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-1 (IGF-1). 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-1. Explants were cultured for up to 2 weeks with 0, 5, and 25 ng/ml IGF-1. Both, 5 and 25 ng/ml. IGF-1 significantly stimulated growth of the mandibular condyles while only 25 ng/ml. IGF-1 stimulated growth of the femoral heads. IGF-1 increased glycosaminoglycan synthesis of both condylar and femoral. cartilage. However, only the DNA synthesis of the mandibular condyles was significantly increased by IGF-1 while that of the femoral heads was not affected. It is concluded that IGF-1 stimulates growth of both secondary condylar cartilage and primary femoral cartilage. The mandibular condyle appears to be more sensitive to IGF-1 than the femoral. head, which may partly be due to the different developmental stage. (C) 2003 Elsevier Ltd. AtI. rights reserved.