title: Evaluation of an AAV2-based rapamycin-regulated glial cell line-derived neurotrophic factor (GDNF) expression vector system.
abstract: Effective regulation of transgene product in anatomically circumscribed brain tissue is dependent on the pharmacokinetics of the regulating agent, the kinetics of transcriptional activation and degradation of the transgene product. We evaluated rapamycin-regulated AAV2-GDNF expression in the rat brain (striatum). Regulated (a dual-component system: AAV2-FBZhGDNF + AAV2-TF1Nc) and constitutive (CMV-driven) expression vectors were compared. Constitutively active AAV2-GDNF directed stable GDNF expression in a dose-dependent manner and it increased for the first month, thereafter reaching a plateau that was maintained over a further 3 months. For the AAV2-regGDNF, rapamycin was administered in a 3-days on/4-days off cycle. Intraperitoneal, oral, and direct brain delivery (CED) of rapamycin were evaluated. Two cycles of rapamycin at an intraperitoneal dose of 10 mg/kg gave the highest GDNF level (2.75±0.01 ng/mg protein). Six cycles at 3 mg/kg resulted in lower GDNF values (1.36±0.3 ng/mg protein). Interestingly, CED of rapamycin into the brain at a very low dose (50 ng) induced GDNF levels comparable to a 6-week intraperitoneal rapamycin cycle. This study demonstrates the effectiveness of rapamycin regulation in the CNS. However, the kinetics of the transgene in brain tissue, the regulator dosing amount and schedule are critical parameters that influence the kinetics of accumulation and zenith of the encoded transgene product.
authors: Department of Neurosurgery, University of California San Francisco, San Francisco, California, United States of America. piotr.hadaczek@ucsf.edu
authors: Piotr
authors: P
authors: Hadaczek
authors: Janine
authors: J
authors: Beyer
authors: Adrian
authors: A
authors: Kells
authors: Wade
authors: W
authors: Narrow
authors: William
authors: W
authors: Bowers
authors: Howard J
authors: HJ
authors: Federoff
authors: John
authors: J
authors: Forsayeth
authors: Krystof S
authors: KS
authors: Bankiewicz
mesh_terms: D000818:Animals; D000229:Dependovirus / Q000235:genetics*; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005822:Genetic Vectors / Q000235:genetics*; D051100:Glial Cell Line-Derived Neurotrophic Factor / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D007700:Kinetics; D008297:Male; D017072:Neostriatum / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020123:Sirolimus / Q000008:administration & dosage / Q000494:pharmacology*; D013048:Specimen Handling; D013997:Time Factors; D014161:Transduction, Genetic / Q000379:methods*
chemical_list: D051100:Glial Cell Line-Derived Neurotrophic Factor; D020123:Sirolimus