A critical role of IFNγ in priming MSC-mediated suppression of T cell proliferation through up-regulation of BT-H1

Bone-marrow-derived mesenchymal stem cells （MSCs） have been shown to possess immunosuppressive properties, e.g., by inhibiting T cell proliferation. Activated T cells can also enhance the immunosuppression ability of MSCs. The precise mechanisms underlying MSC-mediated immunosuppression remain largely undefined, although both cell-cell contact and soluble factors have been implicated; nor is it clear how the immunosuppressive property of MSCs is modulated by T cells. Using MSCs isolated from mouse bone marrow, we show here that interferon gamma （IFNγ）, a well-known proinflammatory cytokine produced by activated T cells, plays an important role in priming the immunosuppressive property of MSCs. Mechanistically, IFNγ acts directly on MSCs and leads to up-regulation of B7-H1, an inhibitory surface molecule in these stem cells. MSCs primed by activated T cells derived from IFNγ-/- mouse exhibited dramatically reduced ability to suppress T cell proliferation, a defect that can be rescued by supplying exogenous IFNγ. Moreover, siRNA-mediated knockdown of B7-H1 in MSCs abolished immunosuppression by these cells. Taken together, our results suggest that IFNγ plays a critical role in triggering the immunosuppresion by MSCs through upregulating B7-H1 in these cells, and provide evidence supporting the cell-cell contact mechanism in MSC-mediated immunosuppression.

Optimal time for mesenchymal stem cell transplantation in rats with myocardial infarction

Background:Bone marrow mesenchymal stem cell (MSC) transplantation is a promising strategy in the treatment of myocardial infarction (MI). However, the time for transplanting cells remains controversial. The aim of this study was to find an optimal time point for cell transplantation. Methods: MSCs were isolated and cultured from Sprague-Dawley (SD) rats. MI model was set up in SD rats by permanent ligation of left anterior descending coronary artery. MSCs were directly injected into the infarct border zone at 1 h, 1 week and 2 weeks after MI, respectively. Sham-operated and MI control groups received equal volume of phosphate buffered saline (PBS). At 4 weeks after MI, cardiac function was assessed by echocardiography; vessel density was analyzed on hematoxylin-eosin stained slides by light microscopy; the apoptosis of cardiomyocytes was evaluated by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay; the expressions of proteins were analyzed by Western blot. Results: MSC transplantation improved cardiac function, reduced the apoptosis of cardiomyocytes and increased vessel density. These benefits were more obvious in 1-week group than in 1-h and 2-week groups. There are more obvious in-creases in the ratio of bcl-2/bax and the expression of vascular endothelial growth factor (VEGF) and more obvious decreases in the expression of cleaved-caspase-3 in 1-week group than those in other two groups. Conclusion: MSC transplantation was beneficial for the recovery of cardiac function. MSC transplantation at 1 week post-MI exerted the best effects on increases of cardiac function, anti-apoptosis and angiogenesis.

Study on semi-active control of mega-sub controlled structure by MR damper subject to random wind loads

The recently proposed mega-sub controlled structure （MSCS）, a new type of structure associated with the design and construction of super-tall buildings, has attracted the attention of designers for use in enhancing the control effectiveness in mega-frame buildings. In this paper, a dynamic equation and method to assemble parameter matrixes for a mega-sub controlled structure under random wind loads is presented. Semi-active control using magnetorheological dampers for the MSCS under random wind loads is investigated, and is compared with a corresponding system without dampers. A parametric study of the relative stiffness ratio and relative mass ratio between the mega-frame and the substructures, as well as the additional column stiffness ratio that influences the response control effectiveness of the MSCS, is discussed. The studies reveal, for the first time, that different control mechanisms exist. The results indicate that the proposed structure employing semi-active control can offer an effective control mechanism. Guidelines for selecting parameters are provided based on the analytical study.

The genomic landscapes of histone H3-Lys9 modifications of gene promoter regions and expression profiles in human bone marrow mesenchymal stem cells

Mesenchymal stem cells （MSCs） of nonembryonic origins possess the proliferation and multi-lineage differentiation potentials. It has been established that epigenetic mechanisms could be critical for determining the fate of stem cells, and MSCs derived from different origins exhibited different expression profiles individually to a certain extent. In this study, ChiP-on-chip was used to generate genome-wide histone H3-Lys9 acetylation and dimethylation profiles at gene promoters in human bone marrow MSCs. We showed that modifications of histone H3-Lys9 at gene promoters correlated well with mRNA expression in human bone marrow MSCs. Functional analysis revealed that many key cellular pathways in human bone marrow MSC self-renewal, such as the canonical signaling pathways, cell cycle pathways and cytokine related pathways may be regulated by H3-Lys9 modifications. These data suggest that gene activation and silencing affected by H3-Lys9 acetylation and dimethylation, respectively, may be essential to the maintenance of human bone marrow MSC self-renewal and multi-potency.

