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Michael Mengel

Publications and source records attributed to Michael Mengel.

At least 55 records · Page 3Linked to original sources
PubMed2003

The renal arterial resistance index and renal allograft survival.

BACKGROUND: Most renal transplants fail because of chronic allograft nephropathy or because the recipient dies, but no reliable factor predicting long-term outcome has been identified. We tested whether a renal arterial resistance index of less than 80 was predictive of long-term allograft survival. METHODS: The renal segmental arterial resistance index (the percentage reduction of the end-diastolic flow as compared with the systolic flow) was measured by Doppler ultrasonography in 601 patients at least three months after transplantation between August 1997 and November 1998. All patients were followed for three or more years. The combined end point was a decrease of 50 percent or more in the creatinine clearance rate, allograft failure (indicated by the need for dialysis), or death. RESULTS: A total of 122 patients (20 percent) had a resistance index of 80 or higher. Eighty-four of these patients (69 percent) had a decrease of 50 percent or more in creatinine clearance, as compared with 56 of the 479 patients with a resistance index of less than 80 (12 percent); 57 patients with a higher resistance index (47 percent) required dialysis, as compared with 43 patients with a lower resistance index (9 percent); and 36 patients with a higher resistance index (30 percent) died, as compared with 33 patients with a lower resistance index (7 percent) (P<0.001 for all comparisons). A total of 107 patients with a higher resistance index (88 percent) reached the combined end point, as compared with 83 of those with a lower resistance index (17 percent, P<0.001). The multivariate relative risk of graft loss among patients with a higher resistance index was 9.1 (95 percent confidence interval, 6.6 to 12.7). Proteinuria (protein excretion, 1 g per day or more), symptomatic cytomegalovirus infection, and a creatinine clearance rate of less than 30 ml per minute per 1.73 m2 of body-surface area after transplantation also increased the risk. CONCLUSIONS: A renal arterial resistance index of 80 or higher measured at least three months after transplantation is associated with poor subsequent allograft performance and death.

Biopsy↗
PubMed2003

IGF-1R, IGF-1 and IGF-2 expression as potential prognostic and predictive markers in colorectal-cancer.

Insulin-like growth factors (IGF-1 and IGF-2) and the IGF-1 membrane receptor (IGF-1R) have been found to play a critical role in the carcinogenesis of several tumors, among them colorectal cancer (CRC). To study the prognostic impact of these molecules, a total number of 713 cases of CRC were examined for the expression of IGF-1, IGF-2, and IGF-1R. The results were correlated with other clinicopathological data and clinical follow-up. IGF-1 expression was noted in 53 (7.5%), IGF-2 in 88 (12.6%), and IGF-1R in 698 (99.6%) of the cases. There were significant associations between the two growth factors ( P<0.00001), between IGF-1 and Ki-67 proliferation activity ( P<0.05), and between IGF-2 and tumor stage ( P<0.005). IGF-2 positivity was significantly correlated to a worse clinical outcome ( P<0.005) only in univariate, but not in multivariate, survival analysis. A similar trend was obtained for patients with IGF-1-positive CRC, but reached statistical significance only in limited tumor stages (pT1/pT2; P<0.01). Although the synchronous expression of IGF-1, IGF-2, and IGF-1R in a subset of CRC is consistent with an auto-/paracrine loop of cancer cell autostimulation, the prognostic effect of IGF-1 and IGF-2 expression seems to be of limited value. However, the identification of IGF-positive CRC might be beneficial for predictive reasons, as new molecular therapeutic approaches are aimed at the IGF system and related pathways.

Adenocarcinoma↗
PubMed2003

Molecular and functional analysis of Shiga toxin-induced response patterns in human vascular endothelial cells.

