[Apparent wall shear rate and leukocyte-endothelium interaction in iris blood vessels in endotoxin-induced uveitis]

Inflammatory stimuli induce the expression of adhesion molecules on leukocytes and endothelial cells. The adhesive forces between leukocytes and the vascular endothelium are antagonized by the shear stress of the flowing blood. The aim of this study was to examine how differences in the apparent wall shear rate measured in iris venules with varying caliber affect leukocyte-endothelium interaction.

METHODS

The microvasculature of the iris in Lewis rats (n = 6) was examined using intravital fluorescence microscopy [2]. Blood flow was visualized with FITC-HES and leukocytes were stained with rhodamine 6G. Venules (n = 110) ranging in diameter from 20-60 microns were analysed with regard to the following parameters: Flux of leukocytes, velocity of leukocytes in the center stream, number of rolling and adherent leukocytes. The apparent wall shear rate was calculated from the center stream velocity and the vessel diameter. Animals were examined 4 h after administration of endotoxin from S. typhimurium (500 mg/kg body wt i.p.), when leukocyte-endothelium interaction is strongly enhanced.

RESULTS

The flux of leukocytes, the absolute number of rolling leukocytes and the velocity of leukocytes in the center stream was higher in larger than in smaller venules. The apparent wall shear rate decreased with increasing vessel diameter. Calculated values were 806 +/- 59 s-1 for vessels 20-30 microns in diameter and 483 +/- 34 s-1 for vessels of 50-60 microns (mean +/- SEM). The number of adherent leukocytes per mm2 endothelial surface and the rolling fraction did not show significant differences between vessels with varying caliber.

CONCLUSION

Although the shear rate declined with increasing vessel diameter, we could not observe an increase in rolling and adherent leukocytes. The effects of vessel diameter on leukocyte adhesion to the vascular endothelium in postcapillary iris venules are minimal.

Prevention of hyperacute rejection by human decay accelerating factor in xenogeneic perfused working hearts

As a potential source of organs for xenotransplantation, pigs that are transgenic for human decay accelerating factor (DAF) have been bred in order to overcome hyperacute rejection. We investigated the protective effect of human DAF in a porcine working heart model perfused by human blood. Hearts of normal landrace pits served as controls. The following parameters were measured: stroke work index, coronary flow and arteriovenous oxygen consumption, 6-keto prostaglandin F1alpha and prostaglandin E2 as markers of endothelial cell activation; creatine phosphokinase and lactate dehydrogenase for evaluation of the extent of myocardial damage; TNFalpha and IL-6 as markers of mononuclear cell activation. Histological and ultrastructural investigations from myocardial tissue sections were done at the end of perfusion. Human (h) DAF appeared to inhibit complement-mediated endothelial cell activation of transgenic pig hearts successfully. This was in contrast to landrace pig hearts, which had a sixfold increase of prostaglandin levels during perfusion with human blood. The cardiac weight increase during perfusion time due to interstitial edema tended to be less in the hDAF group. Myocardial damage was minimal in transgenic hearts, whereas normal pig hearts produced a threefold increase of creatine phosphokinase and lactate dehydrogenase levels. In these hearts, electron microscopy revealed single cell necrosis of myocytes and vacuolization of mitochondria with cristae rupture. According to the results obtained in the working heart model, the breeding of pigs that are transgenic for hDAF represents a promising step to making heart xenotransplantation a clinical reality in the future.

