Mutually exclusive expression of fibronectin and glial fibrillary acidic protein in cultured brain cells

Milk growth factor (MGF)-induced differentiation of NT2/D1 cells

The differentiation activity of milk growth factor (MGF, 200 ng/ml), which also has proliferative activity, was investigated in NT2/D1 cells relative to that of retinoic acid (RA, 10(-7) M). MGF suppressed the proliferation of NT2/D1 cells to the same extent as RA after cultivation for 2x4 days. MGF enhanced Fas expression in NT2/D1 cells and prevented the decrease of Fas expression when RA was also added. MGF induced the synthesis of alpha-smooth muscle actin (alpha-SM-actin) in NT2/D1 cells without fibrils, but RA did not have such a potent activity. MGF extended glial fibrillary acidic protein (GFAP) that existed in a local area of NT2/D1 cell cytoplasm. On the other hand, RA enhanced GFAP expression and dispersed it throughout the cells. MGF slightly induced neurofilament-medium size (NF-M) synthesis in NT2/D1 cells that RA induced in the cells. MGF was less effective than RA in stimulating the synthesis of epinephrine in the cells, and the additive effect of MGF and RA enhanced epinephrine synthesis. While dopamine synthesis was less effectively stimulated by MGF than by RA, an additive effect of MGF and RA for dopamine synthesis was not observed in the cells. It was thus found that MGF differentiated NT2/D1 cells through alpha-SM-actin-synthesis.

Rat glioma cell lines C6 and 9L synthesize type 1 collagen in vitro

Glial cell lines (C6, a glioma and 9L, a gliosarcoma) grown in vitro produce type 1 collagen which is detectable in the extracellular matrix by immunocytochemistry. Northern blot analysis using a cDNA specific for the proalpha2 (I) chain of procollagen indicates the presence of a single transcript with an apparent size of 4.8 kb in the C6 cell line, whereas two transcripts with apparent sizes of 5.8 and 4.8 kb are visualized in the 9L cells. The stimulatory effect of ascorbic acid on collagen production is detectable by a 20-27% increase in the concentration of hydroxyproline in the culture medium from the two glioma cell lines. Therefore these glioma cell lines provide a valuable model system for comparative investigations on the regulation of type 1 collagen synthesis by nonmesenchymal cells of neuroepithelial origin.

Immunocytochemical study of macrophages and microglial cells and extracellular matrix components in human CNS disease. 1. Gliomas

We have used an immunocytochemical approach to investigate the inter-relationships between astrocytes, macrophages and microglia and the extracellular matrix components fibronectin and laminin, in 27 gliomas. Using recently available markers to macrophages and microglia (monoclonals Mac387, KP1 and the lectin RCA-1) and antisera to GFAP, fibronectin and laminin, we have described the reactions of these cells and the extracellular matrix. We found RCA-1 to be the superior marker for detecting most macrophages and microglia. There were more macrophages and microglia in high-grade gliomas than in low-grade. RCA-1 also reacted with endothelial cells in normal and reactive brain but showed markedly less affinity for endothelium in an close to gliomas. A possible role for the extracellular matrix in the astrocyte, macrophage and microglial reactions is discussed in the broader context of their role in the immune response.

Antigenic staining patterns of human glioma cultures: primary cultures, long-term cultures and cell lines

The immunocytochemical staining patterns of cultured glioma cells were investigated. Fifty nine individual cases were stained at different in vitro ages for glial fibrillary acidic protein, fibronectin, galactocerebroside, HNK-1/Leu 7, A2B5, vimentin, factor VIII and A4. Histologically, the cases were composed of eight low-grade astrocytomas, 11 high-grade astrocytomas, four low-grade oligodendrogliomas, seven high-grade oligodendrogliomas and 29 glioblastomas. The 45 cases were analysed within the first 3 weeks of culture, many of them as primary cultures. In 11 cases stainings were performed repeatedly at intervals of up to 6 months. Glial fibrillary acidic protein staining was positive in most of the early cultures of astrocytomas (low and high grade) and glioblastomas; expression in more than 50% of the cells was found in 1 of 5 low-grade astrocytomas, 5 of 11 high-grade astrocytomas and 14 of 29 glioblastomas. Two of the high-grade astrocytomas were stained once more after 6 weeks in culture and were found to be only 1% positive for glial fibrillary acidic protein but strongly positive for fibronectin. The same was true for five of the glioblastoma cases. Two of these cases remained glial fibrillary acid protein positive and developed into stable permanent cell lines. Only one case started with 1% of glial fibrillary acidic protein positive cells and later developed into a 99% glial fibrillary acidic protein positive cell line. Neither HNK-1/Leu 7 expression nor A2B5 staining appeared to have a relationship to the glial fibrillary acidic protein staining. It was observed that glial fibrillary acidic protein and HNK-1/Leu 7 were both 100% in some cases but that later one of the two antigens disappeared but not the other. The amount of glial fibrillary acidic protein staining does not allow the prediction of A2B5 staining. The study shows that initiation of primary cultures on an extracellular matrix yields more glial fibrillary acidic protein positive cells in primary cultures than have been found in other studies. It is concluded that only a rigid standardization of culture conditions will ensure the validity of comparisons of in vitro data obtained in primary cultures.

