A simplified approach to control cell adherence on biologically derived in vitro cell culture scaffolds by direct UV-mediated RGD linkage

In this work, we present a method to fabricate a hyaluronic acid (HA) hydrogel with spatially controlled cell-adhesion properties based on photo-polymerisation cross-linking and functionalization. The approach utilises the same reaction pathway for both steps meaning that it is user-friendly and allows for adaptation at any stage during the fabrication process. Moreover, the process does not require any additional cross-linkers. The hydrogel is formed by UV-initiated radical addition reaction between acrylamide (Am) groups on the HA backbone. Cell adhesion is modulated by functionalising the adhesion peptide sequence arginine-glycine-aspartate onto the hydrogel surface via radical mediated thiol-ene reaction using the non-reacted Am groups. We show that 10 × 10 µm2 squares could be patterned with sharp features and a good resolution. The smallest area that could be patterned resulting in good cell adhesion was 25 × 25 µm2 squares, showing single-cell adhesion. Mouse brain endothelial cells adhered and remained in culture for up to 7 days on 100 × 100 µm2 square patterns. We see potential for this material combination for future use in novel organ-on-chip models and tissue engineering where the location of the cells is of importance and to further study endothelial cell biology.

Intracerebral microdialysis in neurosurgical intensive care patients utilising catheters with different molecular cut-off (20 and 100 kD)

OBJECTIVE

To compare the properties of a new intracerebral micro-dialysis catheter with a high cut-off membrane (molecular cut-off 100 kDalton) with a standard catheter (CMA70, molecular cut-off 20 kDalton).

METHODS

Paired intracerebral microdialysis catheters were inserted in fifteen comatose patients treated in a neurosurgical intensive care unit following subarachnoid haemorrhage or traumatic brain injury. The high-cut-off catheter (D(100)) differed from the CMA 70 catheter by the length (20 mm) and cut-off properties of the catheter membranes (100 kDalton) and the perfusion fluids used (Ringer-Dextran 60). Samples were collected every 4-6 hours, analyzed bedside (for glucose, glutamate, glycerol, lactate, pyruvate and urea) and later in the laboratory (for total protein).

RESULTS

Fluid recovery was similar for the two types of catheters, but significantly more protein was recovered by the D(100) catheter. The recovery of glycerol and pyruvate did not differ, while minor differences in recovery of glutamate and glucose were observed. The recovery of lactate was considerably lower in the D(100) catheter (p < 0.01), influencing the lactate/pyruvate-ratio. The patterns of concentration changes over time were consistent for all metabolites, and independent of type of catheter.

CONCLUSION

Microdialysis catheters with high cut-off membranes can be used in routine clinical practice in the NSICU, adding the possibility of macro-molecule sampling from the extracellular space during monitoring.

Technical prerequisites for in vivo microdialysis determination of interleukin-6 in human dermis

BACKGROUND

Cutaneous microdialysis in vivo in human skin is demonstrably of use in the study of skin metabolism, percutaneous absorption and skin inflammation. A promising area for cutaneous microdialysis is the measurement of cytokines. This requires catheters equipped with membranes permeable to molecules of high molecular weight.

OBJECTIVES

To address technical problems of poor sample volume retrieval and analysis sensitivity in the simplest model of provocation, namely the insertion of the catheter itself in vivo into human dermis.

METHODS

Use of a polyethylenesulphone membrane, with a cut-off value of 100,000 Da, allowed measurement of target molecules of large molecular weight. Using an adaptation of a commercially available high sensitivity enzyme-linked immunosorbent assay, the ubiquitous proinflammatory cytokine interleukin (IL)-6 was measured in the normal skin of six healthy volunteers after insertion of the microdialysis catheter.

RESULTS

Reliable sample volumes and high analyte recovery were achieved either by push-pull pumping or by standard pumping using a perfusate consisting of Ringers Dextran 60 Braun. No IL-6 was detected in 25 of 26 samples taken during the first 100 min after catheter insertion. The IL-6 concentration then increased and remained elevated for the duration of the experiments.

CONCLUSIONS

Technical and analytical modifications in the microdialysis technique have allowed the measurement of IL-6 in vivo in human dermis. It is suggested that the cytokine production is the result of the dermal trauma caused by catheter insertion, but the cellular source of the IL-6 is at present unknown.

