No description available.

No description available.

No description available.

No description available.

While the major source of vitamin D is D₃ from ultraviolet exposure, some supplements supply D₂. The relative potency of vitamin D₂ versus vitamin D₃ remains controversial. The aims of the current study were, 1. To optimize the in vitro model, including use of cell lines, vitamin D concentrations, and outcome biomarkers. 2. To compare the potency of vitamin D₂ and D₃ metabolites on mouse and human bone cellular activity. 3. To explore the expression of VDR in osteoarthritic (OA) bone tissues as well as cellular responses to vitamin D₂ and D₃ metabolites ex-vivo. In mouse 2T3 osteoblasts, at physiological doses, both vitamin D₂ and D₃ metabolites increased ALP activity and mineralisation and up-regulated osteoblastic signature genes and proteins. At supra-physiological doses D₃ metabolites were more potent inhibitors of 2T3 function than D₂ metabolites. Although hBMS cell proliferation was inhibited by both 25(OH)D₂ and D₃, ALP activity was enhanced by both metabolites. However, 25(OH)D₃ was a more potent stimulator of ALP and mineralisation of hBMSCs. D₂ and D₃ equally stimulated expression of CX43 and PHEX markers in osteocytic cell lines. Immunohistochemistry of femoral heads showed much reduced VDR expression in OA osteocytes and osteoclasts, yet both 25(OH)D2 and D₃ increased OA-hBMSCs mineralisation more than non-OA-hBMSCs ex-vivo. While vitamin D₂ or D₃ increased mouse 2T3 osteoblastic activity at physiological doses, OA and non-OA hBMSCs differentiation was more responsive to 25(OH)D₃. Key bone cells such as osteocyte and osteoclasts expressed less VDR in OA. For the first time vitamin D₂ metabolites have been thoroughly examined and emerged as a potent stimulator of bone cell differentiation, at least in vitro. Vitamin D₃ in contrast is confirmed as highly potent in bone cells, but with toxicity at much lower doses than D₂.

Osteocalcin, which is produced by the osteoblast, and the urinary pyridinium compounds (pyridinoline and deoxypyridinoline), which are derived from collagen, are widely used as markers of bone turnover. Osteocalcin was extracted from bone in 20% formic acid and separated using a linear 4-60% acetonitrile gradient containing 0.1% TFA at a flow rate of 1ml/min. The standard curve was linear up to 15 <I>μ</I>g of osteocalcin injected, with inter- and intra-assay coefficients of variation of 6.9 and 8.8% respectively while recovery of osteocalcin added to bone extracts averaged 102.7 ± 6.16 %. Having developed this assay it was then used in a series of experiments designed to study the biological function of osteocalcin in bone. Plasma osteocalcin levels decreased with age and showed large between-animal variations; the variability over 24 h was also large but there was no evidence of consistent circadian rhythm. In bone, changes in osteocalcin levels tended to parallel those for calcium whereas pyridinium crosslink levels tended to increase with age. Neither were sufficiently sensitive to detect differences in bone turnover in lambs of the same age but growing at different rates though osteocalcin levels in blood and in bone were sensitive to P-deficiency in sheep but not in pigs and there was little evidence indicating that osteocalcin plays any direct role in the mineralisation process. In separate studies adult sheep were treated with a bone antiresorptive agent, Ibandronate, and its effects on the metabolism and excretion of the pyridinium crosslinks was examined. At rates which have been shown to be effective in reducing bone resorption in humans this compound had little effect on the overall rate of excretion of these crosslinks in these sheep but did alter the proportions excreted in free or in peptide bound form.

国立情報学研究所で電子化したコンテンツを使用している。

Würzburg, University, Diss., 2007.

Ulm, Univ., Diss., 2008.

Indiana University School of Dentistry / Introduction: The goal of nonsurgical root canal therapy is to reduce the bacterial load within an infected root canal system, and the subsequent objective is to prevent or treat apical periodontitis. Clinical studies have shown more expedient healing of apical periodontitis treated with electromagnetic wave stimulation (EMS) as compared to apical periodontitis not treated with EMS. Stimulation of osteoblasts and growth factors has been shown when EMS was applied to rat calvaria, resulting in increased bone healing. Objective: The purpose of this vitro study was to evaluate the effects of EMS on the proliferation and differentiation of osteoblasts. Using primary neonatal calvaria osteoblast-lineage cells, the effects of different EMS regimens on proliferation, alkaline phosphatase (ALP) activity, and mineral deposition were determined. Materials and Methods: EMS regimen included currents of 0mA, 0.1mA, 1mA, and 10mA delivered for five consecutive 1s pulses per day for one, two, and three days. Cell proliferation was assayed after 1 or 2 days using an MTS assay. Alkaline phosphatase activity and mineral deposition were assayed after culturing the cells in osteogenic media containing ascorbic acid and -glycerol phosphate for 7 days. Comparisons were performed using analysis of variance, with a 5% significance level. Results: There was no statistically significant differences noted in MTS proliferation and mineral deposition between the experiment EMS treatment groups of 0.1, 1.0, and 10.0 mA compared to the control group of 0 mA current on calvaria-derived osteoblast. While there were no statistically significant differences noted in ALP activity in the 0.1, and 1.0 mA EMS groups, compared to 0 mA control, alkaline phosphatase activity was significantly increased in the 10 mA EMS group. Conclusion: There was no significant differences in MTS proliferation and mineral deposition of the EMS group compared to the control group. However, 10 mA EMS favored increased ALP activity suggesting EMS can promote matrix maturation by osteoblasts. Additional in vitro experimental studies, including different stem cell populations, culture duration and EMS treatment regimens are needed to understand the mechanism of action of EMS for future applications in regenerative endodontics.