In vitro inhibitory effects of imatinib mesylate on stromal cells and hematopoietic progenitors from bone marrow

Imatinib mesylate (IM) is used to treat chronic myeloid leukemia (CML) because it selectively inhibits tyrosine kinase, which is a hallmark of CML oncogenesis. Recent studies have shown that IM inhibits the growth of several non-malignant hematopoietic and fibroblast cells from bone marrow (BM). The aim of the present study was to evaluate the effects of IM on stromal and hematopoietic progenitor cells, specifically in the colony-forming units of granulocyte/macrophage (CFU-GM), using BM cultures from 108 1.5- to 2-month-old healthy Swiss mice. The results showed that low concentrations of IM (1.25 µM) reduced the growth of CFU-GM in clonogenic assays. In culture assays with stromal cells, fibroblast proliferation and α-SMA expression by immunocytochemistry analysis were also reduced in a concentration-dependent manner, with a survival rate of approximately 50% with a dose of 2.5 µM. Cell viability and morphology were analyzed using MTT and staining with acrydine orange/ethidium bromide. Most cells were found to be viable after treatment with 5 µM IM, although there was gradual growth inhibition of fibroblastic cells while the number of round cells (macrophage-like cells) increased. At higher concentrations (15 µM), the majority of cells were apoptotic and cell growth ceased completely. Oil red staining revealed the presence of adipocytes only in untreated cells (control). Cell cycle analysis of stromal cells by flow cytometry showed a blockade at the G0/G1 phases in groups treated with 5-15 µM. These results suggest that IM differentially inhibits the survival of different types of BM cells since toxic effects were achieved.

In vitro inhibitory effects of imatinib mesylate on stromal cells and hematopoietic progenitors from bone marrow.

Imatinib mesylate (IM) is used to treat chronic myeloid leukemia (CML) because it selectively inhibits tyrosine kinase, which is a hallmark of CML oncogenesis. Recent studies have shown that IM inhibits the growth of several non-malignant hematopoietic and fibroblast cells from bone marrow (BM). The aim of the present study was to evaluate the effects of IM on stromal and hematopoietic progenitor cells, specifically in the colony-forming units of granulocyte/macrophage (CFU-GM), using BM cultures from 108 1.5- to 2-month-old healthy Swiss mice. The results showed that low concentrations of IM (1.25 µM) reduced the growth of CFU-GM in clonogenic assays. In culture assays with stromal cells, fibroblast proliferation and α-SMA expression by immunocytochemistry analysis were also reduced in a concentration-dependent manner, with a survival rate of approximately 50% with a dose of 2.5 µM. Cell viability and morphology were analyzed using MTT and staining with acrydine orange/ethidium bromide. Most cells were found to be viable after treatment with 5 µM IM, although there was gradual growth inhibition of fibroblastic cells while the number of round cells (macrophage-like cells) increased. At higher concentrations (15 µM), the majority of cells were apoptotic and cell growth ceased completely. Oil red staining revealed the presence of adipocytes only in untreated cells (control). Cell cycle analysis of stromal cells by flow cytometry showed a blockade at the G0/G1 phases in groups treated with 5-15 µM. These results suggest that IM differentially inhibits the survival of different types of BM cells since toxic effects were achieved.

Human periodontal ligament: a niche of neural crest stem cells.

BACKGROUND AND OBJECTIVE: The periodontal ligament is a specialized connective tissue, derived from dental follicle and originated from neural crest cells. Recently it has been suggested, based on animal models, that periodontal ligament could be a niche for neural crest stem cells. However, there is still little knowledge on this subject. The identification of neural crest adult stem cells has received much attention based on its potential in tissue regeneration. The objective of the present work was to verify the human periodontal ligament as a niche for neural crest stem cells. MATERIAL AND METHODS: Cells from human periodontal ligament were isolated from 10 teeth of seven individuals (periodontal ligament pool group) and also from four teeth of one individual (periodontal ligament single group), after enzymatic digestion. The cells were cultured in specific inductive medium. Analyses of protein and gene expression were performed through immunocytochemistry and reverse transcription-polymerase chain reaction techniques, respectively. RESULTS: Mesodermal phenotypes (adipogeneic, osteogenic and myofibroblastic) were identified after culture in inductive medium. Immunocytochemistry analyses showed the presence of the nestin marker of neural stem cells and also markers of undifferentiated neural crest cells (HNK1, p75). When cultured in inductive medium that allowed neural differentiation, the cells showed markers for beta-tubulin III, neurofilament M, peripherin, microtubule-associated protein 2 and protein zero. The results were similar between the two study groups (the periodontal ligament pool group and the periodontal ligament single group). CONCLUSION: This research provides evidence that human periodontal ligament, in addition to its mesodermal derivatives, produces neural crest-like cells. Such features suggest a recapitulation of their embryonic state. The human periodontal ligament revealed itself as a viable alternative source for possible primitive precursors to be used in stem-cell therapies.