Enterohemorrhagic Escherichia coli (EHEC) is the major cause of hemolyticuremic syndrome (HUS) characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure. EHEC produces one or more Shiga toxins (Stx1 and Stx2), and it was assumed that Stx's only relevant biologic activity was cell destruction through inhibition of protein synthesis. However, recent data indicate that in vivo the cytokine milieu may determine whether endothelial cells survive or undergo apoptosis/necrosis when exposed to Stxs. In this study, we analyzed the genome-wide expression patterns of human endothelial cells stimulated with subinhibitory concentrations of Stxs in order to characterize the genomic expression program involved in the vascular pathology of HUS. We found that Stxs elicited few, but reproducible, changes in gene expression. The majority of genes reported in this study encodes for chemokines and cytokines, which might contribute to the multifaceted inflammatory response of host endothelial cells observed in patients suffering from EHEC disease. In addition, our data provide for the first time molecular insights into the epidemiologically well-established higher pathogenicity of Stx2 over Stx1.

Apoptosis↗
PubMed2003

Circulating endothelial cells are a novel marker of cyclosporine-induced endothelial damage.

Microvascular endothelial cells play a key role in transplant immunology. They are also important targets for calcineurin inhibitors. We recently demonstrated elevated numbers of circulating endothelial cells in renal transplant recipients with and without rejection in comparison with healthy controls. Because these patients received either cyclosporine or tacrolimus, we speculated that endothelial damage from calcineurin inhibitors might be responsible for these findings. In the present study, we tested the hypothesis that treatment with calcineurin inhibitors leads to an increase in circulating endothelial cells. We studied 57 renal transplant recipients: 19 on a calcineurin inhibitor-free immunosuppressive regimen and 38 patients on a standard immunosuppressive regimen, including cyclosporine, and matched them for age and serum creatinine. Endothelial cells were isolated from peripheral blood with anti-CD-146-coated immunomagnetic Dynabeads and were counted by fluorescence microscopy. Patients with cyclosporine therapy had elevated numbers of circulating endothelial cells (median 26, range 12 to 82 cells/mL) compared with healthy controls (median 6, range 0 to 82 cells/mL; P<0.001). Patients without calcineurin inhibitor treatment had significantly lower cell numbers (median 12, range 0 to 32 cells/mL; P<0.003) and were not significantly different from normal, untreated controls. In conclusion, renal transplant recipients who do not receive calcineurin inhibitors have significantly lower numbers of circulating endothelial cells than their age- and creatinine-matched counterparts who receive these drugs. We suggest that elevated numbers of circulating endothelial cells indicate damage from calcineurin inhibitors in renal transplant recipients and that circulating endothelial cells are a novel marker of endothelial damage.

Adult↗
PubMed2003

Incidence of polyomavirus-nephropathy in renal allografts: influence of modern immunosuppressive drugs.

BACKGROUND: In recent years an increasing number of cases with polyomavirus (PV)-nephropathy after renal transplantation were reported from several transplant centres. New, highly potent immunosuppressive drugs like tacrolimus or mycophenolate mofetil were accused as risk factors for this increase. However, data about the incidence of PV-nephropathy in correlation to different immunosuppressive therapy concepts are lacking. METHODS: All renal transplant biopsies performed at Hannover Medical School between 1999 and 2001 (n=1276) were immunohistochemically screened for the presence of PV-specific proteins. The results were correlated to the different immunosuppressive therapy protocols and patients with PV-nephropathy were compared with a matched control group. RESULTS: PV-nephropathy was found in <1% of all investigated allograft biopsies (11/1276) and in approximately 1% of all patients (7/638), respectively. All patients being immunohistochemically positive for PV-specific proteins also showed the typical morphological changes of PV-nephropathy. Four out of seven patients with PV-nephropathy were under triple immunosuppression comprising tacrolimus and mycophenolate mofetil. Under this immunosuppressive therapy protocol an eight times higher incidence and a 13 times higher risk (multivariate odds ratio 12.7) of PV-nephropathy was observed in our patients compared with the control group. CONCLUSIONS: PV-nephropathy is a rare but serious complication after renal transplantation. A small group of patients under intensive immunosuppression comprising tacrolimus in combination with mycophenolate mofetil has a significantly increased risk of acquiring this deleterious complication.

Adolescent↗
PubMed2003

Rapid and large-scale transition of new tumor biomarkers to clinical biopsy material by innovative tissue microarray systems.

