Donor-derived transplant acceptance-inducing cells in composite tissue allotransplantation.

BACKGROUND: Composite tissue allotransplantation (CTA) is a newly emerging field of transplantation. Immunological research in CTA has been intensified due to the recent clinical success of hand and face transplantation. Establishing immunological tolerance by adoptive transfer of ex vivo cultured tolerance-inducing cell types is of growing interest. Transplant acceptance-inducing cells (TAICs) are a type of deactivated immunoregulatory macrophages. METHODS: A total of 36 allogeneic hind limb transplantations in the rat were performed in six groups. Group A (Lewis (LW) â†’ Brown-Norway (BN)) received Lewis-donor-derived TAICs locally (i.m.). Group B (LW â†’ BN) received Lewis-donor-derived TAICs systemically (i.v.) and group C (Sprague Dawley (Sp-D) â†’ BN) served as a control group receiving Lewis-donor-derived TAICs systemically (i.v.). Groups D (LW â†’ BN), E (LW â†’ BN), and F (BN â†’ BN) also served as control groups with group D receiving no immunosuppression, group E receiving FK506 and prednisolone and group F receiving no immunosuppression with isograft transplantations (BN â†’ BN). The timing of rejection was assessed by clinical observation and histological findings. RESULTS: Rejection of the allogeneic hind limb occurred on average 7.7 days after transplantation in group A and 7.4 days in group B. Rejection was significantly delayed (Log-rank test, p < 0.01) compared to groups C and D, where rejection of the allogeneic hind limb occurred on average 5.8 days and 5.6 days after transplantation. No rejection was seen in groups E and F. CONCLUSION: For the first time, TAICs have been applied in a CTA model and demonstrated a significant immunosuppressive effect. Even though the immunomodulatory effect is relatively modest, the results of this study justify subsequent research on TAIC therapy to improve experimental and clinical outcome after CTA.

Improved lentiviral transduction of human mesenchymal stem cells for therapeutic intervention in pancreatic cancer.

Genetic modification of human bone marrow mesenchymal stem cells (MSC) is highly valuable for their exploitation in basic science and therapeutic applications, for example in cancer. We present here a new, fast and easy-to-use method to enrich a functional population of lentiviral (LV)-transduced MSC expressing enhanced green fluorescent protein (eGFP). We replaced the eGFP gene by a fusion gene of puromycin acetyltransferase and eGFP. Upon LV gene transfer and puromycin selection, we quickly obtained a pure transduced MSC population, in which growth, differentiation capacity and migration preferences were not compromised. Furthermore, we are the first to report the migration velocity of MSC among which 30% were moving and velocity of about 15 mum h(-1) was not altered by LV transduction. Manipulated MSC underwent senescence one passage earlier than non-transduced cells, suggesting the use for therapeutic intervention in early passage numbers. Upon tail vein application in nude mice, the majority of LV-transduced MSC could be detected in human orthotopic pancreatic tumor xenografts and to a minor extent in mouse liver, kidney and lung. Together, LV transduction of genes to MSC followed by puromycin selection is a powerful tool for basic research and improves the therapeutic prospects of MSC as vehicles in gene therapy.

Taurine protects from liver injury after warm ischemia in rats: the role of kupffer cells.

BACKGROUND/AIMS: Warm ischemia to liver with subsequent Kupffer cell-dependent pathology is associated with many clinical conditions. Taurine prevents Kupffer cell activation and improves graft survival after experimental cold ischemia and liver transplantation. Thus this study was designed to assess its effects after warm hepatic ischemia. METHODS: The left liver lobe of female Sprague-Dawley rats (170-210 g) underwent 60 min of warm ischemia. Animals were given either intravenous taurine or Ringer's solution 10 min prior to warm ischemia. Transaminases, histology, in vivo microscopy, intercellular adhesion molecules-1 (ICAM-1) expression, TNF-alpha and tissue hydroperoxide were compared between groups using analysis of variance (ANOVA) or ANOVA on ranks as appropriate. RESULTS: Taurine significantly decreased transaminases and improved histologic outcome. Phagocytosis of latex beads, serum TNF-alpha levels and tissue hydroperoxide concentrations were also significantly reduced. Stickers in sinusoids and post-sinusoidal venules significantly decreased. In parallel, both leukocyte infiltration and ICAM-1 expression decreased (p < 0.05), while flow velocity of red blood cells as well as sinusoidal perfusion rate were improved (p < 0.05). CONCLUSION: This study demonstrates that taurine blunts Kupffer cell-dependent hepatic pathology after warm ischemia in vivo via mechanisms including leukocyte-endothelial interaction, microcirculation disturbances and protection against lipid peroxidation.

