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At least 613 records · Page 34Linked to original sources
PubMed1993

A bone marrow stromal cell line is a source and target for platelet-derived growth factor.

Platelet-derived growth factor (PDGF) stimulates multipotent and erythroid progenitors as well as stromal fibroblasts. Any of the three dimeric forms of PDGF (AA, AB, or BB) could potentially interact with these cells; however, the precise cellular origin of PDGF production in the bone marrow microenvironment is not known. In the present study, we found that medium conditioned by MBA-2, murine bone marrow-derived endothelial cells, contains PDGF activity that competes for [125I]PDGF binding to human foreskin fibroblasts and is mitogenic for these fibroblasts. Northern analysis of poly(A)+ RNA from MBA-2 shows the expression of both PDGF A-chain and B-chain mRNAs. Because cytokines such as transforming growth factor-beta (TGF-beta) regulate hematopoiesis and stimulate PDGF in certain mesenchymal cells, we determined whether TGF-beta influences PDGF secretion and gene expression in MBA-2. TGF-beta induced PDGF A-chain and B-chain mRNAs and the release of PDGF activity. Each of the three PDGF isoforms also stimulated DNA synthesis in MBA-2, but with different potency (BB > AB > AA). Ligand binding studies showed specific binding of labeled PDGF BB and, to a lesser extent, PDGF AA isoform, consistent with predominant expression of the PDGF-beta receptor in MBA-2. These data show that murine endothelial stromal cells release PDGF activity and respond to PDGF. Local production of PDGF in the marrow microenvironment may play an important role in regulating hematopoietic and stromal cell proliferation.

Animals↗
PubMed1996

Costimulation of fibronectin receptor promotes Fc gamma R-mediated rescue of IL-3-dependent bone marrow-derived cells from apoptosis.

The IL-3-dependent murine bone marrow-derived cell line FDC-P2/185-4 (185-4) undergoes apoptosis when IL-3 is withdrawn from the culture medium. However, a high concentration of aggregated mouse IgG prevents apoptosis of 185-4 cells by an autocrine mechanism, producing IL-3. An analysis of flow cytometry revealed that 185-4 cells expressed Fc gamma RIII on their surface and that these effects of IgG are inhibited by anti-Fc gamma RIII mAb. These results indicated that the effect of IgG is mediated by low affinity Fc gamma RIII. In contrast, a low concentration of mouse IgG cannot prevent the apoptosis of 185-4 cells, but in the presence of fibronectin (FN), cell survival is prolonged. It is generally accepted that the interaction of cells with FN is mediated by several integrins such as alpha 5 beta 1 (VLA-5) or alpha 4 beta 1 (VLA-4), and analysis of flow cytometry showed that 185-4 cells express these integrins on their surface. Furthermore, these effects of FN are blocked specifically by RGD peptide or anti-VLA-4 mAb. These findings indicated that FN induces the costimulatory signal through integrin receptor and enhances the proliferative effect through Fc gamma RIII by a low concentration of IgG. The findings presented here suggested that the engagement of FN-integrin receptors on 185-4 cells increases the sensitivity of the cells for cellular activation of IgG. Since inflammatory cells in the microenvironment are surrounded by extracellular matrix proteins, it is possible that adhesion molecules play important roles in inflammatory states such as autoimmune diseases caused by increased levels of IgG.

Animals↗
PubMed1996

Biologic basis for radiation oncology.

Improved understanding of the underlying biologic mechanisms that pertain to radiation oncology is providing an explanation for the cellular and tissue responses to ionizing radiation and is leading to the potential for novel therapeutic strategies. Among the areas of intensive investigation are: DNA recombination and repair, signal transduction, gene regulation, apoptosis, the cellular stress response, and the effect of the tumor microenvironment. These new biologic concepts, coupled with the superior technical capabilities now available for treatment delivery, are paving the way for new clinical approaches to improving both the quality and quantity of life for the cancer patient.

Apoptosis↗
PubMed1998

Natural killer cell-mediated eradication of neuroblastoma metastases to bone marrow by targeted interleukin-2 therapy.