Effect of growth factors on matrix synthesis by human nasal chondrocytes cultured in monolayer and in agar

Reconstructive surgery of multiple areas of the body may require replacement bone or cartilage transplants to repair defects or lesions of skeletal tissue. Advances in cell and tissue culture techniques now permit synthesis of autologous human cartilage in vitro. Several growth factors regulate the metabolism and activation of cartilage cells. To enhance culture conditions and effectiveness for in vitro cartilage engineering, the aim of our investigations was to characterize the influence of transforming growth factor (TGF)-beta and basic fibroblast growth factor (bFGF) on human nasal septal chondrocytes. The isolated cells were cultured as monolayers on plastic and in soft agar. The biological effects of the growth factors were assessed by determining synthesis of total protein and proteoglycan. TGF-beta caused a dose-dependent stimulation of total protein as well as glycosaminoglycan synthesis by all chondrocytes cultured. This stimulatory effect of TGF-beta was greater for chondrocytes cultured in soft agar than for chondrocytes cultured on plastic. No stimulatory effects of matrix synthesis was observed for bFGF in either culture condition. Our results show that TGF-beta can be employed to enhance in vitro production of cartilage grafts for reconstructive surgery.

Xenoreactive natural antibodies and induced antibodies--their effects of beating cardiomyocytes as a model of a xenograft

Xenotransplantation has been complicated by hyperacute rejection reactions, which are supposedly triggered by preformed natural antibodies (PNAb) of the recipient organism, whereas the role of antibodies specifically induced by previous antigen contact (IAb) is less clear. Primary cultures of spontaneously beating neonatal rat cardiomyocytes were used as a model of the heart to elaborate the effects of both PNAb and IAb from xenogeneic species and to investigate into their mechanisms of action. An experimental setup allowing for rapid medium exchange under continuous observation was employed. Sera containing PNAb reproducibly bring about a stereotype pattern of altered contractility including an initial increase in beating frequency followed by a temporary cessation of beating within the first minutes after administration. After recovery of spontaneous contractions, the cells within the monolayer exhibited a dissociation of the synchronicity of the beating persisting for several hours. The temporary pause in beating was prevented by a very high extracellular calcium concentration, but not by extracellular electrical stimulation sufficient to trigger contractions in control cells. Electrophysiological measurements carried out in adult ventricular guinea pig heart muscle cells under the same experimental conditions revealed an increase of the excitation threshold of the cells after application of sera containing PNAb due to an enhanced input resistance. These results indicate that the effect of PNAb is the consequence rather of a generally reduced excitability of the cell than of the inhibition of a singular ionic conductance. After specific absorption of PNAb directed against rat antigens beating of neonatal rate cardiomyocytes ensued without interruption. Sera specimens devoid of complement produced similar effects on contractility, although the duration of the standstill period was significantly shorter. The increase in input resistance visualized in guinea pig myocytes was absent after removing PNAb against guinea pig antigens but not after absorbing PNAb directed against rat epitopes. Signs of a permanent cytotoxicity after the administration of PNAb were lacking in all experiments. IAb against rat heart tissue raised in rabbits stopped the contractions of neonatal rat cardiomyocytes within 30 min after administration irreversibly and lead concentration-dependently to a destruction of the cells.

In vivo monitoring of splenocytes in NMRI nu/nu- and nu/+,- mice during Lewis lung tumor progression or regression

Splenocytes of T-cell deficient NMRI nu/nu- mice (n=15) and of inbred immunocompetent NMRI nu/+,littermates (n=18) significantly (p<0.05) increased during Lewis lung (LL) tumor growth and eventually decreased. Half of the heterozygous NMRI nu/+,- mice rejected the tumors (LL-regressors). Zymosan-induced and lucigenin-amplified chemiluminescence (CL) of splenic polymorphonuclear leukocytes (PMN) and -precursors significantly (p<0.05) increased in NMRI nu/+,- mice with progressing tumors (LL-progressors) on the 3rd and in LL-regressors and nude mice on the 7th day after tumor inoculation. It subsequently decreased although numbers of PMN/- precursors further multiplied predominantly in the LL-progressors. Another peak of CL was found in those animals after the 20th day. Splenic lymphocytes significantly (p<0.05) increased in all mice from day 5 forward and dropped to original numbers between the 20th and 25th days. Maximal lymphocyte counts were significantly (p<0.05) lower in nude mice as compared to the NMRI nu/+,- littermates. The splenic T-/B-ratio significantly (p<0.005) correlated in LL-regressors and did not in LL-progressors. This correlation could be a suitable marker for tumor progression in NMRI nu/+ mice bearing LL-tumors.