Alterations of tumor and normal tissue of human lung cancer resection specimens after isolation perfusion.

The isolation perfusion model, including transbronchial ventilation of human lung, offers the possibility to study pharmacological interactions under physiological conditions. In view of the increasing importance of targeted therapy of lung diseases, this model of perfusion might attract major interest, particularly, in lung cancer. Our study investigated physiological, histological, and immunohistochemical alterations of lung and tumor tissue during isolated perfusion of lung lobectomy specimens to explore potential limitations of this model. Right after resection, 16 human lung resection specimens for primary lung cancer were isolated, ventilated, and perfused under physiological conditions with a modified Krebs-Henseleit solution over a period of 10, 60, 90, 120, and 240 min. Perfusion pressure, pH, lung weight gain, and histological edema formation were measured continuously before and during perfusion. After perfusion, lung and tumor tissue was investigated by hematoxylin-and-eosin stained sections. Immunohistochemistry of NADH, PECAM-1, angiotensin-converting-enzyme and NF-kappabeta were performed to determine lung tissue viability and changes at the endothelial layer. We found that perfusion up to 120 min could be performed with completely stable physiological conditions. Beyond that time span, edema formation and weight gain of the resection specimen started and were followed by an increase in inspiratory pressure and pulmonary artery pressure. Perfusion of more than 4 h led to a significant edema formation in lung tissue accompanied by loss of viability and significant histological alterations. We conclude that isolated ventilation and perfusion of human lung resections within the setup chosen is reliable for pharmacological studies up to a period of 120 min. Thereafter, edema formation and endothelial damage develop and limit the interpretation and reliability of drug delivery studies.

Development and evaluation of a training module for the clinical introduction of the da Vinci robotic system in visceral and vascular surgery.

BACKGROUND: With the increasing use of the surgical robotic system in the clinical arena, appropriate training programs and assessment systems need to be established for mastery of this new technology. The authors aimed to design and evaluate a clinic-like training program for the clinical introduction of the da Vinci robotic system in visceral and vascular surgery. METHODS: Four trainees with different surgical levels of experience participated in this study using the da Vinci telemanipulator. Each participant started with an initial evaluation stage composed of standardized visceral and vascular operations (cholecystectomy, gastrotomy, anastomosis of the small intestine, and anastomosis of the aorta) in a porcine model. Then the participants went on to the training stage with the rat model, performing standardized visceral and vascular operations (gastrotomy, anastomosis of the large and small intestines, and anastomosis of the aorta) four times in four rats. The final evaluation stage was again identical to the initial stage. The operative times, the number of complications, and the performance quality of the participants were compared between the two evaluation stages to assess the impact of the training stage on the results. RESULTS: The operative times in the final evaluation stage were considerably shorter than in the initial evaluation stage and, except for cholecystectomies, all the differences reached statistical significance. Also, significantly fewer complications and improved quality for each operation in the final evaluation stage were documented, as compared with their counterparts in the initial evaluation stage. These improvements were recorded at each level of experience. CONCLUSIONS: The presented experimental small and large animal model is a standardized and reproducible training method for robotic surgery that allows evaluation of the surgical performance while shortening and optimizing the learning-curve.

A novel model for the investigation of orthotopically growing primary and secondary bone tumours using intravital microscopy.