Targeted interleukin-2 (IL-2) therapy with a genetically engineered antidisialoganglioside GD2 antibody-IL-2 fusion protein induced a cell-mediated antitumor response that effectively eradicated established bone marrow and liver metastases in a syngeneic model of neuroblastoma. The mechanism involved is exclusively natural killer (NK) cell-dependent, because NK-cell deficiency abrogated the antitumor effect. In contrast, the fusion protein remained completely effective in the T-cell-deficient mice or immunocompetent mice depleted of CD8+ T cells in vivo. A strong stimulation of NK-cell activity was also shown in vitro. Immunohistology of the leukocytic infiltrate of livers from treated mice revealed a strong staining for NK cells but not for CD8+ T cells. The therapeutic effect of the fusion protein was increased when combined with NK-cell-stimulating agents, such as poly I:C or recombinant mouse interferon-gamma. In conclusion, these data show that targeted delivery of cytokines to the tumor microenvironment offers a new strategy to elicit an effective cellular immune response mediated by NK cells against metastatic neuroblastoma. This therapeutic effect may have general clinical implications for the treatment of patients with minimal residual disease who suffer from T-cell suppression after high-dose chemotherapy but are not deficient in NK cells.

Animals↗
PubMedDate not supplied

Topographies of extracytoplasmic compartments in developing chick tendon fibroblasts.

The complex topography of the fibroblast leading to the formation of extracellular compartments is demonstrated in the native three-dimensional state in cryofractured chick embryo tendon at different stages of development. Tendon collagen fibrils, fibril bundles, and macroaggregates are intimately associated with these extracytoplasmic domains. The localization of fibrils within narrow channels, bundles within peripheral compartments, and the coalescence of bundles into macroaggregates within larger extracytoplasmic compartments is illustrated at different stages of development. Changing patterns of matrix organization are apparent as morphogenesis proceeds. Our interpretation is that collagen fibrils, oriented along the tendon axis, appear in extracytoplasmic channels defined by the fibroblast which are added at the periphery of the cell until a row of fibrils outlines the cellular border at Day 10. By Day 14, cytoplasmic processes have partitioned the fibrils into groups and then into round bundles. New fibrils are continually added to the fibril bundles through fusion of the extracytoplasmic channels. As the bundles grow larger, the cell boundaries between the bundles retract and bundles begin to coalesce into macroaggregates. The fibroblast becomes attenuated, bundle-forming compartments disappear as processes retract, bundles coalesce, and macroaggregates predominate by Day 17. This work is consistent with the model proposed for the compartmentalization of the extracellular space by the fibroblast, providing distinct microenvironments where collagen fibrillogenesis and matrix morphogenesis occur under close cellular regulation.

Animals↗
PubMed2006

Exploring the regulation of human neural precursor cell differentiation using arrays of signaling microenvironments.

Cells of a developing embryo integrate a complex array of local and long-range signals that act in concert with cell-intrinsic determinants to influence developmental decisions. To systematically investigate the effects of molecular microenvironments on cell fate decisions, we developed an experimental method based on parallel exposure of cells to diverse combinations of extracellular signals followed by quantitative, multi-parameter analysis of cellular responses. Primary human neural precursor cells were captured and cultured on printed microenvironment arrays composed of mixtures of extracellular matrix components, morphogens, and other signaling proteins. Quantitative single cell analysis revealed striking effects of some of these signals on the extent and direction of differentiation. We found that Wnt and Notch co-stimulation could maintain the cells in an undifferentiated-like, proliferative state, whereas bone morphogenetic protein 4 induced an 'indeterminate' differentiation phenotype characterized by simultaneous expression of glial and neuronal markers. Multi-parameter analysis of responses to conflicting signals revealed interactions more complex than previously envisaged including dominance relations that may reflect a cell-intrinsic system for robust specification of responses in complex microenvironments.

Animals↗
PubMed2003

Nuclear microenvironments support physiological control of gene expression.

There is growing recognition that the organization of nucleic acids and regulatory proteins is functionally linked to the assembly, localization and activity of gene regulatory machinery. Cellular, molecular, biochemical and in-vivo genetic evidence support an obligatory relationship between nuclear microenvironments where regulatory complexes reside and fidelity of transcriptional control. Perturbations in mechanisms governing the intranuclear trafficking of transcription factors and the temporal/spatial organization of regulatory proteins within the nucleus occur with compromised gene expression that abrogates skeletal development and mediates leukemogenesis.