The spectrum of inflammatory cell response to dimethyl sulfoxide

Dimethyl sulfoxide (DMSO), depending upon the concentration and mode of application to the skin, can induce either a non-immunological immediate contact urticaria or an irritant reaction. The dermal cellular infiltrate after open application of varying concentrations of DMSO has been studied in an experimental guinea pig model. The composition of the dermal cellular infiltrate showed a spectrum dependent on the concentration and number of applications of DMSO. The immediate reaction infiltrate 3 h after application of 100% DMSO consisted of 50% granulocytes, basophils being predominant. On the other hand, 12% DMSO applied 3 x daily for 3 days (cumulative insult) caused histologically a cellular reaction in which 80% of the infiltrate consisted of mononuclear cells. The present findings are compared to the microscopic findings in 3 other cutaneous reactions previously studied in this animal model, namely, the Type I immediate hypersensitivity reaction, the Type IV delayed hypersensitivity reaction, and the irritant reaction. Differing cellular infiltrate patterns are discernible at the same time points. The study illustrates the spectrum of inflammatory reactions seen in the skin and provides background information for future clinical studies, for instance, on the role of the basophil granulocyte in immediate contact reactions.

The influence of retinoic acid and retinoic acid derivatives on beta2 integrins and L-selectin expression in HL-60 cells in vitro

A decreased expression of the beta2-integrin CD11b molecules on peripheral neutrophils from patients with pustular psoriasis occurred during treatment with retinoid compounds. Since this effect could not be mimicked in vitro with isolated peripheral neutrophils, the effect of retinoid compounds on cell differentiation was investigated. The promyelocytic cell line, HL60, was used to study what effect different retinoid compounds had on the cell surface expression of CD11b and L-selectin (CD62L) molecules, complement-mediated phagocytosis, adhesion and the oxidative burst. Retinoid-differentiated cells showed a significantly lower expression of CD11b and CD62L, and a decreased phagocytosis and oxidative burst compared to DMSO-differentiated HL60 cells or peripheral blood neutrophils. The diminished expression of beta2-integrins or L-selectin did not affect their adhesion to non-activated or lipopolysaccharide-activated endothelial cells in vitro but may however affect adhesion to vascular endothelium under shear forces during blood flow. These results suggest that retinoid treatment could affect several early steps in the inflammatory process.

Acetone has anti-inflammatory effects on experimental contact reactions

The effects of a topically applied corticosteroid and its acetone vehicle on experimental allergic, toxic and irritant reactions are presented. The corticosteroid budesonide in acetone or acetone alone was applied to reactions immediately after and at different time intervals within the 1st h after provocation. Classical naked eye observation was performed and the dermal cellular infiltrate was differentiated and counted using a previously well-characterized method. "Treatment", whether with the steroid in acetone or acetone alone, had anti-inflammatory effects. For all reaction types, erythema and oedema diminished and a significant decrease in mononuclear cells was seen, when application occurred within the first 5 min after provocation. The effects were most marked for the toxic reaction to croton oil, the steroid and the vehicle being anti-inflammatory to the same extent. Application up to 60 min after provocation had anti-inflammatory effects for this reaction type. The mechanisms of acetone's anti-inflammatory effects are at present unclear. One possible explanation is that intercellular lipid organisation and, by extension, cellular membrane lipid organisation, are altered, influencing membrane receptor function. Possible anti-inflammatory effects of acetone should be considered in experimental and perhaps even clinical situations. Further investigation of the therapeutic possibilities of the finding seems warranted.

Expression and function of beta 2 integrin CD11B/CD18 on leukocytes from patients with psoriasis

The expression of beta 2 integrin CD11b on granulocytes and monocytes from patients with psoriasis vulgaris and pustular psoriasis was examined by flow cytometry. The amount of CD11b expressed on both granulocytes and monocytes was greater in 4 patients with pustular psoriasis than in 16 patients with psoriasis vulgaris. Its expression correlated with the development of pustules on the skin. No difference was seen between healthy blood donors and patients with active psoriasis vulgaris. Three patients with pustular psoriasis were followed during retinoid treatment. Granulocytes and monocytes showed a decrease in CD11b expression after administration of retinoids, in parallel with clearing of the skin. The adherence of granulocytes isolated from psoriasis patients was tested on cultured human umbilical vein endothelium. No significant difference in adherence was observed between control cells and cells from patients with active psoriasis vulgaris. These data indicate that the development of microabscesses in the dermis in psoriasis vulgaris is not related to enhanced beta 2 integrin function. The increased CD11b expression found in patients with pustular psoriasis may, however, serve as a triggering factor for pustule formation in pustular psoriasis.

