Microcirculatory dysfunction in acute pancreatitis. A new concept of pathogenesis involving vasomotion-associated arteriolar constriction and dilation

In vivo imaging of human pancreatic microcirculation and pancreatic tissue injury in clinical pancreas transplantation

Pancreatitis remains to be a major complication following clinical pancreas transplantation. We performed orthogonal polarized spectral (OPS) imaging for direct in vivo visualization and quantification of human pancreatic microcirculation in six healthy donors for living donor liver transplantation and 13 patients undergoing simultaneous pancreas-kidney transplantation. We further determined the impact of microvascular dysfunction during early reperfusion on pancreatic graft injury. Exocrine and endocrine pancreatic impairment was determined by analysis of serum lipase, amylase and C-peptide levels. Compared to normal pancreas in liver donors (homogeneous acinar perfusion) functional capillary density (FCD) and capillary red blood flow velocity of reperfused grafts were significantly decreased. Elevated CRP concentrations on day 2 post-transplant and serum lipase and amylase levels determined on days 4-5 significantly correlated with microvascular dysfunction during the first 30 min of graft reperfusion. Post-transplant serum C-peptide also correlated significantly with pancreatic capillary perfusion. OPS imaging allows to intra-operatively assess physiologic pancreatic microcirculation and to determine microcirculatory impairment during early graft reperfusion. This impairment correlated with the manifestation of post-transplant dysfunction of both exocrine and endocrine pancreatic tissue. OPS imaging may be used clinically to determine the efficacy of interventions, aiming at attenuating microcirculatory impairment during the acute post-transplant reperfusion phase.

In vivo characterization of developing chronic pancreatitis in rats

Despite numerous experimental and clinical investigations, there is no unifying concept on pathophysiology and pathogenesis of chronic pancreatitis. Defining the interplay between pancreatic microcirculation and parenchymal tissue, we will provide a basis for the better understanding of pancreatic fibrogenesis using in vivo high-resolution multifluorescence microscopy in dibutyltin chloride (DBTC)-exposed rats. Pancreatic microcirculation at days 3 and 7 after DBTC revealed leukocyte activation with a two-fold higher fraction of rolling cells and a nine- to 10-fold increase of cells firmly adherent to the endothelial lining, followed by subsequent transendothelial migration into tissue, as given by chloracetate esterase histology. In vivo staining of acinar tissue with bisbenzimide presented single cells exhibiting nuclear chromatin condensation and fragmentation. Apoptotic cell death was confirmed by immunohistochemical staining for active caspase-3 as well as by TUNEL analysis. Necrotic cells were found dispersed throughout the exocrine tissue under observation. Both modes of cell death were found highest in extent at days 3 and 7 with 15-20 cells/mm2, but progressively decreased below 10 cells/mm2 up to 28 days after DBTC. By means of in vivo microscopy yellow-green autofluorescent collagen deposits were found at day 7 and progressively increased up to approximately 12% at day 28 after DBTC. Concomitantly, density of capillaries progressively decreased and capillaries failing to conduct blood flow became apparent. Present on-line analysis indicates an early inflammatory response with acinar cell death, most probably triggering progression of disease with collagen deposition, capillary rarefication and manifestation of perfusion failure. These temporal and spatial multiparameter measurements of the in vivo microenvironment provide new insights into the pathological processes of pancreatic fibrogenesis.

Selective cyclooxygenase-2 inhibition reverses microcirculatory and inflammatory sequelae of closed soft-tissue trauma in an animal model

BACKGROUND

Despite the common use of nonsteroidal anti-inflammatory drugs in the treatment of closed soft-tissue injuries, our understanding of the effect of these medications on tissue healing is incomplete. Using high-resolution multifluorescence microscopy, we investigated the efficiency of preinjury and postinjury treatment with the selective cyclooxygenase (COX)-2 inhibitor parecoxib to improve compromised perfusion of traumatized muscle tissue and to minimize secondary tissue damage.