Monoclonal antibodies against human chondrocytes

Cell-specific antigens are mainly found in cells or membrane surfaces rather than in the surrounding matrix. However, until now it was not possible to produce antibodies specific for cellular structures of chondrocytes. In 1989, Lance (Immunol. Lett. 21:63-73; 1989) first established specific monoclonal antibodies for human articular chondrocytes tested only by immunofluorescence. Studies describing the specificity of these five antibodies (HUMC 1-5) and their relevance for immunohistological analysis of cartilage tissue were not available until now. Therefore, the aim of the following study was to investigate the distribution of HUMC 1, 2, 3, 4, and 5 in mesenchymal cells in vivo and in vitro immunohistochemically. Further investigations concentrate on the localization of chondrocyte specific antigens using immunoelectron microscopy. Immunohistological studies showed positive immunostainings with all five antibodies in human chondrocytes in vivo and in vitro. A cross-reaction with human fibroblasts and osteoblasts for the antibodies HUMC 2 and HUMC 5 was observed. Furthermore, a parallel loss of immunoreactivity for HUMC 1, HUMC 3, and HUMC 4 was observed in cultured chondrocytes indicating that the specific antigens vanish during differentiation observed in vitro. Subsequent immunoblot analysis employing collagens as antigens did not show any reactivity. Using immunoelectron microscopy, gold particle labeling was observed in intracytoplasmatic vesicles of isolated chondrocytes. Our results indicate that HUMC 1, HUMC 3, and HUMC 4 are specific for cartilage cells and might be suitable for immunohistological analysis of different cartilage tissues and pathologically altered chondrocytes.

Different action of xenoreactive natural and immune antibodies on functioning cardiomyocytes

PNAB and IAB have totally different action on BCM. PNAB inhibit the contractile function of BCM by producing a reversible standstill and by disturbing the synchronization of the BCM-monolayer. IAB are cytotoxic and depend on the presence of complement.

Defects of the respiratory chain in various tissues of old monkeys: a cytochemical-immunocytochemical study

The aim of the present study was to evaluate if defects of the respiratory chain known to occur in humans, also exist in lower primates. Cytochemical-immunocytochemical studies of the respiratory chain enzymes in five monkeys (10-25 years of age) showed defects of ubiquinone cytochrome-c-oxidoreductase (complex III), of cytochrome-c-oxidase (complex IV) and of ATP-synthase (complex V) in the limb muscles, diaphragm, heart muscle and extraocular muscles of three old animals (about 25 years) and also in the heart muscle of two younger animals (10 and 15 years). Characteristically, the defects were randomly distributed and there was no loss of succinate-dehydrogenase (complex II) in the fibres. Ultracytochemistry-immunocytochemistry of complex IV disclosed that in an involved fibre segment all the mitochondria exhibited the defect. The highest number of defects was observed in the extraocular muscle (up to 340/cm2) while the lowest defect density was present in the limb muscles (2-5/cm2). Defects of complex IV occurred two to three times more often than defects of complex III and besides isolated defects of complex III and IV, combined defects of both complexes were also observed. Defects of complex V occurred exclusively in combination and were rarely seen. Using subunit specific antisera against complex IV, it could be demonstrated at light and electron microscopic level that loss of activity of cytochrome-c-oxidase was associated with a loss both of mitochondrially and nuclearly coded subunits of the enzyme. In summary, aging in lower primates and humans is characterised by a highly similar defect expression of the respiratory chain enzymes, with intercellular and interorgan differences of the aging process, underlining the universal nature of the involved pathogenetic mechanisms.

