Objective/Rationale:
- In animal models of PD, brain injections of certain neurotrophic factors prevent degeneration of midbrain dopaminergic neurons.
- Clinical testing of brain injected gene vectors expressing these neurotrophic factors is underway.
- Frequent intranasal dosing with neurotrophic factor (protein) is also therapeutic in animal models.
- This project will test whether a single intranasal dose of gene vector expressing neurotrophic factor can also deliver potentially therapeutic amounts of neurotrophic factor to midbrain dopaminergic neurons.
Project Description:
- A gene vector will be used that expresses a neurotrophic factor with a tag that allows the gene vector derived neurotrophic factor to be distinguished from neurotrophic factor produced normally by the host brain.
- In control group rats, the gene vector will be injected into the striatum of the brain. Antibodies to the tag will be used to demonstrate that the vector derived neurotrophic factor is internalised and concentrated within midbrain dopaminergic neurons.
- In test group rats, the gene vector will be intranasally administered. Antibodies to the tag will be used test if the intranasal vector derived neurotrophic factor is similarly internalised and concentrated within midbrain dopaminergic neurons.
- A positive test outcome will demonstrate feasibility of developing a single dose intranasal PD treatment method.
Relevance to Diagnosis/Treatment of Parkinson’s Disease:
- A drug delivery problem is created by the fact that neurotrophic factors do not cross the blood brain barrier.
- While clinical studies using direct brain injection of gene vectors expressing neurotrophic factors has pointed to the safety of such vectors, brain injections requires hospitalization and attendant patient safety issues.
- Where this project demonstrates that intranasal gene vector administration may be substituted for direct brain injections of gene vectors, a Nasal PD Treatment may be envisaged.
Anticipated Outcome:
- A single dose Nasal PD Treatment is envisaged as a putative mass-market treatment to slow or halt the neurodegenerative process underlying PD.
- This product concept assumes that intranasal gene vector derived neurotrophic factor can cross the blood-brain barrier and contact target dopaminergic neurons in the brain proper.
- This project will test this assumption. If the assumption is proven, development and testing of the envisaged Nasal PD Treatment may be warranted.
Progress Report
Professor Waszczak reported that intranasal administration of GDNF has a neuroprotective efficacy in a pre-clinical model of Parkinson’s disease. Neuroprotection is also achieved by stereotaxic injection of gene vectors expression GDNF into the striatum. Other studies show that 125I-GDNF undergoes receptor mediated retrograde transport from the striatum to the midbrain dopaminergic neuron cell bodies. To distinguish gene-derived from endogenous GDNF, we used a gene vector expressing GDNF with an epitope tag. This gene vector was intranasally administered to test whether the intranasal (gene-derived) GDNF would appear within the midbrain dopaminergic neuron cell bodies.
Significant technical issues, such as delivery losses due to the “sticky” nature of gene vector, prevented reproducible adequate transfection following intranasal administration. While a sensitive histological/immunohistochemical procedure for visualizing trace GDNFflag in intracellular vesicles was developed, further studies are required to properly test whether intranasal, gene-derived, GDNF can make direct contact with receptors expressed by midbrain dopaminergic neurons.
April 2012
Researchers
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Ian Andrew Ferguson, PhD, MBA