Here is reported the development of an experimental model using intravital microscopy as a tool to orthotopically investigate malignant bone tumours. Although up to 85% of the most frequently occurring malignant solid tumours, such as lung and prostate carcinomas, metastasize into the bone, and despite the knowledge that a tumour's course may be altered by its surrounding tissue, there is no adequate experimental model available enabling the investigation of orthotopically grown bone tumours in vivo. Intravital microscopy is an internationally accepted experimental method, used in various acute and chronic animal models, that enables qualitative and quantitative analysis of the angiogenesis, microcirculation, growth behaviour, etc. of various benign and malignant tissues. Non-invasive investigations of up to several weeks are possible. Additionally, tissue samples can be taken after termination of the in vivo experiments for further ex vivo investigation (histology, immunohistochemistry, molecular biology, etc.), elucidating the mechanisms that underlie the in vivo observations. Severe combined immunodeficient mice were fitted with a cranial window preparation where the calvaria served as the site for orthotopic implantation of the solid human tumours Saos-2 osteosarcoma (primary) and A 549 lung carcinoma and PC-3 prostate carcinoma (secondary). In all preparations, the take rate was 100%. Histological assessment confirmed the data obtained in vivo, showing typical tumour growth with infiltration of the surrounding osseous and soft tissues. This novel model serves as a valuable tool in understanding the biology of primary and secondary bone tumours in physiological and pathophysiological situations, with implications for the most areas of tumour therapy such as chemotherapy, radiation and antiangiogenesis.

Laparoscopic organ retrieval for living donor liver transplantation does not prevent graft injury.

The cause of transplant failure may be difficult to define. However, organ retrieval before preservation and transplantation is an important factor. Organ manipulation during harvesting, which is inevitable with most techniques, leads to injury upon reperfusion including microcirculatory disturbances. Recently, laparoscopic organ retrieval has been successfully performed for human living donor liver transplantation (LDLT). Pneumoperitoneum for laparoscopy changes the pattern of hepatic blood flow. To study the effects of pneumoperitoneum on the graft prior to cold storage, livers from Sprague-Dawley rats underwent pneumoperitoneum with an intra-abdominal pressure of 8 mm Hg for 90 minutes. Subsequently, intravital microscopy was performed to assess intrahepatic microcirculation and transaminases were measured. Serum transaminases increased 1.5-fold compared with sham controls (P < .05). Intrahepatic microcirculation was significantly disturbed immediately after pneumoperitoneum. If this is confirmed in humans, laparoscopic organ retrieval for LDLT would be expected to decrease graft quality and not be beneficial in liver transplantation.

Platelet function in acute experimental pancreatitis induced by ischaemia-reperfusion.

BACKGROUND: Ischaemia-reperfusion (IR)-associated microcirculatory changes play a major role in acute post-transplantation pancreatitis. The pathophysiological role of platelets in these events is unknown. The aim of this study was to examine platelet adhesion and function during early reperfusion after pancreatic ischaemia. METHODS: Rats were subjected to warm pancreatic ischaemia by cross-clamping of the pancreatic vessels for 1 h. After 1 h of reperfusion, platelet-endothelium interaction was evaluated after platelet separation and staining by fluorescence microscopy. Amylase levels and pancreatic histology were evaluated 24 h after reperfusion. Animals treated according to an identical protocol, but without ischaemia, served as controls. RESULTS: Mild pancreatitis had developed by 24 h after IR; serum amylase levels were significantly higher than those in control animals. The numbers of adherent platelets in capillaries and venules were significantly increased, and platelet velocity in capillaries was significantly decreased, in the IR group compared with controls. There was significantly more oedema and inflammation in pancreatic tissue after IR. CONCLUSION: Warm ischaemia for 1 h followed by reperfusion for 24 h caused mild pancreatitis in this experimental model. The pancreatic microcirculation was characterized by pronounced platelet-endothelium interaction in capillaries and venules. These results suggest that platelet activation may play an important role in acute post-transplantation pancreatitis.

In vivo assessment of angioarchitecture and microcirculation in experimental liver cancer: a new model in rats.

