeigen. Die unilaterale, striatale Vektorapplikation resultierte in der Bereitstellung von biofunktionalem GDNF im Striatum und der SN beider Hirnhemisphären, wenn GDNF in Neuonen exprimiert worden ist; dies spricht somit für eine Verteilung von neuronalem GDNF abseits der Vektorapplikation. Im Gegensatz hierzu konnten die Effekte von GDNF durch die Expression in Astrozyten auf die injizierte Hemisphäre beschränkt werden. Astrozytäre GDNF Expression zeigte neuroprotektive Effekte unter Einsatz der niedrigen Titer Dosierung und repräsentiert somit eine sichere Alternative zu der aktuellen Gentherapiestrategie für Parkinson. Höhere Konzentrationen von GDNF übermitteln Signale wahrscheinlich durch zusätzliche, als die prototypischen rearranged during transfection (RET) und glycosyl phosphatidylinositol linked GDNF family (GFR)α Rezeptoren. Jedoch ergab die Verwendung von Mäusen mit einer Gewebe-spezifischen Ablation des Ret codierenden Gens (DAT-Retlx/lx Mäuse), dass es keine Alternative zu einer intakten GDNF-RET-vermittelten Signaltransduktion im nigrostriatalen System für das protektive Potential von GDNF nach MPTP Intoxikation gibt

Correction to: Ret is essential to mediate GDNF’s neuroprotective and neuroregenerative effect in a Parkinson disease mouse model

Correction to: Cell Death Dis. (2016) 7, e2359; https://doi.org/10.1038/cddis.2016.263; published online 08 September 2016</jats:p

Channeled polymeric scaffolds with polypeptide gel filling for lengthwise guidance of neural cells

CNS damages are often irreversible since neurons of the central nervous system are unable to regenerate after an injury. As a new strategy within the nervous system tissue engineering, multifunctional systems based on two different biomaterials to support axonal guidance in damaged connective tracts have been developed herein. These systems are composed of a channeled scaffold made of ethyl acrylate and hydroxyethyl acrylate copolymer, P(EA-co-HEA), with parallel tubular micropores, combined with an injectable and in situ gelable self-assembling polypeptide (RAD16-I) as pores filler. The polymer scaffold is intended to provide a three-dimensional context for axon growth; subsequently, its morphology and physicochemical parameters have been determined by scanning electron microscopy, density measurements and compression tests. Besides, the hydrogel acts as a cell-friendly nanoenvironment while it creates a gradient of bioactive molecules (nerve growth factor, NGF) along the scaffolds channels; the chemotactic effect of NGF has been evaluated by a quantitative ELISA assay. These multifunctional systems have shown ability to keep circulating NGF, as well as proper short-term in vitro biological response with glial cells and neural progenitors.The authors acknowledge funding through the Spanish Ministerio de Ciencia e Innovacion (MAT2011-28791-C03-02 and -03). Dr. J.M. Garcia Verdugo (Department of Comparative Neurobiology, Cavanilles Institute of Biodiversity and Evolutive Biology, Universitat de Valencia) is thanked for kindly providing the cells employed in this work.Conejero García, Á.; Vilarino-Feltrer, G.; Martínez Ramos, C.; Monleón Pradas, M.; Vallés Lluch, A. (2015). Channeled polymeric scaffolds with polypeptide gel filling for lengthwise guidance of neural cells. European Polymer Journal. 70:331-341. doi:10.1016/j.eurpolymj.2015.07.033S3313417

Ret is essential to mediate GDNF’s neuroprotective and neuroregenerative effect in a Parkinson disease mouse model

Glial cell line-derived neurotrophic factor (GDNF) is a potent survival and regeneration-promoting factor for dopaminergic neurons in cell and animal models of Parkinson disease (PD). GDNF is currently tested in clinical trials on PD patients with so far inconclusive results. The receptor tyrosine kinase Ret is the canonical GDNF receptor, but several alternative GDNF receptors have been proposed, raising the question of which signaling receptor mediates here the beneficial GDNF effects. To address this question we overexpressed GDNF in the striatum of mice deficient for Ret in dopaminergic neurons and subsequently challenged these mice with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Strikingly, in this established PD mouse model, the absence of Ret completely abolished GDNF’s neuroprotective and regenerative effect on the midbrain dopaminergic system. This establishes Ret signaling as absolutely required for GDNF’s effects to prevent and compensate dopaminergic system degeneration and suggests Ret activation as the primary target of GDNF therapy in PD

Adeno-associated Virus-mediated, Mifepristone-regulated Transgene Expression in the Brain.

