Detection of glycosaminoglycans on the surface of human umbilical vein endothelial cells using gold-conjugated poly-L-lysine with silver enhancement

Three-dimensional visualization of in vitro cultivated chondrocytes inside porous gelatine scaffolds: A tomographic approach

Synchrotron radiation-based microcomputed tomography (SR-microCT) has become a valuable tool in the structural characterization of different types of materials, achieving volumetric details with micrometre resolution. Biomedical research dealing with porous polymeric biomaterials is one of the research fields which can benefit greatly from the use of SR-microCT. This study demonstrates that current experimental set-ups at synchrotron beamlines achieve a sufficiently high resolution in order to visualize the positions of individual cartilage cells cultivated on porous gelatine scaffolds made by a freeze-structuring technique. Depending on the processing parameters, the pore morphology of the scaffolds investigated was changed from large-pore sized but non-ordered structures to highly directional and fine pored. The cell-seeded scaffolds were stained with a combined Au/Ag stain to enhance the absorption contrast in SR-microCT. While only some cells showed enhanced absorption contrast, most cells did not show any difference in contrast to the surrounding scaffold and were consequently not detectable using conventional greyscale threshold methods. Therefore, using an image-based three-dimensional segmentation tool on the tomographic data revealed a multitude of non-stained cells. In addition, the SR-microCT data were compared with data obtained from scanning electron microscopy, energy dispersive X-ray spectroscopy and histology, while further linking the initial cell density measured via a MTT assay to the pore size as determined by SR-microCT.

Heparan sulfate and syndecan-1 are essential in maintaining murine and human intestinal epithelial barrier function

Patients with protein-losing enteropathy (PLE) fail to maintain intestinal epithelial barrier function and develop an excessive and potentially fatal efflux of plasma proteins. PLE occurs in ostensibly unrelated diseases, but emerging commonalities in clinical observations recently led us to identify key players in PLE pathogenesis. These include elevated IFN-gamma, TNF-alpha, venous hypertension, and the specific loss of heparan sulfate proteoglycans from the basolateral surface of intestinal epithelial cells during PLE episodes. Here we show that heparan sulfate and syndecan-1, the predominant intestinal epithelial heparan sulfate proteoglycan, are essential in maintaining intestinal epithelial barrier function. Heparan sulfate- or syndecan-1-deficient mice and mice with intestinal-specific loss of heparan sulfate had increased basal protein leakage and were far more susceptible to protein loss induced by combinations of IFN-gamma, TNF-alpha, and increased venous pressure. Similarly, knockdown of syndecan-1 in human epithelial cells resulted in increased basal and cytokine-induced protein leakage. Clinical application of heparin has been known to alleviate PLE in some patients but its unknown mechanism and severe side effects due to its anticoagulant activity limit its usefulness. We demonstrate here that non-anticoagulant 2,3-de-O-sulfated heparin could prevent intestinal protein leakage in syndecan-deficient mice, suggesting that this may be a safe and effective therapy for PLE patients.

Distributional characteristics of sulfated glycosaminoglycans in normal human nasal mucosa and nasal polyp

The results of this study suggest that an altered expression pattern of sulfated glycosaminoglycans (GAGs) in nasal polyp may not function as a charge restriction barrier for vascular permeability, contributing to the leakage of protein and fluid. Sulfated GAGs are found on the vascular endothelial surface and in the extracellular matrix in various tissues and organs, suggesting that these materials constitute a negatively charged screen restricting the movement of circulating plasma molecules. This study was designed to elucidate the distributional characteristics of sulfated GAGs in normal human nasal mucosa and nasal polyp in order to understand their roles in the formation of nasal polyp. The expression and localization of sulfated GAGs in normal human nasal mucosa and nasal polyp were detected light microscopically with the histochemical method using poly-L-lysine-conjugated colloidal gold followed by silver enhancement. Sulfated GAGs in normal human nasal mucosa were distributed in the epithelial layer, vascular endothelial surface, submucosal gland and extracellular matrix. In nasal polyp, intense staining was also seen in the glandular structure and epithelial layer. However, the vascular endothelium and extracellular matrix exhibited either a weak reaction or no reaction.

Acute vascular rejection and accommodation: divergent outcomes of the humoral response to organ transplantation

BACKGROUND

The most difficult barrier to organ transplantation is humoral rejection, a condition initiated by binding of antibodies to blood vessels in the graft. Fortunately, humoral rejection is not the only outcome of antibody binding to the graft. In some cases, accommodation, a condition in which the graft does not undergo humoral injury despite the existence of humoral immunity directed against it, occurs and the graft remains seemingly inured. The mechanism underlying accommodation is uncertain, but changes in the function of antibodies, changes in the target antigen, and changes in the graft imparting resistance to injury have been implicated.

