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G Gabbiani

Publications and source records attributed to G Gabbiani.

At least 19 recordsLinked to original sources
PubMed1992

O-acylated heparin derivatives with low anticoagulant activity decrease proliferation and increase alpha-smooth muscle actin expression in cultured arterial smooth muscle cells.

Selectively O-acylated derivatives of various glycosaminoglycans were prepared and tested in vitro for their anticoagulant activity and their antiproliferative effect on rat and rabbit smooth muscle cells. When O-acylation (butyrylation or hexanoylation) had been performed on periodate-depolymerized heparin fragments having very low anticoagulant activity, the antiproliferative potency was markedly increased (IC50 = 2 and 1 micrograms/ml respectively, versus 31 micrograms/ml for starting compound) without an increase in anticoagulant activity. The antiproliferative activity was related to the degree of acylation. The O-acylated derivatives of heparin fragments were also very active in reversing the de-differentiation of smooth muscle cell in culture, as estimated by the increase in the expression of alpha-smooth muscle actin and alpha-smooth muscle actin mRNA.

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PubMed1992

Inhibition of rat hepatic lipocyte activation in culture by interferon-gamma.

Hepatic lipocytes (perisinusoidal, Ito cells) are the primary matrix-producing cells in liver fibrosis. During liver injury they undergo activation, a process characterized by cell proliferation and increased fibrogenesis. We and others have established a culture model in which in vivo features of lipocyte activation can be mimicked by cells grown on plastic. Additionally, we recently showed that activation is associated with new expression of smooth muscle-specific alpha-actin both in vivo and in culture. Although interferon-gamma is known to inhibit collagen production in some systems, its action as a general modulator of lipocyte activation has not been examined; this issue forms the basis for our study. In culture-activated lipocytes, interferon-gamma (1,000 U/ml) significantly inhibited lipocyte proliferation as assessed by [3H]thymidine incorporation assay and nuclear autoradiography. In time-course studies of activation, it also markedly reduced expression of smooth muscle-specific alpha-actin and its messenger RNA. In dose-response experiments, maximal inhibitory effects on smooth muscle-specific alpha-actin mRNA gene expression were achieved with as little as 10 U interferon-gamma/ml. Inhibition of cellular activation was reversible; after interferon-gamma withdrawal, messenger RNA levels of smooth muscle-specific alpha-actin returned to untreated control levels. The effect of interferon-gamma extended to extracellular matrix gene expression, with reduction of type I collagen, type IV collagen and total fibronectin messenger RNAs to 3%, 24% and 15% of untreated control levels, respectively. In contrast to the marked effects on smooth muscle-specific alpha-actin and extracellular matrix gene expression, interferon-gamma reduced total protein synthesis by only 17.7%.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1992

Two cloned cerebral endothelial cell phenotypes: an in vitro model for angiogenesis?

Expression of smooth muscle alpha-actin and migratory behaviour of cloned cerebral endothelial cells (cEC) which exhibited two distinct phenotypes (type I, type II) were studied. Removal of mitogenic factors (alpha ECGF, ECGS) and heparin from the culture medium resulted in a smooth muscle-like appearance (type II) of the cells, expression of smooth muscle alpha-actin protein and smooth muscle actin mRNA and in an increased migratory activity. In contrast, addition of growth factors and heparin led to a cobblestone-like phenotype (type I) which lacked the expression of smooth muscle alpha-actin but expressed other proteins as determined by 2-D-gel electrophoresis.

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PubMed1992

Alpha-smooth muscle actin is expressed in a subpopulation of cultured and cloned fibroblasts and is modulated by gamma-interferon.