Dibutyryl cyclic AMP-induced changes in neuron-astroglia interactions and fibronectin immunocytochemistry in dissociated rat cerebellar cultures

In mixed primary embryonic CNS cultures flat astroglia grow exclusively underneath the initially formed neuronal network. This invasive under-growth results in neuronal detachment and degeneration. The present study sought to find out whether or not morphological differentiation of astroglia, from flat to process-bearing cells, could alter astroglial-neuronal growth relationships in rat cerebellar cultures. Morphological differentiation of astroglia was induced by treatment with dibutyryl cyclic AMP. The results demonstrate that in contrast to flat astroglia, large stellate astroglia can grow over the neurite bundles, and that in these dibutyryl cyclic AMP-treated cultures neurons can persist. Immunocytochemical studies show that the extracellular matrix protein fibronectin is present in these cultures and appears to be associated with flat astroglia rather than with stellate astroglia. The study indicates that in the presence of dibutyryl cyclic AMP transformed stellate astroglia interact differently with neurons and with the growth substratum as compared with flat astroglia.

Stimulation of thromboxane release from primary cell cultures derived from human astrocytic glioma biopsies

Stimulation of primary cultures of rat astrocytes with appropriate agents results in the mobilization of arachidonic acid from intracellular lipid pools and the synthesis of eicosanoids. Thromboxane A2 is one of the major prostanoids released upon stimulation with calcium ionophore, phorbol esters, and ATP; but a number of other predicted effectors are inactive. In an attempt to understand the pathophysiological significance of eicosanoid release from astrocytes, primary cultures have been derived from human astrocytic glioma biopsies. The majority of cells in the cultures expressed glial fibrillary acidic protein (GFAP), frequently in conjunction with vimentin and fibronectin. Cell sorting revealed that a significant proportion of cells in the cultures from the high-grade (malignant) tumors expressed epidermal growth factor receptor, indicative of neoplastic cells. Both effective and ineffective agents in rat cultures were tested for their ability to stimulate release of thromboxane from these gliomas, and also from cultures of medulloblastoma and ependymoma which contained significant numbers of GFAP-positive cells. Only cells from the high-grade tumors released thromboxane in response to the known effective stimuli. While the muscarinic agonist carbachol was ineffective, norepinephrine evoked thromboxane release from malignant astrocytomas. These data show that cells derived from malignant human gliomas retain the ability to release thromboxane upon stimulation and suggest that a transformation in receptor coupling might accompany neoplasia, such that the cells now respond to a previously ineffective agonist.

Heterogeneity and modulation of tumor-associated antigens in human glioblastoma cell lines

Seven human glioblastoma cell lines established in vitro from primary tumor explants were studied. A marked heterogeneity of glial fibrillary acidic protein was observed whereas vimentin was uniformly expressed by all cell lines. Indirect immunofluorescence and flow cytofluorometry revealed a heterogeneous distribution of surface GE 2 and CG 12 tumor-associated antigens (TAA's): three cell lines were positive (greater than 69% TAA-positive cells) and three cell lines were negative (less than 9% TAA-positive cells). One cell line (Hu 228) was moderately positive at early culture passages and subsequently acquired a TAA-negative phenotype. The difference in the relative amounts of surface TAA's of the three positive cell lines was less than twofold. In spite of the heterogeneous distribution of surface TAA's, all cell lines exhibited considerable amounts of intracellular TAA. Treatment with phorbol esters and density-dependent growth arrest decreased the percentage of the TAA-positive cells and the amount of cell-surface TAA's in one cell line (Hu 195). Interferon-gamma treatment in vitro increased the percentage of CG 12-positive cells by 12% and the amount of cell-surface CG 12 antigens by 38% as compared to untreated cells. The percentage of TAA-positive cells among phorbol ester-treated cells of the Hu 195 cell line was lowest 48 hours after treatment, but returned to normal values within the next 48 hours. Reduction of 3H-thymidine incorporation preceded the decrease in number of TAA-positive cells by about 18 hours. Two-color fluorescence analysis performed in positive cell lines for simultaneous determination of surface TAA's and deoxyribonucleic acid content or reactivity with the proliferation-associated Ki67 intracellular marker indicated that GE 2 and CG 12 antigens are expressed preferentially by actively proliferating glioma cells. The results of this study indicate the existence of two different phenotypes in cultured human glioblastoma cells: surface TAA-positive/cytosol TAA-positive and surface TAA-negative/cytosol TAA-positive cell populations. In addition, modulation of TAA expression was dependent on the cell-cycle differentiation stage, culture conditions, and proliferative state of the cells.

The development of an animal model of glioma for use in experimental neuro-oncology

A cell line, 497-P(1), derived from the VM spontaneous murine astrocytoma has been used to develop an in vitro in vivo model of human glioma. This paper describes the growth characteristics of tumours produced after intracerebral or subcutaneous inoculation of 497-P(1) cells into syngeneic VM mice. The results show that cell line 497-P(1) provides the basis for a reproducible animal model of glioma which fulfils many of the criteria required for experimental therapy studies.

