Olaf Dirsch

Synergistic effects of a novel nanoporous stent coating and tacrolimus on intima proliferation in rabbits

To overcome the problem of in‐stent restenosis, the concept of local delivery of antiproliferative or immunosuppressive drugs has been introduced into interventional cardiology. Local drug delivery can be achieved by drug‐eluting stents coated with polymer surfaces used for controlled drug release. However, several polymer coatings have shown an induction of inflammatory response and increased neointima formation. In the present study, the effect of a new inorganic ceramic nanoporous aluminum oxide (Al2O3) coating on neointima proliferation and its suitability as a carrier for the immunosuppressive drug tacrolimus have been investigated. 316 L stainless steel coronary stents were coated with a 500 nm thin nanoporous aluminum oxide layer. This ceramic nanolayer was used as a carrier for tacrolimus. Bare stents (n = 6), ceramic coated stents (n = 6), and ceramic coated stents loaded with 60 (n = 7) and 120 μg (n = 6) tacrolimus were implanted in the common carotid artery of New Zealand rabbits. The ceramic coating caused no significant reduction of neointimal thickness after 28 days. Loading the ceramic stents with tacrolimus led to a significant reduction of neointima thickness by 52% for 60 μg (P = 0.047) and 56% for 120 μg (P = 0.036) as compared to the bare stents. The ceramic coating alone as well as in combination with tacrolimus led to a reduced infiltration of lymphocytes and macrophages in the intima in response to stent implantation. Ceramic coating of coronary stents with a nanoporous layer of aluminum oxide in combination with tacrolimus resulted in a significant reduction in neointima formation and inflammatory response. The synergistic effects of the ceramic coating and tacrolimus suggest that this new approach may have a high potential to translate into clinical benefit. Catheter Cardiovasc Interv 2003;60:399–407.

Marginal Hepatectomy in the Rat: From Anatomy to Surgery

Objective:Based on the 3-dimensional visualization of vascular supply and drainage, a vessel-oriented resection technique was optimized. The new surgical technique was used to determine the maximal reduction in liver mass enabling a 50% 1-week survival rate. Background Data:Determination of the minimal liver mass is necessary in clinical as well as in experimental liver surgery. In rats, survival seems to depend on the surgical technique applied. Extended hepatectomy with removal of 90% of the liver mass was long regarded as a lethal model. Introduction of a vessel-oriented approach enabled long-term survival in this model. Methods:The lobar and vascular anatomy of rat livers was visualized by plastination of the whole organ, respectively, by corrosion casts of the portal vein, hepatic artery and liver veins. The three-dimensional models were used to extract the underlying anatomic structure. In 90% partial hepatectomy, the liver parenchyma was clamped close to the base of the respective liver lobes (left lateral, median and right, liver lobe). Piercing sutures were placed through the liver parenchyma, so that the stem of portal vein and the accompanying hepatic artery but also the hepatic vein were included. Results:A 1-week survival rate of 100% was achieved after 90% hepatectomy. Extending the procedure to 95% resection by additional removal of the upper caudate lobe led to a 1-week survival rate of 66%; 97% partial hepatectomy, accomplished by additional resection of the lower caudate lobe only leaving the paracaval parts of the liver behind, resulted in 100% lethality within 4 days. Conclusions:Using a anatomically based, vessel-oriented, parenchyma-preserving surgical technique in 95% liver resections led to long-term survival. This represents the maximal reduction of liver mass compatible with survival.

Magnetic resonance imaging of experimental atherosclerotic plaque: Comparison of two ultrasmall superparamagnetic particles of iron oxide

To evaluate a new ultrasmall superparamagnetic particles of iron oxide (USPIO) compound, ferumoxytol, as a marker of macrophage activity in atherosclerotic plaques and to compare it to ferumoxtran‐10.