A rapidly increasing number of studies are being published providing significant results by the use of tissue microarrays (TMAs), ie, paraffin blocks composed of multiple specimens. The numerous advantages of this technology are obvious and have thus stimulated many constructors to evolve and improve different technical approaches. With TMAs, multiple specimens can be simultaneously investigated with different in situ techniques under identical laboratory conditions, resulting in a dramatic time and cost reduction compared with conventional pathologic studies. Furthermore, this technology is less exhausting for the finite original donor material, allowing for a significantly increased number of assays per each case. Against the background of decoding the human genome and the widespread application of high-density cDNA microarrays, the next challenge will be to apply the genome discoveries to the clinical setting. For pathologists, TMAs represent an ideal adjunct and can be very useful for the rapid and high-throughput discovery and validation of countless candidate biomarkers, assessing their prognostic and predictive value and identifying further therapy targets. This article provides a review of different TMA technologies and addresses the technical aspects of their construction and their validity in different applications through data from the literature along with the authors' own experiences.

Biomarkers, Tumor↗
PubMed2002

Inhibition of aortic allograft vasculopathy by local delivery of platelet-derived growth factor receptor tyrosine-kinase blocker AG-1295.

BACKGROUND: Signal transduction through the platelet-derived growth factor (PDGF)/PDGF-receptor (PDGFR) system has been linked to vascular smooth muscle cell migration and proliferation leading to allograft vasculopathy. This study describes the effect of the tyrphostin AG-1295, a specific PDGFR tyrosine-kinase inhibitor, on neointimal formation in this disease. METHODS AND RESULTS: Rat aortic allografts transplanted from dark agouti (RT1 ) donors to Wistar-Furth (RT1 ) recipients were assessed in a new treatment model for local drug delivery from polymeric carrier matrices precoated with AG-1295. Matrices were wrapped around the graft immediately after transplantation. The recipients received no background immunosuppression. At day 80 posttransplantation, intimal thickness in AG-1295-treated grafts was reduced when compared to controls (11.8+/-9.1% intimal thickness vs. 23.7+/-6.4% intimal thickness; P=0.042). This finding corresponded to inhibition of intimal PDGFR-beta expression in AG-1295-treated grafts at day 20 posttransplantation (P =0.029 vs. allogeneic controls). CONCLUSIONS: The tyrphostin AG-1295 reduces neointimal formation in aortic allograft vasculopathy by inhibition of PDGFR-beta-triggered tyrosine phosphorylation. Local drug release of specific tyrosine-kinase inhibitors from perivascularly co-implanted polymeric carrier matrices is effective in the prophylaxis of allograft vasculopathy under selected experimental conditions.

Animals↗
PubMed2002

C1-inhibitor for prophylaxis of xenograft rejection after pig to cynomolgus monkey kidney transplantation.

BACKGROUND: Early rejection of discordant porcine xenografts in primate recipients is initiated by the intragraft binding of either preformed (hyperacute xenograft rejection) or induced (acute vascular rejection) antiporcine recipient antibodies with subsequent complement activation via the classical pathway. We have investigated the efficacy of the supplemental administration of C1-inhibitor (C1-INH), a specific inhibitor of the classical complement activation pathway, for prophylaxis of xenograft rejection in a pig to primate kidney xenotransplantation setting. METHODS: Based on the results of pharmacokinetic studies performed in two nontransplanted monkeys, supplemental C1-INH therapy was administered daily to three Cynomolgus monkeys receiving a life-supporting porcine kidney transplant together with cyclophosphamide-induction/cyclosporine A/mycophenolat-mofetil/steroid immunosuppressive therapy. RESULTS: In the three monkeys receiving porcine kidney xenografts and continuous C1-INH treatment none of the grafts underwent hyperacute rejection; all xenografts showed initial function. Recipient survival was 13, 15, and 5 days. No graft was lost due to acute vascular rejection. All animals died with a functioning graft (latest creatinine 96, 112, and 96 micromol/liter) due to bacterial septicemia. CONCLUSION: We conclude that, in our model, supplemental C1-INH therapy together with a standard immunosuppressive regimen can be helpful for prevention of xenograft rejection in a pig to primate kidney xenotransplantation setting. The optimal dose and duration of C1-INH treatment, however, has yet to be determined.

