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Biomedical subjects

G Steinhoff

Publications and source records attributed to G Steinhoff.

At least 37 records · Page 2Linked to original sources
PubMed2000

Effects of cytomegalovirus infection and prolonged cold ischemia on chronic rejection of rat renal allografts.

Previous studies have demonstrated that both cytomegalovirus (CMV) infection and prolonged cold ischemia of the allograft (CI) are associated with chronic rejection of renal transplants. The purpose of this study is to investigate the effect of CMV infection, of CI and of the combination of both, on the progression of chronic rejection, and to obtain a more detailed insight in their effects on the expression of adhesion molecules. Therefore, a rat transplantation model was used. Lewis recipients of renal allografts (with and without CI) from MHC-incompatible Brown Norway rats were inoculated with rat CMV or left uninfected. CMV infection alone resulted in an increased influx of CD4+ cells and macrophages early after infection, and in an increase in glomerular sclerosis and intima proliferation. CI caused an increase in infiltrating NK cells and an effect on intimal proliferation, glomerular sclerosis, and tubular atrophy. When CMV infection and CI were combined, an additive effect could be measured. This was however not the case for the function of the kidney. The creatinin showed a synergistic effect of the two influencing factors. Due to the CMV infection, an increase in CD49d cells was detected. CI resulted in an increase in CD18 cells and an increase in the expression of CD62P on vessels, and CD54 and CD44 on tubules. When CMV infection and CI were combined, all the effects caused by CMV and CI alone were present in an additional way. The results of the present study suggest that special attention should be paid to the recipient of an ischemically injured graft when either the donor or the recipient is CMV-infected. The patterns seen in histology, the infiltration of leukocytes and the expression of adhesion molecules, suggest that CI and CMV infection both have an effect on rejection, but act by different mechanisms.

Animals↗
PubMed2000

Fast determination of trace elements on aerosol-loaded filters by X-ray fluorescence analysis considering the inhomogeneous elemental distribution.

X-ray fluorescence (XRF) analysis was successfully applied for the determination of Ca, Cu, Fe, Mn, Ni, Pb, V and Zn on aerosol filters with a diameter of 150 mm. Ambient aerosol was collected on quartz-fibre filters by Digitel high-volume samplers. For XRF analysis three small filter pieces with a diameter of 32 mm were cut out of each filter, considering the radial dependence of elemental distribution on the filter. Elemental concentration decreases by 8-10% from the centre to the outer circle for coarse mode elements. Distribution of fine mode elements display only small radial dependence (2-4%). Results of quantitative analysis by XRF were compared with atomic spectrometric methods (GF-AAS, ICP-OES). The good agreement between the methods confirmed the application of XRF spectrometry for routine analysis of filter samples loaded with ambient aerosol.

Aerosols↗
PubMed2000

Productive infection of primary human endothelial cells by pig endogenous retrovirus (PERV).

The potential risk of viral transmission in the setting of xenotransplantation has gained major attention. Different porcine cell types have been shown to release retroviral particles, which are infectious for human cell lines in vitro. However, there are only a few data on whether PERV (pig endogenous retrovirus) is able to infect primary human cells. In this study we have analyzed endothelial cells, vascular fibroblasts, mesangial cells, mononuclear cells, hematopoetic stem cells and bone marrow stromal cells for PERV transmission. We now provide evidence for primary human endothelial cells, vascular fibroblasts, and mesangial cells to be susceptible to PERV transmission. PERV infection was productive in endothelial cells and mesangial cells. Our data confirm and extend former reports concerning the PERV infection of human cells. The PERV infection of different primary human cells represents further significant evidence for a viral risk during xenotransplantation. In this context, special attention should be directed towards productive infection of human endothelial cells: in the setting of xenotransplantation this cell type will have close contact with porcine cells and PERV particles.

Animals↗
PubMed2000

Tissue engineering of vascular grafts: human cell seeding of decellularised porcine matrix.

