[Mechanism study of platelet derived growth factor receptor alpha on the bidirectional differentiation regulation of glioma-associated oncogene homolog 1-positive mesenchymal stem cells in mice].

Objective: To investigate the role of platelet derived growth factor receptor alpha (PDGFRα) on bidirectional differentiation of glioma-associated oncogene homolog 1-positive mesenchymal stem cells (Gli1+-MSC). Methods: Breeding double reporter transgenic mice ROSAmT/mG/Gli1-CreERt2/PDGFRαfl (Experimental group) and ROSAmT/mG/Gli1-CreERt2 (Control group), 20 mice in each of the two groups at four weeks of age were selected, MSC were isolated from the mouse aortic epithelium. After tamoxifen inducement, the two groups of Gli1+-MSC were screened by green fluorescent protein (GFP) labeling and flow cytometry sorting. PDGFRα was conditionally knocked out in the experimental group, and the control group Gli1+-MSC expressed PDGFRα normally. The two groups of Gli1+-MSC were subjected to adipogenic induction and fibrogenic induction, the Western blotting was performed to detect PDGFRα, adipocyte markers [perilipin and CCAAT/enhancer binding protein alpha (C/EBPα)] and fibrogenic markers [alpha smooth muscle actin (α-SMA) and fibroblast-specific protein 1 (FSP-1)] and semi-quantitative analysis was performed. The degree of cellular adipose differentiation after bidirectional induction of Gli1+-MSC in both groups was observed by oil red O staining and analyzed semi-quantitatively. Results: After tamoxifen induction, Gli1+-MSC could be accurately isolated from flow cytometry by GFP labeling. Via adipogenic differentiation, the expression of PDGFRα in the experimental group (0.017±0.002) was significantly lower than that in the control group (0.184±0.012) (t=25.48，P=0.002). The protein expressions of perilipin (3.138±0.414) and C/EBPα (3.565±0.289) were significantly higher than those in the control group (2.312±0.218 and 2.179±0.103, respectively) (t=6.21，P=0.025；t=6.69，P=0.022). Thus, the knock-out of PDGFRα enhanced the adipogenic differentiation ability of Gli1+-MSC. After fibrogenesis induction, the protein expressions of PDGFRα, α-SMA and FSP-1 in the experimental group (0.030±0.001, 0.932±0.177 and 0.276±0.020, respectively) were significantly lower than those in the control group (0.439±0.006, 1.352±0.170 and 0.835±0.097, respectively) (t=149.40, P<0.001; t=66.38,P<0.001; t=11.41,P<0.08). This suggested that the knock-out of PDGFRα significantly inhibited Gli1+-MSC differentiation toward fibroblasts. After bidirectional induction, significantly less adipocyte formation was seen in the control group and more in the experimental group. Quantitative analysis showed that the amount of oil red O staining in the experimental group (0.461±0.042) was significantly higher than that in the control group (0.017±0.007) after bidirectional induction (t=23.20, P<0.01). Conclusions: PDGFRα plays an important role in the regulation of bidirectional differentiation of vascular adventitial Gli1+-MSC.

[Antibacterial effectiveness of calcium silicate-based root canal sealer against Enterococcus faecalis biofilms in infected dentinal tubules in vitro].

Objective: To evaluate the antiseptic effect of combined using of 5% sodium hypochlorite and calcium silicate-based root canal sealer against Enterococcus faecalis (Ef) biofilms in infected dentinal tubules in vitro. Methods: Cells of Ef were inoculated into the dentinal tubules of single-rooted teeth (without caries, periapical lesions and malformations extracted due to periodontal disease or orthodontic reasons; collected from Department of Maxillofacial Surgery, The First Affiliated Hospital of Zhengzhou University) with centrifugation and incubated in brain-heart infusion (BHI) to form 3-week-old biofilms. The infected samples were subjected to sodium hypochlorite or sterile water bathing for 10 minutes followed by calcium silicate-based root canal sealer (iRoot SP) (calcium silicate-based group), Gutta-percha group and sterile water group placed on the root canal wall for 1, 4 and 12 weeks. There were two samples in each treatment at each point. The antiseptic effectiveness of combined use of sodium hypochlorite and calcium silicate-based root canal sealer was analyzed by laser scanning confocal microscope (LSCM), ANOVA and LSD-t test. Results: After treatment with 5% sodium hypochlorite, in calcium silicate-based group for 4 and 12 weeks more Ef biofilm cells [(75.3±3.5)% and (74.8±3.8)%] were killed than in Gutta-percha group [(65.9±4.1)% and (63.0±3.7)%] and sterile water group [(63.9±4.0)% and (64.2±3.5)%] (P<0.05). After being treated with sterile water, the proportion of dead bacterial cells in calcium silicate-based group for 1, 4 and 12 weeks [(27.5±4.6)%, (43.0±4.4)% and (40.3±6.1)%] were more than those in Gutta-percha group and sterile water group (P<0.05). After being treated with 5% sodium hypochlorite or sterile water, more biofilm bacteria were killed in calcium silicate-based group for 4 and 12 weeks than in calcium silicate-based group for 1 week (P<0.05). Conclusions: The combined use of sodium hypochlorite and calcium silicate-based root canal sealer kills more biofilm cells in infected dentinal tubules.

