Xylitol is a sugar alcohol with a variety of functions including bactericidal and anticariogenic effects. However, the cellular mechanisms underlying the role of xylitol in bone metabolism are not yet clarified. In our present study, we exploited the physiological role of xylitol on osteoclast dif-ferentiation in a co-culture system of osteoblastic and RAW 264.7 cells. Xylitol treatment of these co-cultures reduced the number of tartrate-resistant acid phosphatase (TRAP)- positive multinucleated cells induced by 10 nM 1α,25(OH)2 D3 in a dose‐dependent manner. A cell viability test revea-led no marked cellular damage by up to 100 mM of xylitol. Exposure of osteoblastic cells to xylitol decreased RANKL, but not OPG, mRNA expression in the presence of 10-8 M 1α,25(OH)2D3 in a dose‐dependent manner. Furthermore, bone resorption activity, assessed on bone slices in the co- culture system, was found to be dramatically decreased with increasing xylitol concentrations. RANKL and OPG proteins were assayed by ELISA and the soluble RANKL (sRANKL) concentration was decreased with an increased xylitol con-centration. In contrast, OPG was unaltered by any xylitol con-centration in this assay. These results indicate that xylitol inhibits 1α,25(OH)2D3-induced osteoclastogenesis by reducing the sRANKL/OPG expression ratio in osteoblastic cells.

The purpose of this study was to examine the effects of vi tamin D3 and 1'etinoic acid(RA) on the human mesenchymal stem ce!ls(MSC) g1'owth and osteogenic differentiations. Cell proliferation, mineralization, cell cycle, expression of cell cycle regu l atOJγ proteins and markers fo1' osteogenic differenatiaiton were determined by MTI assay, mineralization assay, flow cytomet1'Y‘ and Western blot analysis, respectively. Cell viability was dec1'ease by each vitamin D3 and RA added to MSC. it was more decrease by vitamin D3 and RA. Mineralized nodule formation revealed similar expression pattern with positive cont rol group at vitamin D3 and RA mixed add to MSC. At vitamin D3 and RA mixed add to MSC after 7 days of incubation was increase G1 s tage. after 21 days of incubation was inhibit cell cycle prog1'ess by inc1'ease of sub-G1 Treatment vitamin D3 to MSC inhibits p53 and p21, but inc1'ease pRb. RA inhibit p53, but increase p21 and pRb, vitamin D3 plus RA group was same as added RA group. so two vitamin was effect to inhibited cell growth each different mechanism. Expression of BMP-2 protein was prominent in osteogonic supplement treated g1'oup of MSC at 2 weeks cultivation days, but vi tamin D3 treatment decreased BMP-2 expression rather than in (+) control group. BSP protein was notably increased in the OS compa red to positive controls at 2 weeks cultivation, but similar to that of vitamin D3 group t1'eatment group and was least expressed in plus RA mixed group, at 3 weeks, BSP expression was similar to 1'esult of 2 weeks Collectively, these results shows that vitamin D3 and RA have diffe1'ential effects on the MSCs g1'owth and differ entia tion 211

Contents of vitamin D3 and 25-OH-vitamin D3 in marine animal products(20 species) were determined by HPLC. The isomers of vitamin D, D2 and D3, were not clearly separated on a reversed phase, μ Bonda Pak, with 20% methanol-acetonitrile, and on a normal phase, Zorbax SIL. with 0.4% isopropanol-hexane, but 25-OH-vitamin D2 and-D3 were separated on either μ Bonda Pak with 10% methanol-acetonitrile, or on Zorbax SIL with 2.2% isopropanol-hexane, respectively. Although levels of vitamin D3 and 25-OH-vitamin D3 varied remarkably according to species, their average value(fish : l,l87sim36,007 I.U/sample 100g, mussel : 58~1,706 I.U/sample 100g, pickle: 1,208~79,358 I.U/sample 100g) was greatly higher than that of meat(80~100 I.U/sample 100g) and dairy products(400~800 I.U/sample 100g). Fatty tissues of fish and pickled fish intestines contained high level of vitamin D3 and 25-OH-vitamin D3, while the clam and mussel known to have various kinds of sterol including δ7-sterol showed very low levels of vitamin D3 and its derivative.