Elevated insulin-like growth factor (IGF) gene expression in sciatic nerves during IGF-supported nerve regeneration.
Nerve regeneration is augmented by neurotrophic activity, which has long been known to be increased in lesioned nerves. Of identified soluble nerve-derived neurotrophic factors, to date only insulin-like growth factors (IGFs) have been observed to increase the rate of axon regeneration in peripheral nerves. We report that IGF-I and IGF-II mRNA contents were significantly increased (P < 0.0005) distal to the site of crush in rat sciatic nerves, and decreased following axon regeneration. In transected nerves in which axon regeneration was prevented, IGF mRNAs remained elevated. IGF-I mRNAs per mg tissue were increased more in lesioned nerves than denervated muscles, whereas IGF-II mRNAs were increased more in denervated muscles than lesioned nerves. This suggested that IGF-I and IGF-II each play distinct regulatory roles during regeneration. These data bolster the hypothesis that increased IGF mRNA content in nerves supports the rate of nerve regeneration in mammals.
Glazner
G W
GW
Department of Physiology, Colorado State University, Fort Collins 80523.
Morrison
A E
AE
Ishii
D N
DN
D000818:Animals; D001369:Axons / Q000378:metabolism; D015870:Gene Expression; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D007335:Insulin-Like Growth Factor II / Q000235:genetics*; D008099:Liver / Q000378:metabolism; D008297:Male; D009132:Muscles / Q000378:metabolism; D009409:Nerve Crush; D009416:Nerve Regeneration; D012333:RNA, Messenger / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012584:Sciatic Nerve / Q000502:physiology* / Q000648:ultrastructure
D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II