Preparation of new tissue engineering bone-CPC/PLGA composite and its application in animal bone defects

To investigate the feasibility of implanting the biocomposite of calcium phosphate cement(CPC)/polylactic acid-polyglycolic acid(PLGA) into animals for bone defects repairing,the biocomposite of CPC/PLGA was prepared and its setting time,compressive strength,elastic modulus,pH values,phase composition of the samples,degradability and biocompatibility in vitro were tested.The above-mentioned composite implanted with bone marrow stromal cells was used to repair defects of the radius in rabbits.Osteogenesis was histomorphologically observed by using an electron-microscope.The results show that compared with the CPC,the physical and chemical properties of CPC/PLGA composite have some differences in which CPC/PLGA composite has better biological properties.The CPC/PLGA composite combined with seed cells is superior to the control in terms of the amount of new bones formed after CPC/PLGA composite is implanted into the rabbits,as well as the speed of repairing bone defects.The results suggest that the constructed CPC/PLGA composite basically meets the requirements of tissue engineering scaffold materials and that the CPC/PLGA composite implanted with bone marrow stromal cells may be a new artificial bone material for repairing bone defects because it can promote the growth of bone tissues.

Role of Caspase-3 Inhibitor in Induced Anoikis of Mesenchymal Stem Cells In Vitro

By preventing mesenchymal stem cells （MSCs） from adhering to precoated agarose to create a model of MSC suspension in vitro, we investigated anoikis in MSCs and the role of caspase-3 in the anoikis. The cultured MSCs were randomly divided into 3 groups： the anoikis group, caspase-3 inhibitor group and control group. Before experiment, we coated dishes with 1.5 % agarose; in the anoikis group, MSCs were put into the precoated dishes; and in the inhibitor group, caspase-3 inhibitor and MSCs were also put into the precoated dishes; but there were not intervention in the control group. MSCs were collected at 2 h, 6 h, 12 h and 24 h. The alteration of caspase-3 activity was evaluated by caspase-3 fluorometric assay and western blot analysis. The apoptosis rates were detected by flow cytometry. MSCs were round and suspended sufficiently in the anoikis and inhibitor groups. Caspase-3 fluorometric assay showed that there were significant differences in statistics between the anoikis group and the others （P〈0.05）. Western blot analysis discovered that caspase-3 expression.in the anoikis group was more than that in the control and inhibitor groups （P〈0.05）. Flow cytometry showed that the apoptosis peak appeared in all the three groups, but it increased dramatically in the anoikis group. The apoptosis rates in the inhibitor and control groups were low and stable. And there were significant differences in statistics between the anoikis group and the others （P〈0.05）. MSCs will undergo anoikis in suspended condition if they are separated from the extracellular matrix. Caspase-3 inhibitors can suppress caspase-3 activity and reduce the apoptosis rate significantly. Caspase-3 plays a vital part in induced MSC anoikis in vitro. MSCs suspension culture system might be set up with argorose and caspase-3 inhibitor.

Osteogenic differentiation of mesenchymal stem cells promoted by overexpression of connective tissue growth factor

Objective:Large segmental bone defect repair remains a clinical and scientific challenge with increasing interest focusing on combining gene transfection with tissue engineering techniques.The aim of this study is to investigate the effect of connective tissue growth factor(CTGF) on the proliferation and osteogenic differentiation of the bone marrow mesenchymal stem cells(MSCs).Methods:A CTGF-expressing plasmid(pCTGF) was constructed and transfected into MSCs.Then expressions of bone morphogenesis-related genes,proliferation rate,alkaline phosphatase activity,and mineralization were examined to evaluate the osteogenic potential of the CTGF gene-modified MSCs.Results:Overexpression of CTGF was confirmed in pCTGF-MSCs.pCTGF transfection significantly enhanced the proliferation rates of pCTGF-MSCs(P<0.05).CTGF induced a 7.5-fold increase in cell migration over control(P<0.05).pCTGF transfection enhanced the expression of bone matrix proteins,such as bone sialo-protein,osteocalcin,and collagen type I in MSCs.The levels of alkaline phosphatase(ALP) activities of pCTGF-MSCs at the 1st and 2nd weeks were 4.0-and 3.0-fold higher than those of MSCs cultured in OS-medium,significantly higher than those of mock-MSCs and normal control MSCs(P<0.05).Overexpression of CTGF in MSCs enhanced the capability to form mineralized nodules.Conclusion:Overexpression of CTGF could improve the osteogenic differentiation ability of MSCs,and the CTGF gene-modified MSCs are potential as novel cell resources of bone tissue engineering.