Cell Nucleus↗
PubMed1989

Macrophage-derived growth factors in wound healing: regulation of growth factor production by the oxygen microenvironment.

There is a large amount of current research investigating the pathophysiologic aspects of pulmonary hypertension. Results of this research indicate the potential role of the macrophage as one possible mediator of pulmonary hypertension. The macrophage has been shown to produce numerous soluble mediators, including various growth factors, some of which may be involved in the cellular proliferation of the arterial wall. Most of the knowledge regarding oxygen microenvironments, macrophages, and growth factor production comes from research on the healing wound. A considerable amount of what has been learned about the role of the macrophage in cutaneous wound healing may have direct applicability to macrophage function in acute lung injury and repair, and pulmonary hypertension. Macrophages play a pivotal role in cutaneous wound repair. They participate in immunologic and nonspecific host defense responses and produce numerous growth factors that regulate mesenchymal cell proliferation, migration, and synthesis of extracellular matrix proteins. These same responses are probably at work during the progression of pulmonary hypertension.

Growth Substances↗
PubMed2001

The microenvironment of immobilized Arg-Gly-Asp peptides is an important determinant of cell adhesion.

This paper uses self-assembled monolayers on gold as a model system to demonstrate that the attachment and spreading of Swiss 3T3 fibroblasts depends strongly on the microenvironment of immobilized RGD peptides. This work utilized monolayers that present mixtures of Arg-Gly-Asp peptides, which are ligands for cellular integrin receptors, and oligo(ethylene glycol) groups, which resist the nonspecific adsorption of protein. The microenvironment of the peptide ligands was controlled by altering the length of the surrounding oligo(ethylene glycol) groups on the monolayer. By using thiols that present either tri-, tetra-, penta-, or hexa(ethylene glycol) units, the average distance separating the glycol groups and the peptide ligand is altered while the structure and properties of the background remain unchanged. Cell attachment to monolayers presenting a fixed density of peptide decreased as the length of the oligo(ethylene glycol) group increased. The average projected area of attached cells showed a similar trend. At lower densities of immobilized peptide, decreases in both cell attachment and projected cell area were more pronounced. Attachment and spreading did not depend on density of peptide on monolayers presenting tri(ethylene glycol) groups, but showed a high sensitivity to density of ligand on monolayers presenting longer glycol oligomers. Experiments that used a soluble peptide to inhibit the attachment of cells to monolayers demonstrated that the strength of the cell-substrate interaction decreased on monolayers presenting longer glycol groups. Together, these results suggest that the microenvironment of the peptide ligand influences the affinity of the integrin-peptide interaction and that weaker interactions display a density-dependent enhancement of binding during cell attachment and spreading. This finding is an important consideration in studies that correlate biological function with the composition of ligands on a substrate. This finding also represents an important principle for the design of biologically active materials because it illustrates the degree to which the presentation of adhesion motifs can modify the response of mammalian cells.

3T3 Cells↗
PubMed2005

Microdialysis - an in vivo technique for studies of growth factors in breast cancer.

Changes in the microenvironment are important in the development of cancer and further tumor growth. Although landmark discoveries have been made regarding genetic alterations in cancer at a cellular level very little is known about protein regulation in the extracellular space. In the microenvironment many growth factors are activated at a post-translational level by interactions of different cell types such as epithelial cells, fibroblasts, adipose cells, and immune cells. The extracellular space is the bioactive site for the majority of growth factors and increased knowledge of protein activation in this compartment is of utmost importance for our comprehension of tumor biology. Microdialysis is a minimally invasive technique, which enables sampling of molecules in the extracellular space. It is applicable in human cancer as well as in experimental tumors. This review describes microdialysis, its application and the up to date literature of microdialysis for detection of growth factors in cancer with special emphasis on breast cancer.

Animals↗
PubMed2001

Simultaneous measurement of cellular respiration and acidification with a single CMOS ISFET.

