Neuroprotective potential of pleiotrophin overexpression in the striatonigral pathway compared with overexpression in both the striatonigral and nigrostriatal pathways.

Intrastriatal injection of recombinant adeno-associated viral vector serotype 2/1 (rAAV2/1) to overexpress the neurotrophic factor pleiotrophin (PTN) provides neuroprotection for tyrosine hydroxylase immunoreactive (THir) neurons in the substantia nigra pars compacta (SNpc), increases THir neurite density in the striatum (ST) and reverses functional deficits in forepaw use following 6-hydroxydopamine (6-OHDA) toxic insult. Glial cell line-derived neurotrophic factor (GDNF) gene transfer studies suggest that optimal neuroprotection is dependent on the site of nigrostriatal overexpression. The present study was conducted to determine whether enhanced neuroprotection could be accomplished via simultaneous rAAV2/1 PTN injections into the ST and SN compared with ST injections alone. Rats were unilaterally injected in the ST alone or injected in both the ST and SN with rAAV2/1 expressing either PTN or control vector. Four weeks later, all rats received intrastriatal injections of 6-OHDA. Rats were euthanized 6 or 16 weeks relative to 6-OHDA injection. A novel selective total enumeration method to estimate nigral THir neuron survival was validated to maintain the accuracy of stereological assessment. Long-term nigrostriatal neuroprotection and functional benefits were only observed in rats in which rAAV2/1 PTN was injected into the ST alone. Results suggest that superior preservation of the nigrostriatal system is provided by PTN overexpression delivered to the ST and restricted to the ST and SN pars reticulata and is not improved with overexpression of PTN within SNpc neurons.

Characterisation of functional deficits induced by AAV overexpression of alpha-synuclein in rats.

Background: In the last decades different preclinical animal models of Parkinson's disease (PD) have been generated, aiming to mimic the progressive neuronal loss of midbrain dopaminergic (DA) cells as well as motor and non-motor impairment. Among all the available models, AAV-based models of human alpha-synuclein (h-aSYN) overexpression are promising tools for investigation of disease progression and therapeutic interventions. Objectives: The goal with this work was to characterise the impairment in motor and non-motor domains following nigrostriatal overexpression of h-aSYN and correlate the behavioural deficits with histological assessment of associated pathology. Methods: Intranigral injection of an AAV9 expressing h-aSYN was compared with untreated animals, 6-OHDA and AAV9 expressing either no transgene or GFP. The animals were assessed on a series of simple and complex behavioural tasks probing motor and non-motor domains. Post-mortem neuropathology was analysed using immunohistochemical methods. Results: Overexpression of h-aSYN led to progressive degeneration of DA neurons of the SN and axonal terminals in the striatum (STR). We observed extensive nigral and striatal pathology, resembling that of human PD brain, as well as the development of stable progressive deficit in simple motor tasks and in non-motor domains such as deficits in motivation and lateralised neglect. Conclusions: In the present work we characterized a rat model of PD that closely resembles human PD pathology at the histological and behavioural level. The correlation of cell loss with behavioural performance enables the selection of rats which can be used in neuroprotective or neurorestorative therapies.

Lateralized deficits after unilateral AAV-vector based overexpression of alpha-synuclein in the midbrain of rats on drug-free behavioral tests.

BACKGROUND: Preclinical rodent models of Parkinson's aim to recapitulate some of the hallmarks of the disease as it presents in humans, including the progressive neuronal loss of dopaminergic neurons in the midbrain as well as the development of a behavioral phenotype. AAV vector-based models of alpha-synuclein overexpression are a promising tool to achieve such animal models with high face and predictive validity. OBJECTIVE: We have developed a preclinical rodent model of Parkinson's disease using an AAV-vector based overexpression of human alpha-synuclein. In the present work we characterize this model on a behavioral and histopathological level. METHODS: We use a AAV9 vector for transgene delivery to overexpress human alpha-synuclein under a CBA promoter. We compare the behavioral and histopathological changes to a AAV vector control group where the transgene was omitted and to that of a 6-OHDA lesion control. We assessed the behavioral performance of these three groups on a series of tests (Cylinder, Stepping, Corridor) at baseline and up to 22 weeks post-injection at which point we performed electrochemical recordings of dopamine kinetics. RESULTS: The overexpression of human alpha-synuclein led to the progressive manifestation of behavioral deficits on all three behavioral tests. This was accompanied with impaired dopamine release and reuptake kinetics as demonstrated by electrochemical detection methods. Histopathological quantifications corroborated the findings that we induced a moderate cell loss with remaining cells displaying pathological markers which are abundant in the brains of human PD patients. CONCLUSIONS: In the present work we developed a characterized a rat model of PD that closely mimics human disease development and pathology. Such model will be of great use for investigation of disease mechanisms and early therapeutic interventions.

Introducing a Novel Method of Intravascular Adeno-associated Virus-mediated Gene Delivery.

INTRODUCTION: Adeno-associated virus (AAV) has shown therapeutic potential as a viral vector in various studies of gene therapy. However, research on its use in targeting intravascular cells in a localized manner is lacking. We introduce a novel method to deliver various AAV serotypes intravascularly and examine their efficiency in transducing cells of the murine carotid artery. OBJECTIVE: The study aimed to examine the transduction efficiency of AAV-mediated gene delivery in cells of the murine carotid artery both with and without a fully-formed aneurysm. Results of infection were visualized with green fluorescence protein (GFP) reporter gene. METHODS: Naïve murine carotid artery or experimentally-induced murine carotid aneurysm was ligated distally and proximally. A small incision was made and 5 uL AAV2, AAV5, AAV8, or AAV9 was microsurgically injected and allowed to incubate for 30 min. Incision was closed and tissue was excised three weeks following AAV injection. Carotid artery or aneurysm tissue was excised and fixed in 4% paraformaldehyde solution. On both naïve carotid artery tissue and aneurysm tissue, GFP was visualized by immunofluorescence using antibody against GFP. RESULTS: Three out of four serotypes of AAV successfully transduced cells within both the murine aneurysm tissue and the naïve carotid artery tissue. AAV5- and AAV9-transduced aneurysm tissue showed the greatest presence of GFP, with AAV8 showing less overall fluorescence. AAV2 showed no fluorescence. CONCLUSION: AAV-mediated gene delivery is an effective way to transduce cells intravascularly with a transgene of interest. Our method can be generalized across a wide variety of studies to further research or treat other vascular disease.

RNA knockdown as a potential therapeutic strategy in Parkinson's disease.

Parkinson's disease is a prevalent progressive degenerative disorder of the elderly. There is a current need for novel therapeutic strategies because the standard levodopa pharmacotherapy is only temporarily efficacious. Recently, there have been some high-profile successful preclinical results obtained in animal models of neurological disorders using small interfering RNAs delivered by viral vectors. RNA interference can theoretically be applied to Parkinson's disease since over-expression of various proteins is known to kill the dopamine neurons of the substantia nigra in animal models and in familial forms of Parkinson's disease. Potential RNA interfering strategies and caveats are discussed in this review.