Growth cone advance mediated by fibronectin-associated filopodia is inhibited by a phorbol ester tumor promoter

In serum-supplemented medium, exposure to the tumor promoter 4 beta-phorbol 12 beta-myristate 13 alpha-acetate (PMA) increases the proportion of SH-SY5Y neuroblastoma cells with neurites and increases the average neurite length. In the present study, under serum-free conditions, PMA treatment had the opposite effects, i.e., retarded neurite sprouting and partially inhibited neurite elongation. This inhibition in neurite outgrowth was partially antagonized by the addition of serum fibronectin (FN) to the medium or substratum. In the absence of PMA, SH-SY5Y cells grown under serum-free conditions showed extensive neurite outgrowth as well as the capacity to secrete FN into their microenvironment and form FN-containing substratum-attachment sites. Immunogold labeling and whole mount transmission electron microscopy (WMTEM) demonstrated FN-containing contact pads at sites where filopodia attached to the substratum and focal plaques on the underside of growth cone margins. The appearance and abundance of FN-containing contact pads and focal plaques were increased by the addition of exogenous FN to defined medium. Focal plaques appeared in close association with microfilament bundles, and nearly always with bundles that projected into filopodia attached to the substratum by contact pads. A method for immunolabeling FN in the filopodial contact pads of living cultures provided more direct evidence that filopodia and contact pads have a major role in FN-mediated attachment and are central in determining growth cone shape and the rate and direction of advance. In support of this view, we show that PMA treatment retards neurite sprouting, alters growth cone morphology and motility, and eliminates the appearance of microfilament bundles, filopodia, and FN-containing substratum-attachment plaques.

A fibronectin-like molecule is present in the developing cat cerebral cortex and is correlated with subplate neurons

The subplate is a transient zone of the developing cerebral cortex through which postmitotic neurons migrate and growing axons elongate en route to their adult positions within the cortical plate. To learn more about the cellular interactions that occur in this zone, we have examined whether fibronectins (FNs), a family of molecules known to promote migration and elongation in other systems, are present during the fetal and postnatal development of the cat's cerebral cortex. Three different anti-FN antisera recognized a single broad band with an apparent molecular mass of 200-250 kD in antigen-transfer analyses (reducing conditions) of plasma-depleted (perfused) whole fetal brain or synaptosome preparations, indicating that FNs are present at these ages. This band can be detected as early as 1 mo before birth at embryonic day 39. Immunohistochemical examination of the developing cerebral cortex from animals between embryonic day 46 and postnatal day 7 using any of the three antisera revealed that FN-like immunoreactivity is restricted to the subplate and the marginal zones, and is not found in the cortical plate. As these zones mature into their adult counterparts (the white matter and layer 1 of the cerebral cortex), immunostaining gradually disappears and is not detectable by postnatal day 70. Previous studies have shown that the subplate and marginal zones contain a special, transient population of neurons (Chun, J. J. M., M. J. Nakamura, and C. J. Shatz. 1987. Nature (Lond.). 325:617-620). The FN-like immunostaining in the subplate and marginal zone is closely associated with these neurons, and some of the immunostaining delineates them. Moreover, the postnatal disappearance of FN-like immunostaining from the subplate is correlated spatially and temporally with the disappearance of the subplate neurons. When subplate neurons are killed by neurotoxins, FN-like immunostaining is depleted in the lesioned area. These observations show that an FN-like molecule is present transiently in the subplate of the developing cerebral cortex and, further, is spatially and temporally correlated with the transient subplate neurons. The presence of FNs within this zone, but not in the cortical plate, suggests that the extracellular milieu of the subplate mediates a unique set of interactions required for the development of the cerebral cortex.

Glial fibrillary acidic protein, vimentin and fibronectin in primary cultures of human glioma and fetal brain

The expression of glial fibrillary acidic protein (GFAP), vimentin and fibronectin (Fn) was studied in cells cultured from human glioma and fetal brain by indirect immunofluorescence (IIF) microscopy and multiple labelling experiments. In the primary cultures a major part (20%-70%) of the cells usually displayed both GFAP and vimentin and the rest of the cells only vimentin. A prominent variation in GFAP and vimentin fluorescence intensity sometimes made interpretation of double IIF stainings difficult. However, occasional GFAP-positive cells appeared vimentin negative in primary glioma cultures, whereas in fetal brain primary cultures cells that were preferentially GFAP positive also showed at least a weak vimentin immunoreactivity. Only a fraction of the cells, roughly corresponding to the GFAP-negative cells, were Fn positive in the primary cultures. As judged by double IIF, the GFAP-positive cells were usually Fn negative, while the Fn-positive cells were vimentin positive. This could also be demonstrated in triple IIF experiments. During serial subcultivation the amount of cells expressing GFAP decreased, while the number of Fn-positive cells increased. By the third to fourth passage GFAP positivity was usually lost, all cells expressed vimentin and most cells also Fn. The results of the present study demonstrate a general coexpression of GFAP and vimentin in cultured astroglial cells, in addition to cells expressing only vimentin. Interestingly, occasional glioma cells seem to contain GFAP as the only intermediate filament protein as detected by immunocytochemistry.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigenic expression by cells derived from human gliomas does not correlate with morphological classification

We have found that cell populations derived from human gliomas can be divided into antigenic classes which are not predictable on the basis of standard morphological analysis and which, most frequently, do not support the lineage assignations of various tumours as determined by traditional neuropathological methods. For example, only 6/60 cultures derived from astrocytomas expressed glial fibrillary acidic protein (GFAP), an astrocyte specific marker, and all six of these cultures were derived from morphological categories which more frequently gave rise to populations which did not express GFAP. None of the seven oligodendrogliomas or four oligo-astrocytomas examined expressed antigens specifically expressed by oligodendrocytes. Most tumour-derived populations, from all classes of tumour and all grades of malignancy, expressed cell-surface fibronectin, an extracellular matrix protein only rarely found on the surfaces of CNS macroglia; such cells did not express glial-specific antigens (e.g., GFAP) in vitro. Investigation of antigen expression in tumour biopsies indicated that some tumours also consisted largely or wholly of cells which expressed fibronectin in situ. Fibronectin-expressing cells were aneuploid and were not contact inhibited in their growth, indicating that they were transformed cells. We have also identified two previously unknown antigenic phenotypes among the gliomas.