OBJECTIVES: To develop a biocompatible and mechanically stable vascular graft combining human cells and a xenogenic acellular matrix. DESIGN/MATERIALS: Decellularised matrix tubes were obtained by enzymatic cell extraction of native porcine aortas. Endothelial cells and myofibroblasts were isolated from human saphenous veins and grown in cell cultures. The inner surface of the tubes was seeded with endothelial cells or myofibroblasts and exposed to pulsatile flow. RESULTS: After cell extraction, the absence of cellular components, as well as the maintenance of matrix integrity, was demonstrated by means of light microscopy and scanning electron microscopy. Furthermore, the porcine matrix was successfully seeded with human endothelial cells, which grew to a monolayer under flow conditions. Stable biomechanical properties were achieved at physiological perfusion pressures in vitro. CONCLUSIONS: Cellular components can be extracted from native porcine blood vessels. Vascular grafts can be generated in vitro of animal acellular matrix and human cells.

Animals↗
PubMed2000

[Recruitment of immunocompetent cells in a transplanted lung is not impaired despite incompletel reinnervation].

BACKGROUND: It is not clear whether surgical intervention during lung transplantation which includes cutting vegetative nerves, lymphatic vessels and bronchial arteries, leads to alterations in immune responses. Thus, it was studied in an animal model whether an induced pulmonary immune reaction after syngenic lung transplantation was impaired without the influence of immunosuppression and rejection. The recruitment of leukocytes and the status of reinnervation was examined. METHODS: Syngenic transplantation of the left lung was performed in Lewis rats without rejection and therefore without immunosuppressive therapy. In a subgroup of animals host and donor leukocytes were distinguished. An ovalbumin (OVA)-specific pulmonary immune response was induced four months after transplantation. Bronchoalveolar lavage (BAL) and interstitial leukocytes were examined using flow cytometry and immunocytology, comparing the right lung and the grafted left lung. Immunohistology was performed to detect nerve fibers on cryostat sections. RESULTS: An induced cellular inflammation was observed in the right host lung as well as in the grafted left lung. However, the CD4 T cell numbers in the BAL were increased in the left lung. Single donor-type leukocytes could still be observed four months after transplantation. A partial reinnervation was found. CONCLUSIONS: The recruitment of immune cells into the lung interstitium and bronchoalveolar space of grafted lungs is not impaired. The incomplete reinnervation has no influence on leukocyte recruitment.

Animals↗
PubMed2000

Infection of nonhuman primate cells by pig endogenous retrovirus.

The ongoing shortage of human donor organs for transplantation has catalyzed new interest in the application of pig organs (xenotransplantation). One of the biggest concerns about the transplantation of porcine grafts into humans is the transmission of pig endogenous retroviruses (PERV) to the recipients or even to other members of the community. Although nonhuman primate models are excellently suited to mimic clinical xenotransplantation settings, their value for risk assessment of PERV transmission at xenotransplantation is questionable since all of the primate cell lines tested so far have been found to be nonpermissive for PERV infection. Here we demonstrate that human, gorilla, and Papio hamadryas primary skin fibroblasts and also baboon B-cell lines are permissive for PERV infection. This suggests that a reevaluation of the suitability of the baboon model for risk assessment in xenotransplantation is critical at this point.

Animals↗
PubMed1999

Enhanced oxygen delivery reverses anaerobic metabolic states in prolonged sandwich rat hepatocyte culture.

It must be assumed that current petri dish primary hepatocyte culture models do not supply sufficient amounts of oxygen and thus cause anaerobic metabolism of the cells. This is contrary to the physiologic state of the cells. In vivo the liver is a highly vascularized organ with a rather high blood flow rate of a mixture of arterial and venous blood. The aim of the present study was to show the oxygen dependence of primary rat hepatocytes in long-term culture and to define appropriate conditions that could allow hepatocytes to maintain tissue specific functions in an aerobic environment. To this purpose matrix overlaid hepatocytes were either cultured on gas-permeable (fluorinated hydrocarbon films) or gas-impermeable (polystyrene) supports at 10% and 20% ambient oxygen concentration (v/v), respectively. Tissue-specific functions were assessed by studying albumin and urea secretion as well as xenobiotic metabolism. The mRNA expression and catalytic activities of the cytoprotective antioxidant enzymes mitochondrial manganese superoxide dismutase (MnSOD), cytosolic copper and zinc superoxide dismutase, peroxisomal catalase, and cytosolic glutathione peroxidase were investigated to assess intracellular responses to the defined variations in oxygen supply. Hepatocytes could successfully be maintained at aerobic conditions in long-term culture on gas-permeable PTFE films. At 50% (10%, v/v) of currently used oxygen levels lactate accumulation was prevented, a plateau-like albumin secretion reestablished, urea secretion improved, and xenobiotic metabolism proceeded at physiological rates. mRNA expression of cytoprotective enzymes responded to the pericellular availability of oxygen and was most pronounced in the case of MnSOD. However, the biggest stress factor for the hepatocytes still appeared to be the isolation procedure, as mRNA expression and catalytic activities were most elevated shortly thereafter. In conclusion, this study clearly shows the oxygen dependence of primary rat hepatocytes in long-term culture and indicates means to establish appropriate conditions for the aerobic culture of primary rat sandwich hepatocytes with full maintenance of function. The long-term culture of hepatocytes on oxygenating supports at in vivo-like oxygen tensions therefore appears to be more physiologic and beneficial for the cells.

