Qiang Zheng

Osteochondral repair using porous poly(lactide-co-glycolide)/nano-hydroxyapatite hybrid scaffolds with undifferentiated mesenchymal stem cells in a rat model.

In this study, a novel three-dimensional poly (lactide-co-glycolide) (PLGA)/nano-hydroxyapatite (NHA) scaffold was fabricated by a thermally induced phase separation technique and its potential application in cartilage tissue-engineering was investigated. The PLGA scaffold was used as a control and mesenchymal stem cells (MSCs) were seeded in both scaffolds. After 12-days culture, SEM images and confocal laser scanning microscopy illustrated that MSCs attached more moderately and more cells distributed in PLGA/NHA scaffolds. MTT test and DNA assay showed that the viability and proliferation of MSCs in PLGA/NHA scaffolds were significantly superior to PLGA scaffolds during in vitro culture. Through in vivo study, the efficacy of this scaffold combining with MSCs for repairing articular osteochondral defects was evaluated in a rat model. Osteochondral defects in rats knees were left untreated, or treated with PLGA/NHA-MSCs composites or PLGA-MSCs composites. Twelve weeks after operation, histological examination revealed that the defects in the PLGA/NHA-MSCs treated group were filled with smooth and hyaline-like cartilage with abundant glycosaminoglycan and collagen type II deposition, but deficient in collagen type I at 12 weeks after operation. To investigate the final fate of MSCs transplanted into the defect areas, the fluorescent dye CM-DiI was used to prelabel cells. At 12 weeks after transplantation, we still observed the red fluorescence in the repair area. These findings suggest that the PLGA/NHA-MSCs composite may be potentially used for cartilage repair in clinical application. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res, 2010.

Different effects of intermittent and continuous fluid shear stresses on osteogenic differentiation of human mesenchymal stem cells

A reasonable mechanical microenvironment similar to the bone microenvironment in vivo is critical to the formation of engineering bone tissues. As fluid shear stress (FSS) produced by perfusion culture system can lead to the osteogenic differentiation of human mesenchymal stem cells (hMSCs), it is widely used in studies of bone tissue engineering. However, effects of FSS on the differentiation of hMSCs largely depend on the FSS application manner. It is interesting how different FSS application manners influence the differentiation of hMSCs. In this study, we examined the effects of intermittent FSS and continuous FSS on the osteogenic differentiation of hMSCs. The phosphorylation level of ERK1/2 and FAK is measured to investigate the effects of different FSS application manners on the activation of signaling molecules. The results showed that intermittent FSS could promote the osteogenic differentiation of hMSCs. The expression level of osteogenic genes and the alkaline phosphatase (ALP) activity in cells under intermittent FSS application were significantly higher than those in cells under continuous FSS application. Moreover, intermittent FSS up-regulated the activity of ERK1/2 and FAK. Our study demonstrated that intermittent FSS is more effective to induce the osteogenic differentiation of hMSCs than continuous FSS.

Selective COX-2 inhibitor versus nonselective COX-1 and COX-2 inhibitor in the prevention of heterotopic ossification after total hip arthroplasty: a meta-analysis of randomised trials

Whether selective cyclo-oxygenase-2 (COX-2) inhibitors are equally effective compared to nonselective NSAIDs for the prevention of heterotopic ossification (HO) after total hip arthroplasty (THA) is still unclear. We carried out a comprehensive search strategy, in which only randomised controlled trials were included. Two reviewers independently assessed methodological quality and extracted outcome data. Analyses were performed using Stata version 10.0. Four eligible randomised controlled trials totalling 808 patients were included. Meta-analysis results showed that no statistically significant difference was found in overall incidence of HO (RR 1.08; 95% CI 0.71–1.64), incidence of moderate severe HO (Brooker II and III) (RR 0.83; 95% CI 0.48–1.42) and any grade of Brooker classification between two groups. In summary, the selective COX-2 inhibitors are equally effective as nonselective NSAIDs for the prevention of HO after THA. Considering the gastrointestinal side effects of nonselective NSAIDs, we recommend selective COX-2 inhibitors for the prevention of HO after THA. However, future well-designed, randomised controlled trials are still needed to further confirm our results.

Proliferation and osteogenesis of immortalized bone marrow-derived mesenchymal stem cells in porous polylactic glycolic acid scaffolds under perfusion culture