METHODS

Using the swine-to-baboon cardiac xenograft model, we asked which mechanism(s) may distinguish acute vascular rejection from accommodation.

RESULTS

In both acute vascular rejection and accommodation, antibodies were bound and complement activated in blood vessels of the graft. However, in acute vascular rejection, the full complement cascade was activated; while in accommodation, the complement cascade was interrupted, suggesting complement was inhibited in the latter condition. In acute vascular rejection, heparan sulfate and syndecan-4-phosphate, which can aid in complement control, were nearly absent, whereas in accommodation these were present in heightened amounts.

CONCLUSION

These findings suggest that control of complement may underlie accommodation, at least in part, and raise the possibility that this control and possibly other protective mechanisms could be exerted by heparan sulfate.

Increased excretion of urinary glycosaminoglycans in meningococcal septicemia and their relationship to proteinuria

OBJECTIVES

Meningococcal septic shock is a devastating illness associated with an increase in vascular permeability leading to hypovolemia and accumulation of plasma proteins and fluid in tissues. The capillary leak syndrome is often associated with widespread thrombosis in the skin, limbs, and digits. We postulated that the increase in vascular permeability and the intravascular thrombosis might be caused by an inflammation-induced loss of endothelial and basement membrane glycosaminoglycans (GAGs), which play a role in the permeability and thromboresistant properties of the microvasculature.

DESIGN

Prospective, single-center observational study.

SETTING

University-affiliated meningococcal research unit and pediatric intensive care unit.

PATIENTS

Eighteen children requiring intensive care for meningococcal sepsis, 18 children with steroid-responsive nephrotic syndrome, and 18 healthy control children.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Serum concentrations and urine excretion of glycosaminoglycans were measured and related to changes in glomerular permeability to plasma proteins. The size-distribution and nature of glycosaminoglycans were defined by Polyacrylamide Gel Electrophoresis and specific enzyme digestion. Urinary excretion of heparan sulfate, chondroitin-4-sulfate, and chondroitin-6-sulfate were significantly increased in meningococcal disease (MD) relative to healthy controls and children with steroid-responsive nephrotic syndrome. The urinary GAGs in MD were of similar size to those in controls when analyzed after pronase digestion. However, analysis of proteoglycan size before proteolytic digestion showed the urinary GAGs in MD were of lower molecular weight and unattached to proteins. The fractional excretion of albumin and immunoglobulin G in MD increased with severity of disease. Patients with severe or fatal MD had albumin clearances overlapping those seen in steroid-responsive nephrotic syndrome. There was a significant correlation between proteinuria in MD and urinary excretion of heparan sulfate (r2 = 0.611, p < .0001), chondroitin-4-sulfate (r2 = 0.721, p < .0001), and chondroitin-6-sulfate (r2 = 0.395, p < .0001).

CONCLUSIONS

The capillary leak in meningococcal disease is associated with increased plasma and urine concentrations of GAGs, which may be proteolytically cleaved from endothelial and basement membrane sites. The correlation between the severity of protein leakage and the urine excretion of GAGs suggests that loss of GAGs may be causally related to the increase in permeability to proteins.

Suppression of T cell-mediated injury in human gut by interleukin 10: role of matrix metalloproteinases

BACKGROUND & AIMS

Activation of lamina propria T cells with pokeweed mitogen in human fetal gut explant cultures results in severe mucosal injury. In the same system, Staphylococcus aureus enterotoxin B produces villus atrophy and crypt cell hyperplasia. The aim of this study was to examine the ability of interleukin (IL)-10 to modify these changes.

METHODS

Mucosal pathology and lamina propria glycosaminoglycans were assessed histologically, and CD3(+), CD25(+) and alpha-actin smooth muscle-positive cells were determined by immunohistochemistry. Reverse plaque assays and quantitative reverse-transcriptase polymerase chain reaction were used to analyze the cytokine response. Matrix metalloproteinase production was analyzed by Western blotting, in situ hybridization, and zymography.

RESULTS

Both experimental enteropathies produced mucosal damage, although injury was greater after pokeweed mitogen activation than S. aureus enterotoxin B. In both cases, the increase in cytokine-secreting cells and transcripts observed after T-cell activation was inhibited by IL-10. IL-10 also inhibited the increase in collagenase and stromelysin-1 in the explant culture supernatants and the loss of glycosaminoglycans. IL-10 decreased metalloproteinase production in control explants and increased matrix. In mesenchymal cells, IL-10 had a minor effect on metalloproteinase production.