Acute Disease↗
PubMed2002

Ki67, E-cadherin, and p53 as prognostic indicators of long-term outcome after liver transplantation for metastatic neuroendocrine tumors.

BACKGROUND: Patients suffering from hepatic metastases of neuroendocrine tumors (NET) are potential candidates for orthotopic liver transplantation. Because recurrence rates are high and outcome is variable, prognostic indicators are required. The aim of our study was to identify predictors of long-term survival with a focus on the impact of tumor biology. METHODS: We retrospectively analyzed 19 patients who received an orthotopic liver graft for metastatic NET at the Medizinische Hochschule Hannover. Expression of Ki67, E-cadherin, and p53 was studied immunohistochemically in metastases of neuroendocrine tumors of the explanted livers. RESULTS: Patients were followed up to 146 months after liver transplantation. Six patients died during follow-up. The resulting 1-, 5-, and 10-year survival rates are 89%, 80%, and 50%, respectively. All deaths during long-term follow-up were tumor-associated. Recurrence was diagnosed in 12 patients between 2 weeks and 48 months after liver transplantation. Three patients are without tumor recurrence more than 8 years after liver transplantation. Survival in the 5 patients with low Ki67 and regular E-cadherin staining was significantly better than in the 12 patients with high Ki67 or aberrant E-cadherin expression (7-year survival 100% vs. 0%, respectively, log rank P=0.007). p53 expression did not significantly improve prognostic accuracy. CONCLUSIONS: We conclude that analysis of Ki67 and E-cadherin expression may improve the identification of patients with a favorable prognosis after liver transplantation for metastatic neuroendocrine tumors.

Adolescent↗
PubMed2002

Inter-laboratory and inter-observer reproducibility of immunohistochemical assessment of the Ki-67 labelling index in a large multi-centre trial.

Proliferative activity of tumour cells, as assessed by the Ki-67 labelling index, has been suggested as a potential prognostic indicator in many neoplastic diseases. Meaningful application of the immunohistochemically determined tumour cell growth fraction in clinical decision-making requires information about its inter-laboratory reproducibility. To assess the reproducibility of Ki-67 determined growth fraction, a multi-centre immunohistochemical trial was performed with 172 participating laboratories, each testing 30 different tissue samples. Evaluating 5160 Ki-67 labelling indices with a newly developed tissue microarray, good inter-observer reproducibility but high inter-laboratory variability was found. Reassessment of all stainings revealed considerable inter-laboratory differences in the intensity and frequency of labelled nuclei, suggesting that antigen retrieval or staining techniques are predominantly responsible for the inter-laboratory variability found in this trial. Consequently, cut-off levels for Ki-67, suggested to distinguish prognostic subgroups in tumours, appear to have limited reproducibility in a multi-centre approach. It is concluded that there is a need to standardize the immunohistochemical determination of the Ki-67 labelling index when it is used as a prognostic indicator in surgical pathology.

Biomarkers, Tumor↗
PubMed2002

Comparative genomic hybridization (CGH) and fluorescence in situ hybridization (FISH) in the diagnosis of hepatocellular carcinoma.

BACKGROUND: The histomorphological diagnosis of well differentiated hepatocellular carcinoma (HCC) may be a challenging task, because regenerative nodules and adenomas share similar microscopic features. Moreover, the differentiation of intrahepatic metastatic spread from multicentric growth in multinodular HCC is frequently not possible by histological criteria alone. Whether molecular cytogenetic analysis can contribute to the differential diagnosis of HCC was recently investigated by our group. METHODS: We applied comparative genomic hybridization (CGH) and fluorescence in situ hybridization (FISH) to 12 cases of hepatocellular adenoma (HCA) and 28 cases of well differentiated HCC. RESULTS: CGH revealed aberrations in 2/6 HCAs, affecting 7p in 1 sample each and 17q and 20 in the second case. In 4/4 well differentiated HCCs, aberrations occurred, with a mean of eight aberrations per case, focused on 1q, 4q, 8p, 8q, 16p, and 17p. In all HCC samples, at least two of these sites were affected. In 2 multinodular HCCs, six and four different tumor nodes, respectively, were analyzed. In the first case, aberration patterns of chromosomes 1, 4, 5, 9, 13, and 17 were almost identical in all six nodes, indicating metastatic spread. In the second case, three of the nodes showed very similar patterns of chromosome aberrations, including those of chromosomes 1, 4, 5, 7, 8, 10, 12, 14, 17, and 18. Aberrations of chromosomes 4, 5, 8, 10, 12, and 15 were shown in the fourth node, findings conclusive for both the metastatic spread and the multicentric origin of the HCC. Based on the CGH results, five probes, for chromosomes 1, 6, 7, 8, and X, were selected for FISH. Using this panel, we found no aberrations in 14 HCAs. By contrast, 13/14 HCCs demonstrated aberrations for two to five chromosomes in the FISH analysis. CONCLUSIONS: We conclude that CGH and FISH are helpful diagnostic tools for the histopathological differential diagnosis of HCC.