Human bone marrow mesenchymal stem cells (hMSCs) are promising candidates for cell therapy and tissue engineering. However, the life span of hMSCs during in vitro culture is limited. Human telomerase catalytic subunit (hTERT) gene transduction could prolong the life span of hMSCs and maintain their potential of osteogenic differentiation. Therefore, hMSCs transduced with hTERT (hTERT-hMSCs) could be used as a cell model for in vitro tissue engineering experiment because of its prolonged life span and normal cellular properties. A perfusion culture system for proliferation and osteogenesis of hTERT-hMSCs or primary hMSCs in porous polylactic glycolic acid (PLGA) scaffolds is described here. A cell suspension of hTERT-hMSCs or primary hMSCs (5 x 10(5) cells/250 microL) was seeded and then cultured for 12 days in porous PLGA scaffolds (10 mm in diameter, 3 mm in height) under both static and perfusion culture systems. The seeding efficiency, proliferation, distribution and viability, and osteogenesis of cells in scaffolds were evaluated. The perfusion method generated higher scaffold cellularity and proliferation of cells in scaffolds, and hTERT-hMSCs showed the higher proliferation potential than primary hMSCs. Results from fluorescein diacetate (FDA) staining and scanning electron microscopy (SEM) demonstrated homogeneous seeding, proliferation, and viability of hTERT-hMSCs throughout the scaffolds in the perfusion culture system. On the contrary, the static culture yielded polarized proliferation favoring the outer and upper scaffold surfaces, and resulted in decreasing of cells in the central section of the scaffolds. A flow rate of 0.5 mL/min had an effect on osteogenic differentiation of cells in scaffolds. However, the osteogenic medium promoted the osteogenic efficiency of cells. Scaffolds with hTERT-hMSCs had the higher osteogenesis than scaffolds with primary hMSCs. Thus, these results suggest that the flow condition not only allow a better seeding efficiency and homogeneity but also facilitate uniform proliferation and osteogenic differentiation of hTERT-hMSCs in scaffolds. hTERT-hMSCs could be used as stem cell candidates for bone tissue engineering experiments.

Effects of Microgravity Modeled by Large Gradient High Magnetic Field on the Osteogenic Initiation of Human Mesenchymal Stem Cells

Microgravity (MG) leads to a decrease in osteogenic potential of human bone marrow-derived mesenchymal stem cells (hMSCs). In the present study, we used large gradient high magnetic field (LGHMF) produced by a superconducting magnet to model MG (LGHMF-MG) and analyzed the effects of LGHMF-MG on survival, cytoskeleton and osteogenic potential of hMSCs. Results showed that the LGHMF-MG treatment for 6xa0h disrupted the cytoskeleton of hMSCs, and the LGHMF-MG treatment for 24xa0h led to cell death. LGHMF-MG treatments for 6xa0h in early stages of osteogenic induction (the pre-treatment before osteogenic induction, the beginning-treatment in the beginning-stage of osteogenic induction and the middle-treatment in the middle-stage of osteogenic induction) resulted in suppression on osteogenesis of hMSCs. The suppression intensity was reduced gradually as the treatment stage of LGHMF-MG was postponed. The LGHMF-MG treatment for 6xa0h in the ending-stage of osteogenic induction (the ending-treatment) had no obvious effect on osteogenesis of hMSCs. These results indicated that LGHMF-MG should affect the initiation of osteogenesis. Finally, the possible mechanism for the inhibition effect of LGHMF-MG on osteogenesis of hMSCs is discussed.

Could the effect of modeled microgravity on osteogenic differentiation of human mesenchymal stem cells be reversed by regulation of signaling pathways

Abstract Microgravity (MG) results in a reduction in bone formation. Bone formation involves osteogenic differentiation from mesenchymal stem cells (hMSCs) in bone marrow. We modeled MG to determine its effects on osteogenesis of hMSCs and used activators or inhibitors of signaling factors to regulate osteogenic differentiation. Under osteogenic induction, MG reduced osteogenic differentiation of hMSCs and decreased the expression of osteoblast gene markers. The expression of Runx2 was also inhibited, whereas the expression of PPARγ2 increased. MG also decreased phosphorylation of ERK, but increased phosphorylation of p38MAPK. SB203580, a p38MAPK inhibitor, was able to inhibit the phosphorylation of p38MAPK, but did not reduce the expression of PPARγ2. Bone morphogenetic protein (BMP) increased the expression of Runx2. Fibroblast growth factor 2 (FGF2) increased the phosphorylation of ERK, but did not significantly increase the expression of osteoblast gene markers. The combination of BMP, FGF2 and SB203580 significantly reversed the effect of MG on osteogenic differentiation of hMSCs. Our results suggest that modeled MG inhibits the osteogenic differentiation and increases the adipogenic differentiation of hMSCs through different signaling pathways. Therefore, the effect of MG on the differentiation of hMSCs could be reversed by the mediation of signaling pathways.

Active contour model driven by linear speed function for local segmentation with robust initialization and applications in MR brain images

Active contour model (ACM) has been widely used in image segmentation, but the local region based ACM suffers from the sensitivity of the curve initialization, which means that the segmentation can be influenced by the initialized contour greatly. In this paper, we propose a novel local region based ACM. Firstly, we analyze the reason for the sensitivity of the curve initialization, i.e., the blind region and the false edges. Secondly, we propose a novel local region-based linear speed function, in which, the additive factor can solve the blind region and false edge problems, and the multiplicative factor can further improve the additive factor in solving false edge problem. Thirdly, we incorporate the proposed linear speed function into the local approximated signed distanced function based local segmentation framework. In the proposed method, we only need to select one point anywhere inside the object for initialization, which is very convenient for interactive segmentation. Experiments on synthetic and Magnetic Resonance (MR) brain images demonstrate the robustness of the initialization over the ACM driven by the classic local region-based intensity energy, ACM driven by local and global intensity energy and ACM driven by contrast constrained local intensity fitting energy.

