The role of growth factors in the regeneration of skeletal muscle
type: CreativeWork
description: The overall aim of this thesis was to examine myostatin and components of the insulin-like growth factor (IGF) axis during regeneration, to determine whether these factors were temporally regulated during regeneration, whether the absence or presence of growth hormone (GH) affected their levels, and lastly, whether the administration of exogenous IGF-II enhanced muscle regeneration. A histological approach was utilised, to determine specific effects on individual tissue types (regenerating muscle fibres, survivor muscle fibres, undamaged muscle fibres, and connective tissue) within damaged muscle. Regeneration was induced by injection of notexin, a myotoxin, into muscle. The first experiment tested the hypothesis that the IGFs and their receptors are regulated during muscle regeneration, and that the levels of these components are regulated by GH. The experimental model used was the GH-deficient dw/dw rat in which damage and subsequent regeneration were induced by a single intramuscular injection of notexin, then either GH- or saline-administered during the regeneration period. IGF-I and -II mRNA were assessed by in situ hybridisation, and binding determined by in vitro incubations with ¹²⁵I-IGF competed with unlabelled homologous IGF (specific binding). The presence of IGF binding proteins (IGFBPs) was determined by comparison of the specific binding of ¹²⁵I-IGF-I with the residual binding of ¹²⁵I-IGF-I following competition with des(l-3)IGF-I (which has a greatly reduced affinity for IGFBPs relative to IGF-I). Results of the localisation studies revealed up-regulation of IGF-I and -II specific binding in regenerating fibres at the time of myotube formation, and indicated the presence of IGFBPs in damaged muscle tissues at the same timepoint. IGF-I and -II mRNAs were significantly up-regulated in regenerating muscle fibres concurrent with myotube formation and enlargement, while IGF-I mRNA was also elevated in regenerating muscle fibres at the time of muscle precur…
abstract: The overall aim of this thesis was to examine myostatin and components of the insulin-like growth factor (IGF) axis during regeneration, to determine whether these factors were temporally regulated during regeneration, whether the absence or presence of growth hormone (GH) affected their levels, and lastly, whether the administration of exogenous IGF-II enhanced muscle regeneration. A histological approach was utilised, to determine specific effects on individual tissue types (regenerating muscle fibres, survivor muscle fibres, undamaged muscle fibres, and connective tissue) within damaged muscle. Regeneration was induced by injection of notexin, a myotoxin, into muscle. The first experiment tested the hypothesis that the IGFs and their receptors are regulated during muscle regeneration, and that the levels of these components are regulated by GH. The experimental model used was the GH-deficient dw/dw rat in which damage and subsequent regeneration were induced by a single intramuscular injection of notexin, then either GH- or saline-administered during the regeneration period. IGF-I and -II mRNA were assessed by in situ hybridisation, and binding determined by in vitro incubations with ¹²⁵I-IGF competed with unlabelled homologous IGF (specific binding). The presence of IGF binding proteins (IGFBPs) was determined by comparison of the specific binding of ¹²⁵I-IGF-I with the residual binding of ¹²⁵I-IGF-I following competition with des(l-3)IGF-I (which has a greatly reduced affinity for IGFBPs relative to IGF-I). Results of the localisation studies revealed up-regulation of IGF-I and -II specific binding in regenerating fibres at the time of myotube formation, and indicated the presence of IGFBPs in damaged muscle tissues at the same timepoint. IGF-I and -II mRNAs were significantly up-regulated in regenerating muscle fibres concurrent with myotube formation and enlargement, while IGF-I mRNA was also elevated in regenerating muscle fibres at the time of muscle precur…
author: Kirk, Sondra Powers
license: https://researchcommons.waikato.ac.nz/bitstreams/a9784085-6f6a-4b99-b4a5-2bf66a9eee23/download
date published: 2001
date modified: 2026-07-24T05:57:30Z
provider: University Waikato
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: The University of Waikato