Joseph B K, Savage N W, Daley T J, Young W G
Department of Dentistry, University of Queensland, Brisbane, Australia.
Growth Factors. 1996;13(1-2):11-7. doi: 10.3109/08977199609034563.
Insulin-like growth factor-I(IGF-I) has both metabolic and growth-promoting activities in many cell and tissue types. Although IGF-I is present in serum, it is also thought to have important autocrine and paracrine functions. Immunohistochemistry for IGF-I and its receptor have shown that IGF-I is synthesised locally by the tooth forming cells which exhibit both the IGF-I and the growth hormone receptors. This concept required to be tested by in situ hybridization. Using a digoxigenin-labelled synthetic oligodeoxyribonucleotide probe for IGF-I, we investigated the distribution of IGF-I mRNA in the continuously erupting rat incisor by in situ hybridization. The distribution and intensity of the hybridization signal varied with the developmental stage of the rat incisor. The cells of the apical loop expressed a positive hybridization signal, but the earliest polarised odontoblasts and pre-ameloblasts did not show any positive signal. The onset of enamel secretion was accompanied by a strong hybridization signal in the secretory ameloblasts as well as the odontoblasts. Maturation ameloblasts also demonstrated IGF-I message in their cytoplasm as well as their nuclei. The cells of the pulp and the dental follicle were consistently negative. However, in the adjacent alveolar bone, the signal was high in the osteoblasts and osteoclasts. These findings support the notion of paracrine or autocrine function for IGF-I in tooth development.
胰岛素样生长因子-I（IGF-I）在多种细胞和组织类型中具有代谢和促进生长的活性。尽管IGF-I存在于血清中，但也被认为具有重要的自分泌和旁分泌功能。对IGF-I及其受体的免疫组织化学研究表明，IGF-I由同时表达IGF-I和生长激素受体的牙齿形成细胞在局部合成。这一概念需要通过原位杂交进行验证。我们使用地高辛标记的IGF-I合成寡脱氧核糖核苷酸探针，通过原位杂交研究了持续萌出的大鼠切牙中IGF-I mRNA的分布。杂交信号的分布和强度随大鼠切牙的发育阶段而变化。根尖环的细胞表达阳性杂交信号，但最早极化的成牙本质细胞和前成釉细胞未显示任何阳性信号。釉质分泌开始时，分泌期成釉细胞和成牙本质细胞中出现强烈的杂交信号。成熟的成釉细胞在其细胞质和细胞核中也显示出IGF-I信息。牙髓和牙囊的细胞始终为阴性。然而，在相邻的牙槽骨中，成骨细胞和破骨细胞中的信号很高。这些发现支持了IGF-I在牙齿发育中具有旁分泌或自分泌功能的观点。