Clinical and experimental investigations have shown that, during wound healing and fibrocontractive diseases, fibroblasts acquire, more or less permanently according to the situation, morphological and biochemical features of smooth muscle (SM) cells including the expression of alpha-SM actin. Primary and passaged cultures of rat and human fibroblasts contain a subpopulation of cells expressing alpha-SM actin. These cells could derive from SM cells and/or pericytes present in the tissue from which cultures have been produced or represent bona fide fibroblasts. We have investigated the presence of alpha-SM actin in fibroblast cultures, clones, and subclones. In all cases the fibroblastic populations studied showed a proportion of alpha-SM actin expressing cells. Even after cloning, we never obtained populations negative for alpha-SM actin. We conclude that alpha-SM actin expression in fibroblastic cultures is not due to contaminant cells but is a feature of fibroblasts themselves. Our results support the view that fibroblastic cells are a heterogeneous population. It has been previously shown that gamma-interferon (gamma-IFN) decreases alpha-SM actin expression in SM cells. In rat and human fibroblasts, gamma-IFN decreases alpha-SM actin protein and mRNA expression as well as proliferation. The properties of this cytokine make it a good candidate for exerting an anti-fibrotic activity in vivo.

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PubMed1992

Cultured aortic smooth muscle cells from newborn and adult rats show distinct cytoskeletal features.

It is well known that arterial smooth muscle cells (SMC) of adult rats, cultured in a medium containing fetal calf serum (FCS), replicate actively and lose the expression of differentiation markers, such as desmin, smooth muscle (SM) myosin and alpha-SM actin. We report here that compared to freshly isolated cells, primary cultures of SMC from newborn animals show no change in the number of alpha-SM actin containing cells and a less important decrease in the number of desmin and SM myosin containing cells than that seen in primary cultures of SMC from adult animals; moreover, contrary to what is seen in SMC cultured from adult animals, they show an increase of alpha-SM actin mRNA level, alpha-SM actin synthesis and expression per cell. These features are partially maintained at the 5th passage, when the cytoskeletal equipment of adult SMC has further evolved toward dedifferentiation. Cloned newborn rat SMC continue to express alpha-SM actin, desmin and SM myosin at the 5th passage. Thus, newborn SMC maintain, at least in part, the potential to express differentiated features in culture. Heparin has been proposed to control proliferation and differentiation of arterial SMC. When cultured in the presence of heparin, newborn SMC show an increase of alpha-SM actin synthesis and content but no modification of the proportion of alpha-SM actin total (measured by Northern blots) and functional (measured by in vitro translation in a reticulocyte lysate) mRNAs compared to control cells cultured for the same time in FCS containing medium. This suggests that heparin action is exerted at a translational or post-translational level. Cultured newborn rat aortic SMC furnish an in vitro model for the study of several aspects of SMC differentiation and possibly of mechanisms leading to the establishment and prevention of atheromatous plaques.

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PubMed1992

The mammalian anti-alpha-smooth muscle actin monoclonal antibody recognizes an alpha-actin-like protein in planaria (Dugesia lugubris s.l.).

The presence of an alpha-smooth muscle (alpha-sm) actin-like protein in planaria (Dugesia lugubris s.l.) is reported. The protein shows a 42 kDa molecular weight determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis and is specifically recognized by the mammalian anti alpha-sm actin monoclonal antibody. When a planarian is induced to regenerate by head amputation, the immunostaining of the alpha-sm actin-like molecule becomes important in the area of growing blastema, reaching a maximum between 70-120 hours after injury. Conventional electron microscopy at the 4-day-regeneration stage shows that blastema-forming cells are a homogeneous population whose morphological features resemble those of migrating mesenchyme-like cells; only the myoblasts show a recognizable phenotype. The immunocytochemical localization of alpha-sm actin-like molecule by immunoperoxidase (light microscopy) and immunogold stains (electron microscopy) was carried out on both intact and injured worms. The antigen was localized mainly at the basal portion of the epidermal cells and in the undifferentiated mesenchyme-like cells. Myoblasts, but not differentiated myofibers, were also labelled by this antibody. The results indicate that in the lower Eumetazoan planarians, as well as in vertebrates, the alpha-sm actin can be considered to be a marker for myoid differentiation. The suggestion that alpha-sm actin can be used as a marker for mesenchyme-like cells in vertebrates and in invertebrates is also discussed.

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PubMed1992

Cytoskeletal features of alveolar myofibroblasts and pericytes in normal human and rat lung.

