A comparative study of glycosaminoglycans in cultures of human, normal and malignant glial cells

Glioblastoma Spheroid Invasion through Soft, Brain-Like Matrices Depends on Hyaluronic Acid-CD44 Interactions

Increased secretion of hyaluronic acid (HA), a glycosaminoglycan abundant in the brain extracellular matrix (ECM), correlates with worse clinical outcomes for glioblastoma (GBM) patients. GBM cells aggressively invade the brain parenchyma while encountering spatiotemporal changes in their local ECM, including HA concentration. To investigate how varying HA concentrations affect GBM invasion, patient-derived GBM cells are cultured within a soft, 3D matrix in which HA concentration is precisely varied and cell migration observed. Data demonstrate that HA concentration can determine the invasive activity of patient-derived GBM cells in a biphasic and highly sensitive manner, where the absolute concentration of HA at which cell migration peaked is specific to each patient-derived line. Furthermore, evidence that this response relies on phosphorylated ezrin, which interacts with the intracellular domain of HA-engaged CD44 to effectively link the actin cytoskeleton to the local ECM is provided. Overall, this study highlights CD44-HA binding as a major mediator of GBM cell migration that acts independently of integrins and focal adhesion complexes and suggests that targeting HA-CD44-ezrin interactions represents a promising therapeutic strategy to prevent tumor cell invasion in the brain.

The scrambled story between hyaluronan and glioblastoma

Advances in cancer biology are revealing the importance of the cancer cell microenvironment on tumorigenesis and cancer progression. Hyaluronan (HA), the main glycosaminoglycan in the extracellular matrix, has been associated with the progression of glioblastoma (GBM), the most frequent and lethal primary tumor in the central nervous system, for several decades. However, the mechanisms by which HA impacts GBM properties and processes have been difficult to elucidate. In this review, we provide a comprehensive assessment of the current knowledge on HA's effects on GBM biology, introducing its primary receptors CD44 and RHAMM and the plethora of relevant downstream signaling pathways that can scramble efforts to directly link HA activity to biological outcomes. We consider the complexities of studying an extracellular polymer and the different strategies used to try to capture its function, including 2D and 3D in vitro studies, patient samples, and in vivo models. Given that HA affects not only migration and invasion, but also cell proliferation, adherence, and chemoresistance, we highlight the potential role of HA as a therapeutic target. Finally, we review the different existing approaches to diminish its protumor effects, such as the use of 4-methylumbelliferone, HA oligomers, and hyaluronidases and encourage further research along these lines in order to improve the survival and quality of life of GBM patients.

Understanding dynamic changes in live cell adhesion with neutron reflectometry

Neutron reflectometry (NR) was used to examine various live cells adhesion to quartz substrates under different environmental conditions, including flow stress. To the best of our knowledge, these measurements represent the first successful visualization and quantization of the interface between live cells and a substrate with sub-nanometer resolution. In our first experiments, we examined live mouse fibroblast cells as opposed to past experiments using supported lipids, proteins, or peptide layers with no associated cells. We continued the NR studies of cell adhesion by investigating endothelial monolayers and glioblastoma cells under dynamic flow conditions. We demonstrated that neutron reflectometry is a powerful tool to study the strength of cellular layer adhesion in living tissues, which is a key factor in understanding the physiology of cell interactions and conditions leading to abnormal or disease circumstances. Continuative measurements, such as investigating changes in tumor cell - surface contact of various glioblastomas, could impact advancements in tumor treatments. In principle, this can help us to identify changes that correlate with tumor invasiveness. Pursuit of these studies can have significant medical impact on the understanding of complex biological problems and their effective treatment, e.g. for the development of targeted anti-invasive therapies.

Elevated Concentration of Hyaluronan in the Cerebrospinal Fluid is a Secondary Marker of Spinal Disorders

BACKGROUND

Hyaluronan (HA) was measured in cerebrospinal fluid (CSF) to ascertain the clinical significance of this substance in patients with spinal disorders, a topic that, to the best of our knowledge, has not previously been studied.

METHODS

We examined correlations of CSF HA concentration with age, sex, height, body weight, and spinal disorders. By using a sandwich-binding protein assay, HA was measured in CSF samples obtained from 500 patients aged 12 to 104 years who underwent lumbar spinal anesthesia for surgery, myelography, or CSF examination. These patients were classified into 3 groups: (1) a control group (306 patients with injury or benign tumor of the lower limbs); (2) a cervical disorders group (84 patients with cervical disc herniation, cervical spondylotic myelopathy, or ossification of the posterior longitudinal ligament); and (3) a lumbar disorders group (110 patients with lumbar disc herniation, lumbar spinal canal stenosis tethered cord syndrome, lumbar fracture, or spondylolytic spondylolisthesis).

