雷奈酸锶通过TGF-β1/Smad通路促进骨髓间充质干细胞向成骨细胞分化

 [摘 要] 目的:研究转化生长因子β1（TGF-β1）/Smad通路在雷奈酸锶（strontium ranelate,Sr）促进大鼠骨髓间充质干细胞（BMSCs）向成骨细胞分化中的作用。方法: 在大鼠BMSCs向成骨细胞的诱导分化过程中,用Sr处理细胞,用Western blotting法检测磷酸化Smad2（phosphorylated Smad2,p-Smad2）和Runx2的表达。用TGF-β1特异性阻断剂SB431542或Smad2小干扰RNA（Smad2-siRNA）预处理BMSCs后加入Sr,再观察p-Smad2和Runx2表达的改变。应用试剂盒检测碱性磷酸酶（alkaline phosphatase,ALP）活性及钙结节水平。结果: 在大鼠BMSCs向成骨细胞的诱导分化过程中,Sr可增加p-Smad2和Runx2的表达,Sr 浓度为1 mmol/L、作用1 h时,p-Smad2表达最多;Sr 浓度为1 mmol/L、作用5 d时,Runx2表达最多;用SB431542或Smad2-siRNA预处理BMSCs后再加入Sr,不仅可以抑制p-Smad2和Runx2的表达,且ALP活性与钙结节数量也受到明显的抑制。结论: Sr可通过TGF-β1/Smad通路促进大鼠BMSCs向成骨细胞分化。     

Development and clinical trial of a novel bioactive bone cement

Strontium (Sr) and related compounds have become more attractive in the prevention and treatment of osteoporosis. Previously, we developed a novel bioactive bone cement which is mainly composed of strontium-containing hydroxyapatite (Sr-HA) filler and bisphenol A diglycidylether dimethacrylate (Bis-GMA) resin. This bone cement is superior to conventional polymethylmethacrylate (PMMA) bone cement in bioactivity, biocompatibility, and osseointegration. It also has shown sufficient mechanical strength properties for its use in percutaneous vertebroplasty (PVP) and total hip replacement (THR). In this paper, we review the in vitro, in vivo and clinical evidence for the effectiveness of this bioactive bone cement.     

Kinetics of calcium metabolism in lactation

The calcium accretion rate and the size of the exchangeable calcium pool was determined in rats between the 12th and 17th day of lactation after a single intraperitoneal injection of⁴⁷Ca and⁸⁵Sr. The serum specific activity and the retention of both radioactive isotopes in the whole body and tibia (shaft and ends) was determined. The single compartment kinetic model by Bauer was used for the analysis of data.The results show a decrease in the accretion rate and an increase in the exchangeable calcium pool in lactating rats as compared to unmated animals.

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Zusammenfassung Die Geschwindigkeit der Calciumzunahme und die Größe des austauschbaren Calciumpools wurde bei Ratten zwischen dem 12. und 17. Tag der Lactation nach einer einmaligen intraperitonealen Injektion von⁴⁷Ca und⁸⁵Sr bestimmt. Die spezifische Aktivität beider radioaktiven Isotopen im Serum und ihre Retention im ganzen Körper und in der Tibia (Schaft und Epiphysen) wurden bestimmt. Das kinetische Modell von Bauer für ein Kompartiment wurde für die Datenanalyse verwendet.Die Resultate zeigen eine Verminderung der Zunahmegeschwindigkeit und eine Erhöhung des austauschbaren Calciumpools bei laktierenden Tieren, verglichen mit unbegatteten Ratten.

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Résumé Le taux de dépôt du calcium et l'ampleur du calcium total échangeable sont déterminés chez le rat entre le 12ème et 17ème jour de lactation, après une injection intrapéritonéale unique de⁴⁷Ca et⁸⁵Sr. L'activité spécifique du sérum et la rétention des deux isotopes radioactifs dans l'organisme entier et le tibia (diaphyse et épiphyses) sont déterminées. L'analyse des résultats est réalisée à l'aide du modèle cinétique de Bauer à un compartiment unique. C'est ainsi qu'on observe une diminution du taux de dépôt et une augmentation du calcium total échangeable pendant la lactation.

