| Objectve: Osteoporosis is an age-related disease correlated with body regression and the reasons are not identified completely. Recent study showed that advanced glycosylation end products (AGEs) played an important role in osteoporosis pathogenesis,which were formed spontaneously in proteins by a non-enzymatic reaction with sugar, characterized by specific fluorescence and cross-linked structures.It is necessary for normal tissue remodeling and homeostasis.But excessive formation and accumulation of AGEs will induce a series of pathologic changes.The modification of β2 -microglobulin with AGEs might play a pathophysical role in osteoporosis aroud amyloid deposits,associated with dialysis-related amyloidosis. An increase in AGE-modified collagen has been detected in the cortical bone of diabetic and aging rats,In the osteoporosis rats there is a sharp increased in the apoptotic osteoblast and decreasing of type I collagen.In vitro study showed that lower doses of AGEs can eliciting an increase in cellular proliferation and differentation in cultured rat calvaria-derived osteoblast while higher doses of AGEs induced a decrease in both parameters as well asmineralization.Thus indicates that higher doses AGE might induce more osteoblast into apoptosis.Studies have suggested that the nitric oxide synthase pathway may be involved in the AGE-mediated alteration observed in several cell types,such as endothelial cells. Type I collagen is the main component of extracellular matrix in bone, which is up to 90%.It is the substance to keep elasticity and tenacity of bone,and is the site where hydroxyapatite deposit. Many studies showed that deficiency or degeneration of type I collagen had a close relationship with osteoporosis and bone loses The function of collagen altered when it was modified by AGEs,thus affected osteoblast and bone remodling.Cell die by passing through two processes, apoptosis and necrosis.Apoptosis,also known as Programme Cell Death, PCD,is used to describe a process in which a cell actively participates in its own destructive processes.The apoptosis program is mainly characterized by internucleosomal cleavage of DNA and it is a normal physiological process which in the maintenance of tissue homeostasis.With the development of biochemical and molecular biology many achievement of bone repairing and remodling have been made progressly.Caspases,a group of proteases that cleave protein substrate, play a central role in the regulation and execution of apoptosis that function in the apoptotic pathway exist as inactive zymogens in the cytosol of living cells andbecome activated through proteolysis when cells receive apoptotic signals. Caspase-3, who is the chief executive enzyme of apoptosis and can be activated by startup caspases and in turn cleave other protein resulting in characteristic chromatin condensation and fragmentation during apoptosis.In this study, we have investigated the effect of AGEs on the apoptosis of calvaria-derived osteoblast in vitro, in order to explore the role of AGEs in osteoporosis pathogenesis and offer some advice on the prevention and treatment of osteoporosis.Method: Osteoblast obtained from Sprague-Dawley rats which were born less than 24 hours. AGE-protein was prepared by means of the incubation of BSA with glucose.Osteoblast cells were incubated with AGEs-BSA of 500μg/ml, 1500μg/ml and 2500μg/ml for 72h separately. Osteoblast cells incubated with the same concentration of BSA were used accordingly as control.After incubation, the cells were examined under a fluorescence microscope to determine the condensation of chromatin and other morphological changes characteristic of apoptosis, using agrose gel electrophoresis to detect the fragmentation of nuclei, terminal- deoxynucleotidyl transferase mediated d-UTP nick end labeling(TUNEL) also used to observe the cleaved 3'-OH terminal, activaty of caspase-3 were detected using fluorescence as well as immunohistological examinations used to test the expression of iNOS level.Resul...
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