Growth stimulation of mandibular condyles and femoral heads of newborn rats by IGF-I.
Primary and secondary cartilage differ in embryonic origin and are generally considered to have a different mode of growth. However, few experimental studies exist that directly compare the two types of cartilage and their growth regulation. The regulation of cartilage growth is a complex mechanism involving growth factors like insulin-like growth factor-I (IGF-I). The purpose of this study was to compare the growth of mandibular condyles of 4-day-old rats with that of femoral heads in vitro and to analyze the effects of IGF-I. Explants were cultured for up to 2 weeks with 0, 5, and 25 ng/ml IGF-1. Both, 5 and 25 ng/ml IGF-I significantly stimulated growth of the mandibular condyles while only 25 ng/ml IGF-I stimulated growth of the femoral heads. IGF-I increased glycosaminoglycan synthesis of both condylar and femoral cartilage. However, only the DNA synthesis of the mandibular condyles was significantly increased by IGF-I while that of the femoral heads was not affected. It is concluded that IGF-I stimulates growth of both secondary condylar cartilage and primary femoral cartilage. The mandibular condyle appears to be more sensitive to IGF-I than the femoral head, which may partly be due to the different developmental stage.
Delatte
M
M
Department of Orthodontics, Université Catholique de Louvain, Cliniques Universitaires St Luc, Avenue Hippocrate 15, B-1200, Brussels, Belgium
Von den Hoff
J W
JW
Maltha
J C
JC
Kuijpers-Jagtman
A M
AM
D000818:Animals; D000831:Animals, Newborn; D002358:Cartilage, Articular / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D046508:Culture Techniques; D004247:DNA / Q000096:biosynthesis; D005270:Femur Head / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D006025:Glycosaminoglycans / Q000096:biosynthesis; D006909:Hydroxyproline / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008335:Mandibular Condyle / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011994:Recombinant Proteins / Q000096:biosynthesis
D006025:Glycosaminoglycans; D011994:Recombinant Proteins; D007334:Insulin-Like Growth Factor I; D004247:DNA; D006909:Hydroxyproline