The rising incidence of unresectable hepatocellular malignancies remains a therapeutic challenge. Little is known about the mechanisms of angiogenesis and immunological aspects of liver tumor vessels. The aim of this study was to investigate hepatic and tumor microcirculation and leukocyte-endothelium interaction by means of intravital microscopy in a rat model of hepatocellular carcinoma. Off-line analysis showed that the angioarchitecture as well as blood flow velocity in liver cancer is heterogeneous. The leukocyte-endothelium interaction is significantly reduced compared to normal liver tissue. The data suggest that the main mechanism is a reduced expression of adhesion molecules demonstrating an effective immune escape mechanism of this tumor. The model represents a useful experimental tool to explore angiogenesis inhibition or immunological therapeutic strategies in experimental liver cancer.

Angiogenesis inhibition with TNP-470, 2-methoxyestradiol, and paclitaxel in experimental pancreatic carcinoma.

INTRODUCTION: Inhibition of tumor angiogenesis is a novel therapeutic modality for various malignancies. AIM: To investigate the effect of different antiangiogenic agents (TNP-470, 2-methoxyestradiol, and paclitaxel) on growth and neovascularization of experimental pancreatic cancer. METHODOLOGY: In 25 male Lewis rats, tumor induction was achieved by orthotopic and subcutaneous tumor fragment implantation of ductlike pancreatic cancer DSL6A. Four weeks after tumor implantation, the animals were randomly treated with TNP-470, 2-methoxyestradiol, or paclitaxel. After 2 weeks of antiangiogenic therapy, total tumor volume, vital tumor surface, vascular density, and apoptosis were measured. RESULTS: Total tumor volume and vital tumor surface were not significantly different in any of the treatment groups. Similarly, vascular density and apoptosis were not altered by treatment with the various angiogenesis inhibitors at the specific doses used. CONCLUSION: We conclude that in contrast to many earlier studies, angiogenesis inhibition by a single-drug application and by the doses used in the present model did not reveal a favorable therapeutic effect on pancreatic cancer DSL6A. The combination of different angiogenesis inhibitors or higher doses might be more effective.

The role of pre-ischaemic application of the nitric oxide donor spermine/nitric oxide complex in enhancing flap survival in a rat model.

Spermine/nitric oxide complex (Sper/NO) is a new nitric oxide (NO) donor with a long half-life providing controlled biological release of NO in vivo. The purpose of this study was to determine whether flap survival could be improved by pre-ischaemic or post-ischaemic intravenous administration of Sper/NO. We divided 37 male Wistar rats into four experimental groups. An extended epigastric adipocutaneous flap was raised in each animal. The mean area of flap necrosis was assessed for all groups on the fifth postoperative day, using planimetry software. The average area of flap necrosis was mean +/- s.d. = 68.2%+/-18.1% in the control group, and 29.7% +/- 13.3% in the non-ischaemic controls. The group with pre-ischaemic application of Sper/NO demonstrated an average flap necrosis of mean+/-s.d. = 11.2%+/-5.9%, whereas this increased to 59.2%+/-14.4% in the group receiving Sper/NO 5 min prior to reperfusion. The group with pre-ischaemic application of Sper/NO showed a significantly lower area of flap necrosis than either of the control groups or the group receiving Sper/NO just prior to reperfusion (P < 0.05). The group receiving Sper/NO just prior to reperfusion demonstrated a significantly higher mean area of flap necrosis than the non-ischaemic controls (P < 0.05), but did not differ significantly from the control group. Our data show that pharmacological preconditioning and enhancement of flap survival can be achieved by intravenous administration of Sper/NO. The application of Sper/NO at the end of the ischaemia period or in the early reperfusion period provides no protection against ischaemia-reperfusion injury.

Dopexamine attenuates microvascular perfusion injury of the small bowel in pigs induced by extracorporeal circulation.