Stent Coating: A New Approach in Interventional Cardiology

Background: Since its introduction in clinical cardiology, several studies have shown the superiority of coronary stent implantation as compared to conventional angioplasty. However, restenosis still remains a major drawback of this new technique. Basic research in animal models could identify stent-related factors like stent-material and stent-design as major determinants of intima proliferation. Since materials with good biocompatibility often have unsuitable mechanical properties and vice versa, the concept of stent coating has been developed to allow the combination of favorable characteristics from different materials. Passive Coating: In general, passive coatings, which only serve as a barrier between the stainless steel and the tissue, and active coatings, which directly interfere with the process of intima proliferation have been identified. Currently there are several passive coatings commercially available with good results in animal models and preliminary reports from clinical studies. Acitve Coating: As any surface induces some kind of tissue reaction promoting restenosis, an active stent coating with antiproliferative drugs has been proposed. However, while animal studies revealed convincing results, preliminary clinical studies not only showed active stent coating effective in preventing restenosis, but also demonstrated the potential risks of this new approach. Although this technique may harbor some specific risks, with the introduction of stent coating a new chapter of interventional cardiology has been flipped open.Hintergrund: Verschiedene Studien konnten eine Überlegenheit der Stentimplantation gegenüber der alleinigen koronaren Angioplastie belegen. Dennoch bleibt die Restenose ein gravierendes Problem der interventionellen Kardiologie. Bei den zur Restenose disponierenden Faktoren können Patientenfaktoren, wie Diabetes mellitus und Stenosemorphologie, von Stentfaktoren, wie Stentmaterial und -design, unterschieden werden. Passivbeschichtung: In dem Bemühen, die Restenoserate zu senken, ist daher das Konzept der Stentbeschichtung entwickelt worden. Durch dieses Vorgehen lassen sich biokompatible Eigenschaften eines Beschichtungsmaterials mit den guten mechanischen Eigenschaften eines Trägermaterials verbinden. Darüber hinaus erlaubt die Beschichtung koronarer Stents die Bindung von antiproliferativ und antiinflammatorisch wirkenden Substanzen an die Stentoberfläche. Dient die Beschichtung demzufolge lediglich zu einer Verbesserung der Biokompatibilität, bezeichnet man diese auch als Passivbeschichtung. Soll hingegen durch das Aufbringen eines Medikaments direkt die Intimabildung unterdrückt werden, handelt es sich um eine Aktivbeschichtung. Aktivbeschichtung: In den letzten Jahren sind verschiedene Passiv- und Aktivbeschichtungen tierexperimentell und klinisch untersucht worden. Dabei hat sich gezeigt, dass insbesondere die Aktivbeschichtungen ein hohes Potential zur Prävention der Restenose besitzen. Als Medikamente kommen Substanzen wie Sirolimus und Tacrolimus zur Anwendung, die ein vorwiegend immunsuppressives Wirkspektrum aufweisen und in der Transplantationsmedizin eingesetzt werden. Daneben werden jedoch auch Substanzen wie Paclitaxel verwendet, die aus der Tumortherapie bekannt sind. Neben viel versprechenden klinischen Ergebnissen sind jedoch auch erste Risiken dieser neuen Technologie aufgezeigt worden. So zeigen Untersuchungen, dass eine Polymerbindung von Medikamenten zu entzündlichen Reaktionen führen kann. Geht dann die Wirkung des Medikaments zurück, überwiegt die Inflammation und ein lediglich zeitlich versetzter Restenoseprozess beginnt. Auch wenn diese Komplikationen die initiale Euphorie gedämpft haben, stellt die Beschichtung koronarer Stents einen Meilenstein in der Bekämpfung der Restenose dar.

Potential embolization by atherosclerotic debris dislodged from aortic wall during cardiac catheterization:: Histological and clinical findings in 7,621 patients

Embolic events during cardiac catheterization have been attributed to atherosclerotic aortic debris dislodged by catheter manipulation. We evaluated the frequency and the histologic morphology of atherothrombotic material retrieved during placement of coronary catheters in patients undergoing diagnostic or interventional cardiac procedures. Over a 4‐year period, macroscopically visible aortic debris from coronary catheters, if present after advancement to the ascending aorta, was obtained for histologic examination. In 41 of 7,621 patients (0.54%), visible atherothrombotic material was present in the backflow of catheters. Debris occurred most frequently with 8 Fr guiding catheters (98%). Histologic examination showed foam cells, cholesterol crystals, and amorphic lipoid substance as markers of atheromatous material from atherosclerotic plaques in 38/41 patients (93%) with former plaque hemorrhage in 55% of them. In three patients, fresh thrombus material was observed (7%). None of these patients showed in‐hospital ischemic complications. Although visible atheromatous material is a rare phenomenon in cardiac catheterization, an increased risk of scraping debris is associated with large‐lumen guiding catheters. In order to avoid vascular embolization, the use of smaller guiding catheters and sufficient free backflow of catheters after advancement are recommended. Cathet. Cardiovasc. Intervent. 49:389–394, 2000.

