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PubMed1966

Electron microscopy: attachment sites between connective tissue cells.

Regions of attachment have been observed between connective tissue cells from four different structures: fibroblasts in embryonic and fetal tendons, fibroblasts in fetal ligamentum nuchae, odontoblasts, and osteoblasts. Morpho logically these sites appear to be focal and to consist of an approximation of the plasma membranes of adjacent cells to within approximately 200 A. In the region of approximation both the extracellular space and the cytoplasm adjacent to the plasmalemma are increased in density. We have postulated a role for these sites in the maintenance of structural integrity.

Animals↗
PubMedDate not supplied

Surface features and behavior of the connective tissue cell.

The surface features and behavior of the connective tissue cell in normal areas and in healing incisions of the aponeuroses of the abdominal wall of the albino rat were studied with the scanning electron microscope (SEM). The normal cell is smooth, oval or triangular in outline and has a generally rounded surface and very short or no cell processes. The behavior of the fibroblasts and the condition of the fibers in and around the wounds were visualized. Shortly after the incision, the fibroblasts accumulated around the wound, possibly by increased cell division. At the site of the incision the cells responded by a self-protective mechanism in which they withdrew their processes and acquired a spheroid form. During the maximum period of a fibrillogenesis the fibroblasts enlarged, acquired a fusiform outline and long processes, exhibited a roughened surface and were surrounded with small rounded cell particles polymerizing into fine fibrils. The process of collagen secretion and three stages of collagen maturation were visualized. Some abnormal cells were seen; they could be evidence of merocrine or holocrine mode of secretion or possibly signs of cell senility.

Abdominal Muscles↗
PubMed1987

In vitro formation of fibrous septa by liver connective tissue cells.

Active fibrous septa are a common feature in liver fibrosis and cirrhosis. Their etiology and formation were studied using cultures of tissue fragments or cells included in collagen gels. Liver fragments obtained from patients with cirrhosis or severe schistosomal fibrosis were able to reorganize the gel and to form discrete, interconnecting fibrous septa composed of parallel arrays of collagen, subsequently colonized by migrating connective tissue cells. The same was obtained in cultures of fibrogranulomatous lesions isolated from schistosome-infected mice livers. However, fragments of normal human and murine liver tissue did not show the capacity to form fibrous septa. Septa formation was also obtained in cultures of cell spheroids formed by liver connective tissue cells isolated from human fibrotic or cirrhotic liver tissues, but not with spheroids of normal skin fibroblasts or smooth muscle cells. This experimental model may represent the fibrous septa formation in vivo, depending on the activity of liver connective tissue cells. The ability of tissue fragments or cell spheroids to form septa in collagen gels might reflect the degree of fibrosis present in the liver tissue in vivo.

Animals↗
PubMed1992

Collagen synthesis in an established liver connective tissue cell line (GRX) during induction of the fat-storing phenotype.

We have studied collagen synthesis and secretion in an established liver connective tissue cell line (GRX) that can be induced in vitro to express either the myofibroblastic or the fat-storing (lipocyte) phenotype. In lipocytes, collagen synthesis was reduced. Their intracellular collagen degradation corresponded to 15% of newly synthesized collagen. In myofibroblasts, collagen synthesis was high but its secretion was considerably altered by intracellular collagen degradation, which attained up to 60% of newly synthesized collagen. In this in vitro model, we have provided direct evidence that hepatic lipocytes, involved mainly in lipid and retinol metabolism, have a low basal level of collagen synthesis. Myofibroblastic phenotype correlates with increased collagen synthesis and may be directly related to increased collagen deposition in hepatic fibrosis. Modulation of the phenotype of liver connective tissue cells are possibly one of the major points of control in normal and pathological deposition of collagen in liver parenchyma.

Animals↗
PubMed1988

Characterisation of connective tissue cells containing factor XIII subunit a.

Paraffin embedded sections of human liver, lymph node, and placenta showed that certain connective tissue cells were positive for factor XIII subunit a. These cells were further characterised by double immunofluorescence labelling and by combined immunofluorescence and enzyme cytochemical staining on frozen sections. They were labelled by the monoclonal antibodies RFD7 and anti-Leu M3 (markers of the macrophage cell line) but gave a negative reaction for the fibroblast marker IIG10 and showed no alkaline phosphatase activity. Immunoblotting detected factor XIII subunit a in macrophages isolated from placenta but not in human fibroblasts. At lower dilutions, the commercially available antibody against the b subunit of factor XIII also positively reacted with the same cell population. The facts that immunoblotting showed that the antiserum crossreacted with the a subunit and that placental macrophages did not stain strongly for the b subunit also indicate that this antigen is not present in adult connective tissue cells.

