Alkaline phosphatase activity is unregulated in regenerating human periodontal cells

The activity of alkaline phosphatase (ALP) is considered to indicate the pr esence of osteoblast cells and the formation of new bone. In the present st udy this enzyme was investigated in cells obtained from retrieved polytetra fluoroethylene membranes (M cells) of periodontal disease patients treated by guided tissue regeneration (GTR) and from the regenerated tissue underly ing the membrane (RT cells). Normal periodontal ligament (PL) and gingival cells were also grown from the corresponding healthy tissues of human subje cts. ALP activity was measured colourimetrically, using paranitrophenyl pho sphate as the substrate, after 4 and 7 d of culture in the absence and pres ence of dexamethasone (DEX), a synthetic glucocorticoid which induces osteo blast differentiation. The results showed that basal levels of ALP activity were expressed by all the cells and that DEX upregulated ALP levels in the M, RT and PL cells but not in the gingival cells. Moreover, both the basal and DEX-induced ALP activities were statistically significantly higher in the RT cells than in any of the other cells. Our results suggest that both the GTR-associated and normal PL cells express osteoblast-like characterist ics and, furthermore, that the RT cultures in particular contain a high pro portion of osteoprogenitor cells.