RESULTS

CSF HA concentration was found to be positively correlated with age, and was significantly higher in patients with cervical spondylotic myelopathy, ossification of the posterior longitudinal ligament, or lumbar spinal canal stenosis tumor than in the control group.

CONCLUSIONS

CSF HA concentration might be a secondary marker for inflammation in patients with spinal disease.

Syndecans and cell adhesion

Now that transmembrane signaling through primary cell-matrix receptors, integrins, is being elucidated, attention is turning to how integrin-ligand interactions can be modulated. Syndecans are transmembrane proteoglycans implicated as coreceptors in a variety of physiological processes, including cell adhesion, migration, response to growth factors, development, and tumorigenesis. This review will describe this family of proteoglycans in terms of their structures and functions and their signaling in conjunction with integrins, and indicate areas for future research.

Hyaluronan in human cerebrospinal fluid

We studied the concentration of hyaluronan in cerebrospinal fluid (CSF) in various diseases and attempted to define its reference interval. A radioassay utilizing cartilage proteins with affinity for hyaluronan was used in determining the concentration of 200 lumbar and 27 ventricular CSF specimens and 11 brain cyst fluids. Molecular weight distributions were determined by gel chromatography and localization in brain tissue by histochemistry. The hyaluronan level of lumbar CSF showed an increase with age; comparatively healthy children had (mean +/- SD) 50 +/- 41 micrograms/L (n = 40) and adults 166 +/- 77 micrograms/L (n = 9); i.e. significantly different values. The highest level was recorded in a patient with meningitis (> 8000 micrograms/L). More than 4000 micrograms/ L was noted in a patient with tumour metastasis in the cerebellum. Significantly elevated levels were especially found with spinal stenosis, head injury and cerebral infarction, but also in inflammatory medical disorders, hydrocephalus and encephalitis. We found no significant increase in multiple sclerosis and some other neurological diseases. Ventricular CSF of adults contained significantly less hyaluronan (53 +/- 73 micrograms/L; n = 16) than lumbar CSF. Hyaluronan in cyst fluids varied from 31 to 25,000 micrograms/L. Weight average molecular weight of hyaluronan in CSF was 2.9-3.0 x 10(5) and in brain tumour cyst fluid 2.4 x 10(6). In search for the origin of hyaluronan in CSF it was found that its concentration in the choroid plexus and leptomeninges was low, but that hyaluronan was accumulated in the superficial layer of the cerebral cortex. Continued screening for hyaluronan in CSF may be valuable in cases of inflammatory diseases, tumours and obstruction to CSF flow.

The glycosaminoglycan metabolism of chondrocyte monolayer cultures under normal and pathological conditions. A methodic study

Chondrocyte cultures may serve as a model in investigating changes of the cartilage metabolism. Adherent chondrocytes in vitro maintain polygonal morphology at high cell density in the primary and secondary culture. Collagen type II is only clearly detected in multilayered or nodular areas. The differentiation of the chondrocytes is also indicated by a low HA concentration of the cultural medium. It depends on high cell density, a low number of subcultures and their duration. However, the medium GAG of chondrocyte cultures does not exactly mirror the state of cell differentiation but can partly be used to check it. Subcultures of chondrocytes on small cover slides (minicultures) are used to determine proteoglycan synthesis and degradation for 48 h each. Both synthesis and degradation of cell-associated GAG or proteoglycans, resp., follow similar complex kinetics. The half lives of sulfated GAG or proteoglycans are initially 10 h (T-1 for O-6 h of chase), later 39 h or 95 h (T-2 for 6-48 h of chase). Conditioned medium of casein-elicited rat peritoneal macrophages reduce the sulfate incorporation into chondrocyte proteoglycans and their degradation rates increase. In the additional presence of E. coli endotoxin (0.5 microgram/ml) the synthesis of proteoglycans is only little affected; the degradation rate is stronger increased. To peritoneal macrophages of rats manifold pretreated with BCG and perhaps desensitized, LPS is added in vitro. Conditioned medium of these MP does not affect the chondrocyte proteoglycan synthesis but enhances the degradation rates in a concentration-dependent manner. Thus it can be demonstrated that chondrocyte monolayer miniscale cultures may serve to elucidate changes in the proteoglycan synthesis and different degradative steps.