Isolation and replication of rabies virus in C6 rat glioma cells (clone CCL-107).

The susceptibility of the C6 rat glioma cell line (ATCC; CCL-107) to rabies virus was characterized. The kinetics of infection performed with a fixed and a wild strain (from an infected cow) of rabies virus was monitored by direct immunofluorescence. Fluorescent cytoplasmic bodies were readily observed by UV microscopy from 24 hours post-infection (hpi) onwards. The ability of C6 to produce rabies infective virion particles was confirmed by determining the viral titres present in the supernatants of infected cultures, by both BHK-21 cell infection and mice inoculation. C6 cells produced similar viral titres to those produced by BHK-21 for both strains used. In addition, the yield of rabies glycoprotein was assessed by ELISA. In general, BHK-21 and C6 cells infected either by PV or with the wild rabies strain produced similar amounts of rabies glycoprotein. At 96 hpi, however, when the glycoprotein production peaked, BHK-21 infected with the wild strain produced significantly higher amounts of glycoprotein than C6. Subsequently, the optimal conditions for isolation of wild rabies virus strains from C6 cells were established and these proved to be as sensitive as NA cells in detecting 10 wild rabies samples. Due to the high sensitivity exhibited, C6 rat glioma cells present a new and useful system for rabies virus investigation.

Thyroid hormone induces cerebellar astrocytes and C6 glioma cells to secrete mitogenic growth factors.

In this study, the effect of thyroid hormone (triiodothyronine, T(3)) on the secretion of mitogenic growth factors in astrocytes and C6 glioma cells was examined. The proliferating activity of T(3) could be due, at least in part, to the astrocyte secretion of acidic and basic fibroblast growth factor (aFGF and bFGF), tumor necrosis factor-beta, and transforming growth factor-beta. In contrast, the conditioned medium (CM) of T(3)-treated C6 cells was mitogenic to this cell line only after hyaluronidase digestion, suggesting the impairment of growth factor mitogenic activity by hyaluronic acid. Furthermore, the presence of bFGF was significantly greater in the CM of both T(3)-treated astrocytes and T(3)-treated C6 cells than in the corresponding control CM. These data show that T(3) induces cerebellar astrocytes to secrete mitogenic growth factors, predominantly bFGF, that could influence astrocyte and neuronal proliferation via autocrine and paracrine pathways.

Thyroid hormone deficiency alters extracellular matrix protein expression in rat brain.

The effects of thyroid hormone (T3) deficiency on extracellular matrix protein expression were analyzed in newborn rat brain. In hypothyroid animals, a marked increase in the expression of 62 kDa protein was observed in cerebral hemispheres and midbrain, while the 51.6 kDa protein was increased in cerebral hemispheres and decreased in midbrain and the 44.5 kDa protein was down regulated in both structures. On the basis of molecular weights, these proteins may be the proteoglycans cerebroglycan, glypican and N-Syndecan, respectively. In addition, hypothyroidism reduced fibronectin expression in midbrain (-59,7%), but not in cerebral hemispheres. T3 deficiency affects differently the expression of proteins in different brain regions. This may be involved in brain impairment caused by hypothyroidism.

Isolation and replication of rabies virus in C6 rat glioma cells (clone CCL-107)

The susceptibility of the C6 rat glioma line (ATCC; CCL-107) to rabies virus was characterized. The kinetics of infection performed with a fixed and a wild strain (from an infected cow) of rabies virus was monitored by direct immunofluorescence. Fluorescent cytoplasmic bodies were readily observed by UV microscopy from 24 hours post-infection (hpi) onwards. The ability of C6 to produce rabies infective virion particles was confirmed by determining the viral titres present in the supertants of infected cultures by both BHK-21 cell infection and mice inoculation C6 cells produced similar viral titres to those produced by BHK-21 for both strains used. In addition, the yield of rabies glycoprotein was assessed by ELISA. In general, BHK-21 and C6 cells infected either by PV or with the wild rabies strain produced similar amounts of rabies glycoprotein. At 96 hpi, however, when the glycoprotein production peaked, BHK-21 infected with the wild strain produced significantly higher amounts of glycoprotein than C6. Subsequently, the optimal conditions for isolation of wild rabies virus strains from C6 cells were established and these proved to be as sensitive as NA cells in detecting 10 wild rabies samples. Due to the high sensitivity exhibited, C6 rat glioma cells present a new useful system for rabies virus investigation.