Distribution of laminin and fibronectin along peripheral trigeminal axon pathways in the developing chick

The trigeminal region of the chick was studied with indirect immunofluorescence in order to determine whether extracellular matrix components might be distributed in such a way as to guide trigeminal axons to their peripheral targets in the mandibular arch. Tissue sections from stages 13-15 and 21/22 were immunolabeled indirectly with affinity-purified antibodies raised against fibronectin and laminin, two extracellular matrix glycoproteins that support axon growth in vitro. Fibronectin was distributed ubiquitously throughout the head mesenchyme prior to and during initial axon growth from the brainstem (stages 13-15). Shortly after trigeminal axons reached their target tissues (stage 21/22), fibronectin immunolabeling was distributed throughout the head mesenchyme, but was present only at low levels in the trigeminal ganglion and motor nerve. Laminin immunolabeling was distributed in the lateral head mesenchyme at stage 13 as small specks and patches. At stage 14, when the motor axons first exit from the brainstem, short, linear arrays of laminin immunostaining were present from the basement membrane of the neural tube to the core of the mandibular arch, and many were parallel to the direction of axon growth. By stage 21/22 the trigeminal ganglion and motor root showed intense antilaminin immunofluorescence as did the central core of the mandibular arch. These studies suggest that the distribution of fibronectin within the head mesenchyme cannot give directional information to the growing trigeminal axons because of its homogeneous distribution. However, the initial distribution of laminin during the earliest stages of axon outgrowth may provide an extracellular matrix pathway that permits trigeminal axons to reach their targets.

The correlation of neoplastic vulnerability with central neuroepithelial cytogeny and glioma differentiation

The vulnerability of neuroepithelial cells in the central nervous system (CNS) to neoplastic transformation results from the interaction of several factors: the existence of a reserve population of stem cells, the capability of differentiated cells to reenter the kinetic cycle, the number of replicating cells at risk at a particular time, the length of time during which a particular cell population remains in the cycle, the state of differentiation and the further differentiation potential of that population, and the steps of differentiation that are achieved in successive cell generations. This concept explains many aspects of CNS tumor incidence and the relationship of central neuroepithelial embryonal tumors to tumors of adult cell type. The incidence of different types of central neuroepithelial tumors can be correlated with the width of the window of neoplastic vulnerability. Examples illustrating the existence of only a narrow window include such rare tumors as medulloepitheliomas, cerebral neuroblastomas, gangliogliomas and ependymoblastomas. By contrast, cerebellar medulloblastomas, astrocytomas, mixed astrocytomas and oligodendrogliomas, and glioblastomas exemplify instances in which a relatively wider window of vulnerability exists in the light of cellular neuro-ontogeny and of the capacity of glial cells for postnatal replication. The relationship that may occasionally be established between the development of a glioma and the production of cellular gliosis such as may follow brain injury or accompany multiple sclerosis can also be viewed in the light of that concept. Increasing awareness is needed concerning the development of postradiation gliomas, in particular after the apparently successful treatment of acute lymphocytic leukemia.

DNA content and marker expression in human glioma explants

Immunohistochemical studies of astrocytoma tissue have predominantly shown fibronectin (FN) positivity restricted to vessels and glial fibrillary acidic protein (GFAP) positivity in the parenchyma. Cultured glioma cell lines, however, express both FN and GFAP. We measured the DNA content of explants of gliomas to determine if the ploidy of the FN-positive and GFAP-positive cells differed. Thirty-three explants from four high grade gliomas were cultured on slides. FN and GFAP markers were determined by double immunofluorescence. The slides were stained by the Feulgen method, the explants relocated and the DNA content measured by microdensitometry using the CAS-100 instrument. Human leukocytes applied to the slides were used as a diploid standard. Eleven GFAP-positive explants were hyperdiploid and one hypodiploid. Five FN-positive explants were diploid, three hypodiploid and ten hyperdiploid. One FN-positive explant was biclonal with aneuploid subpopulations. Two hyperdiploid explants, each of which had monoclonal histogram patterns, expressed both FN and GFAP. We conclude that most FN-positive cells, in addition to GFAP-positive cells, from cultured gliomas represent neoplastic cells. These may be present in the tumor in low numbers or may result from marker switching in culture.

Translocation of human glial and glioma cells in culture

Two normal glial lines and four selected malignant glioma lines--considered as representative of the varying morphologies previously found among these lines--were studied quantitatively as to their translocatory ability on glass under standard culture conditions. The two glial lines showed very similar characteristics with almost identical results for total and net translocation, as well as in their directional persistence. The glioma lines gave values for these criteria which were either greater or lower than those of the glial cells. These values could to a certain degree be related to phenotypic traits, such as degree of cell polarization and amounts of cytoplasmic microfilament bundles. The findings once again display the heterogeneity of the human malignant glioma lines and raise doubts as to the general applicability of findings in studies of single lines of tumor cells, or of experimentally transformed cells, to all malignant cells.

Heterogeneity of a cultured neoplastic glial line. Establishment and characterisation of six clones

Six clones have been established from a tumorigenic glial cell line (VMDk P497) originally derived from a spontaneous mouse astrocytoma. The clones express dissimilar morphological, antigenic, kinetic and chromosomal properties, thereby indicating the heterogeneity of the parent culture line.