METHODS

With use of a pneumatically driven and computer-controlled impact device, closed soft-tissue trauma of the left hindlimb was induced in anesthetized rats that had had intravenous administration of 10 mg/kg of either parecoxib sodium (seven rats) or an equal volume of saline solution (seven rats). Seven additional animals received parecoxib two hours after the trauma, and seven animals without trauma served as controls.

RESULTS

Time-course studies with use of both Western blot protein analysis and immunohistochemistry demonstrated a transient upregulation of COX-2 protein expression with peak levels eight to twelve hours after trauma and a return to near baseline level at eighteen hours. Regardless of whether parecoxib was administered before or after the injury, it completely restored microcirculatory impairment within the injured muscle. This was indicated by the mean values (and standard error of the mean) for nutritive perfusion (434 +/- 15 cm/cm(2) in animals treated before the injury and 399 +/- 8 cm/cm(2) in those treated after injury), nicotinamide adenine dinucleotide (NADH) levels (73 +/- 2 aU and 74 +/- 1 aU, respectively), and inflammatory cell interaction (184 +/- 36 and 186 +/- 32 n/mm(2), respectively, for leukocytes, and 1.0 +/-0.1 and 0.8 +/- 0.1 n/mm(2), respectively, for platelets) at eighteen hours after trauma, which were not different from those found in noninjured muscle tissue of controls. In contrast, skeletal muscle in saline solution-treated animals revealed persistent perfusion failure (296 +/-30 cm/cm(2)) with tissue hypoxia (NADH, 100 +/- 4 aU), and enhanced endothelial interaction of both leukocytes (854 +/- 73 mm(-2)) and platelets (2.3 +/- 0.5 n/mm(2)) at eighteen hours after trauma.

CONCLUSIONS AND CLINICAL RELEVANCE

Treatment of skeletal muscle soft-tissue trauma with parecoxib before as well as after injury is highly effective in restoring disturbed microcirculation. Moreover, a reduced inflammatory cell response helps to prevent leukocyte or platelet-dependent secondary tissue injury. These results deserve further investigation to prove that selective COX-2 inhibitors improve performance and promote healing following closed soft-tissue injury.

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Endoscopic retrograde cholangiopancreatography in gallstone-associated acute pancreatitis

BACKGROUND

Early endoscopic retrograde cholangio-pancreatography with or without endoscopic sphincterotomy (ERCP+/-ES) has been advocated to reduce complications in patients presenting with a severe attack of gallstone-associated acute pancreatitis (GAP). However, a recent trial has reported contradictory results. Importantly, patients with acute cholangitis were excluded suggesting it may be a major confounding factor affecting previous studies.

OBJECTIVES

To assess the effectiveness of early ERCP+/-ES compared to conservative management stratified according to severity of disease, concealment of randomisation, acute cholangitis and bilirubin level in the reduction of mortality, morbidity, length of hospitalisation and cost in adults suspected of having GAP.

SEARCH STRATEGY

We searched - Cochrane Library (Issue 4 2003), Medline (1966-2004), EMBASE (1980-2004) and LILACS. 'Grey literature' was sought by looking at cited references and hand searched to identify further relevant trials. Conference proceedings of United European Gastroenterology Week (published in Gut) and Digestive Disease Week (published in Gastroenterology) were also hand searched.

SELECTION CRITERIA

Randomized controlled trials (RCT) of adult patients, from 15 years old or greater, presenting with gallstone-associated acute pancreatitis (GAP) comparing ERCP +/- ES versus Conservative management within 72 hours of admission.

DATA COLLECTION AND ANALYSIS

Data were assessed for quality independently by two reviewers. Wherever appropriate, results were pooled together and sub-grouped by predicted severity of disease. Fixed and random effects models were applied. Sensitivity analysis was performed to test the fragility of results.

MAIN RESULTS

Three trials, involving 511 patients, met inclusion criteria. The test for heterogeneity yielded statistically non-significant results (p-value 0.1 to 0.63) suggesting all comparisons were above the established threshold for combinability (p<0.1). Fixed effect and random effect meta-analyses gave identical results. Early ERCP +/- ES was associated with non-significant effect on reduction of mortality in predicted mild (OR = 0.62, 95% CI = 0.27 to 1.41) and severe GAP (OR = 0.62, 95% CI = 0.27 to 1.41). Reduction in complications was non-significant in predicted mild (OR = 0.89, 95% CI = 0.53 to 1.49), but significant in severe GAP (OR = 0.27, 95% CI = 0.14 to 0.53). There was insufficient evidence to draw any conclusions about hospital stay and cost.

