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

Validation of the Back-table Graft Arterial Anastomosis Between the Splenic Artery and Superior Mesenteric Artery: Arterial Complications After a 21-year Single-center Experience of Pancreas Transplantation

OBJECTIVE

To determine the role of the arterial splenomesenteric anastomosis (ASMA) vascular reconstruction technique in terms of arterial vascular complications in pancreas transplantation (PT) recipients.

BACKGROUND

The ASMA technique was first described in 1992 by the Hospital Clínic Barcelona group. Regardless that the iliac Y-graft technique is the most frequently used worldwide, evidence of arterial complications and implications of using a different back-table reconstruction is conspicuously absent in the literature.

METHODS

Descriptive review of 407 PTs performed at a single center (1999-2019) by analyzing the type of arterial reconstruction technique, focusing on ASMA. The end points were the management of arterial complications and long-term patient and graft survival.

RESULTS

ASMA was performed in 376 cases (92.4%) and a Y-graft in 31 cases (7.6%). A total of 34 arterial complications (8.3%) were diagnosed. In the ASMA group (n=30, 7.9%), they comprised 15 acute thrombosis, 4 stenosis, 1 pseudoaneurysm, and 10 diverse chronic arterial complications, whereas in the Y-graft group (n=4, 12.9%), 3 acute thrombosis and 1 chronic artery-duodenal fistula occurred. Graft salvage was achieved in 16 patients (53.3%) from the ASMA group and in 2 (50%) from the Y-graft. After a median follow-up of 129.2 (IQR 25-75%, 77.2-182) months, the overall graft and patient survival for the whole cohort at 1, 5, and 10 years were 86.7%, 79.5%, and 70.5%, and 98.5%, 95.3%, and 92.5%, respectively.

CONCLUSIONS

The ASMA proves to be a safe and more easily reproducible technique and could therefore be considered a safe alternative vascular reconstruction procedure to the Y-graft in the PT population.

The TEG 6s Global Hemostasis System is Useful for Coagulation Management in Simultaneous Pancreas and Kidney Transplantation: The First Two Cases

INTRODUCTION

Hypercoagulability-related graft thrombosis is the leading cause of graft failure after simultaneous pancreas-kidney transplantation (SPK). Addressing this issue is crucial to improve the outcomes of SPK recipients. Thromboelastography (TEG) has been used to assess the coagulation profiles of SPK recipients. Recently, a new-generation TEG device, the TEG 6s Global Hemostasis System, was introduced. This device offers advantages over TEG 5000, including less frequent calibration requirements, ease of use, and reduced sensitivity to movement. We hypothesized that TEG 6s would enhance coagulation management in SPK.

METHODS

We report two cases of Asian female SPK recipients in whom TEG 6s was used to assess coagulation status at six preset times during and after surgery.

RESULTS

Preoperatively, both patients exhibited hypercoagulability on TEG 6s. Postoperative intravenous heparin was administered, and the dose was titrated based on the TEG 6s results. Vascular thrombosis was not observed in either patient. Detailed TEG 6s and standard laboratory test results are reported. This pilot study demonstrates that TEG 6s monitoring can effectively assess coagulation status in SPK recipients, aiding in optimal coagulation management and reducing the risk of thrombotic complications leading to graft loss. The TEG 6s facilitated real-time and accurate coagulation assessment, allowing for tailored anticoagulant therapy.

CONCLUSIONS

This is the first observational study to use TEG 6s in SPK recipients, indicating its potential benefits in improving patient outcomes. Further studies with larger sample sizes are warranted to validate these findings and establish comprehensive guidelines for using TEG 6s in SPK procedures.

Effective Technique for Pancreas Transplantation by Iliac Vascular Transposition, Without Heparin-Based Anticoagulation Therapy

BACKGROUND

To evaluate patients undergoing a new procedure, iliac vascular transposition, in pancreas transplantation regarding the risk of thrombosis and graft survival without heparin-based anticoagulation therapy.

METHODS

Iliac vascular transposition (IVT) involves changing the positions of the external iliac artery and vein relative to each other. In this study, this technique was evaluated in patients undergoing the procedure compared with patients not undergoing the procedure (iliac vascular parallel (IVP) group).

RESULTS

No patients received prophylactic heparin therapy. Two patients in the IVP group (n = 26) developed complete thrombosis and six developed partial thrombosis, compared with no patients with complete thrombosis and one with partial thrombosis in the IVT group (n = 29). The cumulative incidence of thrombosis was significantly higher in the IVP group (p < 0.01). Cox regression revealed that not receiving iliac vascular transposition was the only significant risk factor for thrombosis (odds ratio: 10.1, 95% confidence interval: 1.27-81.2; p = 0.03). One-year graft survival was significantly better in the IVT group vs IVP group (p = 0.03).

