Effects of cell surface α2-3 sialic acid on osteogenesis.

A cell culture model of osteoblast differentiation was applied in our study of the effect of sialic acid on the osteogenesis by using the pre-osteoblast of MC3T3-E1 subclone 14 cells. Following the treatment of different concentrations of α2,3-neuraminidase, which specifically removed the α2-3 sialic acid from cell surface, a significant decrease of α2-3 sialic acid was detected with fluorescein isothiocyanate (FITC)-labeled Maackia amurensis lectin (MAL-II) by flow cytometry analysis. von Kossa staining showed that the bone mineralization decreased in MC3T3-E1 subclone 14 cells after the treatment of α2,3-neuraminidase for 2 weeks. However α2,3-neuraminidase did not affect the formation of osteoblasts in MC3T3-E1 subclone 14 cells, which was demonstrated by positive alkaline phosphatase (ALP)-staining. Characteristic biological markers and osteoblast-like cell-related factors of osteoblastic cells were also examined. Both RT-PCR and Western blot analysis demonstrated that the expression of bone sialoprotein (BSP), osteoprotegerin (OPG), and vitamin D receptor (VDR) were significantly decreased when α2-3 sialic acid expression decreased on the cell surface, while the expression of osteocalcin (OC) and osteopontin (OPN) remained unchanged. We propose a hypothesis that α2-3 sialic acid affects bone mineralization but not osteogenic differentiation.