Extracellular matrix: understanding the complexity.
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Cell Adhesion↗
Biomedical subjects
R Borojevic
Publications and source records attributed to R Borojevic.
Primmorphs generated from dissociated cells of the sponge Suberites domuncula: a model system for studies of cell proliferation and cell death.
Sponges (Porifera) represent the lowest metazoan phylum; they have been shown to be provided with the characteristic metazoan structural and functional molecules. One autapomorphic character of sponges is the presence of high levels of telomerase activity in all cells (or almost all cells, including somatic cells). In spite of this fact previous attempts to cultivate sponge cells remained unsuccessful. It was found that dissociated sponge cells do not replicate DNA and lose their telomerase activity. In addition, no nutrients or metabolites have been detected that would stimulate sponge cells to divide. In the present study we report the culture conditions required for the formation of multicellular aggregates from dissociated single cells of Suberites domuncula, termed primmorphs. These primmorphs are formed in seawater without addition of further supplements, and have an organised tissue-like structure; they have been cultured for more than 5 months. Cross-sections revealed a distinct external layer covered by a continuous pinacoderm, and a central zone composed primarily of spherulous cells. After their association into primmorphs, the cells turn from the telomerase-negative state into the telomerase-positive state; a telomerase level of 4.7 total product generated (TPG) units/5 x 10(3) cell equivalents has been determined. Moreover, a major fraction of the cells in the primmorphs undergoes DNA synthesis and hence has the capacity to grow. Applying the BrdU-labelling and detection assay it is demonstrated that up to 33.8% of the cells in the primmorphs are labelled with BrdU after an incubation period of 12 h. It is proposed that the primmorph system described here is a powerful novel model system to study basic mechanisms of cell proliferation and cell interaction, as well as of morphogenesis, ageing and apoptosis.
Animals↗
Inhibition by the anti-mitotic drug doxorubicin of platelet-activating-factor-induced late eosinophil accumulation in rats.
Platelet-activating factor (PAF) has been shown, in the rat model of pleural inflammation, to induce the generation of an intermediate proteic factor able to cause eosinophil proliferation in vitro. This study was undertaken to investigate the effect of the anti-mitotic compound doxorubicin on PAF-induced eosinophilia in rats, in order to evaluate the contribution of local cell proliferation to this phenomenon. The late eosinophil infiltration caused by another chemoattractant leukotriene B4 was used for comparison. We observed that local treatment with doxorubicin (20 and 40 microg/cavity), given 6 h after PAF (1 microg/cavity), suppressed the eosinophil accumulation within 24 h, whilst only the higher dose was effective when the drug was given 12 h post-PAF. An effect on chemotaxis was ruled out, since local doxorubicin (40 microg/cavity) failed to modify the eosinophil migration noted 24 h after leukotriene B4 (0.5 microg/cavity) and the neutrophil/eosinophil infiltration noted at 6 h after PAF injection. Transfer of the pleural fluids collected 6 h after PAF from donors to recipient rats caused significant eosinophil accumulation in the recipient rats, an effect which was inhibited by the co-administration of doxorubicin (40 microg/cavity). No inhibitory effect was noted when the drug was given 6 h after the pleural fluids were transferred. We also found no change in the number of blood or bone marrow eosinophils after PAF stimulation. We conclude that doxorubicin selectively impaired the late eosinophil accumulation triggered by PAF in the pleural cavity of rats, clearly indicating that local cell proliferation seems to contribute to the development of this inflammatory response.
Animals↗
Sponges (Porifera) model systems to study the shift from immortal to senescent somatic cells: the telomerase activity in somatic cells.
