STIMULATION OF OSTEOBLASTIC PHENOTYPES BY STRONTIUM IN PERIOSTEAL-DERIVED CELLS

ABSTRACT

strontium on osteoblastic phenotypes of cultured human periosteal-derived cells. Periosteal tissues were harvested from mandible during surgical extraction of lower impacted third molar. Periosteal-derived cells were introduced into cell culture. After passage 3, the periosteal-derived cells were further cultured for 28 days in an osteogenic induction DMEM medium supplemented with fetal bovine serum, ascorbic acid 2-phosphate, dexamethasone and at a density of 3 x 104 cells/well in a 6-well plate. In this culture medium, strontium at different concentrations (1, 5, 10, and 100 microg/mL) was added. The medium was changed every 3 days during the incubation period. We examined the cellular proliferation, histochemical detection and biochemical measurements of alkaline phosphatase (ALP), the RT-PCR analysis for ALP and osteocalcin, and von Kossa staining and calcium contents in the periosteal-derived cells. Cell proliferation was not associated with the addition of strontium in periosteal-derived cells. The ALP activity in the periosteal-derived cells was higher in 5, 10, and 100 microg/ml strontium-treated cells than in untreated cells at day 14 of culture. Among the strontium-treated cells, the ALP activity was appreciably higher in 100 microg/ml strontium-treated cells than in 5 and 10 microg/ml strontium-treated cells. The levels of ALP and osteocalcin mRNA in the periosteal-derived cells was also higher in strontium-treated cells than in untreated cells at day 14 of culture. Their levels were increased in a dose-dependent manner. Von Kossa-positive mineralization nodules were strongly observed in the 1 microg/ml strontium-treated cells at day 21 and 28 of culture. The calcium content in the periosteal-derived cells was also higher in 1 microg/ml strontium-treated cells at day 28 of culture. These results suggest that low concentration of strontium stimulates the osteoblastic phenotypes of more differentiated periosteal-derived cells, whereas high concentration of strontium stimulates the osteoblastic phenotypes of less differentiated periosteal-derived cells. The effects of strontium on osteoblastic phenotypes of periosteal-derived cells appear to be associated with differentiation-extent.