CONCLUSIONS

IVT in pancreas transplantation is a simple technique that results in a lower thrombosis risk and better graft survival rates without heparin-based anticoagulation therapy.

Development of ex situ normothermic reperfusion as an innovative method to assess pancreases after preservation

Static cold storage (SCS) is the standard method for pancreas preservation prior to transplantation; however, it does not permit organ assessment. Normothermic reperfusion (NR) is utilized clinically for other organs to assess viability. Our aim was to develop NR using normothermic machine perfusion technique to simulate reperfusion at the time of transplantation, enabling evaluation of oxygenated hypothermic machine perfusion (HMPO2) as a newer strategy to optimize pancreas preservation. 13 porcine pancreases procured after circulatory death were divided into 3 groups: 4 pancreases preserved using SCS, and 2 groups preserved by HMPO2 (n = 4 and n = 5, differing by type of preservation solution). Duration of perfusion or cold storage was 6 hours before the 1-hour assessment using NR. Outcome measures were perfusion characteristics, biochemistry and change in tissue water mass as oedema assessment. During NR, the HMPO2 groups demonstrated better perfusion characteristics, normal macroscopic appearances, decreased water mass and one HMPO2 group demonstrated a response to glucose stimulation. Conversely, the SCS group showed an increased water mass and developed early macroscopic appearances of oedema, interstitial haemorrhage and minimal portal outflow. This study suggests that ex situ assessment of pancreases by NR is promising, and that HMPO2 may be better than SCS.

Donor insulin therapy in intensive care predicts early outcomes after pancreas transplantation

AIMS/HYPOTHESIS

Approximately 50% of organ donors develop hyperglycaemia in intensive care, which is managed with insulin therapy. We aimed to determine the relationships between donor insulin use (DIU) and graft failure in pancreas transplantation.

METHODS

UK Transplant Registry organ donor data were linked with national data from the UK solid pancreas transplant programme. All pancreas transplants performed between 2004 and 2016 with complete follow-up data were included. Logistic regression models determined associations between DIU and causes of graft failure within 3 months. Area under the receiver operating characteristic curve (aROC) and net reclassification improvement (NRI) assessed the added value of DIU as a predictor of graft failure.

RESULTS

In 2168 pancreas transplant recipients, 1112 (51%) donors were insulin-treated. DIU was associated with a higher risk of graft loss from isolated islet failure: OR (95% CI), 1.79 (1.05, 3.07), p = 0.03, and this relationship was duration/dose dependent. DIU was also associated with a higher risk of graft loss from anastomotic leak (2.72 [1.07, 6.92], p = 0.04) and a lower risk of graft loss from thrombosis (0.62 [0.39, 0.96], p = 0.03), although duration/dose-dependent relationships were only identified in pancreas transplant alone/pancreas after kidney transplant recipients with grafts failing due to thrombosis (0.86 [0.74, 0.99], p = 0.03). The relationships between donor insulin characteristics and isolated islet failure remained significant after adjusting for potential confounders: DIU 1.75 (1.02, 2.99), p = 0.04; duration 1.08 (1.01, 1.16), p = 0.03. In multivariable analyses, donor insulin characteristics remained significant predictors of lower risk of graft thrombosis in pancreas transplant alone/pancreas after kidney transplant recipients: DIU, 0.34 (0.13, 0.90), p = 0.03; insulin duration/dose, 0.02 (0.001, 0.85), p = 0.04. When data on insulin were added to models predicting isolated islet failure, a significant improvement in discrimination and risk reclassification was observed in all models: no DIU aROC 0.56; DIU aROC 0.57, p = 0.86; NRI 0.28, p < 0.00001; insulin duration aROC 0.60, p = 0.47; NRI 0.35, p < 0.00001.

CONCLUSIONS/INTERPRETATION

DIU predicts graft survival in pancreas transplant recipients. This assessment could help improve donor selection and thereby improve patient and graft outcomes.