Extracellular matrices in multicellular spheroids of human glioma origin: increased incorporation of proteoglycans and fibronectin as compared to monolayer cultures

Tumor spheroids were cultured from five human glioma cell lines which differed considerably in their relative amount and composition of glycosaminoglycans (GAG), fibronectin and other extracellular matrix (ECM) components when grown as monolayer cultures. These differences were also evident when the cells were grown as spheroids. Under the 3-dimensional geometry of the spheroid system, there was, however, generally a more extensive ECM. Especially noteworthy was the presence of a small proteoglycan, probably a dermatan sulphate proteoglycan, in the ECM of the spheroids, but not in the monolayers. Noteworthy was also the appearance of fibronectin in spheroids which did not show any staining for fibronectin when grown as monolayer. The two spheroid types (U-87MG, U-105MG) with the most extensive matrix, and with the lowest proportion of hyaluronic acid (HA), had a low proliferation rate, whereas the three other spheroid types (U-118MG, U-138MG, U-251MG) with a less extensive ECM, and a relatively high production of HA had a much higher proliferation rate. These data provide further evidence for the usefulness of culturing cell lines as spheroids in the process of understanding important cell biological phenomena.

Glycosaminoglycan changes in human gliomas. A biochemical study

Glycosaminoglycans (GAGs) were isolated, separated by electrophoresis and quantified in 36 neurosurgical specimens of human gliomas and in 8 samples of normal white and gray matter. Gliomas of various degrees of malignancy exhibited different GAG patterns. Total GAG concentration was three times higher in low grade gliomas than in normal white matter. The mean percentage of single GAG classes was usually similar in both tissues, although in certain tumor samples a higher percentage of hyaluronate was found. GAG patterns in anaplastic astrocytomas, however, more closely resembled normal white and gray matter, both quantitatively and qualitatively. Glioblastomas, on the other hand, showed high GAG concentrations, in particular of heparan sulfate and dermatan sulfate. This finding could be secondary to the abundant vessels and mesodermal material associated with this oncotype. The hyaluronate/sulfated GAGs ratio was lower in oligodendrogliomas than in low grade astrocytomas. This biochemical feature may be correlated with the alcianophilia found in the honey-comb degeneration of oligodendrogliomas. The significance of these findings as they relate to tumor histology and biology have been discussed.

The spreading of human normal glial and malignant glioma cells in culture. Studies on standard culture conditions

Using three lines of human normal glial cells and four established lines of human malignant glioma cells we have studied cell spreading following seeding onto glass and plastic substrata. The cells were detached with EDTA and trypsin, suspended in EMEM with 10% calf serum and studied with time-lapse, phase-contrast cinematography in suspension and during attachment and spreading. Cells were fixed and prepared for light microscopy while in suspension and during the spreading process. They were also prepared for scanning and transmission electron microscopy at different times during spreading. The projected areas of stained cells, in suspension and at different stages of spreading, were measured morphometrically and the results compared statistically. The glial cells in suspension were often found to retain somewhat their shape from the previous monolayer. They spread radially outwards with even lamellar cytoplasm and peripheral ruffling, as a group more quickly than the malignant glioma cells. They also became polarized and started to translocate in a shorter time. The glioma cells were spherical in suspension and characterized by pronounced blebbing of the cell surface. Blebbing continued during spreading and was finally replaced by ruffling at the edge. The cells spread like the glial cells radially outwards but the lamellar cytoplasm was occasionally somewhat irregular. Cells from the glioma lines spread as groups slower than the glial cells but with individual rates for the different lines. One of the glioma lines appeared to spread more thinly than the glial cells. Cells which sedimented on top of other cells could not spread. Aggregations of cells spread and became polarized more quickly than single cells in all cases.

Biochemical and metabolic abnormalities in normal and osteoarthritic human articular cartilage

Incorporation of radioactive precursors into macromolecules was studied with human normal and osteoarthritic articular cartilage organ culture. Analysis of the salt extracted matrix components separated by cesium chloride buoyant density gradient centrifugation showed an increase in the specific activities of all gradient fractions prepared from the osteoarthritic cartilage. Further analysis of these fractions showed the osteoarthritic cartilage contained 5 times as much sulfate incorporated into proteoglycans, and an even greater amount of 3H-glucosamine incorporated into material sedimenting to the middle of the gradient. Greater than half of this radioactive middle fraction appears to be hyaluronate, as judged by the position it elutes from a DEAE column and its susceptibility to hyaluronidase digestion. This study supports earlier findings showing increased rates of macromolecular synthesis in osteoarthritis, and in addition, an even greater synthetic rate for hyaluronic acid is demonstrated.