Frozen or paraffin-embedded human and rat lung specimens were stained with antibodies against total actin, alpha-smooth muscle (SM) actin, vimentin, desmin, or gelsolin. Alveolar interstitial myofibroblasts [i.e., contractile interstitial cells (CIC)] were labeled by total actin antibody but not by alpha-SM actin antibody. They stained for vimentin and gelsolin and, in rat lungs, most of them for desmin. Pericytes located around venules at the junction of three alveolar septa were always positive for alpha-SM actin and never for desmin. Tissue samples were also immunostained by an alpha-SM actin antibody and studied by electron microscopy. With this technique we confirmed that cells, identified as pericytes on the basis of their location, were intensely labeled by alpha-SM actin antibodies, whereas alveolar myofibroblasts were not. We conclude that in the lung interstitium pericytes and alveolar myofibroblasts have distinct cytoskeletal features, alpha-SM actin antibody staining being a simple method to distinguish between them. Furthermore, it appears that alveolar myofibroblasts have a peculiar pattern of cytoskeletal protein composition which, in the rat, is similar to that previously described for stromal cells in uterine submucosa, liver sinusoids (Ito cells), or the core of intestinal villi.

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PubMed1992

Heparin induces alpha-smooth muscle actin expression in cultured fibroblasts and in granulation tissue myofibroblasts.

BACKGROUND: Heparin increases alpha-smooth muscle actin expression in smooth muscle cells in vivo and in vitro. It has been recently suggested that alpha-smooth muscle actin expression in fibroblasts is a marker of myofibroblastic differentiation. We have examined the effect of heparin and of four nonanticoagulant heparin derivatives on alpha-smooth muscle actin expression by fibroblasts in vitro and in vivo. EXPERIMENTAL DESIGN: For in vitro experiments, heparin was added for 7 days to different fibroblastic cultures. We studied cell proliferation and alpha-smooth muscle actin protein and mRNA expression. For in vivo studies, osmotic minipumps filled with NaCl or tumor necrosis factor-alpha without or with nonanticoagulant heparin were implanted subcutaneously. After 14 days, newly accumulated connective tissues around the pumps were processed for immunofluorescence and electron microscopic and biochemical studies. RESULTS: In vitro, heparin inhibited proliferation and increased the expression of alpha-smooth muscle actin protein and mRNA. Analysis of [3H]thymidine incorporation in synchronized cells suggested that heparin produces a selection of alpha-smooth muscle actin expressing cells. In vivo, the local application of tumor necrosis factor-alpha resulted in formation of a typical granulation tissue: immunofluorescence showed that accumulated fibroblastic cells express alpha-smooth muscle actin only in the presence of heparin derivatives. In tumor necrosis factor-alpha treated animals, electron microscopic examination established the presence of myofibroblasts, but alpha-smooth muscle actin was expressed in microfilament bundles only in the presence of heparin derivatives. CONCLUSIONS: These results show that heparin and its nonanticoagulant derivatives influence the expression of alpha-smooth muscle actin in fibroblastic cells both in vitro and in vivo and that this effect is probably related to the selection of a particular cell subpopulation. They suggest a possible role for heparin during the formation and evolution of granulation tissue.

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PubMed1992

Rat hepatic lipocytes express smooth muscle actin upon activation in vivo and in culture.