BACKGROUND: Cardio-thoracic surgery with the use of extracorporeal circulation may lead to an impairment of splanchnic perfusion. The aim of this study was to investigate the effect of dopexamine on gastrointestinal microvascular perfusion failure due to extracorporeal circulation. METHODS: Twenty landrace pigs served as laboratory animals. A loop of the terminal ileum was exteriorized for microscopic observation. In 13 animals a partial left-heart bypass (pLHB), with a non-pulsatile pump flow of approximately 50% of the cardiac output, was established for 2 h. Seven animals received a continuous i.v. infusion of 3 micrograms kg-1 min-1 dopexamine from the beginning of pLHB to the end of the experiment. Seven sham-operated animals served as controls. The microcirculatory network was analysed by means of intra-vital microscopy prior to, during pLHB, and 2 h after bypass. RESULTS: Despite normal haemodynamics measured by arterial pressure and cardiac output, pLHB led to significant impairment of microvascular perfusion characterized by arteriolar vasoconstriction, reduction of functional capillary density (FCD) to 30% 2 h after weaning off bypass and diminished blood-cell velocities in submucous venules. Dopexamine attenuated this perfusion impairment, preventing arteriolar vasoconstriction. FCD remained normal. CONCLUSION: Our data demonstrate that treatment with the vasoactive drug dopexamine leads to a significant reduction of the perfusion injury of the small bowel.

Glutathione depletion with L-buthionine-(S,R)-sulfoximine demonstrates deleterious effects in acute pancreatitis of the rat.

A common pathway in the pathogenesis of acute pancreatitis is the generation of free oxygen radicals. The most important defense mechanisms are free radical scavengers, especially glutathione. This study evaluates the influence of the inhibition of glutathione synthesis with L-buthionine-(S,R)-sulfoximine (BSO) on the course of experimentally induced acute pancreatitis in rats and the effects on isolated pancreatic acini and their secretion pattern. Thus acute necrotizing pancreatitis was induced with intraductal infusion of low-dose glycodeoxycholic acid and subsequent hyperstimulation with cerulein with and without pretreatment with BSO. In vitro pancreatic acini were isolated and stimulated with different concentrations of cerulein with and without BSO. The BSO-treated group showed a significantly reduced survival, more necrosis, and a decreased secretion of amylase in vivo. No effect on secretion pattern in either groups was seen in vitro and BSO did not exert toxic effects. Based on the data presented, this study demonstrates deleterious effects of scavenger depletion on the course of experimental pancreatitis. This is due to the systemic effects of free oxygen radicals rather than to local effects.

Influence of steroids on microvascular perfusion injury of the bowel induced by extracorporeal circulation.

BACKGROUND: Extracorporeal circulation is associated with gastrointestinal complications. By means of intravital microscopic methods, we investigated whether preoperative treatment with steroids can attenuate the impairment of the bowel microcirculation. METHODS: In 20 pigs, a partial left heart bypass (pLHB) was established. A loop of the terminal ileum was exteriorized for intravital-microscopic observation. Seven sham-operated animals served as controls. In 13 animals, pLHB was established for 2 hours with a flow rate of 2,000 mL per minute; 7 of the animals received 20 mg/kg body weight prednisolone preoperatively. The microcirculatory network was analyzed before, during pLHB, and 2 hours after bypass. RESULTS: Despite unchanged macro-hemodynamics, pLHB resulted in a significant microvascular perfusion injury of the small bowel. Arteriolar vasoconstriction and a reduction of perfused capillaries per unit area (functional capillary density) to 30% of prebypass values could be found. Blood cell velocities were reduced in submucuous collecting venules. In the steroid-treated animals, the functional capillary density remained normal. In addition, arteriolar vasoconstriction could be prevented. CONCLUSIONS: Treatment with prednisolone largely prevents the microcirculatory alterations in the small bowel induced by extracorporeal circulation.

Differential value of adenosine myocardial contrast echocardiography and dobutamine stress echocardiography in evaluating functional significance of coronary artery stenosis in a porcine model.

