Investigation of the insulin-like growth factor system in the avian epiphyseal growth plate.
Components of the insulin-like growth factor (IGF) system were investigated in chondrocytes isolated from the avian growth plate. The genes for IGF-I, IGF-II, type 1 IGF receptor (IGF-R), IGF binding protein-2 (IGFBP-2), IGFBP-3, IGFBP-5 and IGFBP-7 were found to be expressed in both proliferative and hypertrophic chondrocytes. The expression of IGF-II in proliferative chondrocytes was extremely high relative to IGF-I. Although IGF-I expression was significantly increased in hypertrophic chondrocytes, the level was still low relative to IGF-II. In cell culture, IGF-I stimulated proteoglycan synthesis and increased the expression of Indian hedgehog (Ihh) and type X collagen, markers of chondrocyte differentiation. IGF-II was found to be equally efficacious in stimulating proteoglycan biosynthesis. These observations suggest that IGF-II may play a significant role in avian growth plate physiology, which is consistent with several reports on mammalian endochondral bone growth.
Leach
R M
RM
Department of Poultry Science, The Pennsylvania State University, 205 William L Henning Building, University Park, PA 16802, USA. lnr@psu.edu
Richards
M P
MP
Praul
C A
CA
Ford
B C
BC
McMurtry
J P
JP
D000818:Animals; D049109:Cell Proliferation; D002645:Chickens / Q000254:growth & development / Q000378:metabolism*; D019902:Chondrocytes / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology; D006132:Growth Plate / Q000378:metabolism*; D018969:Insulin-Like Growth Factor Binding Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D011509:Proteoglycans / Q000378:metabolism; D012313:RNA / Q000032:analysis; D013002:Somatomedins / Q000235:genetics / Q000378:metabolism
D018969:Insulin-Like Growth Factor Binding Proteins; D011509:Proteoglycans; D013002:Somatomedins; D012313:RNA