     

Biochemical responses in cultured cells following exposure to SrCl2: potential relevance to the mechanism of action in pain palliation

⁸⁹SrCl₂ is currently used as a systemic radioactive palliative treatment for painful osseous metastases associated with an osteoblastic reaction in bone. However, the biological mechanism by which ⁸⁹SrCl₂ mediates pain palliation remains unclear. In this study, attempts were made to elucidate the mechanisms by which ⁸⁹SrCl₂ might influence pain at these sites. Both the direct radiotoxic effects of ⁸⁹SrCl₂ on cell viability and its influence on cellular biosynthetic activity were investigated. The direct radiotoxic effects of ⁸⁹SrCl₂ and X-rays were compared using the prostate carcinoma cell line, PC-3. Comparable effects upon PC-3 cell viability were seen in response to exposure to an equivalent dose given by ⁸⁹SrCl₂ and X-rays (2 Gy). Experiments to investigate the indirect action of ⁸⁹SrCl₂ exposure employed the MC3T3-E1 cell line and focused on their production of Prostaglandin E₂ (PGE₂) and interleukin-6 (IL-6). Exposure of the MC3T3-E1 cell line to ⁸⁹SrCl₂ resulted in an increased production of PGE₂ in a concentration-dependent manner. No increased PGE₂ production was seen by the MC3T3-E1 cells in response to X-ray exposure either in the presence or absence of SrCl₂. IL-6 was produced by the MC3T3-E1 cells in response to ⁸⁹SrCl₂ exposure via a PGE₂-mediated pathway. This study demonstrates the release of potent biochemical modifiers of bone turnover in response to the systemically applied radiotherapeutic ⁸⁹SrCl₂. This strongly suggests the mechanism of pain palliation by ⁸⁹SrCl₂ is likely to result from a complex interaction of direct and indirect radiation-induced effects.     

MTT比色法评价掺锶羟磷灰石固溶体细胞毒性

利用MTT比色法评价掺锶羟磷灰石固溶体（简称锶磷灰石）的细胞毒性。对自行合成含锶量克分子数比例分别为1％、5％、10％、100％的掺锶羟磷灰石用MTT比色法进行细胞毒性测试。结果表明不同含锶量锶磷灰石的细胞毒性评级均为1级,提示锶磷灰石无明显细胞毒性,掺锶量的多少对细胞相对增殖影响不明显。     

Strontium-90 in Deciduous Teeth Collected in Northern Finland from Children Born in 1952–1964.

Strontium-90 content was measured by means of Cerenkov radiation in deciduous teeth collected in three areas in northern Finland from children bom in 1952–1964.

The ⁹⁰Sr levels in tooth crowns in areas I and II showed a continuous increase in children born in 1952–1958, no further increase during the years 1959–1961, a sharp increase in 1962–1963, and no further change in 1964. In the northernmost part of Finland (area III) the strontium-90 contents of deciduous teeth when plotted against year of birth showed a slightly different trend with no increase during the years 1952–1957 and a steep rise in 1958 and 1959. These changes occurred in both Lapp and non-Lapp children. These differences in the strontium-90 content of deciduous teeth were presumably related to environmental peculiarities and specific dietary habits in area III. The maximum strontium-90 level, 16.76 pCi/gCa, was found in a sample of tooth roots of four Skolt children born in 1963.

The strontium-90 contents in the crowns of the four types of deciduous teeth were related as follows: second molars > cuspids > first molars > incisors.     

A novel and easy-to-prepare strontium(II) modified calcium phosphate bone cement with enhanced mechanical properties

The aim of this study was to evaluate two different approaches to obtaining strontium-modified calcium phosphate bone cements (SrCPCs) without elaborate synthesis of Sr-containing calcium phosphate species as cement precursors that could release biologically effective doses of Sr²⁺ and thus could improve the healing of osteoporotic bone defects. Using strontium carbonate as a strontium(II) source, it was introduced into a hydroxyapatite-forming cement either by the addition of SrCO₃ to an α-tricalcium phosphate-based cement precursor mixture (A-type) or by substitution of CaCO₃ by SrCO₃ during precursor composition (S-type). The cements, obtained after setting in a water-saturated atmosphere, contained up to 2.2 at.% strontium in different distribution patterns as determined by time-of-flight secondary ion mass spectrometry and energy-dispersive X-ray spectroscopy. The setting time of CPC and A-type cements was in the range of 6.5–7.5 min and increased for substitution-type cements (12.5–13.0 min). Set cements had an open porosity between 26 and 42%. Compressive strength was found to increase from 29 MPa up to 90% in substituted S-type cements (58 MPa). SrCPC samples released between 0.45 and 1.53 mg g^?1 Sr²⁺ within 21 days and showed increased radiopacity. Based on these findings, the SrCPC developed in this study could be beneficial for the treatment of defects of systemically impaired (e.g. osteoporotic) bone.     