A biphasic model for sinusoidal liver perfusion remodeling after outflow obstruction

Liver resection can lead to focal outflow obstruction due to transection of hepatic veins. Outflow obstruction may cause additional damage to the small remnant liver. Drainage of the obstructed territories is reestablished via dilatation of sinusoids. Subsequently, sinusoidal canals are formed draining the blood from the obstructed territory to the neighboring unobstructed territories. We raised the phenomenological hypothesis that the blood pressure gradient is the main driving force for the formation of sinusoidal vascular canals. We generated a biphasic mechanical model to describe this vascular remodeling process in relation to the variable pressure gradient. Therefore, we introduced a transverse isotropic permeability relation as well as an evolutional optimization rule to describe the relationship between pressure gradient and the direction of the sinusoidal blood flow in the fluid phase. As a next step, we developed a framework for the calculation concept including the representation of the governing weak formulations. Then, we examined a representative numerical example with simulation of the blood flow under both conditions, the physiological situation as well as after outflow obstruction. Doing so, we were able to reproduce numerically the experimentally observed process of reestablishing hepatic venous drainage via redirection of blood flow and formation of new vascular structures in respect to the fluid flow. The calculated results support the hypothesis that the reorientation of blood flow mainly depends on the pressure gradient. Further investigations are needed to determine the micromechanical influences on the reorientation of the sinusoids.

Lack of elevated serum carcinoembryonic antigen and calcitonin in medullary thyroid carcinoma.

OBJECTIVE Medullary thyroid carcinoma (MTC) originates from C-cells. A wide variety of tumor markers including calcitonin (CT), carcinoembryonic antigen (CEA), and chromogranin A are produced by MTC. Surgery remains the only potentially curative therapy, and early detection of the primary remains the most important prognostic factor for a positive outcome for the patient. The following case concerns a 50-year-old woman with histologically proven MTC, who completely lacked serum elevation of both CT and CEA. METHODS We performed a total thyroidectomy with lymphadenectomy in the central compartment. Histologic sections were stained for CT, CEA, and chromogranin A. Additionally we examined the patients blood for mutations in the RET proto-oncogene. RESULTS Serum CT and CEA were below the detection level in the serum. The tumor showed weak staining for CT, but strong staining for CEA and chromogranin A. Sequencing of the RET-proto-oncogene revealed no mutations. Five years after the operation, the patient remains well and shows no signs of tumor recurrence. CONCLUSIONS We hereby report of a patient with neither plasma elevation of CT nor CEA. From the clinical standpoint, it is important to determine how this subgroup of MTC should be followed because CT and CEA are of no clinical use.

MYCOPHENOLATE MOFETIL IMPAIRS HEALING OF LEFT-SIDED COLON ANASTOMOSES 1

Introduction. Inadequate healing and consequent leakage from bowelanastomoses are a significant cause of postoperative morbidity and mortality.Immunosuppressive drugs are known to disturb healing processes and to impairthe mechanical stability of bowel anastomosis. Mycophenolate mofetil (MMF) isan immunosuppressive agent that selectively inhibits the proliferation of Tand B lymphocytes and has been shown to be effective in preventing allograftrejection after organ transplantation. Adverse effects are few; however,nothing is known in regard to possible adverse effects of MMF administrationon the healing of bowel anastomosis. The aim of the present study was toevaluate the effect of systemic MMF administration on the healing of colonanastomoses inrats. Methods. Rats underwent laparotomy, division of the left colon, andsigmoidostomy. MMF (25 mg/kg) or vehicle was administered intraperitoneally intwo groups (n=21 per group) 3 days before surgery and then once dailyuntil euthanization (7 animals per group; 2, 4, and 6 days after surgery).Bursting pressure measurements, histologic evaluation, morphometric analysis,mucin and collagen staining, and BrdU immunohistochemistry of the anastomoticsite were performed. Furthermore, matrix protein expression at the anastomoticsite was determined by collagen I and fibronectin Westernblots. Results. Administration of MMF significantly decreased anastomoticbursting pressure postoperatively. Accordingly, histology, mucin staining, andBrdU immunohistochemistry and measurements of the colonic crypt depth showedmore extended inflammation, a significantly lower proliferation rate, and asignificantly thinned mucosal layer in the MMF-treated groups when compared tocontrol animals, whereas matrix synthesis at the anastomotic site was notdifferent. Conclusions. The administration of the immunosuppressive agent MMFsignificantly impairs healing and mechanical stability of colon anastomosis inrats during the early postoperative period. MMF act to disturb host reparativeprocesses mainly by impairment of reparative colonic epithelium proliferationand less by a disturbance of matrixsynthesis.

