Intramuscular Injection Transfers Genes To Central Nervous System

Central Nervous System

Date: 7/26/2001

2001 JUL 26 - (NewsRx.com & NewsRx.net) -- by Deborah W. Heinrich, PhD, staff medical writer - Intramuscular injection allowed researchers in Singapore to transfect the central nervous system of rats. Gene therapy in the treatment of central nervous system (CNS) disorders faces the challenge of noninvasive gene delivery, a process that is hindered by the blood-brain barrier, researchers reported in the journal

Molecular Therapy

. "As neurons are capable of taking up exogenous particulates from the muscles that they innervate, we investigated the feasibility of achieving gene transfer in CNS neurons by peripheral intramuscular injection of plasmid DNA complexed with the cationic polymer polyethylenimine (PEI) in the rat hypoglossal system," reported S. Wang and colleagues at the National University of Singapore. To this end, they constructed a vector expressing the reporter gene luciferase under control of the strong Rous sarcoma virus promoter and injected it into the tongues of rats. After delivery of 20 µg of plasmid DNA, Wang and coworkers observed up to 4x10

⁶

RLU (total light units/mg protein) per brain stem. Using the same protocol to administer plasmid expressing beta-galactosidase instead of luciferase, they determined that expression was localized to hypoglossal motor neurons that innervate tongue muscles. After injection into the tongue, constructs were internalized at the nerve terminals. They then migrated by retrograde axonal transport to the neuronal cell bodies where they were detected in the brain stem with polymerase chain reaction assays ("Transgene expression in the brain stem effected by intramuscular injection of polyethylenimine/DNA complexes,"

Mol Ther

, 2001;3(5 Part 1):658-664). Brain stem expression of the apoptosis regulator bcl-2 under control of a strong, constitutive cytomegalovirus promoter after tongue injection was evaluated by Western blot analysis. Wang and colleagues first observed bcl-2 expression at 18 hours after injection and continued to detect expression for up to two weeks. Gene delivery using lipid transfection (GenePORTER and TransFast) was successful while delivery by polymers such as poly-L-lysine and chitosan were not. Thus, lipid transfection agents can deliver transgenes to the CNS via peripheral intramuscular injection. "The nonviral neuronal gene delivery method established in this study bypasses the blood-brain barrier and suggests a possible therapeutic strategy for noninvasive CNS gene transfer," concluded Wang and coauthors. The corresponding author for this study is S. Wang, National University of Singapore, Institute of Material Research and Engineering, Biomaterial Tissue Engineering Program, 3 Res Link, Singapore 117602, Singapore. A search at www.NewsRx.net using the search term "central nervous system injury" yielded seven articles in two specialized reports. Key points reported in this study include: * Peripheral intramuscular injection successfully transfers genes to the CNS * Vectors are internalized at nerve terminals and then migrate to neuronal cell bodies via retrograde axonal transport * Expression can be observed as early as 18 hours after injection and lasts for up to two weeks This article was prepared by Gene Therapy Weekly editors from staff and other reports.