Glycosaminoglycans of solid and ascites forms of the P1798 murine lymphosarcoma

Total glycosaminoglycan levels are similar from subcutaneous, ascites and mesenteric forms of the P1798 lymphosarcoma. However, P1798 cells implanted subcutaneously produce a solid tumor rich in hyaluronic acid with lesser amounts of chondroitin 4-/6-sulfates as well as an undersulfated species of chondroitin sulfate, while cells implanted intraperitoneally produce ascites tumors which generate hyaluronic acid, almost exclusively. Mice bearing advanced ascites tumors develop solid mesenteric tumors which exhibit chondroitin 4-/6-sulfates and under-sulfated chondroitin sulfate in addition to hyaluronic acid.

Biochemical and histochemical evaluation of glycosaminoglycans in brain tumors induced in rats by nitrosourea derivatives

The occurrence, distribution and concentration of GAGs in ENU and MNU experimental brain tumors induced in the rat are reported. GAGs have been histochemically studied by Alcian Blue methods; they have been quantified and qualitatively evaluated by electrophoresis of brain extracts. The pattern of GAGs in normal rats is consistent with the data of the literature. No GAG accumulation precedes the tumor development. Early neoplastic proliferations, oligodendroglial and mixed glial microtumors are strongly alcian-positive; the alcianophilia spares clusters of cells developing a cytoplasm. In large tumors, GAGs are histochemically demonstrable in the honey-comb areas of oligodendrogliomas and in peripheral infiltration areas of polymorphic gliomas. The role of the normal nervous tissue and oligodendroglial cells in the accumulation of the GAGs is discussed. The accumulated GAGs seem to rise from the nervous tissue included in the tumors, rather than from the metabolism of tumor cells.

Glycosaminoglycans in human cerebral tumors. Part II. Histochemical findings and correlations

The occurrence and the distribution of GAGs have been studied histochemically in 224 human cerebral tumors by means of Alcian blue techniques. In the normal peritumoral gray matter the alcianophilia is stronger than in the white matter and demonstrated the presence of HA and CS. In the glioma group the alcianophilia, due to HA and CS, is mainly related to the presence of infiltrated cortex. In the other tumors, GAGs are histochemically disclosed in relation to collagen, reticulin, mesodermic areas, etc. The vessels of every tumor show a positive staining for HA, CS and HS. The histochemical findings are consistent with the biochemical ones as reported in Part I, even though the significance of GAGs in cerebral tumors remains unknown.

Defective basal lamina formation by transformed mammary epithelial cells: a reduced effect of collagen on basal lamina (heparan sulfate-rich) proteoglycan degradation

Invasive, spontaneously transformed mammary epithelial cells derived from the normal NMuMG cell line have lost the ability of their parental cells to respond in vitro to the presence of a collagen substratum by forming a continuous glycosaminoglycan (GAG)-rich basal lamina. On collagen, the cells synthesize 35S-GAG at the same rates, but the transformed cells accumulate less 35S-GAG than the normal cells because a larger fraction of their newly synthesized 35S-GAG is rapidly degraded. Chromatography of the 35SO4-containing materials from cultures on collagen indicates that the reduced accumulation of 35S-GAG by the transformed cells reflects less of a heparan sulfate-rich proteoglycan fraction which has been found in the basal lamina. On plastic substrata, however, the normal and transformed cells have near identical rates of 35S-GAG synthesis and degradation and they accumulate similar low amounts of the basal lamina proteoglycan fraction, which is rapidly degraded. Thus, transformation appears to impair the ability of the cells to reduce basal lamina proteoglycan degradation in response to collagen. This impairment may prevent the neoplastic cells from forming a complete basal lamina and, therefore, allow local invasion.

Establishment of attached and non-attached cell lines from an uncommon human glioma

A New cell line, U-706, established from an uncommon human glioma (possibly giant-cell glioblastoma) is reported in this communication. The tumor gave rise to two permanent sublines, one attached (U-706M) and one non-attached (U-706S) cell line. The growth characteristics, chromosome banding pattern, electronmicroscopic picture and cell surface characteristics of the two sublines are described.