Products of cells cultured from gliomas. IV. Extracellular matrix proteins of gliomas

Five primary and 3 established human glioma cell lines were cultured with ascorbate and examined for expression of extracellular matrix components. All lines except C6 expressed collagen as assessed by silver impregnation, immunofluorescence and lectin staining and expressed laminin and fibronectin. None expressed a lectin marker for endothelial cells. Both epithelial and mesenchymal collagens were expressed. While extracellular components of glioma lines resembled those of fibroblasts more closely than other cell types, subtle differences between gliomas and fibroblasts were present. These included more laminin and collagen type-IV antigenic reactivity and more 11-12 nm diameter extracellular fibrils from individual gliomas, and slight differences in spectra of low-molecular-weight extracellular proteins assessed by gel electrophoresis. One primary and two established glioma lines analysed for DNA content were aneuploid in contrast to diploid fibroblasts. Simultaneous expression of mesenchymal and epithelial markers suggests a dual differentiation potential of glioma cells. Results do not support an endothelial origin for cells cultured from gliomas.

Fibronectin is expressed by astrocytes cultured from embryonic and early postnatal rat brain

In early primary cultures from newborn rat brain, few glial fibrillary acidic protein (GFAP)-positive glial cells expressed intracytoplasmic immunoreactivity for fibronectin. After the second week in culture, however, fibronectin was expressed by a distinct population of GFAP-positive flat astrocytes, irrespective of which brain region was studied. In cerebellar cultures, these cells were more abundant than in cortical or neostriatal cultures and often formed a major population of the GFAP-positive cells. The difference in fibronectin expression between cerebellum and the other areas studied was statistically significant. When cultures were started from 9-day-old postnatal rat brain, fibronectin-positive astrocytes appeared earlier than in those from newborn animals, in all areas studied. Further, especially in the case of cerebellum, the number of fibronectin-positive astrocytes increased as a function of time in culture. In cultures started from whole brains of 12-day-old rat embryos, fibronectin was expressed within 24 h in culture by all the cells with morphology of flat astrocytes, positive for vimentin but negative for GFAP. These results indicate that astrocytes cultured from newborn and early postnatal rat brain are a heterogeneous population of cells: depending on the brain region studied and also depending on the age of brain tissue or the time in culture, less than 1-60% of the GFAP-positive flat astrocytes expressed fibronectin. This, together with the fact that fibronectin was present in early embryonic brain cells in culture, suggests that fibronectin may be a prerequisite for the development or interactions of brain cells.

Immunocytochemical characterization of neuron-rich primary cultures of embryonic rat brain cells by established neuronal and glial markers and by monospecific antisera against cyclic nucleotide-dependent protein kinases and the synaptic vesicle protein synapsin I

Primary cell cultures derived from embryonic rat brain were characterized by immunocytochemical methods using established cell markers and monospecific antisera against cyclic nucleotide-dependent protein kinases and the synaptic vesicle protein, synapsin I. The cultures contained predominantly neurons, few astroglial cells and no oligodendroglial cells, based on immunocytochemical studies of the distribution of neuron-specific enolase, glial fibrillary acidic protein, myelin basic protein and galactocerebroside. Subsequently, the immunocytochemical localization of synapsin I, the cyclic GMP-dependent protein kinase and the various subunits of cyclic AMP-dependent protein kinase was determined. Synapsin I, a substrate for both the cyclic AMP- and Ca2+/calmodulin-dependent protein kinases, appeared particularly useful as a specific neuronal marker in primary cultures. Both immunocytochemical and immunoblotting techniques readily detected synapsin I in neuron-rich embryonic brain cultures, but indicated that synapsin I was absent from glia-rich primary cultures of newborn rat brain cells which lacked neurons. The intracellular localization of synapsin I in neurons changed markedly during the time of cell culture. In the first 10 days of cell culture, synapsin I appeared to be confined to neuronal cell bodies, whereas later it shifted to a patchy distribution in neuronal processes, perhaps indicating the transport of synapsin I in synaptic vesicles from the compartment of protein synthesis to its final synaptic location. Within neuron-rich embryonic cultures, the regulatory subunit (R-II) and the catalytic subunit (C) of cyclic AMP-dependent protein kinase appeared to be highly concentrated in neurons examined immunocytochemically. However, biochemical experiments demonstrated that R-II and C were also present in non-neuronal cell types of brain cell primary cultures. Cyclic GMP-dependent protein kinase, a marker protein for cerebellar Purkinje cells and for smooth muscle cells, was not detected immunocytochemically in neuron-rich cultures of embryonic brain cells, suggesting that Purkinje cells and smooth muscle cells were either absent from or not sufficiently developed in these cultures.

Cytoskeletal properties and endogenous degradation of glial fibrillary acidic protein and vimentin in cultured human glioma cells

The cytoskeletal properties and endogenous degradation of intermediate filaments in cultured human glioma cells (U-251MG) were studied using monoclonal antibodies in immunohistochemical and immunochemical methods. Both glial fibrillary acidic protein (GFAP)- and vimentin-antibodies gave a fibrillar cytoplasmic staining of the cells, and double immunofluorescence experiments showed the presence of both types of intermediate filaments in the same cells. GFAP and vimentin could also be located to typical coiling perinuclear bundles after vinblastine treatment of the cultures. In the detergent-resistant, adherent cytoskeletons of the glioma cells, both GFAP and vimentin persisted as fibrillar cytoplasmic arrays. Scanning and transmission electron microscopy showed that only intermediate filaments were left in the cytoplasmic domain. Electrophoretic analysis, combined with the immunoblotting method, revealed that the two major detergent-resistant cytoskeletal polypeptides of the cells, with molecular weights of 51 kD and 58 kD, were GFAP and vimentin, respectively. On the other hand, neither GFAP nor vimentin were detected in the detergent extracts of the glioma cells. Detergent-extraction in low ionic strength medium as well as inclusion of Ca2+ into the extraction medium resulted into a rapid degradation of both GFAP and vimentin. These degradation conditions produced different, partially soluble, lower MW immunoreactive polypeptides as detected by the immunoblotting technique. Interestingly, the degradation also produced soluble intact GFAP and vimentin. These results indicate that GFAP and vimentin have closely similar physicochemical properties in the cytoskeletons of human glioma cells including a nearly quantitative localization in filaments, rearrangement upon microtubule disruption, and resistance to extractions by detergents. Proteolytic degradation of both proteins can be induced by a protease activated by both low ionic strength and Ca2+.