Connective Tissue↗
PubMed1975

Connective tissue cells, cell proliferation and synthesis of extracellular matrix-a review.

The ubiquitous connective tissues contain a wide range of cells including fibroblasts, osteoblasts and chondroblasts. Recently it has been demonstrated that another principal cell of the connective tissue is the smooth muscle cell in several organ systems. These have been shown to be responsible for the synthesis of the connective tissue matrix components of the uterine myometrium and of the arterial system, including collagen, both elastic fibre proteins and glycosaminoglycan. Microtubule inhibitors such as colchicine and vinblastine, and iron chelators such as alpha,alpha -dipyridyl have been used to study their morphologic and chemical effects on collagen synthesis and secretion. Colchicine produces an increase in large Golgi-associated vacuoles, which sometimes contain material reminiscent of aggregates of collagen macromolecules. Vinblastine produces alterations in the endoplasmic reticulum cisternae similar to alterations seen in ascorbic acid deficiency, and alpha,alpha-dipyridyl increases the frequency of regions in cells, interpretable as potential sites of communication of rough endoplasmic reticulum cisternae with the cell surface. Ferritin conjugated anti-procallagen sera were used to localize procollagen in cells and demonstrated procollagen not only in the cisternae of rough endoplasmic reticulum but in all of the elements of the Golgi complex as well. The studies reported in this review have shown that in cell culture arterial smooth muscle will produce not only the microfibrillar protein of the elastic fibre but soluble and/or insoluble elastin as well. Recent studies on serum factors responsible for the proliferation of connective tissue cells have demonstrated that at least one of the principal factors responsible for fibroblast and/or smooth muscle cell proliferation in culture is derived from thrombocytes. Medium containing serum derived from cell-free plasma lacks most of this proliferative effect which can be reinstated when platelets are present during recalcification to form serum. This effect is due to the platelet release reaction as shown by combining supernatant factors derived from platelets exposed to purified thrombin to cell-free, plasma derived serum. Studies with macrophages have also suggested that phagocytic macrophages release factor(s) into a cell culture medium that may also participate in stimulating fibroblasts to proliferate in vitro. The means by which these factors stimulate fibroblast proliferation and connective tissue synthesis remains to be elucidated.

Animals↗
PubMed1985

Extended life span and tumorigenicity of nonestablished mouse connective tissue cells transformed by the fos oncogene of FBR-MuSV.

We have analyzed the transforming potential of two fos oncogene products in nonestablished cultures of mouse connective tissue cells: p55fos of FBJ-MuSV and p75gag-fos of FBR-MuSV. Although both proteins induced morphological transformation and colony formation at low cell density in a G418 resistance selection assay, p75gag-fos exhibited more pronounced transforming potential than p55fos. In addition, p75gag-fos-transformed cells overcame crisis with a high probability and were tumorigenic in syngenic mice. These properties of the FBR-MuSV appear to be linked to structural alterations in the p75gag-fos oncogene product. Polyoma virus large T protein complemented the transforming potential of fos, in that it not only increased the probability of establishment of fos-transformed cells but also enhanced fos-induced morphological transformation. Our results suggest that different oncogenes affect morphological transformation, low cell density growth, establishment, and tumorigenicity to various degrees.

Animals↗
PubMed1991

Methotrexate inhibits neutrophil function by stimulating adenosine release from connective tissue cells.