Myofibroblasts are mesenchymal cells that are prominent in liver injury. The origin of myofibroblasts in liver is debated, although morphologic evidence to date has suggested that these cells are derived from lipocytes (fat-storing cells, Ito cells). In the present study, we have utilized smooth muscle alpha actin antibody--a marker of myofibroblasts and smooth muscle cells--to study lipocytes in situ in normal and fibrotic rat liver as well as during their 'activation' in culture. Dual immunofluorescence studies on tissue sections from normal liver identified lipocytes as perisinusoidal desmin-positive, smooth muscle alpha actin-negative cells. In bile duct obstructed fibrotic liver, desmin-positive cells were numerous in areas of fibrosis and these cells also exhibited smooth muscle alpha actin. In carbon tetrachloride-induced fibrosis, cells expressing both desmin and smooth muscle alpha actin were present in fibrotic bands and in regenerating nodules. These results suggested that lipocytes had acquired characteristics of myofibroblasts during liver injury. To further address this issue we examined lipocytes immediately after isolation and also in primary culture. In freshly isolated lipocytes from normal liver, smooth muscle alpha actin was absent. In contrast, freshly isolated lipocytes from CCl4-treated animals expressed this smooth muscle marker immediately after isolation. In primary culture on plastic, lipocytes from normal liver began to express smooth muscle alpha actin coincident with culture-induced activation; at 14 days, smooth muscle alpha actin was identified in all cells. Electron microscopy demonstrated a highly developed array of microfilament bundles characteristic of actin filaments. Immunoblot of culture-activated lipocytes using the smooth muscle alpha actin antibody demonstrated the expected 42 kD protein (corresponding to the molecular size of smooth muscle alpha actin). Although smooth muscle alpha actin was readily detectable in culture-activated cells, it was not expressed in cells in which a quiescent phenotype was preserved by maintenance in culture on a laminin-rich gel. These findings demonstrate that the acquisition by lipocytes of a smooth muscle marker accompanies their 'activation', and are consistent with the hypothesis that lipocytes transform to myofibroblasts during liver injury.

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PubMed1992

The cytoskeleton of arterial smooth muscle cells during human and experimental atheromatosis.

Smooth muscle cells (SMCs) implicated in the human atheromatous process show dedifferentiated features characterized by typical changes of cytoskeletal elements. In the normal media, quiescent SMCs express predominantly the alpha-smooth muscle (SM) actin isoform. In the human atheromatous plaque, and in rat experimental intimal thickening 15 days after balloon-induced endothelial injury, a decrease of the alpha-SM actin isoform and a predominance of the beta-cytoplasmic actin isoform develop. Proliferating SMCs in vivo assume fetal phenotypic features which are also observed in cultured SMCs. Thus, the study of cytoskeletal changes allows a better definition of SMC phenotype. Furthermore, in vitro SMCs may represent a useful experimental model to study phenotypic modifications of SMCs during the pathological process. Cytokines and growth factors, released by cells present in the atheromatous plaque, and extracellular components of the arterial wall, such as heparin, modulate the expression of alpha-SM actin in cultured SMCs and represent good candidates to exert important regulatory actions in vivo. A better understanding of the mechanisms leading to cytoskeletal modifications may help in the clarification of the mechanisms playing a role in the development of arterial pathological events.

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PubMed1991

Reversible expression of sm alpha-actin protein and sm alpha-actin mRNA in cloned cerebral endothelial cells.

The expression of smooth muscle (sm) alpha-actin was studied in cloned capillary cerebral endothelial cells of two phenotypes. Type I cells were cultured in medium containing 10% FCS, heparin and ECGS (or alpha-ECGF) and stained positive for a specific endothelial cell marker (Bandeiraea simplicifolia). Depletion of heparin and ECGS resulted in a smooth muscle-like appearance after 2-3 days. Cells of this phenotype, (type II) stained positive for the endothelial cell marker and for sm alpha-actin. In contrast to type I cells, type II cells expressed sm alpha-actin protein and mRNA as evidenced by Immunoblots and Northern blots. This phenotypic switch was shown to be reversible and so was the expression of sm alpha-actin.

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PubMed1991

Expression of alpha-smooth-muscle actin in stromal cells of the uterine cervix during epithelial neoplastic changes.

A total of 55 formalin-fixed and paraffin-embedded specimens of normal, inflamed and neoplastic uterine cervix have been studied in order to correlate the epithelial changes with the expression of alpha-smooth-muscle actin in stromal cells. This actin isoform is typical of smooth-muscle cells, but appears also temporarily in fibroblasts during wound healing and permanently during fibrocontractive diseases and stromal reaction to epithelial tumors. While positive stromal cells were absent in normal and inflamed cervix, they accumulated in relation to neoplastic tissues. The number of alpha-smooth-muscle actin positive cells and the intensity of stain were related to the increasing grading of cervical intra-epithelial neoplasia. Our results suggest that alpha-smooth-muscle actin is a marker of stromal-cell reaction to the development of neoplastic lesions. The evaluation of alpha-smooth-muscle actin in stromal cells of the uterine cervix may be a useful adjunct to diagnostic criteria of cervical intra-epithelial neoplasia and may help understanding of the mechanisms of mesenchymal-epithelial interactions during neoplasia.

