技术资料

Germ line mutations in the Adenomatous polyposis coli tumor suppressor gene cause a hereditary form of intestinal tumorigenesis in both mice and man. Here we show that in Apc(Min/+) mice,which carry a heterozygous germ line mutation at codon 850 of Apc,there is progressive loss of immature and mature thymocytes from approximately 80 days of age with complete regression of the thymus by 120 days. In addition,Apc(Min/+) mice show parallel depletion of splenic natural killer (NK) cells,immature B cells,and B progenitor cells in bone marrow due to complete loss of interleukin 7 (IL-7)-dependent B-cell progenitors. Using bone marrow transplantation experiments into wild-type recipients,we have shown that the capacity of transplanted Apc(Min/+) bone marrow cells for T- and B-cell development appears normal. In contrast,although the Apc(Min/+) bone marrow microenvironment supported short-term reconstitution with wild-type bone marrow,Apc(Min/+) animals that received transplants subsequently underwent lymphodepletion. Fibroblast colony-forming unit (CFU-F) colony assays revealed a significant reduction in colony-forming mesenchymal progenitor cells in the bone marrow of Apc(Min/+) mice compared with wild-type animals prior to the onset of lymphodepletion. This suggests that an altered bone marrow microenvironment may account for the selective lymphocyte depletion observed in this model of familial adenomatous polyposis. View Publication

It is well accepted that umbilical cord blood has been a source for hematopoietic stem cells. However,controversy exists as to whether cord blood can serve as a source of mesenchymal stem cells,which can differentiate into cells of different connective tissue lineages such as bone,cartilage,and fat,and little success has been reported in the literature about the isolation of such cells from cord blood. Here we report a novel method to obtain single cell-derived,clonally expanded mesenchymal stem cells that are of multilineage differentiation potential by negative immunoselection and limiting dilution. The immunophenotype of these clonally expanded cells is consistent with that reported for bone marrow mesenchymal stem cells. Under appropriate induction conditions,these cells can differentiate into bone,cartilage,and fat. Surprisingly,these cells were also able to differentiate into neuroglial- and hepatocyte-like cells under appropriate induction conditions and,thus,these cells may be more than mesenchymal stem cells as evidenced by their ability to differentiate into cell types of all 3 germ layers. In conclusion,umbilical cord blood does contain mesenchymal stem cells and should not be regarded as medical waste. It can serve as an alternative source of mesenchymal stem cells to bone marrow. View Publication

The ultimate destination for most gene therapy vectors is the nucleus and nuclear import of potentially therapeutic DNA is one of the major barriers for nonviral vectors. We have developed a novel approach of attaching a nuclear localization sequence (NLS) peptide to DNA in a non-essential position,by generating a fusion between the tetracycline repressor protein TetR and the SV40-derived NLS peptide. The high affinity and specificity of TetR for the short DNA sequence tetO was used in these studies to bind the NLS to DNA as demonstrated by the reduced electrophoretic mobility of the TetR.tetO-DNA complexes. The protein TetR-NLS,but not control protein TetR,specifically enhances gene expression from lipofected tetO-containing DNA between 4- and 16-fold. The specific enhancement is observed in a variety of cell types,including primary and growth-arrested cells. Intracellular trafficking studies demonstrate an increased accumulation of fluorescence labeled DNA in the nucleus after TetR-NLS binding. In comparison,binding studies using the similar fusion of peptide nucleic acid (PNA) with NLS peptide,demonstrate specific binding of PNA to plasmid DNA. However,although we observed a 2-8.5-fold increase in plasmid-mediated luciferase activity with bis-PNA-NLS,control bis-PNA without an NLS sequence gave a similar increase,suggesting that the effect may not be because of a specific bis-PNA-NLS-mediated enhancement of nuclear transfer of the plasmid. Overall,we found TetRNLS-enhanced plasmid-mediated transgene expression at a similar level to that by bis-PNA-NLS or bis-PNA alone but specific to nuclear uptake and significantly more reliable and reproducible. View Publication

Human bone marrow-derived mesenchymal stem cells (MSCs) have the potential to differentiate into mesenchymal tissues like osteocytes,chondrocytes,and adipocytes in vivo and in vitro. The aim of this study was to investigate the in vitro differentiation of MSCs into cells of the endothelial lineage. MSCs were generated out of mononuclear bone marrow cells from healthy donors separated by density gradient centrifugation. Cells were characterized by flow cytometry using a panel of monoclonal antibodies and were tested for their potential to differentiate along different mesenchymal lineages. Isolated MSCs were positive for the markers CD105,CD73,CD166,CD90,and CD44 and negative for typical hematopoietic and endothelial markers. They were able to differentiate into adipocytes and osteocytes after cultivation in respective media. Differentiation into endothelial-like cells was induced by cultivation of confluent cells in the presence of 2% fetal calf serum and 50 ng/ml vascular endothelial growth factor. Laser scanning cytometry analysis of the confluent cells in situ showed a strong increase of expression of endothelial-specific markers like KDR and FLT-1,and immunofluorescence analysis showed typical expression of the von Willebrand factor. The functional behavior of the differentiated cells was tested with an in vitro angiogenesis test kit where cells formed characteristic capillary-like structures. We could show the differentiation of expanded adult human MSCs into cells with phenotypic and functional features of endothelial cells. These predifferentiated cells provide new options for engineering of artificial tissues based on autologous MSCs and vascularized engineered tissues. View Publication

