Expression and Regulation of Insulin-Like Growth Factor-I in the Rat Incisor

Abstract

Growth factors play an important role in the regulation of cell growth, division and differentiation. In this study the distribution and regulation of insulin-like growth factor-I (IGF-I) in the continuously erupting rat incisor was determined by immunohistochemistry. Results were evaluated both visually and with a computer-based image analysis system. The distribution and intensity of IGF-I immunoreactivity varied with developmental stage of the rat incisor. Strong IGF-I immunoreactivity was observed in differentiating odontoblasts and ameloblasts. The most intense immunoreactivity was observed in secretory ameloblasts, secretory odontoblasts and in maturation ameloblasts. Staining was weak or absent in post-secretory ameloblasts but persisted in post-secretory odontoblasts. Weak to moderate immunoreactivity was also seen in cells of the stratum intermedium and in the reduced enamel epithelium. Surrounding alveolar bone showed strong IGF-I immunoreactivity in osteoblasts and in the stratum basale and stratum spinosum of the adjacent labial gingival epithelium. In order to assess the role of GH in IGF-I expression, GH (65 micrograms/100 g bw) was administered for six days to dwarf GH deficient rats, producing a significant increase in body weight (P < 0.01). Measurements at different stages of odontogenesis showed that the staining intensity of secretory ameloblasts (P < 0.01) and maturation ameloblasts (P < 0.001) was significantly different between untreated and treated animals. These results indicate that IGF-I is present in cell populations of the enamel organ of the rat incisor found previously to exhibit growth hormone receptors, and that expression of IGF is GH dependent.(ABSTRACT TRUNCATED AT 250 WORDS)

Gene Expression and Localization of Insulin-like Growth Factors and Their Receptors throughout Amelogenesis in Rat Incisors

“…Although the expression pattern of IGF-I throughout enamel formation has been previously reported (Joseph et al 1993(Joseph et al ,1994a(Joseph et al ,1996, this is the first comprehensive description for IGF-II. The level of expression of these two ligands and their receptors varies across the incisor.…”

“…IGFs are believed to influence ameloblast differentiation and the production of various enamel matrix constituents (Joseph et al 1993(Joseph et al ,1994a(Joseph et al ,1996(Joseph et al ,1997Takahashi et al 1998;Caton et al 2005).…”

Rejenerati̇f Endodonti̇de Büyüme Faktörleri̇

“…İGF'ler odontogenezise ve hücre çoğalması ve farklılaşması ile sağlanan dental doku tamirine katkıda bulunurlar. 115 İGF-1, somatomedin C olarak bilinir ve dental pulpa hücrelerinin büyüme ve farklılaşmasında etkileri 116 İGF-1, serum içermeyen medyumda köpek dental pulpa hücrelerinin çoğalmasını ve odontoblast benzeri hücrelere farklılaşmasını indüklemek-tedir. 116 İGF ve PDGF-BB ile birlikte in vitro ortamda dental pulpa hücrelerinin çoğalmasında sinerjistik bir etkiye sahiptir.…”

Growth Hormone Receptor and Insulin-like Growth Factor-I Immunoreactivity in Osteoclast-like Cells During Tooth Eruption in the Toothless (Osteopetrotic) Rat Following Treatment with Colony-Stimulating Factor-1

“…Specific techniques for detection of GHr (Symons et al, 1994(Symons et al, , 1996b(Symons et al, , 1998Zhang et al, 1992) and IGF-I (Joseph et al, 1993(Joseph et al, , 1999 in rat tissue have previously been described. Sections were counterstained with Mayer's haematoxylin, dehydrated, mounted, and viewed using a light microscope magnification of 100×.…”

“…A polyclonal antibody to IGF-I was raised in rabbit against recombinant human IGF-I. This antibody has been shown to cross-react with rat tissues and has been demonstrated to have less than 0.5% cross-reactivity with IGF-II (Breier et al, 1991;Joseph et al, 1993Joseph et al, , 1999Ong et al, 2001). …”