Cellular heterogeneity in primary cultures of brain cells revealed by immunocytochemical localization of glutamine synthetase

The co-localization of glutamine synthetase, glial fibrillary acidic protein, galactocerebroside and fibronectin was investigated by immunofluorescence double staining in primary cultures of dissociated brain cells from newborn mice. In cultures, grown in serum-free medium, containing dibutyryl-cAMP, glutamine synthetase was found in about half of the glial fibrillary acidic protein containing astroblasts. After addition of dexamethasone to the cultures, glutamine synthetase appeared also in another cell type, in which no glial fibrillary acidic protein, but fibronectin was detectable. This demonstrates that these cells, which are present in substantial amounts, are not of glial nature. In cultures treated with dibutyryl-cAMP no other cell type was found positive for fibronectin. For cultures grown in serum-containing medium lacking dibutyryl-cAMP, evidence was obtained that glutamine synthetase was induced by dexamethasone only in part of all cells staining for fibronectin. This suggests the presence of two different populations of fibronectin-positive cells. Oligodendrocytes, revealed by staining for galactocerebroside, never contained detectable amounts of glutamine synthetase, irrespective of the presence of dexamethasone. This also holds for cultures grown in serum-free medium containing dibutyryl-cAMP. However, under these conditions, oligodendroblasts are seen only very rarely. Our results demonstrate an unexpected heterogeneity in the cellular composition of primary cultures from newborn mouse brain.

Neurite outgrowth of neuroblastoma cells: dependence on adhesion surface--cell surface interactions

Neurite outgrowth of C 1300 neuroblastoma cells, which were dispersed from adherent cultures or grown in suspension, was studied on different protein-coated surfaces. Of 29 different surface structures studied, including surfaces treated with various fibronectins, lectins, glycosidases, or glycosyltransferases capable of stimulating fibroblast spreading, only the surfaces coated with plasma fibronectin or with a protein mixture secreted by C6 glioma cells displayed an extensive activity in the sprouting assay. Neurite outgrowth was inhibited by brain gangliosides and by colominic acid (a sialic acid polymer). A 50% inhibition of neurite outgrowth of N18 neuroblasts induced by the glioma cell proteins was observed at the following approximate concentration: 100 microM (0.2 mg/ml) GD1A ganglioside, 20 microM (0.04 mg/ml) GT1B ganglioside, and 5 mg/ml colominic acid. Specificity of inhibition was suggested by the finding that a few polyanionic substances tested were not inhibitory in the sprouting assay, and that the type of gangliosides inhibiting sprouting were found to be major sialoglycolipids of the neuroblasts. A hypothesis is discussed, according to which neurite outgrowth of neuroblasts is stimulated by adhesion involving interactions of the adhesion-mediating protein with cell surface carbohydrates characteristic of brain gangliosides.

Collagenase in the immunohistochemical demonstration of laminin, fibronectin and factor VIII/RAg in nervous tissue after fixation

The effects of collagenase on the immunohistochemical demonstrability of laminin, fibronectin and Factor VIII/RAg in human nervous tissue have been studied. The influence of this, and other proteolytic enzymes such as pepsin and trypsin, has been investigated in relation to different fixatives. Collagenase gave better results with Carnoy fixed material than after formalin fixation; unlike trypsin and pepsin, it did not produce tissue digestion.

Morphologic, cytochemical and neurochemical characterization of the human medulloblastoma cell line TE671

Medulloblastoma cell line TE671 was characterized by morphologic, cytochemical, neurochemical, and growth criteria. In contrast to the uniform, in vivo histopathologic appearance of the tumor, TE671 in vitro exhibits six morphologic subtypes (Types I-VI) in varying percentages over 14 days in culture. TE671 grows as a monolayer by the merging of separate foci. Cells were positive for Periodic acid Schiff (PAS) and reticulum, and negative for the glial marker, glial fibrillary acid protein (GFAP). Receptors for human C3b (EAC) were present on 19% of the cells. Neural associated isoenzymes, neuron specific enolase (NSE) and creatine kinase (CK-BB) were demonstrated in TE671. Progeny of a single clonogenic cell manifested the morphologic heterogeneity of cell types (I-VI). The absence of markers specific for glial cells suggests that TE671 is an early (less differentiated) precursor. TE671, the only continuous human medulloblastoma cell line, provides an experimental model with which to compare and identify the subpopulation of neoplastic cells in medulloblastoma ex vivo.

Immunocytochemical characterization of cloned cells from normal adult rat brain

A cell clone, isolated from normal adult rat brain and maintained in culture for many passages, has been previously characterized by electron microscopy. Immunohistochemistry has now been shown that it possesses glutamine synthetase (GS) which supports its astrocytic origin. Cells failed, however, to express glial fibrillary acidic protein (GFAP) but did express the intermediate filament protein vimentin. The presence of fibronectin confirms the normal derivation of these cells and excludes the possibility of malignant transformation.