Alterations in proteins of bone marrow extracellular matrix in undernourished mice.

The objective of the present study was to determine the effect of protein malnutrition on the glycoprotein content of bone marrow extracellular matrix (ECM). Two-month-old male Swiss mice were submitted to protein malnutrition with a low-protein diet containing 4% casein as compared to 20% casein in the control diet. When the experimental group had attained a 20% loss of their original body weight, we extracted the ECM proteins from bone marrow with PBS buffer, and analyzed ECM samples by SDS-PAGE (7.5%) and ECL Western blotting. Quantitative differences were observed between control and experimental groups. Bone marrow ECM from undernourished mice had greater amounts of extractable fibronectin (1.6-fold increase) and laminin (4.8-fold increase) when compared to the control group. These results suggest an association between fluctuations in the composition of the hematopoietic microenvironment and altered hematopoiesis observed in undernourished mice.

Alterations in proteins of bone marrow extracellular matrix in undernourished mice

The objective of the present study was to determine the effect of protein malnutrition on the glycoprotein content of bone marrow extracellular matrix (ECM). Two-month-old male Swiss mice were submitted to protein malnutrition with a low-protein diet containing 4 percent casein as compared to 20 percent casein in the control diet. When the experimental group had attained a 20 percent loss of their original body weight, we extracted the ECM proteins from bone marrow with PBS buffer, and analyzed ECM samples by SDS-PAGE (7.5 percent) and ECL Western blotting. Quantitative differences were observed between control and experimental groups. Bone marrow ECM from undernourished mice had greater amounts of extractable fibronectin (1.6-fold increase) and laminin (4.8-fold increase) when compared to the control group. These results suggest an association between fluctuations in the composition of the hematopoietic microenvironment and altered hematopoiesis observed in undernourished mice

In vivo and in vitro responses to poly(ethylene terephthalate-co-diethylene glycol terephthalate) and polyethylene oxide blends.

Although biocompatible polymeric compounds are generally nontoxic, nonimmunogenic, and chemically inert, implants made from these materials may trigger acute and chronic inflammatory responses. These inflammatory reactions may induce degeneration of implanted biopolymer. Interactions between implanted biomaterial and inflammatory cells are mediated by many cellular events involving cellular adhesion and activation. We studied the inflammatory responses in vivo and in vitro to samples of biopolymers composed of poly(ethylene terephthalate-co-diethylene glycol terephthalate) plus 0, 5, 25% of polyethylene oxide. We observed that these biopolymers did not induce inflammatory responses when implanted in the peritoneal cavity of mice for 28 days. However we observed deposition of hyaluronic acid at the surface of implanted biomaterial, suggesting that tolerance to biomaterial occurred after surgical implantation. No significant adhesion of inflammatory cells such as mononuclear phagocytes and peripheral leukocytes were observed in vitro, when poly(ethylene terephthalate-co-diethylene glycol terephthalate) blends were used as substratum to cellular adhesion. These results suggest that blends composed of poly(ethylene terephthalate-co-diethylene glycol terephthalate) induce low inflammatory cell adhesion, since no rejection of biopolymer was observed when implanted in experimental animal models.

Thyroid hormone regulates protein expression in C6 glioma cells

Thyroid hormone (T3) is essential to normal brain development. Previously, we have shown that T3 induces cerebellar astrocyte proliferation. This effect is accompanied by alteration in glial fibrillary acidic protein (GFAP) and fibronectin organization. In the present study, we report that the C6 glioma cell line, which expresses GFAP and is classified as an undifferentiated astrocytic cell type, is a target for T3 action. The C6 monolayers were treated with 50 nM T3 for 3 days, after which the cells were maintained for 2 days without medium changes. In C6 cells, T3 induced the expression of proteins of 107, 73 and 62 kDa. The hormone also up-regulated protein bands of 100 (+50 per cent), 37 (+50 per cent) and 25.5 kDa (+50 per cent) and down-regulated proteins of 94 (-100 per cent), 86.5 (-100 per cent), 68 (-100 per cent), 60 (-100 per cent), 54 (-33 per cent), 51 (-33 per cent) and 43.5 kDa (-33 per cent). We suggest, on the basis of molecular mass, that the 54-, 51- and 43.5-kDa proteins could be the cytoskeletal proteins vimentin, GFAP and actin, respectively. The down-regulation of these proteins may be involved in the effects of thyroid hormone on C6 differentiation.