The use of pulse pressure variation for predicting impairment of microcirculatory blood flow

Dynamic parameters of preload have been widely recommended to guide fluid therapy based on the principle of fluid responsiveness and with regard to cardiac output. An equally important aspect is however to also avoid volume-overload. This accounts particularly when capillary leakage is present and volume-overload will promote impairment of microcirculatory blood flow. The aim of this study was to evaluate, whether an impairment of intestinal microcirculation caused by volume-load potentially can be predicted using pulse pressure variation in an experimental model of ischemia/reperfusion injury. The study was designed as a prospective explorative large animal pilot study. The study was performed in 8 anesthetized domestic pigs (German landrace). Ischemia/reperfusion was induced during aortic surgery. 6 h after ischemia/reperfusion-injury measurements were performed during 4 consecutive volume-loading-steps, each consisting of 6 ml kg⁻¹ bodyweight⁻¹. Mean microcirculatory blood flow (mean Flux) of the ileum was measured using direct laser-speckle-contrast-imaging. Receiver operating characteristic analysis was performed to determine the ability of pulse pressure variation to predict a decrease in microcirculation. A reduction of ≥ 10% mean Flux was considered a relevant decrease. After ischemia–reperfusion, volume-loading-steps led to a significant increase of cardiac output as well as mean arterial pressure, while pulse pressure variation and mean Flux were significantly reduced (Pairwise comparison ischemia/reperfusion-injury vs. volume loading step no. 4): cardiac output (l min⁻¹) 1.68 (1.02–2.35) versus 2.84 (2.15–3.53), p = 0.002, mean arterial pressure (mmHg) 29.89 (21.65–38.12) versus 52.34 (43.55–61.14), p < 0.001, pulse pressure variation (%) 24.84 (17.45–32.22) versus 9.59 (1.68–17.49), p = 0.004, mean Flux (p.u.) 414.95 (295.18–534.72) versus 327.21 (206.95–447.48), p = 0.006. Receiver operating characteristic analysis revealed an area under the curve of 0.88 (CI 95% 0.73–1.00; p value < 0.001) for pulse pressure variation for predicting a decrease of microcirculatory blood flow. The results of our study show that pulse pressure variation does have the potential to predict decreases of intestinal microcirculatory blood flow due to volume-load after ischemia/reperfusion-injury. This should encourage further translational research and might help to prevent microcirculatory impairment due to excessive fluid resuscitation and to guide fluid therapy in the future.

Prediction of Insulin Secretion Ability With Microcirculation Evaluated by Contrast-enhanced Ultrasonography in Pancreas Transplantation

OBJECTIVES

Contrast-enhanced ultrasonography can evaluate microcirculation. Thus, we used contrast-enhanced ultrasonography in evaluating pancreas graft perfusion and examined the relationship between graft circulation and function.

METHODS

Contrast-enhanced ultrasonography was performed in 17 cases within 24 hours and at 1, 3, 5, 7, 14, 21, and 28 days after transplantation (Tx). The time between the time to peak intensity in the parenchyma and that in the vein was defined as delta-Tp(P-V). Graft function was evaluated with oral glucose tolerance test (OGTT) at 1 and 3 months after Tx, and glucagon stimulation test at 1 month after Tx.

RESULTS

Differences in delta-Tp(P-V) between individual cases were more significant early after Tx, and delta-Tp(P-V) within 24 hours (delta-Tp[P-V]24h) was used in the subsequent analysis. Delta-Tp(P-V)24 hours showed a negative correlation with C-peptide increment in the glucagon stimulation test and the area under the curve of insulin level in oral glucose tolerance test. The cases were divided into the following 2 groups: the standard group (delta-Tp[P-V]24h ≤6.10 seconds) and the delayed group (>6.10 seconds). The area under the curve of insulin level increased significantly from 1 to 3 months after Tx in the standard group only.

CONCLUSIONS

These results suggest that delta-Tp(P-V)24 hours affects insulin secretion after Tx. Contrast-enhanced ultrasonography is useful in predicting endocrine function of the graft.

Techniques of pancreas graft salvage/indications for allograft pancreatectomy

PURPOSE OF REVIEW

Despite improvements in pancreas allograft outcome, graft complications remain a significant cause of morbidity and mortality. This review analyses the issues involved in the management of conditions that may require graft pancreatectomy, including the indications and techniques for graft salvage.

RECENT FINDINGS

With early recognition of graft complications, liberal use of radiological interventions, improved infection control, access to critical care and innovative surgical techniques, graft salvage is now feasible in many circumstances where graft pancreatectomy would previously have been necessary.

SUMMARY

The outcome of pancreas transplantation continues to improve with advances in the management of graft-threatening complications.