Effects of insulin-like growth factor-1 on the properties of mesenchymal stem cells in vitro

Objective:To explore the effects of insulin-like growth factor-1(IGF-1) on migration,proliferation and differentiation of mesenchymal stem cells(MSCs).Methods:MSCs were obtained from Sprague-Dawley rats by a combination of gradient centrifugation and cell culture techniques and treated with IGF-1 at concentrations of 5-20 ng/ml.Proliferation of MSCs was determined as the mean doubling time.Expression of CXC chemokine receptor 4(CXCR4) and migration property were determined by flow cytometry and transwell migration essay,respectively.mRNA expression of GATA-4 and collagen II was determined by reverse transcription-polymerase chain reaction(RT-PCR).Results:The mean doubling time of MSC proliferation was decreased,and the expression of CXCR4 on MSCs and migration of MSCs were increased by IGF-1,all in a dose-dependent manner,while the optimal concentration of IGF-1 on proliferation and migration was different.IGF-1 did not affect the expression of GATA-4 or collagen II mRNA.Conclusions:IGF-1 dose-dependently stimulated the proliferation of MSCs,upregulated the expression of CXCR4,and accelerated migration.There was no apparent differentiation of MSCs to cardiomyocytes or chondrocytes after culturing with IGF-1 alone.

Multipotent mesenchymal stromal cells are fully permissive for human cytomegalovirus infection

Congenital human cytomegalovirus(HCMV) infection is a leading infectious cause of birth defects.Previous studies have reported birth defects with multiple organ maldevelopment in congenital HCMV-infected neonates. Multipotent mesenchymal stromal cells(MSCs) are a group of stem/progenitor cells that are multi-potent and can self-renew, and they play a vital role in multiorgan formation. Whether MSCs are susceptible to HCMV infection is unclear. In this study, MSCs were isolated from Wharton's jelly of the human umbilical cord and identified by their plastic adherence, surface marker pattern, and differentiation capacity. Then, the MSCs were infected with the HCMV Towne strain, and infection status was assessed via determination of viral entry,replication initiation, viral protein expression, and infectious virion release using western blotting,immunofluorescence assays, and plaque forming assays. The results indicate that the isolated MSCs were fully permissive for HCMV infection and provide a preliminary basis for understanding the pathogenesis of HCMV infection in non-nervous system diseases, including multi-organ malformation during fetal development.

Imipramine Inhibits Adipogenic Differentiation in Both 3T3-L1 Preadioocvtes and Mouse Marrow Stromal Cells

Imipramine （IM） has been widely used clinically for the treatment of mental disorders. Its actions on tissues or organs other than the nervous system also need to be understood for its proper clinical use. In this study, the effects of IM on adipogenic differentiation in both 3T3-L1 preadipocytes and mouse marrow stromal cells （MSCs） were investigated. The results showed that fewer adipocytic cells were developed from 3T3-L1 preadipocytes in the presence of 0.001 to 1 μmol/L of IM as compared to control. Similar inhibitory effect was also observed in mouse MSCs. The decrease in the formation of adipocytes was accompanied with significant down-regulation at mRNA expression of the early adipogenic transcription factor, peroxisome proliferator-activated receptor γ2 （PPARγ2）. Western blot analysis further revealed that the protein expression of PPARγ2 was reduced markedly in ceils treated with IM at concentrations of 0.01, 0.1 and 1 μmol/L, suggesting that the suppression on PPAR72 was involved in IM＇s inhibition on MSCs adipogenesis. Moreover, IM at the above concentrations could stimulate the mRNA expression of β2-adrenergic receptor （AR） and β3-AR, which implicated that the effect of IM on adipogenic differentiation was partially mediated by β-ARs. Our results demonstrated for the first time that the conventional antidepressive imipramine exerts accompanied inhibitory effect on adipocyte formation, which may have possible clinical implications.