Cell lines (VMDk) derived from a spontaneous murine astrocytoma. Morphological and immunocytochemical characterization

Three cell lines (VMDk) derived from a spontaneous, murine astrocytoma, which produce tumours when injected either subcutaneously or intracranially into syngeneic mice, have been examined in vitro. Ultrastructurally, the cells show astrocytic features but each line differs in its degree of differentiation. Treatment with both dexamethasone and dibutyryl adenosine 3',5'-cyclic monophosphate (dbcAMP) increases intracytoplasmic differentiation and causes surface structural changes. The addition of dbcAMP also induces a statistically significant increase in the length and number of cell processes. All three cell lines express the astrocyte-specific markers, glial fibrillary acidic protein (GFAP) and glutamine synthetase (GS), by indirect immunofluorescence, with two lines showing an increased propensity to stain for GFAP following dbcAMP treatment. The cell surface antigen fibronectin is also detected in all lines. Thus these VMDK cell lines exhibit both the morphological and antigenic characteristics of astrocytes and respond to dexamethasone and dbcAMP and may be used to provide a suitable in vivo-in vitro model system for the study of astrocytoma.

Expression of glial fibrillary acidic protein, actin, fibronectin and factor VIII antigen in human astrocytomas

Frozen sections and cell cultures of 50 human astrocytomas, fetal and adult human brain were examined for immunofluorescence reactivity with antisera to glial fibrillary acidic protein (GFAP), actin, fibronectin and factor VIII antigen. In frozen tissue sections GFAP expression was restricted to normal and neoplastic astrocytes while fibronectin and factor VIII antigen were localized to blood vessels. In primary cell culture, 80-100% neoplastic astrocytes expressed GFAP but not fibronectin or factor VIII antigen while actin was present as diffuse cytoplasmic staining of the cell body and cell processes. By the 5th-6th passage in vitro, GFAP immunoreactivity was lost while fibronectin and actin cables were prominently expressed. Factor VIII antigen remained negative throughout serial subculture. In double fluorochrome experiments, GFAP positive cells did not express fibronectin or actin cables, while GFAP negative cells expressed fibronectin and had prominent actin cables. Our results suggest a change in population of astrocytoma cells with increasing passage in vitro, reflecting either an overgrowth of tumour glioblasts or dedifferentiation of tumour astrocytes.

Monoclonal antibodies to glial fibrillary acidic protein. 1. Characterization

Mouse hybridomas producing antibodies to glial fibrillary acidic protein (GFAP) have been cloned and their immunoglobulins characterized biochemically, immunochemically and immunocytochemically. Immunoaffinity columns were prepared using cyanogen bromide activated sepharose 4R and the antibodies of the C9 clone. A protein giving a single band in the 50-55 kd range was thus isolated from aqueous extracts of bovine brain. The clone yields antibodies which are, on the basis of these studies, specific for GFAP. The antibody belongs to the class IgG1 and has been applied to human tissues, both frozen sections and sections embedded in paraffin wax following fixation in formaldehyde. The results show that the antibody may be of assistance in the classification of human brain tumors.

Laminin is produced by early rat astrocytes in primary culture

The production of laminin by early rat astrocytes in primary culture was investigated by double immunofluorescence staining for laminin and the glial fibrillary acidic protein (GFAP), a defined astrocyte marker. In early cultures (3 d in vitro; 3 DIV) cytoplasmic laminin was detected in all the GFAP-positive cells which formed the major population (80%) of the nonneuronal cells present in cultures from 20-21-d embryonic, newborn, or 5-d-old rat brains. Monensin treatment (10 microM, 4 h) resulted in accumulation of laminin in the Golgi region, located using labeled wheat germ agglutinin. Laminin started gradually to disappear from the cells with the time in culture, was absent in star-shaped, apparently mature astrocytes, but remained as pericellular matrix deposits. The disappearance of cellular laminin was dependent on the age of the animal and the time in culture so that it started earlier in cultures from 5-d-old rat brains (5 DIV) and approximately following the in vivo age difference in cultures from newborn (12 DIV) and embryonic (14 DIV) rat brains. Our results indicate that laminin is a protein of early astrocytes and also deposited by them in primary culture, thus suggesting a role for this glycoprotein in the development of the central nervous system.

Immunohistochemical study of fibronectin in human glioma and meningioma

The presence of fibronectin (FN) and glial fibrillary acidic protein (GFAP) in two astrocytomas, 17 glioblastomas, and five meningiomas was studied by indirect immunoperoxidase staining of formalin-fixed and paraffin-embedded surgical specimens. Angiogenesis in tumor was scored by the microscopic angiogenesis grading system (MAGS), and plasma FN levels were measured by single radial immunodiffusion. In astrocytomas and glioblastomas, GFAP-positive tumor cells had no FN expression and FN was confined to proliferating vessel walls and the leptomeninges, showing a mutually exclusive FN and GFAP expression. GFAP-positive tumor cells were occasionally surrounded by a network of FN-positive matrix produced by cells derived from the leptomeninges or blood vessels. In meningiomas, FN expression was found in vessel walls and meningioma cells including whorl formations and psammoma bodies. In general, deep immunoperoxidase staining for FN was shown in the endothelial cells and the psammoma bodies. Plasma FN levels were correlated significantly not to the degree of leptomeningeal proliferation but to the MAGS scores in gliomas.