Efficacy of combined lamivudine and adefovir dipivoxil treatment for severe HBV graft reinfection after living donor liver transplantation

Abstract: Resistance to lamivudine and hyperimmune globulin (HBIG) may cause severe graft reinfection with progression to fulminant hepatic failure in liver transplant recipients. In this report, we describe the clinical course of a patient with perinatally acquired chronic hepatitis B virus (HBV) infection and hepatocellular carcinoma who developed severe fibrosing cholestatic hepatitis after living donor liver transplantation because of the emergence of lamivudine and HBIG‐resistant chronic hepatitis B. Immunohistochemistry demonstrated that more than 30% of hepatocytes stained positively for hepatitis B core antigen. Hepatitis B virus sequence analysis revealed several mutations in the polymerase gene (L528M, M552I, M552V) as well as in the surface gene region encoding the immunogenic major hydrophilic loop of the small surface protein (G130N, M133T, D144G). The amino acid exchange at codon 144 has already been described to escape neutralization by HBIG. Combined treatment with lamivudine and adefovir dipivoxil (ADV) was associated with a dramatic biochemical, virological and clinical response with resolution of jaundice, ascites, peripheral edema and pleural effusions. Serum bilirubin normalized, HBV DNA levels significantly decreased and liver biopsy was remarkable for the absence of viral protein. These results indicate that ADV may provide a sustained rescue treatment for aggressive courses of HBV graft reinfection in liver transplant recipients.

Oxidation of HMGB1 Causes Attenuation of Its Pro-Inflammatory Activity and Occurs during Liver Ischemia and Reperfusion

High mobility group box 1 (HMGB1) is a nuclear transcription factor. Once HMGB1 is released by damaged cells or activated immune cells, it acts as danger molecule and triggers the inflammatory signaling cascade. Currently, evidence is accumulating that posttranslational modifications such as oxidation may modulate the pro-inflammatory potential of danger signals. We hypothesized that oxidation of HMGB1 may reduce its pro-inflammatory potential and could take place during prolonged ischemia and upon reperfusion. Liver grafts were cold preserved for 24 h and flushed with saline in hourly intervals to collect the effluent. Liver grafts, cold-preserved for 6 h, were transplanted into syngeneic recipients to obtain serum and liver samples 24 h after initiation of reperfusion. Addition of the effluent to a macrophage culture induced the synthesis of tumor necrosis factor-alpha (TNF-α) and interleukin (IL)-6. The stimulatory activity of graft effluent was reduced after depletion of HMGB1 via immunoprecipitation. Oxidation of the effluent HMGB1 using H2O2 attenuated its stimulatory activity as well. Liver transplantation of cold preserved grafts caused HMGB1 translocation and release as determined by immunohistochemistry and ELISA-assay, respectively. Using Western blot with non-reducing conditions revealed the presence of oxidized HMGB1 in liver samples obtained after 12 h and in effluent samples after 16 h of cold preservation as well as in liver and serum samples obtained 24 h after reperfusion. These observations confirm that post-translational oxidation of HMGB1 attenuates its pro-inflammatory activity. Oxidation of HMGB1 as induced during prolonged ischemia and by reoxygenation during reperfusion in vivo might also attenuate its pro-inflammatory activity. Our findings also call for future studies to investigate the mechanism of the inhibitory effect of oxidized HMGB1 on the pro-inflammatory potential.