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  • 2005-2009  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Allergy 60 (2005), S. 0 
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background:  The transcription factor activator protein (AP)-2 regulates cell-type specific gene expression during development and differentiation, but its role in mast cell development has so far not been explored.Methods:  Gene expression and regulation of AP2 was assessed in normal skin, diseases with increased mast cell numbers, and in vitro models of mast cell differentiation.Results:  AP-2α-protein was not detectable in normal skin but in mastocytoma lesional mast cells. AP-2α-mRNA and -protein were also detected in leukemic mast cells (HMC-1), in the adherent fraction of peripheral blood (PBMC) and umbilical cord blood mononuclear cells (CBMC), and AP-2α-mRNA at low levels in isolated-purified mast cells. During culture with fibroblast supernatants or SCF, AP-2α-mRNA was de novo expressed in KU812-cells, maintained at about the same level in PBMC and CBMC, and upregulated in HMC-1-cells. On extended culture, a down-regulation was noted at mRNA and/or protein levels. In contrast, tryptase expression increased in all cells throughout culture, as did c-Kit in normal cells, whereas in both leukemic cell lines, c-Kit was maintained unchanged at about the same level.Conclusions:  These findings suggest a continuous activation of AP-2α in mastocytomas and mast cell leukemia and its transient upregulation during c-Kit dependent early steps of normal mast cell differentiation.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background:  Atopic dermatitis skin lesions are characterized by inflammatory changes and epithelial hyperplasia requiring angiogenesis. As mast cells may participate in this process via bidirectional secretion of tissue-damaging enzymes and pro-angiogenic factors, the present study aimed to assess the occurrence and possible function of mast cells in the papillary dermis and in epidermal layers of atopic dermatitis lesions.Methods:  Semi-thin and serial sections in combination with immunohistochemistry, histochemistry and proliferating cell nuclear antigen (PCNA)-activity assays were used and related to epidermal thickness and targeted gene expression studies.Results:  Mast cells were located in the papillary dermis and migrated through the basal lamina into the epidermis of atopic dermatitis lesions. An increased PCNA-activity in cells of superficial epidermal layers indicated an activation of keratinocytes and stimulation of endothelial growth. Only ∼30% of the papillary mast cells stained with the tryptase were toluidin-blue-positive, and ∼80% were chymase positive. A high number of mast cells expressed c-kit. Most papillary and epidermal mast cells were localized close to endothelial cells. Vascular expression of endoglin (CD105) demonstrated neoangiogenic processes. Mast cells stimulation led to the expression of proangiogenic factors. Also, gene expression of tissue-damaging factors such as matrix metalloproteinases was increased.Conclusions:  These data suggest that in atopic dermatitis, mast cells are abundantly localized close to and within the epidermis where they may stimulate neoangiogenesis. Via the new vessels, inflammatory cells, together with complement components and antibodies, can be transported to the epidermis to aid in the defense against environmental antigens and to maintain chronic inflammation.
    Type of Medium: Electronic Resource
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