Heparin infusion in simultaneous pancreas and kidney transplantation reduces graft thrombosis and improves graft survival

INTRODUCTION

Thrombosis of the pancreas after transplantation is the most common cause of relaparotomy and resultant graft loss. There is currently no standard protocol consistently proven to prevent thrombosis following transplantation. Our objective was to determine whether our protocol of post-operative low-dose intravenous (IV) heparin infusion would prevent graft thrombosis without additional complications in our patients.

METHODS

A total of 66 simultaneous pancreas kidney (SPK) transplants were performed at our institution from 2004 to 2014. Patients were divided into 2 retrospective cohort groups. Group 1 patients received only acetylsalicylic acid (ASA) 81 mg/d started on post-operative day 1. Group 2 patients received IV heparin infusion beginning in the recovery room at a rate of 500 IU/h for the first 24 hours, reduced by 100 IU/h every day to stop on day 5, and then received ASA 81 mg/d afterward. Outcome and complication rates were compared between the two groups for 5 years post-transplant.

RESULTS

We observed a significant reduction in graft thrombosis and graft loss with (0/29) patients in the heparin group vs (7/33) 25.7% from the non-heparin (P<.01) with no differences in complication rates.

CONCLUSIONS

We present a heparin infusion protocol which may help prevent graft thrombosis and graft loss in SPK transplantation.

Treatment with tetrahydrobiopterin overcomes brain death-associated injury in a murine model of pancreas transplantation

Brain death (BD) has been associated with an immunological priming of donor organs and is thought to exacerbate ischemia reperfusion injury (IRI). Recently, we showed that the essential nitric oxide synthase co-factor tetrahydrobiopterin (BH4) abrogates IRI following experimental pancreas transplantation. We therefore studied the effects of BD in a murine model of syngeneic pancreas transplantation and tested the therapeutic potential of BH4 treatment. Compared with sham-operated controls, donor BD resulted in intragraft inflammation reflected by induced IL-1ß, IL-6, VCAM-1, and P-selectin mRNA expression levels and impaired microcirculation after reperfusion (p < 0.05), whereas pretreatment of the BD donor with BH4 significantly improved microcirculation after reperfusion (p < 0.05). Moreover, BD had a devastating impact on cell viability, whereas BH4-treated grafts showed a significantly higher percentage of viable cells (p < 0.001). Early parenchymal damage in pancreatic grafts was significantly more pronounced in organs from BD donors than from sham or non-BD donors (p < 0.05), but BH4 pretreatment significantly ameliorated necrotic lesions in BD organs (p < 0.05). Pretreatment of the BD donor with BH4 resulted in significant recipient survival (p < 0.05). Our data provide novel insights into the impact of BD on pancreatic isografts, further demonstrating the potential of donor pretreatment strategies including BH4 for preventing BD-associated injury after transplantation.

Obestatin Accelerates the Recovery in the Course of Ischemia/Reperfusion-Induced Acute Pancreatitis in Rats

Objective

Several previous studies have shown that obestatin exhibits protective and regenerative effects in some organs including the stomach, kidney, and the brain. In the pancreas, pretreatment with obestatin inhibits the development of cerulein-induced acute pancreatitis, and promotes survival of pancreatic beta cells and human islets. However, no studies investigated the effect of obestatin administration following the onset of experimental acute pancreatitis.

Aim

The aim of this study was to evaluate the impact of obestatin therapy in the course of ischemia/reperfusion-induced pancreatitis. Moreover, we tested the influence of ischemia/reperfusion-induced acute pancreatitis and administration of obestatin on daily food intake and pancreatic exocrine secretion.

Methods

Acute pancreatitis was induced by pancreatic ischemia followed by reperfusion of the pancreas. Obestatin (8nmol/kg/dose) was administered intraperitoneally twice a day, starting 24 hours after the beginning of reperfusion. The effect of obestatin in the course of necrotizing pancreatitis was assessed between 2 and 14 days, and included histological, functional, and biochemical analyses. Secretory studies were performed on the third day after sham-operation or induction of acute pancreatitis in conscious rats equipped with chronic pancreatic fistula.

Results

Treatment with obestatin ameliorated morphological signs of pancreatic damage including edema, vacuolization of acinar cells, hemorrhages, acinar necrosis, and leukocyte infiltration of the gland, and led to earlier pancreatic regeneration. Structural changes were accompanied by biochemical and functional improvements manifested by accelerated normalization of interleukin-1β level and activity of myeloperoxidase and lipase, attenuation of the decrease in pancreatic DNA synthesis, and by an improvement of pancreatic blood flow. Induction of acute pancreatitis by pancreatic ischemia followed by reperfusion significantly decreased daily food intake and pancreatic exocrine secretion. Administration of obestatin at doses used was without significant effect with regard to daily food intake or pancreatic exocrine secretion in sham-operated rats, as well as in rats with acute pancreatitis. On the other hand, obestatin abolished a statistical significance of difference in food intake between animals with AP and control animals without pancreatic fistula and induction of AP.