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PubMed1991

The striated body: a new structure in the sperm head of the rabbit spermatozoon.

The striated body, a new structure lying in the perinuclear substance of rabbit spermatozoa, is described. It is composed of protein cords displaying a perpendicular periodic arrangement of dark and light bands. It appears in late spermatids, immediately prior to spermiation and is still present in epididymal spermatozoa, mostly, but not exclusively close to the perforatorium. The nature of this component has been analysed using a series of cytochemical techniques, as well as various antibodies and immunocytochemistry. The absence of RNA and of DNA favours a nonviral origin for this structure. The striated body is devoid of actin, differing in that respect from the rest of the perinuclear substance.

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PubMed1991

Locally applied GM-CSF induces the accumulation of alpha-smooth muscle actin containing myofibroblasts.

We have examined the histological and cytoskeletal changes in rat connective tissues induced by subcutaneous perfusion with cytokines. Granulocyte macrophage-colony stimulating factor (GM-CSF), tumor necrosis factor-alpha (TNF-alpha), interleukin-1-alpha (IL-1-alpha), transforming growth factor-beta (TGF-beta) and platelet-derived growth factor (PDGF) produced a significant fibroblast accumulation, neovascular development and a weak to moderate leukocyte infiltration, while interleukin-2 (IL-2) and gamma-interferon (gamma-IFN) induced intense mononucleated leukocyte infiltration. Immunofluorescence staining showed that accumulated fibroblastic cells were positive for alpha-smooth muscle (SM) actin (but negative for the desmin and muscle myosin) only in GM-CSF-treated tissues. Electron microscopic examination established that a significant proportion of fibroblastic cell in GM-CSF-, IL-1-alpha- or TGF-beta-treated animals were typical myofibroblasts. Only in GM-CSF-treated animals did microfilament bundles of myofibroblasts contain alpha-SM actin, when examined by immuno electron microscopy. Our results suggest that locally applied cytokines induce the formation of distinct granulation tissues. In particular, GM-CSF stimulates alpha-SM actin synthesis in myofibroblasts, illustrating an unexpected extra-hematopoietic in vivo effect of this factor.

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PubMed1991

Smooth muscle alpha-actin is a marker for hair follicle dermis in vivo and in vitro.

We have examined the expression of smooth muscle alpha-actin in hair follicles in situ, and in hair follicle dermal cells in culture by means of immunohistochemistry. Smooth muscle alpha-actin was present in the dermal sheath component of rat vibrissa, rat pelage and human follicles. Dermal papilla cells within all types of follicles did not express the antigen. However, in culture a large percentage of both hair dermal papilla and dermal sheath cells were stained by this antibody. The same cells were negative when tested with an antibody to desmin. Overall, explant-derived skin fibroblasts had relatively low numbers of positively marked cells, but those from skin regions of high hair-follicle density displayed more smooth muscle alpha-actin expression than fibroblasts from areas with fewer follicles. 2-D SDS-PAGE confirmed that, unlike fibroblasts, cultured papilla cells contained significant quantities of the alpha-actin isoform. The rapid switching on of smooth muscle alpha-actin expression by dermal papilla cells in early culture, contrasts with the behaviour of smooth muscle cells in vitro, and has implications for control of expression of the antigen in normal adult systems. The very high percentage of positively marked cultured papilla and sheath cells also provides a novel marker of cells from follicle dermis, and reinforces the idea that they represent a specialized cell population, contributing to the heterogeneity of fibroblast cell types in the skin dermis, and possibly acting as a source of myofibroblasts during wound healing.

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