In Vitro Impact of Conditioned Medium From Demineralized Freeze-Dried Bone on Human Umbilical Endothelial Cells

Angiogenesis is essential for the consolidation of bone allografts. The underlying molecular mechanism, however, remains unclear. Soluble factors released from demineralized freeze-dried bone target mesenchymal cells; however, their effect on endothelial cells has not been investigated so far. The aim of the present study was therefore to examine the effect of conditioned medium from demineralized freeze-dried bone on human umbilical endothelial cells in vitro. Conditioned medium was first prepared from demineralized freeze-dried bone following 24 hours incubation at room temperature to produce demineralized bone conditioned media. Thereafter, conditioned medium was used to stimulate human umbilical vein endothelial cells in vitro by determining the cell response based on viability, proliferation, expression of apoptotic genes, a Boyden chamber to determine cell migration, and the formation of branches. The authors report here that conditioned medium decreased viability and proliferation of endothelial cells. Neither of the apoptotic marker genes was significantly altered when endothelial cells were exposed to conditioned medium. The Boyden chamber revealed that endothelial cells migrate toward conditioned medium. Moreover, conditioned medium moderately stimulated the formation of branches. These findings support the concept that conditioned medium from demineralized freeze-dried bone targets endothelial cells by decreasing their proliferation and enhancing their motility under these in vitro conditions.