Effects of alendronate on the proliferation and osteogenic differentiation of MG-63 cells.

Previous studies of the direct actions of bisphosphonates on bone have mainly been limited to their effects on bone-resorbing osteoclasts and little is known about the direct effects of bisphosphonates on osteoblasts. Here we report the direct effects of alendronate on the proliferation and osteogenic differentiation of the MG-63 osteoblast-like cell line. Cell proliferation was determined with the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay, osteogenic differentiation was evaluated with an alkaline phosphatase bioassay and by analysis of gene expression by reverse transcription-polymerase chain reaction, and the extent of calcium deposition was measured using Alizarin Red S staining. Alendronate significantly increased cell numbers over control values, with the greatest effect at 10(-8) M. Alkaline phosphatase activity and gene expression of bone morphogenetic protein 2, type I collagen and osteocalcin were increased after alendronate treatment. Alendronate also stimulated calcium deposition. We conclude that alendronate, apart from inhibiting osteoclastic bone resorption, is also a promoter of osteoblast proliferation and maturation.

YKL-40: a potential biomarker for osteoarthritis.

Current pharmacotherapy for osteoarthritis (OA) alleviates pain and inflammation but does not protect the articular cartilage from further damage or affect disease progression. Biological markers such as YKL-40 may provide a snapshot of current events in joint tissues, allowing rapid assessment of treatments. This review discusses recent data regarding YKL-40, with an emphasis on the relationship between YKL-40 and OA. The presence of YKL-40 in cartilage and synovium in OA patients correlates with histopathological changes and may reflect local disease activity. In addition, the levels of YKL-40 in serum and synovial fluid also seem to correlate with disease severity. The functional role of YKL-40 is not yet clear, but its production as part of the inflammatory response in articular chondrocytes may modulate the cellular response to proinflammatory cytokines, acting to limit connective tissue degradation. Further elucidation of its roles and relationships may enable YKL-40 to act as a useful biomarker in the development of therapies for OA.

Visfatin: a potential therapeutic target for rheumatoid arthritis.

Rheumatoid arthritis (RA) is usually a chronic, systemic inflammatory disorder primarily targeting the synovium and articular cartilage. It is incurable, costly and responds poorly to treatment. Methotrexate alone or in combination with conventional and/or biological disease-modifying antirheumatic drugs (DMARDs) is often used to induce remission of active disease. The effectiveness of treatment is, however, limited and most patients develop chronic disability and require total knee arthroplasty or total hip replacement. Emerging therapies targeting specific cytokines and growth factors in the RA inflammatory cascade offer potent new means of modifying disease activity. Recently, increased concentrations of adipokines, including visfatin, mainly produced by adipocytes in serum and joint synovial fluid, were found in RA patients. Visfatin has important pro-inflammatory and catabolic roles in RA pathogenesis and is now being studied as a potential therapeutic target for RA. Here we discuss the relationship between visfatin and RA and its potential as a therapeutic target for RA.

Aggrecanase and aggrecan degradation in osteoarthritis: a review.

Aggrecanase-mediated aggrecan degradation is a significant event in early-stage osteoarthritis (OA). Aggrecanases belonging to the 'A Disintegrin And Metalloproteinase with ThromboSpondin motifs' (ADAMTS) family of proteinases play a significant role in aggrecan depletion in osteoarthritic cartilage. There has been considerable interest in the possible role of these aggrecanases, especially ADAMTS-4 and ADAMTS-5, as therapeutic targets in OA. This article discusses recent data regarding ADAMTS-4 and ADAMTS-5 in OA, with emphasis on the relationship between aggrecanase and aggrecan degradation as well as the role of aggrecanase in OA.

Stress analysis of different wall thicknesses of implant fixture with various boundary levels.

The aim of the present work is to develop 3D finite element models of implant fixture with different wall thicknesses to predict maximum stress concentration sites and distribution contours after loading. A maximum lateral force of 150 N was applied to simulate horizontal occlusal forces. When the fixtures were constrained to simulate different boundary levels, the maximum equivalent stress (max EQV) was always located at the implant-bone interface. Max EQV increased when the wall thickness or boundary level was reduced to a certain extent. The fixture with a wall thickness of 0.97 mm demonstrated the smallest stress increase ratio when the boundary level was lowered. Our results indicated that both wall thickness and the boundary level played important roles in maintaining a well-distributed stress level within the fixture. The stress concentration decreased when the fixture wall became thicker, however, this effect was less significant when the surrounding bone level was reduced.

A piecewise linear approximation based on a statistical model.

A statistical model is introduced and then, based on it, a piecewise linear approximation algorithm of linear computational complexity is presented. The advantages of the algorithm are proved experimentally in small sample cases and theoretically in the large sample case. The paper is closed with a discussion on some possible extensions.

On the chain code of a line.

In 1970 Freeman suggested the following criteria which the chain code of a line must meet [1], [2]: 1) at most two basic directions are present and these can differ only by unity, modulo eight, 2) one of these values always occurs singly, 3) successive occurrences of the principal direction occurring singly are as uniformly spaced as possible. In this correspondence we give the following: 1) an algorithm presentation of Freeman's three properties about the chain code of a line and the proof that it is also the algorithm recognizing whether a chain code is the chain code of a line, 2) the proof of the equivalence of the above presentation and Rosenfeld's chord property [3].