Age-related changes in the distribution pattern of glycosaminoglycans synthesized by cultured human diploid fibroblasts (WI-38)

A gradual decline in the synthesis of glycosaminoglycans, as evidenced by reduced rates of incorporation of [35S] sulfate and [14C] glucosamine into cellular and medium glycosaminoglycans, was observed during the last (about 5) population doublings before phase-out. The decline was accompanied by a change in the distribution pattern of individual glycosaminoglycans with a relative decrease in the incorporation rate of [14C] glucosamine into cellular and medium hyaluronic acid. The incorporation rate of [14D] glucosamine and [35S] sulfate into cellular and medium heparan sulfate continually increased during the last population doublings ("senescence"). The possibility of a coupling between cell growth and hyaluronic acid synthesis or an involvement of hyaluronic acid in the adhesion of cells (among one another or/and to the substratum), and the functional significance of heparan sulfate as a growth inhibitor were discussed.

Effect of short- or long-term treatment with exogenous glycosaminoglycans on growth and glycosaminoglycan synthesis of human fibroblasts (WI-38) in culture

Short-term (several days) or long-term (several weeks and months) treatment of cultured human diploid fibroblasts (WI-38; phase II) with heparin at 20--500 micrograms/ml inhibited cell proliferation and stimulated glycosaminoglycan synthesis (as measured by the incorporation rates of [35S] sulfate and [14C] glucosamine into cellular and medium glycosaminoglycans). Characterization of the individual glycosaminoglycan types revealed an increased portion of incorporated radioactivity in the heparan sulfate and hyaluronic acid fractions of heparin-treated cells. Treatment with chondroitin-4-sulfate, chondroitin-6-sulfate, dermatan sulfate of hyaluronic acid at concentrations up to 500 micrograms/ml exhibited no or slightly inhibitory (especially in the case of hyaluronic acid) effects on growth and glycosaminoglycan synthesis. The average cellular protein and RNA content of short- or long-term heparin (100 micrograms/ml)-treated cells was elevated by about 70--80%. "Senescent" (phase III) WI-38 cells exhibited a relative increase of [35S] sulfate and [14C] glucosamine incorporation into cell-bound and medium heparan sulfate. Possible mechanisms for the action of heparin (for example, interaction with specific cell-surface sites) and a potential role of heparan sulfate in the regulation of cell growth are discussed.

Cell-surface glycosaminoglycans: turnover in cultured human embryo fibroblasts (IMR-90)

As constituents of both extracellular matrix and the cell surface, glycosaminoglycans are in a strategic position to influence several basic cell features. The localization and turnover of glycosaminoglycans was investigated in cultured normal human embryo fibroblasts of lung origin (IMR-90). Attention was directed particularly toward that compartment of the culture which could be released by gentle proteolysis (trypsin, 0.1 mg/ml, 15 min) and is considered to represent the cell surface. In the presence of NA2SO4, sulfated glycosaminoglycans (S-GAGs) of the cell surface were labeled rapidly, but within 30 min some 35S-GAG appeared in the extracellular medium. The intracellular pool of S-GAGs labeled during a 10-min period was lost during the first hr of chase with a half-life of 18 min, compared with 16 hr for S-GAGs labeled over a 48-hr period. Pulse-labeled S-GAGs of the surface turned over with an initial half-life of 60 min, compared with 7 hr for surface material labeled over a 48-hr period. These rapid movements of the early chase period were followed by similar movement at a much slower rate. The results are consistent with a model in which most of the S-GAGs synthesized in the cell move rapidly to the surface. The surface GAGs are then released immediately to the medium or accumulate at the membrane to be shed more slowly at a later time or to be degraded. The S-GAG which left the cell layer most rapidly during chase was dermatan sulfate, while heparan sulfate made up an increasing percentage of the cell layer as chase progressed. These cultures produce a fibrillar matrix of fibronectin, but the kinetics of this study suggest that the S-GAGs of the surface are membrane-bound, and an extracellular glycosaminoglycan matrix does not form.

Protein-coated agarose surfaces for attachment of cells

Plastic dishes were coated with an agarose layer. The layer was modified by covalently binding proteins to it, using the CNBr-method. Cells were seeded on the dishes and the number of attached cells was evaluated. The specificity of the attachment was demonstrated by showing that cells, carrying specific membrane-bound immunoglobulins, attached only to the corresponding anti-immunoglobulins. This indicated that the method could be used for cell sorting. The attachment of cells to proteins was influenced by the amount of bound protein, incubation time, temperature and the degree of trypsinization. Most attached cells were viable for several days and when dying they detached. Detailed morphological and cytochemical analyses of the dynamics of attachment and cytoplasmic spreading on the chemically well-defined surfaces were possible using the new method.