Journal of cell science
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Journal of cell science · Feb 2004
Biography Historical ArticleAnna Starzinski-Powitz. Interview by Fiona Watt.
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Journal of cell science · Sep 2003
Rat aorta-derived mural precursor cells express the Tie2 receptor and respond directly to stimulation by angiopoietins.
Recent studies have implicated the Tie2 tyrosine-kinase receptor and its main ligands--angiopoietin-1 (Ang-1) and angiopoietin-2 (Ang-2)--as crucial regulators of mural cell recruitment during angiogenesis. Angiopoietin-mediated activation of Tie2 promotes perivascular mural cell assembly, but the mechanisms regulating this process are poorly understood because differentiated mural cells do not have the Tie2 receptor, which is reportedly expressed only in endothelial cells. There is also no direct evidence that Tie2 activation results in production of mural cell chemoattractants by the endothelium. ⋯ Surface expression of Tie2 was further demonstrated by isolating Tie2+/alpha-smooth muscle actin+ MPCs from primary aortic outgrowths with anti-Tie2-IgG-coated magnetic beads. Immunostaining of the rat aorta confirmed expression of Tie2 not only in endothelial cells but also in nonendothelial mesenchymal cells located in the aortic intimal/subintimal layers, which are the source of MPCs. These data indicate that the aortic wall contains Tie2+ nonendothelial mesenchymal cells and suggest that Tie2-related recruitment of mural cells during angiogenesis may occur through angiopoietin-mediated direct stimulation of these cells.
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Journal of cell science · Jul 2003
Epidermal tissue regeneration and stromal interaction in HaCaT cells is initiated by TGF-alpha.
The human keratinocyte cell line HaCaT expresses essentially all epidermal differentiation markers but exhibits deficiencies in tissue organization as surface transplants in nude mice and even more so in organotypic co-cultures with fibroblasts. Whereas tissue differentiation by normal keratinocytes (NEKs) is regulated by stromal interactions, this mechanism is impaired in HaCaT cells. This regulatory process is initiated by interleukin-1 (IL-1) release in keratinocytes, which induces expression of keratinocyte growth factor (KGF/FGF-7) and granulocyte macrophage-colony stimulating factor (GM-CSF) in fibroblasts. ⋯ Addition of TGF- alpha or EGF stimulated HaCaT cell proliferation but, even more effectively, suppressed apoptosis, thus facilitating the formation of a regularly stratified epithelium. Furthermore, TGF-alpha enhanced the expression of the receptors for KGF and GM-CSF so that addition of these growth factors, or of their inducer IL-1, further improved epidermal tissue differentiation leading to in vitro skin equivalents comparable with cultures of NEKs. Thus, supplementing TGF-alpha normalized epidermal tissue regeneration by immortal HaCaT keratinocytes and their interaction with stromal cells so that regular skin equivalents are produced as standardized in vitro models.
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Journal of cell science · Oct 2001
A novel assay to study autophagy: regulation of autophagosome vacuole size by amino acid deprivation.
Autophagy is a normal degradative pathway that involves the sequestration of cytoplasmic portions and intracellular organelles in a membrane vacuole called the autophagosome. These vesicles fuse with lysosomes and the sequestered material is degraded. Owing to the complexity of the autophagic pathway and to its inaccessibility to external probes, little is known about the molecular mechanisms that regulate autophagy in higher eukaryotic cells. ⋯ Conversely, vinblastine, a microtubule depolymerizing agent that induces the accumulation of autophagic vacuoles by preventing their degradation, increased the accumulation of MDC and altered the distribution and size of the autophagic vacuoles. Our results indicate that in the presence of vinblastine very large MDC-vacuoles accumulated mainly under starvation conditions, indicating that the expansion of autophagosomes is upregulated by amino acid deprivation. Furthermore, these MDC-vacuoles were labeled with LC3, one of the mammalian homologues of the yeast protein Apg8/Aut7 that plays an important role in autophagosome formation.