Timing of human insulin-like growth factor-1 gene transfer in reinnervating laryngeal muscle.
OBJECTIVE
The authors have designed a rat laryngeal paralysis model to study gene transfer strategies using a muscle-specific expression system to enhance local delivery of human insulin-like growth factor-1 (hIGF-1). In preliminary studies, a nonviral vector containing the alpha-actin promoter and human hIGF-1 sequence produced both neurotrophic and myotrophic effects 1 month after single injection of plasmid formulation into paralyzed rat thyroarytenoid muscle in vivo. Based on these findings, it is hypothesized that the effects of hIGF-1 will enhance the results of laryngeal muscle innervation procedures. The timing of gene delivery relative to nerve repair is likely to be important, to optimize the results.


METHODS
Prospective analysis.


METHODS
The effects of nonviral gene transfer for the delivery of hIGF-1 were evaluated in rats treated immediately following recurrent laryngeal nerve transection and repair and in rats receiving a delayed treatment schedule, 30 days after nerve transection and repair. Gene transfer efficiency was determined using polymerase chain reaction and reverse transcriptase-polymerase chain reaction techniques. Muscle fiber diameter, motor endplate length, and percentage of motor endplates with nerve contact were examined to assess hIGF-1 trophic effects.


RESULTS
Compared with reinnervated untreated control samples, both early and delayed hIGF-1 transfer resulted in significant increase in muscle fiber diameter. Motor endplate length was significantly decreased and nerve/motor endplate contact was significantly increased following delayed gene transfer, but not after early treatment.


CONCLUSIONS
We infer from results of the study that delayed hIGF-1 gene transfer delivered by a single intramuscular injection will enhance the process of muscle reinnervation. The clinical relevance of these findings supports the future application of gene therapy using nonviral vectors for management of laryngeal paralysis and other peripheral nerve injuries.
Nakagawa
Hideki
H
Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University School of Medicine, University of Maryland Medical Center, Baltimore, Maryland, USA.
Shiotani
Akihiro
A
O'Malley
Bert W
BW
Coleman
Michael E
ME
Flint
Paul W
PW
D000818:Animals; D018014:Gene Transfer Techniques; D015316:Genetic Therapy / Q000379:methods*; D018970:Insulin-Like Growth Factor Binding Protein 1; D018969:Insulin-Like Growth Factor Binding Proteins / Q000235:genetics*; D007821:Laryngeal Muscles / Q000294:innervation*; D018485:Muscle Fibers, Skeletal / Q000473:pathology; D011257:Pregnancy Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014826:Vocal Cord Paralysis / Q000473:pathology* / Q000628:therapy*
C032231:IGFBP1 protein, human; D018970:Insulin-Like Growth Factor Binding Protein 1; D018969:Insulin-Like Growth Factor Binding Proteins; D011257:Pregnancy Proteins; D012333:RNA, Messenger