Conclusion

Treatment with the exogenous obestatin reduces severity of ischemia/reperfusion-induced acute pancreatitis and accelerates recovery in this disease. The involved mechanisms are likely to be multifactorial, and are mediated, at least in part, by anti-inflammatory properties of obestatin.

Pretreatment with obestatin reduces the severity of ischemia/reperfusion-induced acute pancreatitis in rats

Obestatin, as ghrelin, has been originally extracted from the stomach, which remains its major source. Previous studies have shown that administration of obestatin exhibits protective and healing-promoting effects in several organs, including the stomach and kidney. In pancreas, pretreatment with obestatin inhibits the development of cerulein-induced acute pancreatitis and promotes survival of pancreatic beta cells and human islets. The aim of the present study was to check the universality of protective effect of obestatin in the pancreas. For this reason we investigated the influence of obestatin administration on the development of ischemia/reperfusion-induced pancreatitis. Acute pancreatitis was induced by pancreatic ischemia followed by reperfusion of the gland. Obestatin (4, 8 or 16 nmol/kg/dose) was administered intraperitoneally twice: 0.5h before exposure to ischemia, and 3h after the first injection. The effect of obestatin on the course of necrotizing pancreatitis was assessed after 6-h reperfusion, and included histological, functional, and biochemical analyses. Treatment with obestatin reduced morphological signs of pancreatic damage including edema, vacuolization of acinar cells, hemorrhages, acinar necrosis, and leukocyte infiltration of the gland. These effects were accompanied by an improvement of pancreatic DNA synthesis and superoxide dismutase activity, and a decrease in serum level of lipase and pro-inflammatory interleukin-1β. Moreover pretreatment with obestatin reduced myeloperoxidase activity and malondialdehyde concentration in pancreatic tissue of rats with acute pancreatitis.

CONCLUSIONS

Administration of obestatin inhibits the development of ischemia/reperfusion-induced acute pancreatitis. This observation, taken together with previous findings that obestatin protects the pancreas against cerulein-induced pancreatitis, indicates that protective effect of obestatin in the pancreas is universal and independent of the primary cause of acute pancreatitis.

Crucial role for neuronal nitric oxide synthase in early microcirculatory derangement and recipient survival following murine pancreas transplantation

OBJECTIVE

Aim of this study was to identify the nitric oxide synthase (NOS) isoform involved in early microcirculatory derangements following solid organ transplantation.

BACKGROUND

Tetrahydrobiopterin donor treatment has been shown to specifically attenuate these derangements following pancreas transplantation, and tetrahydrobiopterin-mediated protective effects to rely on its NOS-cofactor activity, rather than on its antioxidant capacity. However, the NOS-isoform mainly involved in this process has still to be defined.

METHODS

Using a murine pancreas transplantation model, grafts lacking one of the three NOS-isoforms were compared to grafts from wild-type controls. Donors were treated with either tetrahydrobiopterin or remained untreated. All grafts were subjected to 16 h cold ischemia time and transplanted into wild-type recipients. Following 4 h graft reperfusion, microcirculation was analysed by confocal intravital fluorescence microscopy. Recipient survival was monitored for 50 days.

RESULTS

Transplantation of the pancreas from untreated wild-type donor mice resulted in microcirculatory damage of the transplanted graft and no recipient survived more than 72 h. Transplanting grafts from untreated donor mice lacking either endothelial or inducible NOS led to similar outcomes. In contrast, donor treatment with tetrahydrobiopterin prevented microcirculatory breakdown enabling long-term survival. Sole exception was transplantation of grafts from untreated donor mice lacking neuronal NOS. It resulted in intact microvascular structure and long-term recipient survival, either if donor mice were untreated or treated with tetrahydrobiopterin.

CONCLUSION

We demonstrate for the first time the crucial involvement of neuronal NOS in early microcirculatory derangements following solid organ transplantation. In this model, protective effects of tetrahydrobiopterin are mediated by targeting this isoform.