Aerobiosis↗
PubMed1999

[Porcine endogenous retroviruses (PERV): in vitro artifact or a big problem for xenotransplantation?].

The pig is the favorized donor species for clinical xenotransplantation. However, PATIENCE et al. could show, that porcine endogenous retroviruses (PERV), released by a porcine kidney cell line, are capable of infecting human cell lines in vitro. Based on this discovery there is an ongoing discussion concerning the risks of zoonosis combined with xenotranplantation, which culminated in the demand for a moratorium on clinical transplantation of porcine organs. Recent findings exclude the possibility of an artifact due to the use of an immortalized cell line: Release of infectious PERV was also shown for mitogenic stimulated primary porcine peripheral blood mononuclear cells and, even more important, for primary porcine endothelial cells. In contrast, none of the recent retrospective in vivo studies showed evidence for PERV transmission, neither in patients after transplantation of porcine pancreas islet cells or after extracorporal perfusion of porcine kidneys, nor in baboons after transplantation of porcine endothelial cells. Currently it is not known, whether impairments of the immunological responses against foreign pathogens, which are associated with different xenotransplantation strategies, could enable PERV in vivo infection. Only in vivo experiments, if possible in suitable subhuman primate models, offer the prospect for a final risk assessment.

Animals↗
PubMed1999

[Experimental xenogenic lung transplantation].

Lung transplantation has become a valuable therapeutical option for patients with end stage vascular and parenchymal pulmonary disease. The main limitation is the donor organ shortage, which is for lung transplantation even more pronounced than for other solid organs. Therefore, the search for alternative sources in the field of xenotransplantation as potential bridging to human allograft transplantation has emerged over the last few years. Pulmonary xenotransplantation at this stage is still an experimental procedure. Different concordant and discordant models have been investigated for specific organ functions, but in subhuman models no long-term function could be achieved to date. The purpose of this article is to present recent results in pulmonary xenotransplantation models.

Animals↗
PubMed1998

Expression of pig endogenous retrovirus by primary porcine endothelial cells and infection of human cells.

BACKGROUND: The risk of interspecies transmission of retroviruses during xenotransplantation is suggested by reports of pig endogenous retrovirus (PERV) released from porcine cell lines productively infecting human cell lines in vitro and of infectious PERV being released from pig peripheral blood mononuclear cells after mitogenic stimulation. Endothelial cells are the main interface between a xenograft and the recipient's leucocytes and tissues. METHODS: We have analysed pig primary aortic endothelial cells (PAEC) together with other transplantation-relevant porcine cells and tissues for expression of PERV mRNA. Release of virus particles by PAEC was monitored by reverse transcriptase (RT) activity in the medium of cultured PAEC. Infectivity for human cells was tested by co-cultivation of irradiated PAEC with the human embryonal kidney cell line HEK293 and looking for virus release from the human cells. FINDINGS: PAECs, hepatocytes, lung, and skin from a variety of pig strains and breeds expressed PERV mRNA. PAEC released infectious particles. Co-cultivation of PAEC and HEK293 led to productive infection of the human cells and expression of PERV types A and B. INTERPRETATION: Release of infectious virus from PAEC occurred without mitogenic stimulation, suggesting a serious risk of retrovirus transfer after xenotransplantation.

Animals↗