CONCLUSIONS

IL-10 down-regulates mucosal T-cell activation, metalloproteinase production, and loss of extracellular matrix and prevents mucosal damage in the gut.

Detection of fibronectin expression by human endothelial cells using a enzyme-linked immunosorbent assay (ELISA): enzymatic degradation by activated plasminogen

An enzyme-linked immunosorbent assay (ELISA) has been developed to measure cellular fibronectin (cFN) in association with human umbilical vein endothelial cells (HUVEC) in culture. The expression of a number of functional domains on the cFN molecule was demonstrated using three specific murine monoclonal antibodies. This system was found to be sensitive, detecting as little as 0.156 microg/ml of cFN, and required only 1.3 x 10(5) cells per well confluent cells per experimental condition. This allowed multiple experiments to be performed on one batch of endothelial cells. cFN was detected on both viable and methanol fixed endothelial cells without significant non-specific antibody binding. The utility of this experimental model was studied by exploring the effect of urokinase activated plasminogen, a potent protease, on the expression of cFN and its functional domains.

Congenital enterocyte heparan sulphate deficiency with massive albumin loss, secretory diarrhoea, and malnutrition

BACKGROUND

The molecular basis of protein-losing enteropathy is unknown. However it has been shown that sulphated glycosaminoglycans may be important in regulating vascular and renal albumin loss.

METHODS

We describe three baby boys who presented within the first weeks of life with massive enteric protein loss, secretory diarrhoea, and intolerance of enteral feeds. All required total parenteral nutrition and repeated albumin infusions. No cause could be found in any case despite extensive investigations, including small intestinal biopsy sampling, which were repeatedly normal.

FINDINGS

By specific histochemistry, we detected gross abnormality in the distribution of small intestinal glycosaminoglycans in all three infants, with complete absence of enterocyte heparan sulphate. The distribution of vascular and lamina propria glycosaminoglycans was, however, normal.

INTERPRETATION

The presentation of these infants suggests that enterocyte heparan sulphate is important in normal small intestinal function.

Control of lymphocyte adhesion to brain and aortic endothelium: ICAM-1, VCAM-1 and negative charge

Lymphocyte adhesion to CNS endothelium is low by comparison with non-CNS endothelium. It has been proposed that this could be due to the high surface charge of brain endothelium, or a low constitutive expression of adhesion molecules. In this study we compared the influence of these factors on lymphocyte adhesion to BEC and aortic endothelium (AEC) in culture. Brain endothelium expresses very low levels of VCAM-1, and lower levels of ICAM-1 than aortic endothelium. The negative charge differed between the endothelia, but this had a minimal effect on lymphocyte adhesion. The anionic sites were, however, more stable on brain endothelium, remaining unchanged after endothelial cell activation with cytokines, while redistribution was observed on cytokine-activated aortic endothelium.

Intestinal glycosaminoglycans in neonatal necrotizing enterocolitis

Advanced necrotizing enterocolitis (NEC) is a common neonatal surgical emergency of unknown aetiology. Despite improvements in the prognosis, the aggressive form of the disease is still associated with significant rates of morbidity and mortality. Recent evidence indicates that the extracellular matrix (ECM) is important in gastrointestinal development and glycosaminoglycans, major constituents of the ECM, are attenuated in inflammatory bowel disease. The hypothesis of this study was that changes in the nature and distribution of intestinal glycosaminoglycans occur in NEC. The distribution and nature of glycosaminoglycans were determined in 31 sections of well preserved resection margins and severely diseased bowel from eight neonates affected by NEC. An established histological method of glycosaminoglycans analysis using cationic gold with silver enhancement was employed in this study. The identity of specific glycosaminoglycans was also elucidated using a combination of cationic gold staining and glycanase digestion. In well preserved tissue, staining was seen throughout the full thickness of the bowel. The epithelial basement membrane and basolateral surfaces, lamina propria and submucosa were particularly prominent. In moderate disease, patchy loss of anionic sites was frequently observed with glycosaminoglycans-deficient areas adjacent to intact sites. In severe NEC, there was extensive loss of glycosaminoglycans in most of the sections examined. Glycanase analysis revealed that the glycosaminoglycans in well preserved tissue were sensitive to chondroitinase ABC and only vascular sites were sensitive to heparinase III. The consequences of glycosaminoglycans loss in NEC as demonstrated in this study are not known but modulation of gastrointestinal glycosaminoglycans could be important in the pathogenesis of NEC and may underlie some of the clinical manifestations of this condition.

Is Graves' dermopathy a generalized disorder?

