[Research progresses in the cytoskeleton and its functions in osteoblasts].

Osteoblasts are cells that are in charge of bone formation and play an important role in bone remodeling. Cytoskeleton is widely found in eukaryotic cells, and not only plays an important role in maintaining the order of cell morphology and internal structure, but also may be involved in mechanotransduction, the regulation of cell differentiation, proliferation, apoptosis, migration and the expression of related genes. The studies on the function of the cytoskeleton in osteoblasts may provide new ideas for dental fields in such aspects as guided bone regeneration, orthodontic tooth movement, distraction osteogenesis and postoperative bone healing. This article reviewed the research progresses about cytoskeleton in osteoblasts.

[(*)AG490 could suppress bone marrow mesenchymal stem cells migration, mineralization and bone defect healing via inhibiting Jak2-STAT3 pathway].

Objective: To study the effect of Jak2-STAT3 pathway on cell proliferation, migration, mineralization and bone defect healing via simulating Jak2-STAT3 pathway inhibitor AG490 to bone marrow mesenchymal stem cells (BMSC) and bone defect mice models. Methods: The effect of AG490 on BMSC proliferation was measured by MTT (methyl thiazolyl tetrazolium) assay. Regulation of AG490 on BMSC migration was tested by scratch assay and transwell assay. The BMSC migration related gene, matrix metalloproteinase (MMP)-7, MMP-9 and CXC subfamily receptor 4 (CXCR4), regulated by AG490 was studied by real-time PCR. Western blotting was adopted to analyze the regulation of Jak2-STAT3 phosphorylation through the simulation of AG490. The alizarin red staining and alkaline phosphatase (ALP) activity assay were performed to measure the effect of AG490 on BMSC mineralization and osteogenic differentiation. Mice femur bone defect models were built to analyzed the effect of AG490 on bone remodeling. Results: AG490 significantly suppressed the migration rate of BMSC at 1 d and 2 d in the experiment group [(12.42±7.50) %, (41.8±2.6)%] compared with the control group [(55.5±9.9)%, (86.9±8.7)%] in scratch assay (P=0.000, P=0.000), the number of migrated BMSC in the experiment group (22.8± 5.9) was significantly suppressed compared with the control group (58.3±6.6) in Transwell assay (P=0.000). The expression of MMP-7, MMP-9 and CXCR4 were significantly downregulated in experiment group [(0.5± 0.1), (0.1±0.1) and (0.35±0.07)] compared with the control group [(1.1±0.1), (1.06±0.33), (1.08±0.13)] (P= 0.0003, P=0.000 and P=0.000). Also, the phosphorylation of Jak2-STAT3 was downregulated by AG490 in western blotting. After BMSCs were osteogenic induced for 14 days, the formation of mineralized nodule and the ALP activity of BMSC is significantly suppressed in experiment group (8.0±2.1) compared with the control group (35.7 ± 1.8) (P=0.0005). AG490 suppressed the bone defects healing,the expression level of phosphorylated Jak2 and phosphorylated STAT3, and the number of alkaline phosphatase positive cell at defect area in vivo is lower in experiment group than the control group. AG490 suppressed the relatively bone density at the defect area significantly (P=0.0004) at 5(th) week after the surgery. Conclusions: AG490 could suppress proliferation, migration and mineralization to of BMSCs regulate bone defect healing via inhibiting Jak2-STAT3 pathway.

Functional role of NKX2-5 and Smad6 expression in developing rheumatic heart disease.

OBJECTIVE: Rheumatic heart disease (RHD) results due to the cross reaction of the host immune system when it develops immunity against group A streptococcal infection. This autoimmune disease progress with different pathological conditions and the genes associated with it are still less understood. MATERIALS AND METHODS: To understand the role of NKX2-5 and Smad-6 in developing an RHD, we successfully developed RHD model using BALB/c mice and we evaluate the expression of NKX2-5 and Smad-6 in different conditions. RESULTS: The disease conditions are confirmed through histological sectioning of RHD heart tissue with its associated Aschoff bodies. The histological of control heart tissue in the absence of NKX2-5 looks abnormal with an enlarged nucleus and in the absence of Smad-6 the solid nature of heart tissue loosens. The mice developed a complex form of acute RHD with tissue hardening in the absence of either NKX2-5 or Smad-6 which are confirmed in NKX2-5 or Smad-6 null mice. Immunohistochemical studies reveal that the NKX2-5 and Smad-6 expression get down regulated on developing with RHD. Through experiments, we detected that both Nkx2-5 and Smad-6 are both inter-dependable and it negatively regulated each other by inhibiting them. In the absence of NKX2-5 or Smad-6, a severe form of RHD is observed together with down-regulation of either NKX2-5 or Smad-6. CONCLUSIONS: The present investigation of NKX2-5 and Smad-6 in RHD provides a new insight of data that helps to understand the disease pathogenesis.

[Osteoclast size regulation and its mechanism].

Osteoclasts are multinucleated cells deriving from the monocyte/macrophage haematopoietic lineage. They contain large amount of tartrate resistant acid phosphatase and cathepsin K and play an important role in resorption of mineralized tissues such as bone and dentine. The resorption capabilities by osteoclasts are thought to be associated with several oral diseases such as periodontitis, periapical periodontitis, peri-implantitis and osteoporosis. Osteoclast size is one of the key evaluating parameters of osteoclast resorption activities. Findings of osteoclast size regulation research may provide a novel breakthrough for the treatment of bone resorption disorder diseases. This article summarized and reviewed the previous relevant experiments and studies of osteoclast size regulation and its mechanism.

Analysis and clinical significance of microRNA-499 expression levels in serum of patients with acute myocardial infarction.

The aim of this study was to investigate the expression level of microRNA-499 and its clinical significance in serum of patients with acute myocardial infarction (AMI). We recruited 59 patients with AMI and 60 healthy individuals undergoing physical examination in our hospital during the same period as controls. Peripheral blood was drawn in the morning on the same day of microRNA extraction. The expression level of microRNA-499 was analyzed by real-time fluorescent quantitative polymerase chain reaction (qPCR). The sensitivity and specificity of the clinical diagnosis of AMI were analyzed by a receiver operating characteristic (ROC) curve. Fluorescent qPCR analysis showed that the expression of microRNA-499 in serum of patients with AMI was significantly higher than in controls (P < 0.05). MicroRNA-499 was detected in blood serum 3 h post-AMI, reaching a peak after 12 h and declining after 15 h. The area under the ROC curve (AUC) for the gold standard cardiac troponin I (cTnI) was 0.971 [95% confidence interval (CI): 0.951-1.000], and for the microRNA-499, AUC = 0.915 (95%CI: 0.826-1.000). When the microRNA-499 levels in patient and control (> 1.5) sera were compared, the sensitivity of microRNA-499 in judging AMI was found to be 86.37% and the specificity was 93.47%. Our results demonstrated that the expression levels of microRNA-499 in serum of patients with AMI were abnormal. Its high sensitivity and specificity for the diagnosis of AMI suggest that it would be useful as an auxiliary index for clinical diagnosis of AMI.