Fig. 3. rhBMP-2 induces ALPase activity in PDL-L2 cells in vitro. Cells were cultured either in the normal medium or the differentiation medium. After 3 days of incubation, cells were given 250 ng/ml rhBMP-2 or vehicle and incubated for an additional 3 days. Cells were then fixed and subjected to ALPase staining. Consistent with previous reports, MC3T3-E1 expressed more ALPase activity as the incubation increased, and this was markedly enhanced by rhBMP-2. ALPase staining of PDL-L2 is faint and scarce in the absence of rhBMP-2. However, addition of rhBMP-2 is markedly induced to a level close to that of unstimulated MC3T3-E1 cells. Note that fibroblastic NIH3T3 cells did not respond to rhBMP at all. Original magnification was x4. See text for details.