Phenotypic alterations in circulating monocytes induced by open heart surgery using heparinized and nonheparinized cardiopulmonary bypass systems

In this study of 31 patients with coronary bypass surgery, we used flow cytometry to compare heparin-coated and noncoated cardiopulmonary bypass systems on leukocyte activation. We found significant differences between the groups during bypass, with activation of the complement system, measured as elevated levels of C3a desArg, upregulation of granulocyte beta2 integrin (CD11b), and a loss of circulating monocytes when noncoated systems were used. In both groups an early increase in the monocyte cell surface CD62L expression was obvious while the percentage of human leukocyte antigen (HLA)-DR positive monocytes did not alter. The morning after the operation, leukocytosis was present, together with a highly significant reduction in the monocyte expression of CD11b and HLA-DR, indicating the recruitment to the peripheral blood of cells with altered phenotypes. This alteration in phenotype on potent inflammatory cells may be one part of the impaired function of the immunological system reported after major surgery.

Infiltration of mononuclear inflammatory cells into primary colorectal carcinomas: an immunohistological analysis

Local immunoregulation mediated by mononuclear tumour-infiltrating cells is considered of importance for tumour progression of colorectal cancer, although the balance between immunosuppressor and cytotoxic activities is unclear. Colorectal cancers from 26 patients were investigated using a panel of monoclonal antibodies in order to identify subsets of mononuclear inflammatory cells and to study their pattern of distribution in relation to tumour stage and cytotoxic immune reactivity against the tumour. In all but five tumours, mononuclear cells, lymphocytes or monocytes were present in fairly large numbers, particularly in the stroma. The infiltration of CD4+ mononuclear cells predominated over the CD8+ subset. Infiltration near the tumour cells was found in four cancers only. Stromal infiltration of CD11c+ macrophages was found in all but eight tumours. Small regressive areas, in which the histological architecture of the tumours was broken down, were found in 17 tumours with intense or moderate infiltration by CD4+ lymphocytes or CD11c+ macrophages. Probably this destruction of tumour tissue was caused by cytotoxic activity of the tumour-infiltrating mononuclear cells. In Dukes' class A and B tumours, CD4+ lymphocytes predominated over CD4+ cells with macrophage morphology, but the latter were increasingly found in Dukes' class C and D disease. The occurrence of MHC II-positive macrophages and lymphocytes in different Dukes' classes was similar to that of CD4+ cells. In contrast to this, CD11c+ and CD11a+ cells were more frequent in Dukes' A and B class tumours compared with Dukes' C and D. Four out of nine tumours of the latter stages showed a poor inflammatory reaction. The interpretation of our results is that the subsets of tumour-infiltrating mononuclear cells change with advancing Dukes' class and that the local immune control is gradually broken down in progressive tumour growth, even if some cytotoxic activity is still present.

Sulfatide-induced L-selectin activation generates intracellular oxygen radicals in human neutrophils: modulation by extracellular adenosine

The sulfated form of galactocerebrosides (sulfatides) have recently been established as ligands for L-selectin. In this study we show that exposure of human neutrophils to sulfatides induces a transient generation of oxygen radicals, revealed by the luminol-enhanced chemiluminescence (CL) technique. The CL response was mainly located intracellularly, and was dependent on sulfation of the galactose ring, since non-sulfated galactocerebrosides had no effect. Sulfatides also dramatically amplified the CL response triggered by the chemotactic peptide formylmethionyl-leucyl-phenylalanine (fMLP). This effect was primarily due to an increased (up to 10-fold) intracellular generation of oxygen metabolites. Removal or blocking of L-selectin with chymotrypsin and monoclonal antibodies, respectively, markedly reduced the effects of sulfatides. Furthermore, sulfatides amplified the CL response triggered by ionomycin, whereas the response induced by phorbol-12-myristate-13-acetate was slightly reduced. The tyrosine kinase inhibitor, genistein, markedly inhibited the oxygen radical production induced by sulfatides, and totally abolished the potentiating effects of sulfatides in fMLP- and ionomycin-stimulated neutrophils. Sulfatides also triggered a transient rise in the intracellular free calcium concentration, [Ca2+]i. Consequently, L-selectin activation through sulfatides appear to affect oxidase activity through a Ca(2+)-dependent pathway involving tyrosine phosphorylation. Adenosine is an anti-inflammatory agent predominately released from the vascular endothelium which might suppress an inappropriate activation of the oxidase during L-selectin-mediated rolling of neutrophils. Indeed, we found that adenosine inhibited the oxidative burst induced by sulfatides, mainly by attenuating the intracellular generation of oxygen radicals. However, 10-100 times higher concentration of exogenous adenosine was required to inhibit the CL response induced by sulfatides to the same extent as the adenosine-mediated inhibition of the fMLP-induced response. This difference in sensitivity to adenosine could be explained by various expression of extracellular adenosine deaminase (ADA), since we found that the ADA-inhibitor erythro-9-(2-hydroxy-3-nonyl)-adenine (EHNA) markedly reduced the oxygen radical production caused by sulfatides and almost totally abolished the potentiating effects of sulfatides on the fMLP-induced respiratory burst. In contrary, EHNA only slightly reduced the fMLP-triggered CL response. We suggest that the initial activation of L-selectin prepare the neutrophil for an effective microbicidal activity in the extravascular space. This process might be dependent on a L-selectin-mediated increase in the expression and activity of ADA, which locally reduces the extracellular level of adenosine.