Although commonly used to control a variety of inflammatory diseases, the mechanism of action of a low dose of methotrexate remains a mystery. Methotrexate accumulates intracellularly where it may interfere with purine metabolism. Therefore, we determined whether a 48-hr pretreatment with methotrexate affected adenosine release from [14C]adenine-labeled human fibroblasts and umbilical vein endothelial cells. Methotrexate significantly increased adenosine release by fibroblasts from 4 +/- 1% to 31 +/- 6% of total purine released (EC50, 1 nM) and by endothelial cells from 24 +/- 4% to 42 +/- 7%. Methotrexate-enhanced adenosine release from fibroblasts was further increased to 51 +/- 4% (EC50, 6 nM) and from endothelial cells was increased to 58 +/- 5% of total purine released by exposure to stimulated (fMet-Leu-Phe at 0.1 microM) neutrophils. The effect of methotrexate on adenosine release was not due to cytotoxicity since cells treated with maximal concentrations of methotrexate took up [14C]adenine and released 14C-labeled purine (a measure of cell injury) in a manner identical to control cells. Methotrexate treatment of fibroblasts dramatically inhibited adherence to fibroblasts by both unstimulated neutrophils (IC50, 9 nM) and stimulated neutrophils (IC50, 13 nM). Methotrexate treatment inhibited neutrophil adherence by enhancing adenosine release from fibroblasts since digestion of extracellular adenosine by added adenosine deaminase completely abrogated the effect of methotrexate on neutrophil adherence without, itself, affecting adherence. One hypothesis that explains the effect of methotrexate on adenosine release is that, by inhibition of 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) transformylase, methotrexate induces the accumulation of AICAR, the nucleoside precursor of which (5-aminoimidazole-4-carboxamide ribonucleoside referred to hereafter as acadesine) has previously been shown to cause adenosine release from ischemic cardiac tissue. We found that acadesine also promotes adenosine release from and inhibits neutrophil adherence to connective tissue cells. The observation that the antiinflammatory actions of methotrexate are due to the capacity of methotrexate to induce adenosine release may form the basis for the development of an additional class of antiinflammatory drugs.

Adenine↗
PubMedDate not supplied

[Cytophotometric determination of the DNA content in epithelial and connective tissue cells of the human prostate].

A study of the quantitative parameters of DNA in cells nuclei of epithelium and connective tissue allowed establishing certain periods which are characterized by an increase in the percentage of ploidy. The causes and importance of this phenomenon for the development of pathological processes in tissues of the prostate gland and the possibility of its use for the diagnosis are discussed.

Adolescent↗
PubMed1988

Expression of platelet-derived growth factor receptors is induced on connective tissue cells during chronic synovial inflammation.

The tissue distribution of the receptor for platelet-derived growth factor (PDGF) was investigated by immunohistochemistry on frozen sections from normal and inflamed synovial tissue using monoclonal antibodies to the receptor. Non-inflamed synovial tissue showed no staining, indicating that PDGF receptor expression is low or absent in normal tissue. In contrast, tissue from synovitis with prominent neovascularization showed a strong staining in the tunica media of the proliferating blood vessels as well as on connective tissue cells in the stroma. Tissue from synovitis with prominent proliferation of synovial lining showed intense staining for PDGF receptors in fibroblast-like cells of the lining and a less intense staining on vascular and connective tissue cells deeper in the stroma. Staining for PDGF receptors was also intense in the pannus tissue close to infiltrated bone and cartilage. In all these forms of synovitis, PDGF receptor staining was associated with increased HLA-DR staining and infiltration of macrophages and T lymphocytes. The finding that PDGF receptor expression is induced in conjunction with the chronic synovial inflammation associated with rheumatoid arthritis and some other forms of arthritides suggests that PDGF may play a role in the stimulation of mesenchymal cell proliferation that often accompanies chronic inflammatory disease.

Chronic Disease↗
PubMed1978

[DNA biosynthesis in the muscular and connective tissue cells of the heart in experimental myocardial infarct].

In 60 rabbits with experimental myocardial infarction induces by ligation of the anterior branch of the left coronary artery, DNA synthesis was studied by means of H3-thymidine in muscular and connective tissue cells depending on the period of myocardial infarction. The development of myocardial infarction in the cardiac muscle was stated to be accompanied by activation of DNA synthesis in the connective tissue cells not only in the necrotic zone but in the adjacent, as well as in distant areas of the myocardium and in stromal cells of the auriculum. Indices of H3-thymidine labeled nuclei were of high value during the acute period of myocardial infarction and gradually decreased with the time elapsed since the operation. During the period of the myocardical infarction organization high activity in DNA synthesis was revealed in connective tissue elements of the epicardium and the subepicardial zone of the heart. Myocardial cells of the cardiac auriculi incorporated H3-thymidine but extremely seldom-single labels per thousands of nuclei. In the auriculi with application of prolonged sessions of the labeled precussor introduction, DNA synthesising nuclei were revealed, sometimes with paired nuclei of cardiomyocytes.

Animals↗