Sponges (Porifera) represent the lowest metazoan phylum, characterized by a pronounced plasticity in the determination of cell lineages. In a first approach to elucidate the molecular mechanisms controlling the switch from the cell lineage with a putative indefinite growth capacity to senescent, somatic cells, the activity of the telomerase as an indicator for immortality has been determined. The studies were performed with the marine demosponges Suberites domuncula and Geodia cydonium. It was found that the activity for the telomerase in the tissue of both sponges is high; a quantitative analysis revealed that the extract from S. domuncula contained 10.3 TPG units per 5000 cell equivalents and the one from G. cydonium 8.3 TPG units; hence the activity reached approximately 30-20% of the activity seen in telomerase-positive reference cells. In contrast, dissociated spherulous cells from G. cydonium, after an incubation period of 24 h, contained no detectable telomerase activity. From earlier studies it is known that isolated sponge cells do not proliferate. Based on these findings it is assumed that the separation of the senescent sponge cell lineage from the immortal germ/somatic cell lineage is triggered by the loss of contact with cell adhesion factors. First evidence is included which suggests that the final progress of the senescent, telomerase-negative cells to cell death is caused by apoptosis.
Animals↗
Sponges (Porifera) molecular model systems to study cellular differentiation in Metazoa.
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Amino Acid Sequence↗
Murine schistosomiasis mansoni: experimental analysis of bone marrow and peripheral myelopoiesis.
In schistosomiasis a systemic hyperplasia of the monomacrophagic cell lineage is associated with its mild modifications in myelograms and hemograms. We monitored the in vitro proliferation of myeloid precursors obtained from bone marrow, blood, spleen, and liver. The macrophage colony-forming unit (M-CFU) numbers were stable in bone marrow but increased progressively in spleen and in liver, reaching in each organ the values equivalent to one femur. The bone marrow had an increased production and enhanced capacity to release M-CFU. Their quantitative increase in blood and in peripheral tissues of schistosome-infected mice was associated with their qualitative modifications: augmented proliferative capacity, enhanced adhesion, and accelerated differentiation. The accelerated release of monomacrophage progenitors and their enhanced proliferation in peripheral tissues potentially account for the relatively low involvement of the bone marrow and for an efficient in situ production of phagocytes, which participate in host reactions to parasites.
Animals↗
Experimental murine schistosomiasis mansoni: modulation of the B-1 lymphocyte distribution and phenotype expression.
We studied the B-1 lymphocyte involvement in host reactions to parasites in the murine model of schistosomiasis. No modifications were observed in the prepostural phase of the disease. From the acute phase on, we observed sequentially an increase of Mac1- B-1 cells in the spleen, followed by their appearance in Peyer's patches and in mesenteric ganglia, suggesting that a fraction of splenic B-1 cells might follow this pathway of migration, acquiring progressively the Mac1 expression. These results are consistent with a primary activation of the splenic B cell compartment, with the subsequent mobilization of B-1 cells into the tissue involved by parasites. Conversely, we found no evidence of an increase of B-1 cells in the peritoneum, nor a mobilization of B-1 cells expressing the peritoneal phenotype (CD5lo, IgMhi) into the tissues involved by infection, despite the general inflammatory reactivity of peritoneal cells. In schistosomiasis, the peritoneal cavity B-1 cells on one side, and those involved in inflammatory reactions to parasites in the spleen, Peyer's patches, and mesenteric ganglia on the other, represent two distinct B-1 lymphocyte pools.
Animals↗
Retinol uptake and metabolism, and cellular retinol binding protein expression in an in vitro model of hepatic stellate cells.
Liver is a major site of retinoid metabolism and storage, and more than 80% of the liver retinoids are stored in hepatic stellate cells. These cells represent less than 1% of the total liver protein, reaching a very high relative intracellular retinoid concentration. The plasma level of retinol is maintained close to 2 microM, and hepatic stellate cells have to be able both to uptake or to release retinol depending upon the extracellular retinol status. In view of their paucity in the liver tissue, stellate cells have been studied in primary cultures, in which they loose rapidly the stored lipids and retinol, and convert spontaneously into the activated myofibroblast phenotype, turning a long-term study of their retinol metabolism impossible. We have analyzed the retinol metabolism in the established GRX cell line, representative of stellate cells. We showed that this cell line behaves very similarly, with respect the retinol uptake and release, to primary cultures of hepatic stellate cells. Moreover, we showed that the cellular retinol binding protein (CRBP-I) expression in these cells, relevant for both uptake and esterification of retinol, responds to the extracellular retinol status, and is correlated to the retinol binding capacity of the cytosol. Its expression is not associated with the overall induction of the lipocyte phenotype by other agents. We conclude that the GRX cell line represents an in vitro model of hepatic stellate cells, and responds very efficiently to wide variations of the extracellular retinol status by autonomous controls of its uptake, storage or release.