Endotoxemia and complement activation after severe burn injuries--effects on leukocytes, soluble selectins, and inflammatory cytokines

In this study we followed the development of an inflammatory response in a group of patients the first week after a burn injury. We detected elevated plasma endotoxin levels, on at least one occasion, in 6 of 8 patients. No endotoxin was detected in the two patients with the lowest total burned surface area (< or = 30%). We found evidence of complement activation as increased C3a levels, in parallel with a production of inflammatory cytokines (TNF-alpha, IL-6). The TNF-alpha levels increased significantly during the observation period, while the IL-6 levels were elevated already at admission, and remained so. Elevated levels of soluble E-selectin were detected, indicating endothelial cell activation. Despite the inflammatory response and a loss of inflammatory cells during the first days of the monitoring period, we found no evidence of cellular activation measured as increased expression of beta 2 integrin CD11b, nor increased plasma levels of soluble L-selectin.

The cellular dermal infiltrate in experimental immediate type cutaneous hypersensitivity

A previously developed guinea pig model for the study of the dermal inflammatory cell infiltrate of allergic, toxic, and irritant reactions was adapted to the study of the immediate intradermal reaction to ovalbumin. Comparison of qualitative and quantitative counts of infiltrating cells at three levels in the dermis showed that counting 20 subepidermal fields starting from the injection point of the allergen gave reliable figures. The reaction showed microscopically two phases. The first was of rapid onset and characterized by a high proportion of neutrophils, unlike the picture seen in the previously studied (allergic and toxic) reaction types. In the second phase, which can be termed "late phase" reaction, mononuclear cells and basophil granulocytes predominated. The late phase of the reaction bears similarities to the delayed allergic contact reaction at the same timepoint in that the response was rich in basophils. There were, however, other differences; e.g. eosinophils and neutrophils were more common.

Transient endotoxemia during burn wound revision causes leukocyte beta 2 integrin up-regulation and cytokine release

After severe burns, a wound revision is often done to remove devitalized tissue and minimize bacterial growth. After such revision, the patient may show signs of sepsis. In a group of burned patients we found a transient endotoxemia, and a subsequent leukocyte activation, monitored as increased expression of the beta 2-integrin CD11b, after such wound revision. In most patients we could detect elevated levels of plasma TNF-alpha before the operation, with no increases in these levels after the operation. Plasma levels of IL-6 were elevated in all patients and increased after the wound revision in all patients. They also had elevated plasma levels of soluble E-selectin, indicating systemic inflammation. The close relation between endotoxin levels and CD11b expression, and lack of evidence for additional production of TNF-alpha, suggests that up-regulation of the beta 2 adhesion protein during wound revision is mainly caused by endotoxin interaction with the leukocyte.

Presence of IgA and IgG antigliadin antibodies in healthy adults as measured by micro-ELISA. Effect of various cutoff levels on specificity and sensitivity when diagnosing coeliac disease

In this study a micro-ELISA (ELISA = enzyme-linked immunosorbent assay) was established and used to evaluate IgA and IgG antigliadin antibodies in 1,866 healthy adults. There was a covariation between the level of IgA antigliadin antibodies and the total serum IgA concentration, probably due to an increased IgA response in some healthy subjects. We could not find any correlation between the presence of IgG and IgA antibodies in the healthy population using the 97.5th percentile as a cutoff value. The specificity of various cutoff levels was compared with the sensitivity of the test in a population of 40 patients with coeliac disease. IgA antigliadin antibodies had a high specificity (95%) at a cutoff value giving a high sensitivity (80%). This was not possible with IgG antigliadin antibodies which had a low sensitivity (40%) when the cutoff value was selected to give a high specificity. Due to the low prevalence of coeliac disease, a decrease in the specificity of the test will have a pronounced effect on the positive predictive value. The results indicate that only IgA antigliadin antibodies are useful markers when screening subjects with few typical symptoms for biopsy when diagnosing coeliac disease, whereas IgG antibodies are of low value because of their low specificity.