BACKGROUND & AIMS: Bone marrow (BM) cells may transdifferentiate into or fuse with organ parenchymal cells. BM therapy shows promise in murine models of cirrhosis,and clinical trials of bone marrow stem cell therapy for organ healing are underway. However,the BM may contribute to scar-forming myofibroblasts in various organs including the liver. We have studied this axis of regeneration and scarring in murine models of cirrhosis,including an assessment of the temporal and functional contribution of the BM-derived myofibroblasts. METHODS: Female mice were lethally irradiated and received male BM transplants. Carbon tetrachloride or thioacetamide was used to induce cirrhosis. BM-derived cells were tracked through in situ hybridization for the Y chromosome. BM transplants from 2 strains of transgenic mice were used to detect intrahepatic collagen production. RESULTS: In the cirrhotic liver,the contribution of BM to parenchymal regeneration was minor (0.6%); by contrast,the BM contributed significantly to hepatic stellate cell (68%) and myofibroblast (70%) populations. These BM-derived cells were found to be active for collagen type 1 transcription in 2 independent assays and could influence the fibrotic response to organ injury. These BM-derived myofibroblasts did not occur through cell fusion between BM-derived cells and indigenous hepatic cells but,instead,originated largely from the BM's mesenchymal stem cells. CONCLUSIONS: The BM contributes functionally and significantly to liver fibrosis and is a potential therapeutic target in liver fibrosis. Clinical trials of BM cell therapy for liver regeneration should be vigilant for the possibility of enhanced organ fibrosis. View Publication

Supplementation of mesenchymal stem cells (MSCs) during hematopoietic stem cell (HSC) transplantation alleviates complications such as graft-versus-host disease,leading to a speedy recovery of hematopoiesis. To meet this clinical demand,a fast MSC expansion method is required. In the present study,we examined the feasibility of using a rotary bioreactor system to expand MSCs from isolated bone marrow mononuclear cells. The cells were cultured in a rotary bioreactor with Myelocult medium containing a combination of supplementary factors,including stem cell factor and interleukin-3 and -6. After 8 days of culture,total cell numbers,Stro-1(+)CD44(+)CD34(-) MSCs,and CD34(+)CD44(+)Stro-1(-) HSCs were increased 9-,29-,and 8-fold,respectively. Colony-forming efficiency-fibroblast per day of the bioreactor-treated cells was 1.44-fold higher than that of the cells without bioreactor treatment. The bioreactor-expanded MSCs showed expression of primitive MSC markers endoglin (SH2) and vimentin,whereas markers associated with lineage differentiation,including osteocalcin (osteogenesis),type II collagen (chondrogenesis),and C/EBP-alpha (CCAAT/enhancer-binding protein-alpha) (adipogenesis),were not detected. Upon induction,the bioreactor-expanded MSCs were able to differentiate into osteoblasts,chondrocytes,and adipocytes. We conclude that the rotary bioreactor with the modified Myelocult medium reported in this study may be used to rapidly expand MSCs. View Publication

Mesenchymal stem cells (MSCs) are widespread in adult organisms and may be involved in tissue maintenance and repair as well as in the regulation of hematopoiesis and immunologic responses. Thus,it is important to discover the factors controlling MSC renewal and differentiation. Here we report that adult MSCs express functional Toll-like receptors (TLRs),confirmed by the responses of MSCs to TLR ligands. Pam3Cys,a prototypic TLR-2 ligand,augmented interleukin-6 secretion by MSC,induced nuclear factor kappa B (NF-kappaB) translocation,reduced MSC basal motility,and increased MSC proliferation. The hallmark of MSC function is the capacity to differentiate into several mesodermal lineages. We show herein that Pam3Cys inhibited MSC differentiation into osteogenic,adipogenic,and chondrogenic cells while sparing their immunosuppressive effect. Our study therefore shows that a TLR ligand can antagonize MSC differentiation triggered by exogenous mediators and consequently maintains the cells in an undifferentiated and proliferating state in vitro. Moreover,MSCs derived from myeloid factor 88 (MyD88)-deficient mice lacked the capacity to differentiate effectively into osteogenic and chondrogenic cells. It appears that TLRs and their ligands can serve as regulators of MSC proliferation and differentiation and might affect the maintenance of MSC multipotency. View Publication

