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  • 1
    ISSN: 0014-4827
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden, USA : Blackwell Science Inc
    Wound repair and regeneration 13 (2005), S. 0 
    ISSN: 1524-475X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Considering that nitric oxide (NO) plays an important role on cutaneous wound repair, but its effects have not been defined, an inhibitor of NO synthesis (LNAME) was used. Control group received free water and LNAME group received LNAME (20 mg/kg/day) in drinking water. A full-thickness excisional wound was performed (0d), and the animals were sacrificed 7, 14, and 21 days later. Wound contraction was evaluated by lesion surface measurement at 0d, 7d, 14d, and 21d. The blood pressure of all rats was measured in the beginning and at the each time point of the experiment with a plethysmography method. The wound and normal skin surrounding was formol fixed and paraffin embedded. To evaluate the vessels, an immunohistochemistry for α-smooth muscle actin was done and stereological parameters were estimated in superficial and deep dermis. At 7d, 14d, and 21d the blood pressure of LNAME group was higher compared with control group (p 〈 0.001 for all). The wound contraction of LNAME group was slower compared with control group at 14d and 21d (p = 0.004 for both). In superficial dermis, vessels were more dilated in control group compared with LNAME group at 14d and 21d (p = 0.02; p 〈 0.0001, respectively) and longer in control group compared with LNAME group at 7d and 14d (p = 0.043; p = 0.002, respectively). Deep dermal vessels were more prominent and dilated in control group compared with LNAME group at 21d (p = 0.003; p = 0.0007, respectively), but at 7d, vessels were more dilated in LNAME group compared with control group (p = 0.015). In deep dermis, vessels were longer in control group compared with LNAME group at 14d and 21d (p = 0.002; p = 0.046, respectively). Our results show that nitric oxide inhibition affects the wound contraction and the vascularization pattern, mainly in the later phases of skin wound repair.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden, USA : Blackwell Science Inc
    Wound repair and regeneration 13 (2005), S. 0 
    ISSN: 1524-475X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Liver myofibroblasts are the key cells of liver fibrogenesis. Recent data show that the serine proteinase thrombin is involved in fibrogenesis through a mitogenic effect on myofibroblasts. The aim of this study was to evaluate the effects of thrombin on the migration of human liver myofibroblasts; another major parameter in fibrogenesis.In a Boyden chamber assay, thrombin dose-dependently (10−10–10−7 M) decreased spontaneous myofibroblast migration down to 49 ± 1% of control values (p = 5.10−10) without affecting cell adhesion or viability. Thrombin effect was blocked by its specific catalytic inhibitor hirudin and could be reproduced by using the proteinase-activated receptor-1 (PAR-1) agonist SFLLRNP. Thrombin also completely inhibited migration when induced by the chemotactic agent platelet-derived growth factor-BB. We then investigated the signaling mechanisms involved. The COX-2 inhibitor NS398 dose-dependently (2.5–10 μM) blunted the inhibitory effect of thrombin on spontaneous migration. However, NS398 did not reverse the inhibitory effect of thrombin on PDGF-BB-induced migration. Phosphatidylinositol 3-kinase (PI3-K) is a major determinant of chemotaxis induced by PDGF. Whereas thrombin did not itself induce PI3-K activity, as shown by the lack of detectable phosphorylation of Akt-1, it inhibited PDGF-BB-induced Akt-1 phosphorylation. This effect was dependent of the Rho/ROCK pathway since it was abolished in the presence of the ROCK inhibitor Y-27632.In summary, thrombin, acting via a proteinase-activated receptor, inhibits human liver myofibroblasts migration. Inhibition of basal migration is dependent on COX-2, while inhibition of PDGF-BB-induced migration involves decreased PI3-K activation via a Rho/ROCK mechanism. We suggest that thrombin could thus stabilize activated myofibroblasts on the site of active fibrogenesis.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1600-0625