In vivo, the pH value and oxygen partial pressure are the most important physico-chemical parameters in the microenvironment of human tissues. In vitro, the extracellular acidification rate of cell cultures is an indicator of global cellular metabolism, while the rate of oxygen consumption is a measure of mitochondrial activity. Earlier approaches had the disadvantage that these two values had to be measured with two separate sensors at different loci within the tissue or cell culture. Furthermore, conventional Clark-type oxygen sensors are not very compatible for miniaturisation, making it impossible to measure at small cell volumes or even at the single cell level. We have, therefore, developed an ISFET based sensor structure which is able to measure both pH and oxygen partial pressure. This sensor structure was tested in vitro for simultaneous records of cellular acidification and respiration rates at the same site within the cell culture. This sensor is manufactured by a CMOS-process.

Biosensing Techniques↗
PubMed2002

Embryonal subregion-derived stromal cell lines from novel temperature-sensitive SV40 T antigen transgenic mice support hematopoiesis.

Throughout life, the hematopoietic system requires a supportive microenvironment that allows for the maintenance and differentiation of hematopoietic stem cells (HSC). To understand the cellular interactions and molecules that provide these functions, investigators have previously established stromal cell lines from the late gestational stage and adult murine hematopoietic microenvironments. However, the stromal cell microenvironment that supports the emergence, expansion and maintenance of HSCs during mid-gestational stages has been largely unexplored. Since several tissues within the mouse embryo are known to harbor HSCs (i.e. aortagonads-mesonephros, yolk sac, liver), we generated numerous stromal cell clones from these mid-gestational sites. Owing to the limited cell numbers, isolations were performed with tissues from transgenic embryos containing the ts SV40 Tag gene (tsA58) under the transcriptional control of constitutive and ubiquitously expressing promoters. We report here that the growth and cloning efficiency of embryonic cells (with the exception of the aorta) is increased in the presence of the tsA58 transgene. Furthermore, our results show that the large panel of stromal clones isolated from the different embryonal subregions exhibit heterogeneity in their ability to promote murine and human hematopoietic differentiation. Despite our findings of heterogeneity in hematopoietic growth factor gene expression profiles, high-level expression of some factors may influence hematopoietic differentiation. Interestingly, a few of these stromal clones express a recently described chordin-like protein, which is an inhibitor of bone morphogenic proteins and is preferentially expressed in cells of the mesenchymal lineage.

Animals↗
PubMed2004

Cellular niches controlling B lymphocyte behavior within bone marrow during development.

In bone marrow, hematopoiesis is thought to depend on special microenvironments known as niches that maintain blood cells. However, the identity of niches and interaction of blood cells with niches remain poorly understood. Here we identify stage-specific cellular niches for B lymphopoiesis. The earliest precursors, pre-pro-B cells and end-stage B cells, plasma cells require CXC chemokine ligand (CXCL)12. CXCL12-expressing cells are a small population of stromal cells, scattered throughout bone marrow and located some distance from the cells expressing interleukin (IL)-7. Multipotent hematopoietic progenitors are attached to the processes of CXCL12-expressing cells and pre-pro-B cells adjoin their cell bodies. Maturer pro-B cells that require IL-7 have moved away and adjoin the IL-7-expressing cells. Plasma cells again seed CXCL12-expressing cells. We demonstrate the B lymphocyte characteristic location and movement between specific niches within bone marrow during development and suggest that CXCL12 maintains the cells in the niche.

Animals↗
PubMed1999

Molecular and cellular aspects of induced thymus development in recombinase-deficient mice.

Thymus development and microenvironment organization require stage- and site-specific cross-talk between thymocyte and stroma. In this study we have used recombinase-activating gene-deficient (RAG-2(-/-)) mice to analyze regulated gene expression both in thymocytes and stromal cells following injection of anti-CD3 monoclonal antibodies as inducer of thymus development. We show that IFN-gamma, TNF-alpha and lymphotactin are transcriptionally regulated in thymocytes, whereas cytoskeletal keratin 14, IL-1alpha and TNF-alpha are regulated in the stroma, quantitatively reproducing the variations associated with beta selection of thymocytes. In addition, RAG-2(-/-) thymus development is associated with entry of epithelial cells into the cell cycle. The histochemical evidence that expanded RAG-2(-/-) thymus becomes undistinguishable from wild-type cortex further suggests that cross-talk phenomena occurring during beta selection of thymocyte are reproduced in this system.