Adipocytes↗
Protein malnutrition: some aspects of the in vitro adhesion of peritoneal mouse macrophages.
Protein calorie malnutrition and disease are frequently associated. Protein malnutrition modifies both the specific and nonspecific resistance of the organism to infectious agents. The exact mechanisms underlying these findings are not clear. Cellular adhesion is a crucial step in the process of phagocytosis as well as cellular migration. The effect of a low-protein diet on adhesion of macrophages was studied using an experimental murine model. We used malnourished mice that had lost 30% of their initial body weight. We then injected them with a suspension of sodium caseinate and harvested the peritoneal macrophages after 5 days. The cells were then allowed to adhere to cover slips in the presence or absence of 10% fetal calf serum (FCS) in the medium for time periods of 30, 60, 90 and 120 min. Macrophage adhesion to glass slips whose surface had been covered with type I collagen was performed only for 90 min. The expression of fibronectin was studied using an immunohistochemical technique only in the 90-min assay. The results indicate that (1) protein malnutrition impairs the activation potential of macrophages, decreasing their adhesion and expression of fibronectin; (2) when FCS is present in the medium, there is a decrease in the number of adhered cells.
Animals↗
Origin of the metazoan bodyplan: characterization and functional testing of the promoter of the homeobox gene EmH-3 from the freshwater sponge Ephydatia muelleri in mouse 3T3 cells.
Porifera [sponges] represent the lowest metazoan phylum, probably already existing prior to the 'Cambrian explosion'. Based on amino acid sequences deduced from cDNAs that code for structural proteins, the monophyly of Metazoa was established. Now we analyzed for the first time a promoter of a sponge gene for its activity in a heterologous cell system from higher Metazoa. The promoter of the homeobox gene EmH-3 was cloned and sequenced from a genomic library of the freshwater sponge Ephydatia muelleri. For the determination of functional promoter activity, transient transfection experiments in mouse NIH 3T3 cells were performed; the promoter was fused with the luciferase reporter gene. The data revealed that a 401 nt long promoter fragment, comprising several binding elements for metazoan transcription factors, showed the highest activity, while the 175 bp long promoter segment, comprising solely the TATA- and Cap boxes, showed only 25% of that activity. This result demonstrates that the sponge promoter is activated by factors present in mammalian cells and supports the view that Porifera, together with the other metazoan phyla, are of monophyletic origin.
3T3 Cells↗
Liver granulomas in schistosomiasis: mast cell-dependent induction of SCF expression in hepatic stellate cells is mediated by TNF-alpha.
Mast cell proliferation, survival, and differentiation are under control of the surrounding stroma and are largely mediated by the stem cell factor (SCF). Mast cells are abundant in liver fibrosis and are proposed to be causally related with its persistence and intensity through secretion of fibrogenic cytokines. In normal adult liver, local connective tissue cells (stellate cells) do not constitutively express SCF. We studied primary cultures of stellate cells obtained from fibrogranulomatous reactions elicited in mouse liver by schistosomal infection. We have shown that the SCF expression can be induced in vitro by co-culture with mast cells and this induction was dependent on the release of tumor necrosis factor alpha (TNF-alpha). Because SCF induces in mast cells proliferation and release of both fibrogenic factors and TNF-alpha, the described interaction between liver stroma and mast cells represents an auto-stimulatory loop, which may explain the progressive and persistent character of liver fibrosis associated with chronic inflammations or infections. Granulomatous reactions in liver elicited by chronic schistosomiasis sustain a local production of inflammatory cells, and this extramedular myelopoiesis is potentially also dependent on the induction of SCF expression in the liver stellate cells.
Animals↗
Haematopoietic capacity of colony-forming cells mobilized in hepatic inflammatory reactions as compared to that of normal bone marrow cells.