We reconstituted type I collagen nanofibers prepared by electrospin technology and examined the morphology,growth,adhesion,cell motility,and osteogenic differentiation of human bone marrow-derived mesenchymal stem cells (MSCs) on three nano-sized diameters (50-200,200-500,and 500-1,000 nm). Results from scanning electron microscopy showed that cells on the nanofibers had a more polygonal and flattened cell morphology. MTS (3-[4,5-dimethythiazol-2-yl]-5-[3-carboxy-methoxyphenyl]-2-[4-sul-fophenyl]-2H-tetrazolium compound) assay demonstrated that the MSCs grown on 500-1,000-nm nanofibers had significantly higher cell viability than the tissue culture polystyrene control. A decreased amount of focal adhesion formation was apparent in which quantifiable staining area of the cytoplasmic protein vinculin for the 200-500-nm nanofibers was 39% less compared with control,whereas the area of quantifiable vinculin staining was 45% less for both the 200-500-nm and 500-1,000-nm nanofibers. The distances of cell migration were quantified on green fluorescent protein-nucleofected cells and was 56.7%,37.3%,and 46.3% for 50-200,200-500,and 500-1,000 nm,respectively,compared with those on the control. Alkaline phosphatase activity demonstrated no differences after 12 days of osteogenic differentiation,and reverse transcription-polymerase chain reaction (RT-PCR) analysis showed comparable osteogenic gene expression of osteocalcin,osteonectin,and ostepontin between cells differentiated on polystyrene and nanofiber surfaces. Moreover,single-cell RT-PCR of type I collagen gene expression demonstrated higher expression on cells seeded on the nanofibers. Therefore,type I collagen nanofibers support the growth of MSCs without compromising their osteogenic differentiation capability and can be used as a scaffold for bone tissue engineering to facilitate intramembranous bone formation. Further efforts are necessary to enhance their biomimetic properties. View Publication

Implanted materials,such as medical devices,provoke the body to initiate an inflammatory reaction,known as the foreign body reaction (FBR),which causes several complications for example in hip prostheses,silicone implants,peritoneal dialysis catheters and left ventricular assist devices. FBR is initiated by macrophage adherence and results in granulation tissue formation. The early immunobiology and development of this tissue is not completely understood,but there are indications from related myofibroblast-forming diseases such as vascular repair and fibrosis that primitive stem cells also play a role in the formation of FBR-tissue. To investigate this,acellular photo-oxidized bovine pericardium patches were implanted intraperitoneally in rats and retrieved at time-points ranging from 6h to 7 days. A significant fraction of Sca-1(+) (6h-2 days),c-kit(+),CD34(+) and CD271(+) (2-3 days) stem/progenitor cells were detected. Colony-forming and differentiation capacity of the primitive stem cells into adipo-,osteo-,and myofibroblasts were shown. The presence of these primitive cells and their myofibroblastic differentiation potential were also confirmed at RNA level. The identification of specific primitive cells during FBR may have important implications for the inflammatory responses to inert materials and their use in tissue prostheses. View Publication

Stem cells have been shown to respond to extracellular mechanical stimuli by regulating their fate through the activation of specific signaling pathways. In this work,an array of iron nanowires (NWs) aligned perpendicularly to the surface was fabricated by pulsed electrodepositon in porous alumina templates followed by a partial removal of the alumina to reveal 2-3 μm of the NWs. This resulted in alumina substrates with densely arranged NWs of 33 nm in diameter separated by 100 nm. The substrates were characterized by scanning electron microscopy (SEM) energy dispersive x-ray analysis and vibrating sample magnetometer. The NW array was then used as a platform for the culture of human mesenchymal stem cells (hMSCs). The cells were stained for the cell nucleus and actin filaments,as well as immuno-stained for the focal adhesion protein vinculin,and then observed by fluorescence microscopy in order to characterize their spreading behavior. Calcein AM/ethidium homodimer-1 staining allowed the determination of cell viability. The interface between the cells and the NWs was studied using SEM. Results showed that hMSCs underwent a re-organization of actin filaments that translated into a change from an elongated to a spherical cell shape. Actin filaments and vinculin accumulated in bundles,suggesting the attachment and formation of focal adhesion points of the cells on the NWs. Though the overall number of cells attached on the NWs was lower compared to the control,the attached cells maintained a high viability (>90%) for up to 6 d. Analysis of the interface between the NWs and the cells confirmed the re-organization of F-actin and revealed the adhesion points of the cells on the NWs. Additionally,a net of filopodia surrounded each cell,suggesting the probing of the array to find additional adhesion points. The cells maintained their round shape for up to 6 d of culture. Overall,the NW array is a promising nanostructured platform for studying and influencing hMSCs differentiation. View Publication