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      Murine Metanephric Mesenchyme Possesses Characteristics of Vascular Endothelial Cells in vitro

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          Background/Aims: Although the renal microvasculature, including the glomerular capillaries, is generally considered to develop from the metanephric mesenchyme, this has not been unequivocally demonstrated. Using a murine metanephric mesenchymal cell line (MS7), we tested whether the metanephric mesenchyme expresses phenotypic characteristics of endothelial cells and differentiates into vascular endothelial cells in vitro. Methods: MS7 cells were examined for the mRNA expression of endothelial markers by reverse transcription (RT)-PCR. Moreover, we attempted to induce the appearance of new endothelial markers by stimulation with growth factors and exposure to hypoxia. Results: Before induction, MS7 cells expressed mRNA of fetal liver kinase 1 (Flk1), fms-like tyrosine kinase (Flt1), tyrosine kinase with Ig and EGF homology domains 2 (Tie2), CD31, and podocalyxin. However, they did not express mRNA for vascular endothelial-cadherin (VE-cadherin) or von Willebrand factor (vWF), which are markers specific for endothelial cells and mature endothelial cells. In the immunocytochemical analysis, MS7 absorbed DiI-acetylated LDL virtually, but the results of staining with anti-VE-cadherin, vWF, or CD31 antibodies were negative. MS7 cells that were cultured for 14 days after reaching confluence began to express VE-cadherin and vWF mRNA. In addition, immunofluorescence showed abundant granules stained with anti-vWF antibody in the cytoplasm. Stimulation with vascular endothelial growth factor (VEGF), or basic fibroblast growth factor (bFGF), or exposure to a hypoxic condition did not influence their characteristic changes. Conclusion: Our results suggest that metanephric mesenchymal (MS7) cells possess some characteristics of endothelial cells, and they are potent to differentiate into mature vascular endothelium in vitro.

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          Most cited references 11

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          Vascular endothelial growth factor is an essential molecule for mouse kidney development: glomerulogenesis and nephrogenesis.

          Homeostasis of body fluid is maintained by the kidneys, which contain two million glomeruli for blood filtration. A glomerulus is formed by growth of Bowman's capsule harmonized with a capillary during kidney development. The vascular endothelial growth factor (VEGF) is an essential angiogenic cytokine, and VEGF deficiency is known to be fatal in mice in early embryonic stages. As secretions of VEGF from cultured kidneys vary according to developmental stages, the role of VEGF in kidney development was studied in vivo by blocking the endogenous VEGF activity with antibody in newborn mice, in which most organs are already developed but kidneys are still developing. The antibody-treated animals showed normal growth but systemic edema. Vessel formation in the superficial renal cortex was disturbed, nephrogenic areas were diminished, and the number of developing nephrons decreased significantly. Many abnormal glomeruli, lacking capillary tufts, were observed in the antibody-treated mice, and VEGF expression in their Bowman's capsule showed a compensatory increase. These results suggest that VEGF mediates communication between the Bowman's capsule and capillary endothelial cells for developing a glomerulus as well as promoting nephrogenesis. In conclusion, VEGF is likely to be an essential molecule for kidney development, and especially for glomerulogenesis.
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            Analysis of cell cycle arrest in adipocyte differentiation.

             M Reichert,  D Eick (1999)
            Confluent 3T3-L1 preadipocytes differentiate to adipocytes in the presence of insulin, dexamethasone, and isobutylmethylxanthine (IDI). A transient increase of DNA synthesis is induced in 3T3-L1 cells 18 h after addition of IDI, followed by an arrest in the G1 phase of the cell cycle. Growth arrested cells express the proto-oncogene c-myc and the gene for the CCAAT/enhancer binding protein (C/EBPalpha) between day 2 and 5. While c-Myc is strongly implicated in cell proliferation, C/EBPalpha: is a differentiation-specific transcription factor with antiproliferative activity. Here we have characterized the cell cycle arrest in differentiating 3T3-L1 cells. Arrested cells express the Cdk inhibitors p21 and p27, but, at the same time, show hyperphosphorylation of Rb and expression of the E2F-regulated thymidine kinase gene. The addition of new serum to arrested cells resulted in cyclin A expression and Cdk2 activity, but not in DNA synthesis. Simian virus 40 large tumor antigen (LTAg) is a potent mitogen. The mutant LTAg-K1, deficient in binding of pocket proteins and unable to induce DNA synthesis in serum-starved 3T3-L1 cells, efficiently induced DNA synthesis in differentiating 3T3-L1 cells. This indicates that pocket proteins are probably not involved in the control of the cell cycle arrest during 3T3-L1 cell differentiation. Our data suggest that the differentiation-specific cell cycle block in 3T3-L1 cells is resistant to high levels of c-Myc, inactivation of pocket proteins, upregulation of cyclin A levels, and Cdk2 activation, but can be abolished by a function of LTAg that is independent of binding to pocket proteins.
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              Differential effects of laminin, intact type IV collagen, and specific domains of type IV collagen on endothelial cell adhesion and migration

              Laminin and type IV collagen were compared for the ability to promote aortic endothelial cell adhesion and directed migration in vitro. Substratum-adsorbed IV promoted aortic endothelial cell adhesion in a concentration dependent fashion attaining a maximum level 141-fold greater than controls within 30 min. Aortic endothelial cell adhesion to type IV collagen was not inhibited by high levels (10(-3) M) of arginyl-glycyl-aspartyl-serine. In contrast, adhesion of aortic endothelial cells on laminin was slower, attaining only 53% of the adhesion observed on type IV collagen by 90 min. Type IV collagen when added to the lower well of a Boyden chamber stimulated the directional migration of aortic endothelial cells in a concentration dependent manner with a maximal response 6.9-fold over control levels, whereas aortic endothelial cells did not migrate in response to laminin at any concentration (.01-2.0 X 10(-7) M). Triple helix-rich fragments of type IV collagen were nearly as active as intact type IV collagen in stimulating both adhesion and migration whereas the carboxy terminal globular domain was less active at promoting adhesion (36% of the adhesion promoted by intact type IV collagen) or migration. Importantly, aortic endothelial cells also migrate to substratum adsorbed gradients of type IV collagen suggesting that the mechanism of migration is haptotactic in nature. These results demonstrate that the aortic endothelial cell adhesion and migration is preferentially promoted by type IV collagen compared with laminin, and has a complex molecular basis which may be important in angiogenesis and large vessel repair.

                Author and article information

                Nephron Exp Nephrol
                Cardiorenal Medicine
                S. Karger AG
                February 2006
                11 November 2005
                : 102
                : 3-4
                : e93-e98
                Department of Pathology and Nephrology, Majors of Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan
                89687 Nephron Exp Nephrol 2006;102:e93–e98
                © 2006 S. Karger AG, Basel

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                Figures: 4, Tables: 1, References: 22, Pages: 1
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