AIM: Myocardial contrast echocardiography (MCE) during adenosine induced hyperemia is an experimental method that detects flow limiting coronary artery stenosis by visualizing myocardial perfusion defects. Noninvasive detection of flow limiting coronary artery stenosis in clinical routine is a frequent domaine of dobutamine stress echocardiography (DSE) visualizing ischemia related regional wall motion abnormalities. This study investigated the values of adenosine MCE and DSE in the detection of functionally significant coronary artery stenosis in an experimental open chest pig model. METHODS: A total of 28 proximal LAD stenoses were instrumented in 12 animals. Reduction of coronary blood flow reserve (delta CFR [%] ) was calculated as a marker of functional significance of coronary artery stenosis (mild to moderate stenosis: delta CFR < or = 50%; severe stenosis: delta CFR > 50%). Fractional area shortening (FAS) and wall thickening (WT) were calculated to evaluate regional wall motion. Peak myocardial contrast intensities (PCI) were measured following aortic root injections of Levovist' to detect mocardial perfusion defects. RESULTS: As a group, severe stenosis significantly reduced wall motion response to dobutamine (delta FAS: 12.0 +/- 3.0%, vs. 20 +/- 3.0% without stenosis, p < 0.05; delta WT: 2.2 +/- 0.9 mm vs. 0.0 +/- 0.8 mm without stenosis, p < 0.05) and diminished myocardial opacification during hyperemia (PCI: 59 +/- 8 units vs. 143 +/- 16 units without stenosis, p < 0.05). Mild to moderate stenosis did not influence wall motion but reduced myocardial opacification (PCI 89 +/- 14 units vs. 143 +/- 16 units). PCI correlated more closely with alterations in CFR (r = -0.7, p < 0.0001) than did FAS (r = -0.5, p < 0.002) or WT (r = -0.2, p = 0.3). CONCLUSION: Adenosine myocardial contrast echocardiography detects flow limiting coronary artery stenosis and compares favorably to regional wall motion analysis during dobutamine infusion.

Reduction of hepatic reperfusion injury by antithrombin III and aprotinin.

Disturbance in hepatic microcirculation and leucocyte-endothelium interaction after warm ischaemia represents one of the leading mechanisms for postoperative organ dysfunction. Recent studies have shown that pretreatment with antithrombin III (AT III) and aprotinin reduces the leucocyte-endothelium interaction in ischaemic small intestine and during extracorporal circulation in cardiac surgery. Standardized warm hepatic ischaemia and intravital fluorescence videomicroscopy was performed in an experimental study with rats. Animals were pretreated with AT III or aprotinin. Analysis of intravital videomicroscopy showed that the hepatic microcirculation after warm hepatic ischaemia in rats was significantly enhanced by AT III and aprotinin, most likely by reducing the leucocyte-endothelium interaction. We concluded that drug application before the Pringle manoeuvre might reduce the reperfusion damage after liver resection.

Cigarette smoke enhances ethanol-induced pancreatic injury.

Alcohol induces pancreatic ischemia, but the mechanisms promoting pancreatic inflammation are unclear. We investigated whether cigarette smoke inhalation is a cofactor in the development of ethanol-induced pancreatic injury. Cigarette smoke was administered to anesthetized rats alone or in combination with intravenous ethanol infusion. Control animals received either saline or ethanol alone. Pancreatic capillary blood flow and leukocyte-endothelium interaction in postcapillary venules were evaluated by intravital microscopy. Leukocyte sequestration was assessed by measurement of myeloperoxidase activity in pancreatic tissue, and pancreatic injury evaluated by histology. Ethanol decreased pancreatic blood flow progressively over 90 minutes (p < 0.001 vs. baseline), but neither leukocyte-endothelium interaction nor leukocyte sequestration was altered. Cigarette smoke alone reduced pancreatic blood flow temporarily (p < 0.01 vs. baseline) and increased leukocyte-endothelium interaction (roller p < 0.001, sticker p < 0.01 vs. baseline). Cigarette smoke potentiated the impairment of pancreatic capillary perfusion caused by ethanol, and both the number of rolling leukocytes and myeloperoxidase activity levels were increased compared to ethanol or nicotine administration alone (p < or = 0.05 and p < or = 0.01, respectively). This study demonstrates that ethanol induces pancreatic ischemia and that cigarette smoke leads to both temporary pancreatic ischemia and minimal leukocyte sequestration. Cigarette smoke potentiates the amount of pancreatic injury generated by ethanol alone. Smoking therefore seems to be a contributing factor in the development of alcohol-induced pancreatitis in the rat model.