Animals↗
PubMed2005

[Correlations of expressions of Glut1 and HIF-1alpha to cellular proliferation of colorectal adenocarcinoma].

BACKGROUND & OBJECTIVE: Malignant cells exhibit increased glucose metabolism and microenvironment hypoxia. Glucose transporter-1 (Glut1) and hypoxia-inducible factor 1 alpha (HIF-1alpha) enhance glucose metabolism under hypoxia. This study was to investigate the expressions of Glut1 and HIF-1alpha in colorectal adenocarcinoma, and explore their correlations to cell proliferation. METHODS: Immunohistochemistry was used to detect expressions of Glut1, HIF-1alpha, and proliferating cell nuclear antigen (PCNA) in 60 specimens of colorectal adenocarcinoma and 20 specimens of normal colorectal tissues. Their interrelations were analyzed. RESULTS: Positive rates of Glut1 and HIF-1alpha were significantly higher in colorectal adenocarcinoma tissues than in normal colorectal tissues (58.3% vs. 0, P < 0.01; 73.3% vs. 0, P < 0.01). PCNA level was significantly higher in colorectal adenocarcinoma tissues than in normal colorectal tissues (65.25+/-16.35 vs. 15.20+/-3.47, P < 0.01). Glut1 and HIF-1alpha levels were positively correlated with PCNA level (r(1)=0.409, P < 0.01; r(2)=0.323, P < 0.05), and were associated with Dukes' stage and lymph node metastasis. CONCLUSIONS: The overexpressions of Glut1 and HIF-1alpha play important roles in carcinogenesis and progression of colorectal adenocarcinoma, and closely correlate with cell proliferation of colorectal adenocarcinoma.

Adenocarcinoma↗
PubMedDate not supplied

An engineered microenvironment for multidimensional microscopy of live cells.

Multidimensional imaging (MD) of live cells is gaining importance in biomedical research as the commercial availability of confocal, nonlinear optical microscopes, environmental chambers, and specific fluorescence probes grows. One crucial aspect of the MD live cell imaging involves the proper immobilization of cells, which refers to the rapid and sufficient immobilization of cells on the microscope stage, neither disrupting the cellular structure and functions nor affecting the optical properties of the cells and the environments. Conventional cell immobilization methods glue the anchoring cells to coated surfaces, but such methods require centrifugation or extended incubation and are not suitable for cells in suspension. Most of the current three-dimensional (3-D) gels either exhibit unsatisfactory optical properties or have adverse effects on cell functions in culture. Recently, an engineered 3-D microcapsule has been developed that involves the complex coacervation of a positively charged collagen and a negatively charged polymer of 2-hydroxyethyl methacrylate--methacrylic acid--methyl methacrylate (HEMA-MMA-MAA). Hence, confocal imaging of live cells in this engineered 3-D microenvironment was investigated for its optical properties and cellular function compatibility. We report here that this microenvironment facilitates efficient cell immobilization, exhibits good optical properties, and can preserve cellular structures and functions, which will be useful in MD imaging of live cells for various applications.

Animals↗
PubMed2004

Integrative radiation carcinogenesis: interactions between cell and tissue responses to DNA damage.

Tissue function requires coordinated multicellular behavior as a consequence of diverse signals integrated through the tissue microenvironment; importantly, these cell-cell and cell-microenvironment interactions also actively suppress cancer. Ionizing radiation (IR) elicits a well-defined cellular response to DNA damage that mediates the fate of the individual cell, concomitantly with a less well-characterized overarching tissue stress response that coordinates the response of multiple cell types via microenvironment signaling. We have now shown that these programs to reestablish homeostasis intersect via mutual regulation by transforming growth factor beta1 (TGF beta 1), which acts as an extracellular sensor and signal of stress. In this review, the concept that this type of functional integration of cell and tissue stress response programs is essential to cancer suppression will be discussed. Our experiments using IR, and several recent studies that experimentally manipulate stromal TGF beta, show that disruption of microenvironment signaling actively promotes malignant progression. Understanding the dynamic interactions between tissue and cell stress responses will be necessary for an accurate assessment of cancer risk and may also provide targets for prevention.

Animals↗