Comparison of fetal and adult human bone: identification of a chemotactic factor in fetal bone

Studies employing the matrix-induced endochondral bone formation system have outlined the processes involved in bone induction. An initial event is increased migration of mesenchymal cells to the implant site prior to endochondral calcification. This suggests that chemotactic factors in the bone matrix may be involved in the osteogenic process. Extracts of human fetal bone, obtained by sequential demineralization, stimulated the migration of osteoblast-like cells in a dose-dependent fashion, as assayed in the Boyden chamber. In contrast, comparable extracts of normal adult bone (40-year-old male) did not stimulate osteoblast migration. Monocytes, potential osteoclast precursors, did not migrate in response to either of these extracts. These studies suggest that significant differences exist in protein composition and/or distribution between fetal and adult human bones. These differences may well influence the remodeling potential of these bones.