Role of epidermal growth factor receptor in osteoblastic differentiation of rat bone marrow stromal cells
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In an attempt to understand the role of epidermal growth factor (EGF) and its receptor (EGF-R) in osteoblastic cell differentiation, the changes in [125I]-EGF binding capacity, synthesis of EGF-R protein, and expression of EGF-R mRNA were investigated during osteoblastic differentiation of cultured bone marrow stromal cells which were collected from the femora of young adult rats. In addition, the ability of EGF to suppress osteoblastic differentiation was also studied. Dexamethasone at a concentration of 0.1 mM increased the expression of osteoblastic markers by bone marrow stromal cells cultured in alpha-modified minimum essential medium (α-MEM) con taining 1% fetal bovine serum (FBS), 50 mg/ml ascorbic acid, and 10 mM β-glycerophosphate, as revealed by elevated alkaline phosphatase activity, an increase in osteopontin mRNA expression, and bone nodule formation. This osteoblastic differentiation was accompanied by a decreased expression of EGF-R mRNA, decreased synthesis of EGF-R protein, and a decreased number of EGF-binding sites without any change in affinity. When these cells were incubated with dexamethasone and EGF in combination throughout the culture, they exhibited significantly lower levels of all osteoblastic markers than did dexamethasonetreated cells, indicating suppression of osteoblastic differentiation by EGF. In contrast, EGF treatment of the cells induced expression of EGF-R mRNA. Thus, a decrease in EGF binding associated with osteoblastic differentiation could lead to decreased responsiveness of bone marrow cells to EGF, whereas the EGF-induced increase in expression of EGF-R could facilitate the inhibition of cell differentiation by EGF. These findings suggested that upregulation of EGF-R on bone marrow stromal cells antagonizes their differentiation, and thus possibly functions as a negative regulator of osteoblastic differentiation.
Key wordsbone marrow stromal cells epidermal growth factor receptor osteoblastic differentiation dexamethasone
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- 2.Carpenter G, Wahl MI (1990) Epidermal growth factor. Handb Exp Pharmacol 95(I):69–171Google Scholar
- 5.Hiramatsu M, Kumegawa M, Hatakeyama K, Yajima T, Minami N, Kodama H (1986) Effect of epidermal growth factor on collagen synthesis in osteoblastic cells derived from newborn mouse calvaria. Endocrinology 111:1810–1816Google Scholar
- 14.Owen ME (1985) Lineage of osteogenic cells and their relationship to the stromal system. In: Peck WA (ed) Bone and mineral research. Elsevier, Amsterdam, pp 1–25Google Scholar
- 15.Beresford JN (1988) Osteogenic stem cells and the stromal system of bone and marrow. Clin Orthop 240:270–280Google Scholar
- 17.Kasugai S, Todescan R, Nagata T, Yao KL, Butler WT, Sodek J (1991) Expression of bone matrix proteins associated with mineralized tissue formation by adult rat bone marrow cells in vitro: inductive effects of dexamethasone on the osteoblastic phenotype. J Cell Physiol 147:111–120CrossRefPubMedGoogle Scholar
- 30.Ullrich A, Coussens L, Hayflick JS, Dull TJ, Gray A, Tam AW, Lee J, Yarden Y, Libermann TA, Schlessinger J, Downward J, Mayes ELV, Whittle N, Waterfield MD, Seeburg PH (1984) Human epidermal growth factor receptor cDNA sequence and aberrant expression of the amplified gene in A431 epidermoid carcinoma cells. Nature 309:418–425Google Scholar
- 33.Owen TA, Aronow M, Shalhoub V, Barone LM, Wilming L, Tassinari MS, Kennedy MB, Pockwinse S, Lian JB, Stein GS (1990) Progressive development of the rat osteoblast phenotype in vitro: reciprocal relationships in expression of genes associated with osteoblast proliferation and differentiation during formation of the bone extracellular matrix. J Cell Physiol 143:420–430CrossRefPubMedGoogle Scholar
- 34.Earp HS, Helper JR, Petch LA, Miller A, Berry AR, Harris J, Raymond VW, McCune BK, Lee LW, Grisham JW, Harden TK (1988) Epidermal growth factor (EGF) and hormone stimulate phosphoinositide hydrolysis and increase EGF receptor protein synthesis and mRNA levels in rat liver epithelial cells. J Biol Chem 263:13868–13874PubMedGoogle Scholar