Adenoma, Liver Cell↗
PubMed2002

Transplanted fetal cardiomyocytes as cardiac pacemaker.

BACKGROUND: While morphologic integration of transplanted fetal cardiomyocytes into the ventricular myocardium is a well-known fact, no studies have yet shown transplanted cells to coherently contribute to contraction and electrical excitation of the host myocardium. The aim of this study was to prove the hypothesis that by transplanting cardiomyocytes with a higher intrinsic rhythmic rate into the myocardium of the left ventricle, these cells could act as an ectopic pacemaker by functional coupling with host cardiomyocytes. METHODS AND RESULTS: Dissociated fetal canine atrial cardiomyocytes including sinus nodal cells were delivered into the free wall of the left ventricle of adult canine X-linked muscular dystrophy dogs (n=2). These dogs fail to express Dystrophin in both cardiac and skeletal muscle. In the control group (n=2) fetal skin fibroblasts were used for grafting. A total of 3-4 weeks after transplantation the dogs underwent catheter ablation of the atrioventricular node (AV-node) and subsequent electrophysiological mapping studies. Transplanted cells were identified by Dystrophin immunoreactivity, indicating survival and morphological integration in the recipient heart. The expression of Connexin 43 between donor and recipient cells suggested formation of gap junctions between injected and host cardiomyocytes. After catheter ablation of the AV-node, a ventricular escape rhythm emerged driving the pace of the heart and originating from the labeled transplantation site. This effect could not be observed in the control group (n=2). CONCLUSIONS: The results constitute the first observation of phenomena indicating electrical and mechanical coupling between allogeneic donor cardiomyocytes and recipient myocardium in-vivo. Further experiments are necessary to evaluate the technique as a potential therapy for atrioventricular block.

Animals↗
PubMed2002

Detection of chromosomal aberrations in well-differentiated hepatocellular carcinoma by bright-field in situ hybridization.

Differentiation between well-differentiated hepatocellular carcinoma (HCC) and nonmalignant lesions with increased cellular proliferation may be difficult in needle biopsies. Based on recurrent chromosome aberrations known for HCC, we developed a nonfluorescent in situ hybridization technique that allows combination with morphological analysis in bright-field microscopy. Fourteen biopsies of HCC and 31 samples of regenerative nodules (n = 10), chronic hepatitis (n = 10), fibrosis or cirrhosis of unknown origin (n = 5), focal nodular hyperplasia (n = 2), primary biliary cirrhosis (n = 2), steatosis (n = 1), and adenomatous hyperplasia (n = 1) were analyzed with probes specific for the centromeric regions of chromosomes 1, 6, 7, and 8. After microwave pretreatment and in situ hybridization, signals were detected using a tyramine-based system and AEC as substrate. Evaluation of signals was done by conventional bright-field microscopy. Using this approach, aberrant counts were seen for at least one chromosome in 12/14 cases of HCC. In contrast, none of the nonmalignant lesions revealed aberrant counts for any of the chromosomes analyzed. In conclusion, this new combination of in situ hybridization and tyramine amplification allows fast and reliable evaluation of chromosome aberrations in a histomorphological context similar to paraffin immunohistochemistry. Registration of imbalances contributes to a reliable differentiation between malignant and nonmalignant lesions of the liver.

