Expression of biologically active human insulin-like growth factor-I following intramuscular injection of a formulated plasmid in rats.
Recent evidence has shown that insulin-like growth factor-I (IGF-I) plays an important role in the development, maintenance, and regeneration of peripheral nerves and skeletal muscle. IGF-I offers the potential to treat neuromuscular diseases in humans. We have developed a nonviral gene therapy method to express and produce localized and sustained therapeutic levels of IGF-I within target muscles by intramuscular injection of formulated plasmids. The purpose of the present study was to demonstrate that intramuscular injection of a plasmid encoding human IGF-I (hIGF-I) and engineered to restrict expression to skeletal muscle produces sustained local concentrations of biologically active hIGF-I. Normal rats received a single intramuscular injection of plasmids formulated as a complex with polyvinylpyrrolidone (PVP). Results show that hIGF-I mRNA and hIGF-I protein were detectable in the injected muscles for the duration of the study (28 days), whereas the hIGF-I protein was not detected in blood. Biological activity of hIGF-I was determined by immunodetection of a nerve-specific growth-associated protein, GAP-43, an indicator of motor neuron sprouting. Placement of human growth hormone (hGH) 3' untranslated region enhanced GAP-43 staining, probably due to improved secretion of hIGF-I. Enhanced immunoreactivity of GAP-43 was observed in muscles injected with the formulated hIGF-I plasmid when compared to controls. These results demonstrate that intramuscular injection of hIGF-I plasmid formulated as a complex with PVP produces a localized and sustained level of biologically active hIGF-I.
Alila
H
H
GeneMedicine, Inc. The Woodlands, TX 77381-4248, USA.
Coleman
M
M
Nitta
H
H
French
M
M
Anwer
K
K
Liu
Q
Q
Meyer
T
T
Wang
J
J
Mumper
R
R
Oubari
D
D
Long
S
S
Nordstrom
J
J
Rolland
A
A
D000818:Animals; D002460:Cell Line; D015870:Gene Expression; D018014:Gene Transfer Techniques; D005822:Genetic Vectors; D006801:Humans; D007273:Injections, Intramuscular; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis / Q000235:genetics*; D008297:Male; D051379:Mice; D010957:Plasmids / Q000008:administration & dosage; D051381:Rats; D011916:Rats, Inbred F344
D007334:Insulin-Like Growth Factor I