Insulin-like growth factor-II delays early but enhances late regeneration of skeletal muscle.
This study tested whether administration of insulin-like growth factor-II (IGF-II) enhances muscle regeneration. Rat biceps femoris muscle was damaged with notexin and then IGF-II was administered for up to 7 days. Results show that the proportion of nuclei containing or surrounded by immunoreactivity to MyoD, myogenin, and developmental myosin heavy chain (dMHC) is less in the IGF-II treatment group relative to the control group on days 1 (p=0.057), 2 (p=0.034), and 3 (p=0.047), respectively. This indicates a delay in muscle precursor cell (MPC) proliferation and differentiation with IGF-II administration. This effect was not associated with decreased binding capacity of the type 1 IGF receptor, as determined by receptor autoradiography in day 1 muscle sections (NS), but was associated with inhibition of phagocytic processes. The cross-sectional area of regenerating muscle fibers was significantly greater in the IGF-II treatment group than in the control group by day 7 (p=0.0092). The enhancing effect of IGF-II on late muscle regeneration, when the main process taking place is fiber enlargement, coincides with the period in which IGF-II is normally expressed by regenerating muscle, indicating that greater endogenous production of IGF-II would be associated with improved regeneration.
Kirk
Sonnie P
SP
Functional Muscle Genomics, AgResearch, Ruakura Agricultural Research Centre, Hamilton, New Zealand.
Oldham
Jenny M
JM
Jeanplong
Ferenc
F
Bass
John J
JJ
D000818:Animals; D001345:Autoradiography; D002454:Cell Differentiation; D002455:Cell Division; D002467:Cell Nucleus / Q000378:metabolism; D007150:Immunohistochemistry; D007335:Insulin-Like Growth Factor II / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism; D008297:Male; D032342:Muscle Cells / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000502:physiology / Q000648:ultrastructure; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D010446:Peptide Fragments / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D012038:Regeneration; D013234:Stem Cells / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D013997:Time Factors
D010446:Peptide Fragments; D007335:Insulin-Like Growth Factor II; D017526:Receptor, IGF Type 1