REVIEWERS' CONCLUSIONS

Odds of having complications are reduced in predicted severe disease by early ERCP +/- ES. This effect was however, non-significant in predicted mild disease and for reduction of mortality in either predicted mild or severe disease. These results are controlled for confounding due to associated acute cholangitis and are robust for clinical and statistical heterogeneity.

Dynamic intravital fluorescence microscopy--a novel method for the assessment of microvascular permeability in acute pancreatitis

Edema formation is the first manifestation of acute pancreatitis. Microcirculatory derangements like leukocyte-endothelial cell interaction and perfusion failure result in enhancement of microvascular permeability to large molecules playing a pivotal role in the progression of the acutely altered pancreatic tissue. Due to the lack of suitable methods the crucial mechanisms of enhanced permeability in vivo are not very well investigated. Sprague-Dawley rats were randomly assigned to three groups: (a) sham operated animals with normal pancreas, (b) the pancreatitis group induced by 60 min temporary occlusion of the arterial supply followed by reperfusion and (c) the histamine group in which the pancreas was superfused with 10(-5)M histamine. The pharmacokinetics of tetramethylrhodamine-labelled BSA in the intravital microscopic images of a capillary network of the pancreas were densitometrically quantified over 20 min. From these data the effective microvascular permeability was calculated taking also into account morphology of microvessels, elimination rate of the tracer from the intravascular space and capillary microhematocrit. In addition macromolecular leakage of gold-labelled BSA was investigated by electron microscopy. Microvascular permeability was 0.10 +/- 0.02 x 10(-7) cm/s, 0.49 +/- 0.04 x 10(-7) cm/s and 1.21 +/- 0.29 x 10(-7) cm/s for control, ischemia and histamine group, respectively (P < 0.05 ischemia, histamine vs. control and ischemia vs. histamine). Electron microscopy revealed albumin extravasation in the last two groups. We established a technique allowing to quantify microvascular permeability in pancreatic tissue by dynamic intravital microscopy being independent of the investigator. This technique enabling accurate pathophysiologic characterisation in terms of edema formation can form the basis for evaluating in the future novel treatment strategies directed against acute pancreatitis.

Ischemic preconditioning attenuates capillary no-reflow and leukocyte adherence in postischemic pancreatitis

BACKGROUND AND AIMS

Ischemic preconditioning (IPC) has been shown to protect several organs from ischemia-reperfusion injury. Postischemic microvascular dysfunction is considered to be the key mechanism of early graft pancreatitis after transplantation. The aim of the study was to determine whether brief ischemia and reperfusion before prolonged ischemia followed by reperfusion is protective in respect to microcirculatory derangement in postischemic pancreatitis.

METHODS

In an in-situ model of ischemia-reperfusion was induced in the isolated pancreatic tail segment. Wistar rats were randomized to one group ( n=7/group) with 2-h ischemia and reperfusion (I/R) and another group with 10-min ischemia and 10-min reperfusion (IPC) before the prolonged ischemia time. Microcirculation was observed for 2 h by intravital-fluorescence microscopy that analyzed functional capillary density and leukocyte adherence in postcapillary venules. Histological damage was quantified by a semiquantitative score (edema, vacuolization, PMN infiltration, necrosis).

RESULTS

IPC resulted in a significant improvement of functional capillary density (248+/-20 vs 372+/-8 cm(-1), P<0.001), a significant reduction in leukocyte adherence in postcapillary venules (476+/-79 vs 179+/-15 cells/mm(2), P<0.001) and in significantly lower histological damage (score 9+/-0.8 vs 5+/-1.4, P<0.001), when compared with the ischemia-reperfusion group.

CONCLUSION

IPC reduces pancreatic inflammatory reaction by preservation of postischemic microcirculation. Therefore, it might become a useful procedure before organ procurement in pancreas transplantation.