The pathogenesis of the extrathyroidal manifestations of Graves' disease-ophthalmopathy and pretibial myxedema (Graves' dermopathy)-involves fibroblast activation and increased mucin (glycosaminoglycan) production. It is nuclear why fibroblasts are activated at these sites and evidence for site-specific and generalized fibroblast activation is conflicting. One previous report has demonstrated an increase in glycosaminoglycan deposition in the forearm skin of patients with Graves' disease but without pretibial myxedema. We have sought to confirm the existence of subclinical dermopathy in the forearm tissue from patients with untreated (UG) and treated (TG) Graves' disease and compared the histological changes with normal controls (C), treated toxic nodular goiter (MNG) and Graves' dermopathy specimens (PTM), using stains for mucin, elastin, glycosaminoglycans (GAGs), and HLA-DR molecules. Four of 4 PTM specimens stained positive for mucin, with varying sparse, fragmented, or dense elastin fibers. Four of 5 PTM specimens stained heavily for GAGs using colloidal iron and 2 of 5 stained heavily using colloidal gold. None of the patients in groups UG, TG, MNG, or the controls, showed mucin deposition or elastin changes. Mild staining with colloidal gold for GAGs was seen in 1 each of the UG, the TG, and MNG groups, and 4 of 8 controls. Heavy staining with colloidal iron for GAGs was seen in 1 TG patient and 1 control, while moderate staining was found in several TG, UG, and controls. In 2 of 4 PTM specimens the monoclonal antibody CR3/43 (against HLA-DR) stained frequent dermal fibroblast-like cells and in 2 a lymphocytic infiltrate was seen. Only 1 of 8 UG patients had multiple CR3/43 staining cells present in the dermis: 3 of 8 TG and 1 of 8 controls had a few CR3/43 stained cells. Overall we found no evidence of dermal mucin deposition in the forearms of 16 patients with Graves' disease and a similar GAG distribution to normal controls. HLA-DR expression by fibroblast-like cells in the dermis suggests activation of these cells in the dermis of the PTM specimens, but no evidence of widespread fibroblast activation was found in the forearms of patients with Graves' disease.

Distribution and analysis of surface charge on brain endothelium in vitro and in situ

Vascular endothelial cells are associated with a number of anionic molecules. These anions are important in endothelial function, particularly in regulating permeability, haemostasis and cellular traffic. To explore the nature and distribution of anions on the brain endothelial cell (BEC) surface, we have examined rat brain endothelium in culture, and in situ. The anionic sites were probed with cationic colloidal gold and cationised ferritin, and visualised by light microscopy. Additionally we compared the distribution of the anionic sites on BEC with that present on other endothelial cell types in culture. The predominant anion detected on BEC was heparan sulphate (HS). This was distributed throughout the cell membrane, but was most densely associated with intercellular junctions. This pattern was distinct from the anionic locations observed in endothelia from aorta and epididymal fat microvessels. The distribution of anions was dependent on the age of cultured cells, with only minimal levels of HS seen at the periphery of younger cells. The nature and distribution of negative charge was different in situ. Here, sialic acid was the major surface anion, with only a small contribution from HS. The significance of these findings are discussed in relation to endothelial function in normal tissue and in pathological conditions.

Disruption of sulphated glycosaminoglycans in intestinal inflammation

We have studied the distribution and nature of sulphated glycosaminoglycans (GAGs) within normal and inflamed intestine. There is increasing evidence that these negatively charged polysaccharides, which both regulate the ability of albumin to leave the vasculature and inhibit thrombosis, may be affected by inflammatory cells and their products. We obtained samples of freshly resected intestinal tissue from eight controls, eleven patients with Crohn's disease, and six with ulcerative colitis. Sulphated GAGs were detected by means of a gold-conjugated poly-L-lysine probe, and the tissue density of anionic sites was assessed semiquantitatively by means of a Lennox graticule. In normal intestine there was staining in the vascular endothelium and the subepithelial basal lamina and throughout the extracellular matrix of the lamina propria and submucosa. Tissue from the patients with inflammatory bowel disease showed inflammation macroscopically and on histology. There were profound abnormalities of extracellular matrix GAGs, limited to the mucosa in ulcerative colitis and greatest in the submucosa in Crohn's disease. There was also substantial loss of GAGs from the subepithelial basal lamina in both disorders and from the vascular endothelium in submucosa in Crohn's disease. The extent of local GAG disruption was associated with the distribution of macrophages immunoreactive for tumour necrosis factor alpha and the activation marker RM 3/1. We suggest that inflammatory disruption of vascular and connective tissue GAGs may be an important pathogenetic mechanism, contributing to the leakage of protein and fluid, thrombosis, and tissue remodelling seen in inflammatory bowel disease.