Showing papers by "Masamichi Takami published in 2007"

Interleukin-4 inhibition of osteoclast differentiation is stronger than that of interleukin-13 and they are equivalent for induction of osteoprotegerin production from osteoblasts

Abstract: Interleukin (IL)-4 and IL-13 are closely related cytokines known to inhibit osteoclast formation by targeting osteoblasts to produce an inhibitor, osteoprotegerin (OPG), as well as by directly targeting osteoclast precursors. However, whether their inhibitory actions are the same remains unclear. The inhibitory effect of IL-4 was stronger than that of IL-13 in an osteoclast-differentiation culture system containing mouse osteoblasts and osteoclast precursors. Both cytokines induced OPG production by osteoblasts in similar time- and dose-dependent manners. However, IL-4 was stronger in direct inhibition that targeted osteoclast precursors. Furthermore, IL-4 induced phosphorylation of signal transducer and activator of transcription-6 (STAT6) at lower concentrations than those of IL-13 in osteoclast precursors. IL-4 but not IL-13 strongly inhibited the expression of nuclear factor of activated T-cells, cytoplasmic 1 (nuclear factor-ATc1), a key factor of osteoclast differentiation, by those precursors. Thus, the activities of IL-4 and IL-13 toward osteoclast precursors were shown to be different in regards to inhibition of osteoclast differentiation, whereas those toward osteoblasts for inducing OPG expression were equivalent.

Nitric Oxide in Pulp Cell Growth, Differentiation, and Mineralization

Abstract: Dental preparation sometimes causes transient congestion, edema, and necrosis of the pulp. We hypothesized that nitric oxide (NO) is involved in the pathophysiological changes in pulp after preparation. The mRNA and protein expression of the inducible isoform of NO synthase (iNOS) was examined in murine pulp after dental preparation. The effects of NO on the proliferation, mineralization, and apoptosis of pulp cells were also studied in vitro. We found that not only iNOS, but also mRNAs for alkaline phosphatase and plasma membrane glycoprotein-1, were expressed in the pulp after preparation. NOC-18, an NO donor, suppressed the proliferation of pulp cells without inducing cell death, whereas it promoted the mineralization of cells cultured in the presence of β-glycerophosphate, ascorbic acid, dexamethasone, and KH2PO4. Under these conditions, NOC-18 induced the apoptosis of pulp cells. These results suggest that NO regulates the growth, apoptosis, and mineralization of pulp cells.

Osteoblastic Cell Differentiation on BMP-2 Pre-Adsorbed Octacalcium Phosphate and Hydroxyapatite

Abstract: The present study was designed to investigate whether bone morphogenetic protein-2 (BMP-2) adsorbed onto octacalcium phosphate (OCP) and hydroxyapatite (HA) surfaces influences osteoblastic cell differentiation. Osteoblastic cell line, UAMS32, were cultured on plastic plate that was coated of synthetic OCP and HA. BMP-2 was pre-adsorbed on these calcium phosphates at 4°C or room temperature for 24h. The cells more proliferated on the BMP-2 pre-adsorbed OCP and HA than that of the controls (OCP and HA coating without BMP-2). ALP activities were higher on HA than on OCP when BMP-2 were pre-adsorbed at 4°C than at room temperature. The results suggest that pre-adsorption of BMP-2 in different temperature affects osteoblastic cell differentiation, most probably through different adsorption state of BMP-2 on this calcium phosphate.