Thyroid hormone regulates protein expression in C6 glioma cells.

Thyroid hormone (T3) is essential to normal brain development. Previously, we have shown that T3 induces cerebellar astrocyte proliferation. This effect is accompanied by alteration in glial fibrillary acidic protein (GFAP) and fibronectin organization. In the present study, we report that the C6 glioma cell line, which expresses GFAP and is classified as an undifferentiated astrocytic cell type, is a target for T3 action. The C6 monolayers were treated with 50 nM T3 for 3 days, after which the cells were maintained for 2 days without medium changes. In C6 cells, T3 induced the expression of proteins of 107, 73 and 62 kDa. The hormone also up-regulated protein bands of 100 (+50%), 37 (+50%) and 25.5 kDa (+50%) and down-regulated proteins of 94 (-100%), 86.5 (-100%), 68 (-100%), 60 (-100%), 54 (-33%), 51 (-33%) and 43.5 kDa (-33%). We suggest, on the basis of molecular mass, that the 54-, 51- and 43.5-kDa proteins could be the cytoskeletal proteins vimentin, GFAP and actin, respectively. The down-regulation of these proteins may be involved in the effects of thyroid hormone on C6 differentiation.

Undersulfation of glycosaminoglycans reduces the proliferation of a leukemia cell line in vitro.

Leukemia represents the clonal expansion of an individual cell lineage of the hematopoietic system at a specific point of its maturation and development. This dysregulated expansion of cells is often accompanied by altered adherence to the bone marrow microenvironment and abnormalities in endogenous cytokine production by neoplastic cells. Proteoglycans (PGs) synthesized by neoplastic cells may interact with extracellular matrix (ECM) molecules and/or locally produced cytokines. It is believed that these events may be mediated by the glycosaminoglycan (GAG) moiety of PGs such as heparan or chondroitin sulfate, and depends on its charge. The strength of GAG-cytokine binding may be determined by the extent of sulfation of the GAG chains. The synthesis, metabolism and biological role of PGs in hematopoietic malignancies have not been clearly defined. In order to study how alterations of GAGs in leukemic cells may alter cellular behavior, we treated the murine myeloid leukemic cell line WeHi-3B with sodium chlorate. This drug reduces the sulfation of GAGs, since chlorate is a potent inhibitor of sulfate adenylyltransferase. The undersulfated GAGs produced by WeHi-3B cells were not efficient in controlling the mitotic rate of the cells, since a decrease in cell proliferation was observed in vitro. These data suggest that the complexes formed by GAGs with ECM components and/or cytokines may have an important role in the induction of leukemic cell proliferation. It is possible that the stimulatory activity elicited by this binding may be dependent upon the organization of these complexes.

Undersulfation of glycosaminoglycans reduces the proliferation of a leukemia cell line in vitro

Leukemia represents the clonal expansion of an individual cell lineage of the hematopoietic system at a specific point of its maturation and development. This dysregulated expansion of cells in often accompanied by altered adherence to the bone marrow microenvironment and abnormalities in endogenous cytokine production by neoplastic cells. Proteoglycans (PGs) synthesized by neoplastic cells may interact with extracellular matrix (ECM) molecules and/or locally produced cytokines. It is believed that these events may be mediated by the glycosaminoglycan (GAG) moiety of PGs such as heparan or chondroitin sulfate, and depends on its charge. The strength of GAG-cytokine binding may be determined by the extent to sulfation of the GAG chains. The synthesis, metabolism and biological role of PGs in hematopoietic malignancies have not been clearly defined. In order to study how alterations of GAGs in leukemic cells may alter cellular behavior, we treated the murine myeloid leukemic cell line WeHi-3B with sodium chlorate. This drug reduces the sulfation of GAGs, since chlorate is a potent inhibitor of sulfate adenylyltransferase. The undersulfated GAGs produced by WeHi-3B cells were not efficient in controlling the mitotic rat of the cells, since a decrease in cell proliferation was observed in vitro. These data suggest that the complexes formed by GAGs with ECM components and/or cytokines may have an important role in the induction of leukemic cell proliferation. It is possible that the stimulatory activity elicited by this binding may be dependent upon the organization of these complexes.

