title: Repeated intrathecal administration of plasmid DNA complexed with polyethylene glycol-grafted polyethylenimine led to prolonged transgene expression in the spinal cord.
abstract: Gene delivery into the spinal cord provides a potential approach to the treatment of spinal cord traumatic injury, amyotrophic lateral sclerosis, and spinal muscular atrophy. These disorders progress over long periods of time, necessitating a stable expression of functional genes at therapeutic levels for months or years. We investigated in this study the feasibility of achieving prolonged transgene expression in the rat spinal cord through repeated intrathecal administration of plasmid DNA complexed with 25 kDa polyethylenimine (PEI) into the lumbar subarachnoid space. With a single injection, DNA/PEI complexes could provide transgene expression in the spinal cord 40-fold higher than naked plasmid DNA. The transgene expression at the initial level persisted for about 5 days, with a low-level expression being detectable for at least 8 weeks. When repeated dosing was tested, a 70% attenuation of gene expression was observed following reinjection at a 2-week interval. This attenuation was associated with apoptotic cell death and detected even using complexes containing a noncoding DNA that did not mediate any gene expression. When each component of the complexes, PEI polymer or naked DNA alone, were tested in the first dosing, no reduction was found. Using polyethylene glycol (PEG)-grafted PEI for DNA complexes, no attenuation of gene expression was detected after repeated intrathecal injections, even in those rats receiving three doses, administered 2 weeks apart. Lumbar puncture is a routine and relatively nontraumatic clinical procedure. Repeated administration of DNA complexed with PEG-grafted PEI through this less invasive route may prolong the time span of transgene expression when needed, providing a viable strategy for the gene therapy of spinal cord disorders.
authors.affiliation: Molecular and Biomaterials Laboratory, Institute of Materials Research & Engineering, National University of Singapore, 3 Research Link, Singapore 117602, Republic of Singapore.
authors.forename: L
authors.initials: L
authors.lastname: Shi
authors.forename: G P
authors.initials: GP
authors.lastname: Tang
authors.forename: S J
authors.initials: SJ
authors.lastname: Gao
authors.forename: Y X
authors.initials: YX
authors.lastname: Ma
authors.forename: B H
authors.initials: BH
authors.lastname: Liu
authors.forename: Y
authors.initials: Y
authors.lastname: Li
authors.forename: J M
authors.initials: JM
authors.lastname: Zeng
authors.forename: Y K
authors.initials: YK
authors.lastname: Ng
authors.forename: K W
authors.initials: KW
authors.lastname: Leong
authors.forename: S
authors.initials: S
authors.lastname: Wang
mesh_terms: D000818:Animals; D017209:Apoptosis; D004247:DNA / Q000008:administration & dosage* / Q000009:adverse effects; D015870:Gene Expression; D015316:Genetic Therapy / Q000009:adverse effects / Q000379:methods*; D020287:In Situ Nick-End Labeling; D007278:Injections, Spinal; D008156:Luciferases / Q000235:genetics; D008297:Male; D011092:Polyethylene Glycols; D011094:Polyethyleneimine; D051381:Rats; D017208:Rats, Wistar; D013116:Spinal Cord / Q000378:metabolism* / Q000473:pathology; D013124:Spinal Injuries / Q000628:therapy*; D013997:Time Factors
chemical_list: D011092:Polyethylene Glycols; D011094:Polyethyleneimine; D004247:DNA; D008156:Luciferases