FIG. 2.

Osteoblasts, periosteal cells, and fibroblasts stain positively for the osteogenic marker, ALP, when cultured at a high density in osteo-inductive medium. MC3T3-E1 osteoblasts expressed significantly (p < 0.05) higher levels of ALP activity than either periosteal cells of fibroblasts initially seeded at a high density; however, there was no expression of ALP in osteoblast cultures initially seeded at low densities. In both high- and low-density cultures, periosteal cells and NIH3T3 fibroblasts had relatively similar levels of ALP expression with no significant difference.