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract:  The aim of this work was to validate an image analysis method, based on cell nuclei form factor determination, for counting fibroblasts within human dermis. We first used reconstructed dermal equivalents in which fibroblasts can also be counted directly after lysis of the collagen matrix. We found a good correlation between the results of direct counting and those of image analysis from day 10 to day 28 of culture. When applied to young normal donors' skin biopsies fixed in Bouin's solution and embedded in paraffin, the image analysis method yielded mid-dermis fibroblast counts of between 2100 and 4100 per mm3 of fresh tissue. A nuclear form factor (FF) comprised between 0.35 and 0.84 was found to be a biologic marker of fibroblasts. This was confirmed after fibroblast discrimination from other cell types, which had rounder nuclei (FF ≥ 0.85) and were identified either by their location (e.g. endothelial cells) or by labeling with specific antibodies (e.g. lymphocytes and monocytes/macrophages). Similar results were obtained with seven healthy donors' skin biopsies that had been frozen in nitrogen liquid and cryostat-sectioned, showing that this counting method is independent of the histologic procedure. Finally, analysis of samples of hypertrophic scars from two patients revealed that fibroblast density in some parts of the dermis was more than twice the value found in other parts presenting a fibroblast density almost normal, showing that this cell counting method can also be used to assess fibroblast heterogeneity within a given tissue.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-2307
    Keywords: Cytoskeleton ; Wound healing ; Fibrosis ; Extracellular matrix ; Cytokine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Granulation tissue fibroblasts (myofibroblasts) develop several ultrastructural and biochemical features of smooth muscle (SM) cells, including the presence of microfilament bundles and the expression of α-SM actin, the actin isoform present in SM cells and myoepithelial cells and particularly abundant in vascular SM cells. Myofibroblasts have been suggested to play a role in wound contraction and in retractile phenomena observed during fibrotic diseases. When contraction stops and the wound is fully epithelialized, myofibroblasts containing α-SM actin disappear, probably as a result of apoptosis, and the scar classically becomes less cellular and composed of typical fibroblasts with well-developed rough endoplasmic reticulum but with no more microfilaments. In contrast, α-SM actin expressing myofibroblasts persist in hypertrophic scars and in fibrotic lesions of many organs, including stroma reaction to epithelial tumours, where they are allegedly involved in retractile phenomena as well as in extracellular matrix accumulation. The mechanisms leading to the development of myofibroblastic features remain to be investigated. In vivo and in vitro investigations have shown that γ-interferon exerts an antifibrotic activity at least in part by decreasing α-SM actin expression whereas heparin increases the proportion of α-SM actin positive cells. Recently, we have observed that the subcutaneous administration of transforming growth factor-β1 to rats results in the formation of a granulation tissue in which α-SM actin expressing myofibroblasts are particularly abundant. Other cytokines and growth factors, such as platelet-derived growth factor, basic fibroblast growth factor and tumour necrosis factor-α, despite their profibrotic activity, do not induce α-SM actin in myofibroblasts. In conclusion, fibroblastic cells are relatively undifferentiated and can assume a particular phenotype according to the physiological needs and/or the microenvironmental stimuli. Further studies on fibroblast adaptation phenomena appear to be useful for the understanding of the mechanisms of development and regression of pathological processes such as wound healing and fibrocontractive diseases.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-6822
    Keywords: dermal equivalent ; fibrosis ; in vitro ; TGF-β1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Why initially normal wound healing sometimes shifts toward an impaired cicatrization is poorly understood. Collagen gels with incorporated fibroblasts constitute valuable in vitro models to study mechanisms of connective tissue reorganization. Such 1-week-old, partially contracted normal dermal equivalents were treated with concentrations of TGF-β1 ranging from 1 to 10 ng/ml. The cytokine was applied in a single dose or four times at regular intervals, over a 2-week period. Dose-dependent activation of fibroblasts was observed after treatment. The cytokine induced a myofibroblastic transformation of dermal cells, significantly enhanced the process of dermal contraction, and stimulated synthesis of such proteins as cellular fibronectin, tenascin and smooth-muscle actin. Our approach is more informative than models using pathological or pretreated dermal cells, since it demonstrates newly induced modulation of fibrotic transformation in an initially normal dermal equivalent. This in vitro assay will enable us to study mechanisms involved in the shift between normal and impaired fibrotic transformation during wound healing.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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