Quantitative analysis of interleukin-1-alpha gene expression in middle ear cholesteatoma

Regardless of its origin, cholesteatoma is characterized by the presence of a keratinizing epithelium with an hyperproliferative behavior leading to a very important bone resorption. Previous studies have demonstrated overexpression of interleukin-1 (IL-1 protein in middle ear cholesteatoma by immunohistochemistry and enzyme-linked immunosorbent assay, suggesting a significant role for IL-1-alpha. In this study, the presence of IL-1-alpha messenger ribonucleic acid (mRNA) was quantified by in situ hybridization on frozen sections (n = 10) and by computer-assisted image analysis. Human skin obtained from the external ear canal (n = 10) was used as the control. A higher percentage of cells hybridized for the antisense probes IL-1-alpha mRNA was found in cholesteatoma epithelium. Furthermore, keratinocytes of the suprabasal cell layers were also found to contain specific hybridizations. Some cells in cholesteatoma stroma also contained IL-1-alpha mRNA transcripts. The results of this study confirm the central role of IL-1-alpha in the epithelium hyperproliferation and bone resorption observed in middle ear cholesteatoma.

Expression of ICAM-1 on intact cartilage and isolated chondrocytes

A major factor in cellular cytotoxicity is the interaction between LFA-1 on leukocytes and ICAM-1 on targets. Because several inflammatory cartilage diseases are characterized by the presence of leukocyte infiltrates, the expression of ICAM-1 on human cartilage, cultured chondrocytes, and transplanted cartilage was investigated using monoclonal antibodies. Frozen tissue sections, chondrocytes in suspension, as well as total cellular mRNA were prepared from human cartilage samples. ICAM-1 expression was studied with two different monoclonal antibodies directed against ICAM-1 by immunohistochemical APAAP-staining and additional flow cytometric analyses. The expression of ICAM-1-mRNA in cartilage tissue was analyzed using the northern blot hybridization technique. Furthermore, chondrocytes were treated in culture with interleukin-1 (IL-1) and gamma-interferon (gamma-IFN). ICAM-1 expression after culture was quantified using flow cytometric analysis. We could detect ICAM-1 mRNA in cartilage tissue, however, the immunostaining of tissue sections using monoclonal antibodies did not give clear positive reactions. Isolated chondrocytes showed strongly positive staining patterns in comparison with adequate negative controls as assessed by flow cytometry. A dose-dependent increase of the expression of ICAM-1 on chondrocytes was observed when stimulated with IL-1 and gamma-IFN. Finally, two of the three studied transplanted autologous cartilage samples with advanced resorption showed the presence of ICAM-1 molecules as assessed by immunohistochemistry. This expression of ICAM-1 suggests that the molecule plays a role in severe cartilage inflammatory processes, where tissue damage leads to the exposure of chondrocyte surfaces.

Microsurgical reconstruction of the lymphatic and nerve system in small bowel transplantation: the rat model, first results

The goal in tissue transplantation is the restoration of all natural (physiological) communication pathways between the host and the graft. To this end, the effects of microsurgical reconstruction of artery, vein, lymphatic vessel, and nerve during grafting were investigated. Allogenic (MHC class II incompatible) and isogenic orthotopic (graft in functional continuity) small bowel recipients with immediate microsurgical lymphatic and nerve anastomosis were observed clinically as well as by immunological and histological examination. To explain the influence of the lymphatic system in allograft survival, short-term therapy was applied with the immunosuppressant cyclosporin A (10 mg/kg i.m.) for only 5 postoperative days. Average allograft survival ended in the control group after 10 days without any therapy, increased up to 20 days after immunosuppressive therapy (in both groups acute rejection and graft-versus-host disease were seen) and increased further to more than 200 days following lymphatic connection of the host and the graft during allografting. In this group no lymphatic edema of the graft was seen. To determine the optimal location of nerve anastomoses between the host and the graft without irritating the host nerve system, isografts in the same model were investigated. No paralysis of graft neighboring tissues was seen when the last ganglion function, and its following nerve plexus, of the host is saved. Nerve reconstruction must be undertaken after this last crossing of regional nerve fibers before entering the organ. The same rule is effective for organ explantation.