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.

Myelopoietic competence of stroma composed of hepatic granuloma-derived connective tissue cells or skin fibroblasts.

1. Connective tissue cells isolated from hepatic granulomas (GR cells), induced in mouse liver tissue by schistosomal infection, are able to sustain myelopoiesis, while other connective tissue cells such as skin fibroblasts (SF) are not. 2. We compared the ability of SF and GR cells to sustain in vitro proliferation of the FDC-P1 myeloid cell line, dependent upon IL-3 or GM-CSF. 3. Only the GR stroma sustained the proliferation of co-cultured FDC-P1 cells. RT-PCR analysis showed that both cell lines expressed the message for GM-CSF, but not for IL-3. We showed that GM-CSF was produced by, and remained bound to the cell layer through heparan sulfate; this growth factor could be released by high-salt treatment in a biologically active form from both cell types. The same activity could be restored to NaCl-treated GR cells, but not to SF, by incubation with recombinant murine GM-CSF. 4. These results indicate that the ability of connective tissue cells to sustain myelopoiesis depends directly upon the capacity of their heparan sulfate-bearing molecules to bind and present the GM-CSF to the target cells in a biologically active form. Alternatively, a yet unidentified set of cell layer-associated molecules may be required for the positive or negative control of the membrane-bound GM-CSF.

Myelopoietic competence of stroma composed of hepatic granuloma-derived connective tissue cells or skin fibroblasts

1. Connective tissue cells isolated form hepatic granulomas (GR cells), induced in mouse liver tissue by schistosomal infection, are able to sustain myelopoiesis, while other connective tissue cells such as skin fibroblasts (SF) are not. 2. We compared the ability of SF and GR cells sustain in vitro proliferation of the FDC-P1 myeloid cell line, dependent upon IL-3 or GM-CSF. 3. Only the GR stroma susteined the proliferation of co-cultured FDC-P1 cells. RT-PCR analysis showed that both cell lines expressed the message for GM-CSF, but not for IL-3. We showed that GM-CSF was produced by, and remained bound to the cell layer through heparan sulfate; this growth factor could be released by high-salt treatment in a biologically active form from both cell types. The same activity could be restored to NaCl-treated GR cells, but not to SF, by incubation with recombinant murine GM-CSF. 4. These results indicate that the ability of connective tissue cells to sustain myelopoiesis depends directly upon the capapcity of their heparan sulfate-bearing molecules to bind and present the GM-CSF to the target cells in a biologically active form. Alternatively, a yet unidentified set of cell layer-associated molecules may be required for the positive or negative control of the membrane-bound GM-CSF

Cell membrane-associated proteoglycans mediate extramedullar myeloid proliferation in granulomatous inflammatory reactions to schistosome eggs.

In chronic murine schistosomiasis, extramedullar myelopoiesis was observed, with proliferation of myeloid cells in liver parenchyma and in periovular granulomas. We have studied the question of whether cells obtained from granulomatous connective tissue may act as myelopoietic stroma, supporting long-term myeloid proliferation. Primary cell lines (GR) were obtained in vitro from periovular granulomas, induced in mouse livers by Schistosoma mansoni infection. These cells were characterized as myofibroblasts, and represent liver connective tissue cells involved in fibro-granulomatous reactions. They were able to sustain survival and proliferation of the multipotent myeloid cell lines FDC-P1 and DA-1 (dependent on interleukin-3 and/or granulocyte-macrophage colony stimulating factor, GM-CSF) without the addition of exogenous growth factors. This stimulation was dependent upon myeloid cell attachment to the GR cell layer; GR cell-conditioned medium had no activity. Primary murine skin fibroblasts could not sustain myelopoiesis. The endogenous growth-factor was identified as GM-CSF by neutralization assays with monoclonal antibodies. The stimulation of myelopoiesis occurred also when GR cells had been fixed with glutardialdehyde. The observed stimulatory activity was dependent upon heparan sulphate proteoglycans (HSPGs) associated with GR cell membranes. It could be dislodged from the cell layer with heparin or a high salt buffer. Our results indicate a molecular interaction between endogenous growth-factor and HSPGs; this interaction may be responsible for the stabilization and presentation of growth factors in myelopoietic stromas, mediating extramedullar proliferation of myeloid cells in periovular granulomas.