Effect of glia maturation factor on glial fibrillary acidic protein and fibronectin: a comparative study on glioblasts and fibroblasts using immunofluorescence

Glia maturation factor (GMF) was tested on separate cultures of glioblasts and fibroblasts isolated from the same rate fetuses. The astrocytic marker glial fibrillary acidic (GFA) protein and the fibroblast marker fibronectin were visualized with immunofluorescence. Before GMF stimulation, glioblasts showed only background fluorescence for GFA protein and fibronectin. After GMF stimulation, glioblasts showed intense fluorescence for GFA protein, especially in the processes and end-feet. GMF-stimulated glioblasts also showed a slight increase in intracellular fluorescence for fibronectin, mainly in the perinuclear cytoplasm but never in the process terminals. At no time was extracellular fibronectin observed in glioblast cultures. In contrast, fibroblast cultures formed an extensive extracellular network of fibronectin whether or not they were exposed to GMF. GFA protein never showed up in fibroblast cultures regardless of stimulation by GMF. The results indicate that GMF stimulates an increase of GFA protein in glial processes and confirms the astrocytic nature of these glioblasts.

Fibronectin promotes rat Schwann cell growth and motility

Techniques are now available for culturing well characterized and purified Schwann cells. Therefore, we investigated the role of fibronectin in the adhesion, growth, and migration of cultured rat Schwann cells. Double-immunolabeling shows that, in primary cultures of rat sciatic nerve, Schwann cells (90%) rarely express fibronectin, whereas fibroblasts (10%) exhibit a granular cytoplasmic and fibrillar surface-associated fibronectin. Secondary cultures of purified Schwann cells do not express fibronectin. Exogenous fibronectin has a small effect on promoting the adhesion of Schwann cells to the substrate and does not significantly affect cell morphology, but it produced a surface fibrillar network on fibronectin on the secondary Schwann cells. Tritiated thymidine autoradiography revealed that addition of fibronectin to the medium, even at low concentrations, markedly stimulates Schwann cell proliferation, in both primary and secondary cultures. In addition, when cell migration was measured in a Boyden chamber assay, fibronectin was found to moderately, but clearly, stimulate directed migration or chemotaxis.

Proliferation of glial-derived cells in defined media

A serum-free defined medium has been formulated that supports proliferation and morphologic differentiation of U-251 MGsp human and C6-2BD rat glioma cells. This defined medium consists of a basal medium supplemented with transferrin, fibroblast growth factor, hydrocortisone, selenium, biotin, and fibronectin (G2 medium). When U-251 cells were plated in G2 medium on poly-D-lysine precoated dishes, their growth rate was 77% and final cell density was 82% of serum-grown counterparts. The growth rate of C6 cells in G2 medium was 67% compared to cells cultured in serum supplemented medium. Although G2 medium supported the growth of human and rat glioma cells, LA-N-1 human neuroblastoma and WI-38 human fibroblast cells showed no increase in cell number when grown in G2 medium compared to basal medium. A similar formulation (G3 medium), lacking fibroblast growth factor and hydrocortisone, supported the proliferation of RN-22 rat schwannoma cells. Morphologic differences were observed between cells grown in the presence of serum and in defined media. All three glial cell lines changed from a flattened shape in serum supplemented medium to a more spherical appearance in defined medium. In addition, both U-251 and C6 cells developed numerous processes, some reaching several cell diameters in length. These defined media will facilitate studies of the growth and differentiation of glial-derived cells.

Expression of glial and vimentin type intermediate filaments in cultures derived from human glial material

Several cultures established from biopsies of apparently normal adult human glial material showed no cells positive for glial fibrillary acidic protein (GFA) when examined after seven or more cumulative population doublings (CPD), although the established glioma line U251 MG showed approximately 3% GFA-positive cells, and U333 CG/343 MG clone 3 showed greater than 98% GFA-positive cells. Both the human glia delivered cultures and the glioma lines were positive when assayed with sera specific for vimentin. We therefore investigated the expression of GFA as a function of cumulative population doublings after the establishment of primary cultures. Under our experimental conditions, although GFA-positive cells were clearly present in the primary cultures accounting for some 3%-14% of the cells present, the GFA marker was subsequently lost, and the proliferating cultures expressed only the vimentin type of intermediate filament. Those cells that were GFA-positive also appeared to be vimentin-positive. GFA expression was not reinduced in cultures that had lost the GFA marker by treatment with dibutyryl cyclic AMP. We discuss two alternate hypotheses for the origin of the GFA-negative cells: (1) the cultures area of astrocyte origin but lost the ability to express GFA on culturing; (2) the cultures originate from cells of nonastrocyte origin present in the primary material.

Extracellular matrix proteins characterize human tumor cell lines

Extracellular matrix proteins synthesized and secreted by adherent human tumor cell lines were analyzed using metabolic labelling with glycine and proline in the presence of ascorbate, polypeptide analysis and polyacrylamide gel electrophoresis, affinity chromatography, collagenase digestion, and immunofluorescence staining. The results showed a characteristic pattern of matrix proteins for each tumor cell type. Tumor cell lines of mesenchymal origin produced mostly interstitial types (I and II) of collagen and fibronectin. Carcinoma cell lines secreted only basement membrane proteins, type IV collagen, laminin and fibronectin, but not interstitial collagen. A melanoma and a rhabdomyosarcoma cell line produced type V of procollagen that has not previously been described in cell culture. Neuroblastoma cells were shown to be phenotypically heterogeneous also with respect to matrix protein production. We propose that the analysis of extracellular matrix proteins may serve as an adjunct in the classification of human tumors.