Insulin-like Growth Factor-Ⅰ Prevents Ethanol-Induced Inhibition And Apoptosis Of Rat Osteoblasts In Vitro

Background Increasing numbers of people-especially the young-are drinking well above the safe limits. Excessive ethanol (EtOH) consumption has been closely associated with the development of low bone mass and an increased prevalence of skeletal fractures and osteonecrosis of the femoral head, but the mechanisms remain unclear. Ethanol has direct cytototic effects on osteoblasts in vitro and reduces their proliferation. In chronic alcoholic subjects, malnutrition and micro-vascular change make the inhibitory effects worsen. The changes of osteoblast proliferation and function after stimulation by ethanol under serum starvation condition in vitro partly reflect the mechanism in vivo. Insulin-like growth factor-I (IGF-I) has been shown to exert significant effects on osteoblast proliferation and differentiation. The circulating levels of IGF-I decrease in alcoholics and ethanol inhibits the auto-phosphorylation of the IGF-I receptor tyrosine kinase. The preservation of exogenous IGF-I to osteoblasts makes it possible for therapeutic intervenetions. Apoptosis is a process in which the cell undergoes programmed suicide with orderly activation of specific intracellular signaling pathways. Many kinds of factors regulate osteoblasts through apoptosis. Bcl-2 and Bax are two representatives in the regulators, which determine the development of apoptosis through the ratio of Bcl-2/Bax.Chapter I Osteoblasts preparation and characterization in vitroObjectives: Isolation, culture and characterization of osteoblasts from rat calvaria with modified explant culture of bone.Methods: Calvaria were aseptically isolated from four newborn Sprague-Dawley (SD) rats, and snipped with scissors. The chips were inoculated in flasks according to traditional explant culture of tissue after 20 minutes' digestion in 0.25% Trypsin and 0.02% EDTA. The primary osteoblasts were maintained in Dulbecco's modified Eagle medium...