Chronic inflammatory periovular granulomatous reactions elicited in liver by schistosomal infection are a site of active myelopoiesis. We quantified the colony-forming cells (CFCs) in granulomas and found that the whole liver contains a number of CFCs roughly equivalent to 50% of a femur. Clonogenic analysis showed the presence of committed as well as pluripotent and totipotent CFCs. Long-term Dexter-type cultures showed that the granuloma-derived totipotent CFCs do not have self-renewal capacity. Hence, they did not correspond functionally to haematopoietic stem cells, despite the fact that the stroma established by adherent cells harvested from granulomas had the capacity to sustain long-term proliferation of bone-marrow-derived haematopoietic stem cells. We conclude that myelopoietic cytokines produced by inflammatory reactions in schistosomiasis elicit mobilization of bone marrow CFCs into the circulation, which can settle in hepatic granulomas. This environment may induce their proliferation and differentiation, but not their self-renewal, sustaining temporary production of myeloid cell lineages which nevertheless depends upon cell renewal from the bone marrow pool of haematopoietic precursors.
Animals↗
Lipid metabolism during in vitro induction of the lipocyte phenotype in hepatic stellate cells.
Molecular mechanisms of lipid synthesis and their controls in hepatic stellate cells are not known. We have previously proposed that, in contrast to other fat storing cells, hepatic stellate cells are not involved in energy storage, but they represent a particular cell population specialized in storage of lipid-soluble substances, the major one being probably retinol. In agreement with this hypothesis, induction of the lipocyte phenotype in stellate cells is not under the control of insulin, but responds to retinoids and other molecules that modify the gene expression program in these cells. In the present study we have monitored the activity of the two major enzymes involved in lipid synthesis during the induction of the lipocyte phenotype in hepatic stellate cells: glycerol-3-phosphate dehydrogenase (GPDH) that mediates the de novo lipid synthesis, and lipoprotein lipase that mediates incorporation of plasma lipids. In early stages of lipocyte induction, both pathways of lipid synthesis are activated. When lipocytes have already constituted the lipid droplets, lipoprotein lipase pathway is downregulated, while GPDH activity remains high. Adult liver has been reported to lack lipoprotein lipase, but under stress, lipase activity was detected around and at the surface of the intrahepatic vasculature. We have now shown that the lipase activity can be induced in the hepatic stellate cells, located in the Disse's space. The high lipoprotein lipase activity under acute induction of lipocyte phenotype, followed by the low activity under conditions of metabolic equilibrium, are in compass with the increased activity of this enzyme under stress, and its low activity in adult liver parenchyma under normal conditions.
Cell Line↗
GM-CSF and IL-3 activities in schistosomal liver granulomas are controlled by stroma-associated heparan sulfate proteoglycans.
Connective tissue cells (myofibroblasts) from liver inflammatory granulomatous reactions to schistosome eggs are able to sustain a long-term proliferation of myeloid cells, both in vivo and in vitro. We have addressed the question of the molecular mechanisms involved in control of this extramedullar stroma-dependent production of inflammatory cells. Heparan sulfate proteoglycans (HSPGs) were purified from granuloma-derived connective tissue cells and bound to plastic or collagen substrate. Their ability to bind recombinant murine granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3), to stimulate proliferation of the FDC-P1 myeloid cell lineage, and to modify growth factor activity was monitored. The specificity of this stroma cell-derived glycosaminoglycan interaction with the myeloid growth factors was analyzed by comparing other glycosaminoglycans and sulfated polysaccharides. HSPGs could act as an artificial myelopoietic stroma; they were both required and sufficient for binding and presenting GM-CSF and IL-3 in biologically active form. Moreover, they were able to mediate an increase in the specific growth-promoting activity of GM-CSF and IL-3. This was specific for stroma-derived heparan sulfate and heparin, since heparan sulfate derived from other cells, other glycosaminoglycans and related molecules had no effect. These results indicate that HSPGs can stimulate and control the in situ proliferation of myeloid cells, modifying in both quantitative and qualitative terms the composition of inflammatory cell infiltrates in hepatic granulomas.
Animals↗
Coelom-associated lymphomyeloid tissue (milky spots): site of lymphoid and myelomonocytic cell generation.