The interaction between β1 integrins and ERK1/2 in osteogenic differentiation of human mesenchymal stem cells under fluid shear stress modelled by a perfusion system

Fluid shear stress (FSS) is an important biomechanical factor regulating the osteogenic differentiation of human mesenchymal stem cells (hMSCs) and is therefore widely used in bone tissue engineering. However, the mechanotransduction of FSS in hMSCs remains largely unknown. As β1 integrins are considered to be important mechanoreceptors in other cells, we suspect that β1 integrins should also be important for hMSCs to sense the stimulation of FSS. We used a perfusion culture system to produce FSS loading on hMSCs seeded in PLGA three‐dimensional (3D) scaffolds and investigated the roles of β1 integrins, FAK and ERK1/2 in FSS‐induced osteogenic differentiation of hMSCs. Our results showed that FSS not only markedly increased ALP activity and the expression of ALP, OCN, Runx2 and COLIα genes but also significantly enhanced the phosphorylation of ERK1/2, Runx2 and FAK. FSS‐induced activation of ERK1/2 and FAK was inhibited by blockade of the connection between β1 integrins and ECM with RGDS peptide and integrins β1 monoclonal antibody. Our study also found that FSS could upregulate the expression level of β1 integrins and that this upregulation could be abolished by PD98059. Further investigation indicated that FSS‐activated ERK1/2 led to the phosphorylation of IκBα and NFκB p65. The activation of NFκB p65 resulted in the upregulation of β1 integrin expression. Therefore, it could be inferred that β1 integrins should sense the stimulation of FSS and thus activate ERK1/2 through activating of FAK, and FSS‐activated ERK1/2 feedback to upregulate the expression of β1 integrins through activating NFκB. Copyright

Extracellular signal-regulated kinase1/2 activated by fluid shear stress promotes osteogenic differentiation of human bone marrow-derived mesenchymal stem cells through novel signaling pathways.

It is a classical signaling pathway that the activation of extracellular signal-regulated kinase1/2 (ERK1/2) results in the phosphorylation of runt-related transcription factor 2 (Runx2) and thereby initiates the transcription of osteogenic genes. Recently, it is found that the activation of ERK1/2 resulted from fluid shear stress (FSS) also increased the expression of Runx2 and β1 integrins, and finally enhanced osteogenic differentiation. However, it has been remained largely unknown how ERK1/2 regulates the expression of Runx2 and β1 integrins. We use the perfusion culture system to produce FSS exerting on human bone marrow-derived mesenchymal stem cells (hMSCs) and thus activate ERK1/2. Our study demonstrated that FSS-activated ERK1/2 mediated the expression of osteogenic genes via two novel signaling pathways except for the classical signaling pathway: feedback up-regulation of β1 integrins expression via activating nuclear factor kappa B (NF-κB), and activation of bone morphogenesis proteins (BMPs)/mothers against decapentaplegic (Smad) pathway via activating NF-κB and thereby regulating Runx2 expression. These signaling pathways combined with the classical signaling pathway, with ERK1/2 as a hub node molecule, form a molecular signaling cross-talking network to induce the osteogenic differentiation of hMSCs. The understanding on the mechanism of FSS inducing the osteogenic differentiation of hMSCs will not only be helpful to develop the bone tissue engineering but also provide new targets for drug discovery for treatment of osteoporosis and other related bone-wasting diseases.

Reamed and unreamed intramedullary nailing for the treatment of open and closed tibial fractures: a subgroup analysis of randomised trials.

The choice between reamed and unreamed intramedullary nailing for the treatment of open and closed tibial fractures is an ongoing controversy. We carried out a comprehensive search strategy. Six eligible randomised controlled trials were included. Three reviewers independently assessed methodological quality and extracted outcome data. Analyses were performed using Review Manager 5.0. The results showed lower risks of tibial fracture nonunion and implant failures with reamed nails compared to unreamed nails in closed tibial fractures [relative risk (RR): 0.41, 95% confidence interval (CI): 0.21–0.89, Pu2009=u20090.008 for nonunion and RR: 0.35, 95% CI: 0.22–0.56, Pu2009<u20090.0001 for implant failures], but no statistical differences in risk reduction of malunion, compartment syndrome, embolism and infection. Our results suggested no statistical differences in risk reduction of all the complications evaluated between reamed and unreamed nails in open tibial fractures. In conclusion, our study recommended reamed nails for the treatment of closed tibial fractures. But the choice for open tibial fractures remains uncertain.