Influence of gastrointestinal hormones on tumor microcirculation of experimental pancreatic cancer in the rat.

BACKGROUND/AIMS: Gastrointestinal hormones influence the microcirculation in the normal pancreas. In the present study, we studied the effect of cerulein and somatostatin on pancreatic cancer microcirculation after orthotopic and nonorthotopic tumor implantation. METHODS: In 36 male Lewis rats (150-180 g) induction of a ductlike pancreatic cancer was achieved by intrapancreatic or intraperitoneal tumor fragment interposition between two inert transparent polymethyl methacrylate plates. After 4 weeks, intravital microscopy of the tumor microcirculation was performed in a temperature-controlled immersion chamber. The animals received 5 microg/kg cerulein or 3 mg/kg somatostatin for 1 h intravenously. The erythrocyte velocity in normal pancreatic capillaries or in tumor vessels was measured. RESULTS: The erythrocyte velocity in the capillaries of the normal pancreas was 1.01 +/- 0.11 mm/s at baseline and increased to 1.64 +/- 0.09 mm/s after cerulein stimulation (p = 0.007). Pancreatic cancer vessels demonstrated no increase in erythrocyte velocity after orthotopic (baseline 0.95 +/- 0.14 mm/s, after 1 h 0.86 +/- 0.13 mm/s; n.s.) and nonorthotopic tumor implantation (baseline 0.91 +/- 0.12 mm/s, after 1 h 0.95 +/- 0.14 mm/s; n.s.) after cerulein stimulation. Somatostatin decreased the erythrocyte velocity both in normal pancreas (baseline 0.87 +/- 0.02 mm/s, after 1 h 0.60 +/- 0.07 mm/s; p = 0.01) and in pancreatic cancer (baseline 0.85 +/- 0.20 mm/s, after 1 h 0.63 +/- 0.18 mm/s; p = 0.02) after orthotopic tumor implantation. There was no effect of somatostatin after nonorthotopic tumor implantation (baseline 0.90 +/- 0.10 mm/s, after 1 h 0.88 +/- 0.14 mm/s; n.s.). CONCLUSION: These data suggest that pancreatic cancer microcirculation lacks physiological blood flow control by stimulatory hormones, in contrast to the normal pancreas.

Vascular structure and microcirculation of experimental pancreatic carcinoma in rats.

OBJECTIVE: To study angiogenesis and microcirculation in experimental pancreatic carcinoma. DESIGN: Open experimental study. SETTING: 2 University hospitals, Germany and USA. ANIMALS: 16 male Lewis rats. INTERVENTIONS: Induction of a duct-like pancreatic cancer in the pancreas and peritoneum by interposition of fragments of tumour between 2 inert transparent polymethylmethacrylate plates. MAIN OUTCOME MEASURES: Microcirculation in the tumour and interaction between leucocytes, tumour, and endothelium investigated by intravital microscopy. RESULTS: The density of vessels in the carcinoma was significantly less than in normal pancreatic tissue (p = 0.0004). The vasculature of the tumour was characterised by a lack of differentiation in architecture of vessels, formation of sinusoidal and lacunar vessels and sudden changes in diameter of vessels. Red blood cell velocity differed among tumour vessels, but mean values were similar to those of normal exocrine pancreas. The mixed lymphocyte culture test indicated that the cell line DSL6A was immunogenic. However, high-affinity leucocyte-endothelium-interaction was significantly reduced in the tumour's microcirculation after both orthotopic and heterotopic implantation (p = 0.002). Rates of apoptosis were suppressed in heterotopic tumours compared with orthotopic ones. Tumour growth was faster in heterotopic tumours. CONCLUSIONS: Experimental duct-like pancreatic carcinoma can be differentiated from normal pancreas by: chaotic arrangement of vessels with loss of differentiation of architecture and heterogeneous distribution; the formation of sinusoidal or lacunar vessels; lower vascular density with similar erythrocyte velocity; increase in mean diameter of vessels; reduced leucocyte-endothelium interaction despite confirmed immunogeneity independent of wall shear rates. The site of implantation influences apoptosis and growth rates.