Gene therapy, in its current configuration, is irreversible and does not allow control over transgene expression in case of side effects. Only few regulated vector systems are available, and none of these has reached clinical applicability yet. The mifepristone (Mfp)-regulated Gene Switch (GS) system is characterized by promising features such as being composed of mainly human components and an approved small-molecule drug as an inducer. However, it has not yet been evaluated in adeno-associated virus (AAV) vectors, neither has it been tested for applicability in viral vectors in the central nervous system (CNS). Here, we demonstrate that the GS system can be used successfully in AAV vectors in the brain, and that short-term induced glial cell line-derived neurotrophic factor (GDNF) expression prevented neurodegeneration in a rodent model of Parkinson's disease (PD). We also demonstrate repeated responsiveness to the inducer Mfp and absence of immunological tissue reactions in the rat brain. Human equivalent dosages of Mfp used in this study were lower than those used safely for treatment of psychiatric threats, indicating that the inducer could be safely applied in patients. Our results suggest that the GS system in AAV vectors is well suited for further development towards clinical applicability.Molecular Therapy-Nucleic Acids (2013) 2, e106; doi:10.1038/mtna.2013.35; published online 16 July 2013.peerReviewe

Generating fast logic circuits for m-select n-port round Robin arbitration

Due to copyright restrictions, the access to the full text of this article is only available via subscription.This paper generalizes the problem of Round Robin Arbitration (RRA) from 1-select to m-select (mRRA) and offers new circuit architectures for it. RRAs are found in networking equipment and computer systems with high throughput buses. We first propose fast/novel circuits for the fundamental problem of finding the first m 1's in an n-bit vector (from the left or right), i.e., generalized select Priority Encoder (mPE). The obvious solution to mPE is cascading m regular (1-select) PEs. Our solutions, however, are based on parallel prefix networks, where the nodes are replaced by "saturated adder"s. We use mPE as a building block to construct an mRRA, which has single cycle latency and can arbitrate up to m requests per clock cycle. We took two arbiters from the liter rature, TC-PPA (1-select) and 3DP2S (2-select), and generalized them into mRRAs, which we call mTC-PPA and 3DPmS-RRA. We wrote fully parameterized HDL code generators. Logic synthesis results show that mTC-PPA and 3DPmS-RRA are up to 100% faster than the cascade solution and have up to 65% smaller Area-Timing Products (ATP). Comparing mTC-PPA and 3DPmS-RRA, 3DPmS-RRA circuits are slightly faster than mTC-PPA on the average. In terms of ATP, mTC-PPA is superior by far and can be as small as 30% of 3DPmS-RRA

Efficient Gene Therapy for Parkinson's Disease Using Astrocytes as Hosts for Localized Neurotrophic Factor Delivery

Current gene therapy approaches for Parkinson’s disease (PD) deliver neurotrophic factors like glial cell line-derived neurotrophic factor (GDNF) or neurturin via neuronal transgene expression. Since these potent signaling-inducing neurotrophic factors can be distributed through long-distance neuronal projections to unaffected brain sites, this mode of delivery may eventually cause side effects. To explore a localized and thus potentially safer alternative for gene therapy of PD, we expressed GDNF exclusively in astrocytes and evaluated the efficacy of this approach in the mouse 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine (MPTP) and rat 6- hydroxy-dopamine (6-OHDA) models of PD. In terms of protection of dopaminergic cell bodies and projections, dopamine (DA) synthesis and behaviour, astrocyte- derived GDNF demonstrated the same efficacy as neuron-derived GDNF. In terms of safety, unilateral striatal GDNF expression in astrocytes did not result in delivery of bio-active GDNF to the contralateral hemispheres (potential off-target sites) as happened when GDNF was expressed in neurons. Thus, astrocytic GDNF expression represents a localized but efficient alternative to current gene therapeutic strategies for the treatment of PD, especially if viral vectors with enhanced tissue penetration are considered. Astrocytic neurotrophic factor expression may open new venues for neurotrophic factor-based gene therapy targeting severe diseases of the brain.peerReviewe