Non-enzymatic glycosylation of a type I collagen matrix: effects on osteoblastic development and oxidative stress

AGE-collagen decreased the adhesion of UMR106 cells, but had no effect on the attachment of MC3T3E1 cells. In the UMR106 cell line, AGE-collagen also inhibited cellular proliferation, spreading and alkaline phosphatase (ALP) activity. In preosteoblastic MC3T3E1 cells (24-hour culture), proliferation and spreading were significantly increased by AGE-collagen. After one week of culture (differentiated MC3T3E1 osteoblasts) AGE-collagen inhibited ALP activity, but had no effect on cell number. In mineralizing MC3T3E1 cells (3-week culture) AGE-collagen induced a decrease in the number of surviving cells and of extracellular nodules of mineralization, without modifying their ALP activity. Intracellular ROS production, measured after a 48-hour culture, was decreased by AGE-collagen in MC3T3E1 cells, but was increased by AGE-collagen in UMR106 cells. After a 24-hour culture, AGE-collagen increased the expression of endothelial and inducible NOS, in both osteoblastic cell lines.These results suggest that the accumulation of AGE on bone extracellular matrix could regulate the proliferation and differentiation of osteoblastic cells. These effects appear to depend on the stage of osteoblastic development, and possibly involve the modulation of NOS expression and intracellular ROS pathways.Recent research indicates that an increase in the steady-state levels of highly reactive dicarbonylic compounds ("carbonyl stress") may lead to the formation of advanced glycation endproducts or AGE. These AGE products could be involved in the etiology of the long-term complications of several human afflictions, such as Diabetes mellitus, ageing, uremia and Alzheimer's disease [1,2]. In diabetic patients with long-standing hyperglycemia, an increase in the generation of AGE products can be partly explained by the process of non-enzymatic glycosylation of proteins. In this reaction, glucose reacts reversibly with the free amino groups of proteins to form unstable Schiff bases, which may underg