Expressions of IGF-1 and TGF-beta 1 in the condylar cartilages of rapidly growing rats.
OBJECTIVE
This study was designed to investigate the expressions of IGF-I and TGF-beta 1 in condyles and to determine if the special modeling and remodeling of the condylar cartilages are regulated by growth factors.


METHODS
Fifty 5-weeks-old male rats were assigned to five groups randomly, and one group was sacrificed every week. The condyles were harvested from rats whose ages ranged from 5- to 9-weeks-old and they were inspected by using S-P immunocytochemical techniques.


RESULTS
IGF-I and TGF-beta 1 are expressed during condylar cartilage development in a temporally and spatially regulated fashion, and different growth factors have different expressing characteristics. The expressions of IGF-I are more intense in germinal and transitional layers, while TGF-beta 1 expression was high in the mature and degenerated layers. In germinal and transitional layers, IGF-I expression was high at the beginning of rapid growth, while TGF-beta 1 expression was low. At the end of the rapid growth, IGF-I expression was lower and TGF-beta 1 expression was still high. In the mature and degenerated layers, TGF-beta 1 expression was very high, while IGF-I expression was lower throughout rapid growth.


CONCLUSIONS
The growth factors are expressed differentially, and each shows specific or overlapping localization patterns depending on the stage of developmental process, meaning that IGF-I and TGF-beta 1 may regulate condylar cartilage proliferation and differentiation in an interrelated system. This study suggests that growth factors can be produced locally by condylar cartilages and play an important role in the metabolism of condylar cartilages.
Li
X B
XB
Department of Orthodontics, College of Stomatology, West China University of Medical Science, Chengdu Sichuan, P. R. China.
Zhou
Z
Z
Luo
S J
SJ
D000818:Animals; D002358:Cartilage, Articular / Q000254:growth & development / Q000378:metabolism*; D020219:Chondrogenesis / Q000502:physiology; D007150:Immunohistochemistry; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis*; D008297:Male; D008335:Mandibular Condyle / Q000254:growth & development* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D016212:Transforming Growth Factor beta / Q000096:biosynthesis*
D016212:Transforming Growth Factor beta; D007334:Insulin-Like Growth Factor I