Pleural and peritoneal milky spots (MS) are small morphofunctional structures representing subsidiary foci of coelom-associated lymphomyeloid tissue (CALT). In this paper we studied the cellular composition of CALT in normal and Schistosoma mansoni-infected mice. In the healthy mouse, CALT is mainly composed of IgM (+) B cells and presents lower numbers of CD23 and CD45R (B220) B2 lymphocytes. When activated by the infection, it may show pronounced lymphocytosis, plasmocytogenesis (IgM > IgG > IgA > IgG2a > IgG1) and myelomonocytosis. The lymphocytes were mainly of the B1 type (double positive CD5/IgM), with smaller number of T cells (TCR alpha beta (+), TCR gamma delta (+), CD3 (+) and CD5 (+)) and conventional B2 cells (B220 (+), CD23 (+)). The myeloid compartment was composed of immature and mature cells of monocyte/macrophage, eosinophil, neutrophil and megakaryocytic lineages, especially in the omental milky spots. CALT is also a favorable microenvironment for LFA-1 (+) mast cells. Thus, CALT appears to be a mixed lymphoid organ, with secondary and/or primary lymphoid organ functions, being an important site of B1 cell generation, plasma cell maturation and extramedullar hematopoiesis. CALT operates as an interface between blood and lymphatic circulation and coelomic cavities, because locally or externally produced cells have easy and ready access to the pleural and peritoneal cavities. Furthermore, MS cells can escape into blood and lymphatic vessels, providing lymphocytes to other lymphoid organs and to the mucosa-associated lymphoid tissue.
Animals↗
Transmission of visceral leishmaniasis by blood transfusion in hamsters.
We have studied the transmission of visceral leishmaniasis by blood transfusion in the CB hamster model. Five normal CB hamsters (females, 2.5 months old) received a 0.1-ml blood transfusion from a donor that had been infected with 10(7) amastigotes of Leishmania donovani 90 days prior to the blood harvest. The development of the disease in transfused animals was monitored by the increase in anti-Leishmania serum antibodies, splenomegaly, and spleen and liver parasitic burdens. The transfused hamsters developed all the typical signs of the disease, i.e., ascites, cachexia and death. The scores of anti-Leishmania antibodies (1.345) and the level of parasite load (spleen Leishman Donovan units of Stauber (LDU) = 471, liver LDU = 378) in transfuse hamsters were similar to those observed in hamsters experimentally infected with 10(7) amastigotes (P > 0.05, Student t-test). Our results demonstrate that blood transfusion is an effective route for transmission of visceral leishmaniasis, and we point out that adequate precautions should be taken at blood banks in the regions where leishmaniasis is endemic.
Animals↗
Genome size and chromosomes in marine sponges [Suberites Domuncula, Geodia Cydonium].
The genome size of the marine sponges Suberites domuncula and Geodia cydonium has been determined by flow cytofluorometric analysis using diamidino-phenylindole [DAPI]. Using human lymphocytes as reference the amount of DNA in cells from S. domuncula has been determined to be 3.7 pg and that of G. cydonium 3.3 pg. While no chromosomes could be identified in G. cydonium, the karyotype of the Suberites domuncula is 32 chromosomes in the diploid state. The size of the chromosomes was between 0.25 and 1.0 micron. No pronounced banding pattern was visible.
Animals↗
Complement-dependent induction of DNA synthesis and cell proliferation in human liver connective tissue cells in vitro.
Liver connective tissue cells (LCTC) isolated from patients with fibrotic livers have morphological and biochemical characteristics of myofibroblasts. We have examined the proliferation of LCTC derived from normal livers and from livers with fibrosis of different etiologies, as well as proliferation of skin fibroblasts. We have compared proliferation rates in the presence of fresh human serum and heat-inactivated serum. While skin fibroblast and LCTC from normal liver showed no difference, proliferation of LCTC from fibrotic livers was markedly decreased in the presence of heat-inactivated serum. We demonstrate that the native complement component C1 is a factor involved in the induction of DNA synthesis and proliferation of LCTC isolated from fibrotic livers. We propose that native C1, acting probably in cooperation with other growth factors, is involved in the expansion of connective tissue cells during the development of liver fibrosis.
Blood↗