Adult↗
PubMed2002

Prognostic significance of calcium-binding protein S100A4 in colorectal cancer.

BACKGROUND & AIMS: Prognostication in colon cancer almost exclusively still rests on the tumor stage. Furthermore, tumor-derived markers to improve discrimination of low- and high-risk subtypes generally are not in use. S100A4 has been reported to be associated with invasion and metastasis; however, no data are available on its prognostic value in colorectal carcinoma. Therefore, we investigated the prognostic significance of immunohistochemical S100A4 expression in colorectal carcinoma compared with clinicopathologic parameters and expression of cell-cycle markers p16, p21, p27, p53, Ki-67, and RB. METHODS: Archival tissue from 709 patients with colorectal cancer were retrieved, applied in tissue array technology, and investigated immunohistochemically. Univariate and multivariate survival analyses were carried out on all investigated parameters. RESULTS: Sixteen percent of cases showed high; 31%, low; and 53%, no S100A4 expression. In Kaplan-Meier analysis, S100A4 positively stained cases showed a significantly decreased survival time compared with negatively stained cases (P < 0.0001). In multivariate regression analysis, S100A4 expression emerged as a highly significant independent parameter (P < 0.001) with the highest relative-risk factor among other covariates. Nodal status (pN) lost its prognostic value if S100A4 was added to the model. High S100A4 expression was associated with tumor stage pT3/4, secondary metastasis, women, p16, and RB expression. CONCLUSIONS: S100A4 expression represents a highly significant prognostic marker in colorectal carcinoma, which is able to identify a subset of patients at high risk. In this respect, it is superior to established prognostic markers such as nodal status, pT stage, and p53 expression.

Colorectal Neoplasms↗
PubMed2002

Gnotobiotic piglets develop thrombotic microangiopathy after oral infection with enterohemorrhagic Escherichia coli.

Oral infection with enterohemorrhagic Escherichia coli (EHEC) may cause severe enteritis, followed in up to 10% of cases by an extraintestinal complication, the hemolytic uremic syndrome (HUS). HUS is characterized by a triad of symptoms: anemia, thrombocytopenia, and acute renalfailure due to thrombotic microangiopathy. EHEC produces several virulence factors, among which a family of phage-encoded cytotoxins, called Shiga toxin 1 and Shiga toxin 2, seems to be most important. However, since an appropriate animal model is not available, pathogenicity of these emerging enteric pathogens is still poorly understood. Germ-free gnotobiotic piglets infected orally with an O1577:H7 or an O26:H11 EHEC wild-type isolate, both producing Shiga toxin 2, developed intestinal and extraintestinal manifestations of EHEC disease, including thrombotic microangiopathy in the kidneys, the morphologic hallmark of HUS in humans. Thus, gnotobiotic piglets are suitable to further study the pathophysiology of EHEC-induced HUS. It can be expected that data obtainedfrom this animal model will improve our current standard of knowledge about this emerging infectious disease.

Animals↗
PubMed2002

Tissue array technology for testing interlaboratory and interobserver reproducibility of immunohistochemical estrogen receptor analysis in a large multicenter trial.

Semiquantitative immunohistochemical assessment of estrogen receptor (ER) is used to predict the likelihood of response to antiestrogen therapy in breast carcinoma. If semiquantitative immunohistochemical analysis leads to therapeutic decisions, the importance of standardization and quality control increases. ER assessment reproducibility was studied among 172 laboratories using tissue microarray slides with 20 tissue spots negative and 10 tissue spots expressing ER at low, medium, or high levels. More than 80% of the laboratories demonstrated ER positivity in the medium- and high-expressing tissue spots, but only about 43% succeeded with tissue spots with low expression. Poor interlaboratory agreement was based on insufficient retrieval efficacy as shown by additional tests using autoclave pretreatment. The immunohistochemical scores used to quantify therapeutic target molecules remain inconclusive as long as progress toward standardized immunohistochemical procedures and evaluation is not achieved. Tissue microarray technology has proved its suitability for large-scale immunohistochemical trials, giving rise to new dimensions in control assessment.

Female↗