A novel strontium(II)-modified calcium phosphate bone cement stimulates human-bone-marrow-derived mesenchymal stem cell proliferation and osteogenic differentiation in vitro

In the present study, the in vitro effects of novel strontium-modified calcium phosphate bone cements (SrCPCs), prepared using two different approaches on human-bone-marrow-derived mesenchymal stem cells (hMSCs), were evaluated. Strontium ions, known to stimulate bone formation and therefore already used in systemic osteoporosis therapy, were incorporated into a hydroxyapatite-forming calcium phosphate bone cement via two simple approaches: incorporation of strontium carbonate crystals and substitution of Ca²⁺ by Sr²⁺ ions during cement setting. All modified cements released 0.03–0.07 mM Sr²⁺ under in vitro conditions, concentrations that were shown not to impair the proliferation or osteogenic differentiation of hMSCs. Furthermore, strontium modification led to a reduced medium acidification and Ca²⁺ depletion in comparison to the standard calcium phosphate cement. In indirect and direct cell culture experiments with the novel SrCPCs significantly enhanced cell proliferation and differentiation were observed. In conclusion, the SrCPCs described here could be beneficial for the local treatment of defects, especially in the osteoporotic bone.     

The effects of fluoride,strontium, theobromine and their combinations on caries lesion rehardening and fluoridation

ObjectiveThe aim was to investigate the effects of fluoride, strontium, theobromine and their combinations on caries lesion rehardening and fluoridation (EFU) under pH cycling conditions.DesignHuman enamel specimens were demineralized at 37 °C for 24 h using a pH 5.0 solution containing 50 mM lactic acid and 0.2% Carbopol 907 which was 50% saturated with respect to hydroxyapatite. Lesions were assigned to nine treatment groups (n = 16) based on Knoop surface microhardness indentation length.Treatmentaqueous solutions were: placebo, 11.9 mM sodium fluoride (F), 23.8 mM sodium fluoride (2 × F), 1.1 mM strontium chloride hexahydrate (Sr), 1.1 mM F theobromine, Sr + theobromine, F + Sr, F + theobromine, F + Sr + theobromine. Lesions were pH cycled for 5d (daily protocol: 3 × 1min-treatment; 2 × 60min-demineralization; 4 × 60 min & overnight-artificial saliva). Knoop indentation length was measured again and%surface microhardness recovery (%SMHr) calculated. EFU was determined using the acid-etch technique. Data were analysed using ANOVA.ResultsModel showed fluoride dose-response for both variables (2 × F > F > placebo). For%SMHr, F + Sr+/−theobromine resulted in more rehardening than F, however less than 2 × F. F + theobromine was similar to F. For EFU, F + Sr was inferior to F, F + theobromine and F + Sr + theobromine which were similar and inferior to 2 × F. In absence of fluoride, Sr, theobromine or Sr + theobromine were virtually indistinguishable from placebo and inferior to F.ConclusionsIt can be concluded that a) strontium aids rehardening but not EFU and only in presence of fluoride; b) theobromine does not appear to offer any anti-caries benefits in this model; c) there are no synergistic effects between strontium and theobromine in the presence or absence of fluoride.     

Radiation-induced meningeal and pituitary tumors in the rat after prenatal application of strontium-90

Summary Strontium-90 was injected i. v. into pregnant rats on day 18 post conception (p. c.). This caused a remarkable transplacental radioactivity uptake and accumulation in the ossification centers of the skull basis. The total radiation dose within the surface of these regions was consequently calculated to be 0.6–1.2 Gy within the entire lifespan. About 50% of it was delivered during the 7 days following the injection of the isotope. the pathologic examination of the offspring throughout their lifetime revealed a pituitary tumor frequency in the exposed groups which was about tenfold in the males and threefold in the females in comparison to the controls. A very outstanding result in the animals treated was the occurrence of metastasizing meningeal sarcomas in about 6% of all cases. In four cases (=2%) the simultaneous occurrence of a pituitary adenoma and of a meningeal sarcoma could be observed.