Donor risk factors, retrieval technique, preservation and ischemia/reperfusion injury in pancreas transplantation

PURPOSE OF REVIEW

Pancreas transplantation is still hampered by a high incidence of early graft loss, and organ quality concerns result in high nonrecovery/discard rates. Demographic donor characteristics, surgical retrieval strategy, preservation fluid and ischemia time are crucial factors in the process of organ selection and are discussed in this review.

RECENT FINDINGS

The donor shortage is driving an increasing utilization of nonideal organs which would previously have been identified as unsuitable. Recent literature suggests that organs from extended criteria donors - older (>45 years), BMI >30  kg/m(2), and donation after cardiac death (DCD) - can achieve the same graft and patient survival as those from standard criteria donors, with the proviso that the accumulation of risk factors and long ischemic times should be avoided. Visual assessment of the pancreas is advisable before declining/accepting a pancreas. University of Wisconsin represents the gold standard solution; however, histidine-tryptophan-ketoglutarate and Celsior result in equal outcomes if cold ischemia time (CIT) is less than 12  h. Currently in pancreas transplantation, there is no proven effective ischemia/reperfusion injury prophylaxis than trying to keep CIT as short as possible.

SUMMARY

Demographic risk factors, inspection of the pancreas by an experienced surgeon and predicted CIT are crucial factors in deciding whether to accept a pancreas for transplantation. However, there is a need for an improved evidence base to determine where to set the 'cut-off' for unsuitable pancreatic grafts.

Intercellular adhesion molecule-1 blockade attenuates inflammatory response and improves microvascular perfusion in rat pancreas grafts

OBJECTIVES

After pancreas transplantation (PTx), early capillary malperfusion and leukocyte recruitment indicate the manifestation of severe ischemia/reperfusion injury (IRI). Oscillatory blood-flow redistribution (intermittent capillary perfusion, IP), leading to an overall decrease in erythrocyte flux, precedes complete microvascular perfusion failure with persistent blood flow cessation. We addressed the role of intercellular adhesion molecule-1 (ICAM-1) for leukocyte-endothelial interactions (LEIs) after PTx and evaluated the contribution of IP and malperfusion.

METHODS

Pancreas transplantation was performed in rats after 18-hour preservation, receiving either isotype-matched IgG or monoclonal anti-ICAM-1 antibodies (10 mg/kg intravenously) once before reperfusion. Leukocyte-endothelial interaction, IP, erythrocyte flux, and functional capillary density, respectively, were examined in vivo during 2-hour reperfusion. Nontransplanted animals served as controls. Tissue samples were analyzed by histomorphometry.

RESULTS

In grafts of IgG-treated animals, IP was encountered already at an early stage after reperfusion and steadily increased over 2 hours, whereas erythrocyte flux declined continuously. In contrast, inhibition of ICAM-1 significantly improved erythrocyte flux and delayed IP appearance by 2 hours. Further, anti-ICAM-1 significantly reduced LEI and leukocyte tissue infiltration when compared to IgG; edema development was less pronounced in response to anti-ICAM-1 monoclonal antibody.

CONCLUSION

Intercellular adhesion molecule-1 blockade significantly attenuates IRI via immediate reduction of LEI and concomitant improvement of capillary perfusion patterns, emphasizing its central role during IRI in PTx.

Prevention of lethal murine pancreas ischemia reperfusion injury is specific for tetrahydrobiopterin

Tetrahydrobiopterin has been shown to efficiently abrogate ischemia reperfusion injury (IRI). However, it is unclear, whether its beneficial action relies on cofactor activity of one of the five known tetrahydrobiopterin-dependent reactions or on its antioxidative capacity. We therefore compared tetrahydrobiopterin with the pterin derivate tetrahydroneopterin (similar biochemical properties, but no nitric oxide synthase cofactor activity) and the antioxidants vitamin C and 5-methyltetrahydrofolate. Donor mice were pretreated with tetrahydrobiopterin, tetrahydroneopterin, vitamin C, or 5-methyltetrahydrofolate. Pancreatic grafts were subjected to 16-h cold ischemia time and implanted in syngeneic recipients. Untreated and nontransplanted animals served as controls. Following 2-h reperfusion, microcirculation was analyzed by intravital fluorescence microscopy. Graft damage was assessed by histology and nitrotyrosine immunostaining, and tetrahydrobiopterin levels were determined by HPLC. Recipient survival served as ultimate readout. Prolonged cold ischemia time resulted in microcirculatory breakdown. Only tetrahydrobiopterin pretreatment succeeded to preserve the capillary net, whereas all other compounds showed no beneficial effects. Along with increased intragraft tetrahydrobiopterin levels during recovery and implantation, only tetrahydrobiopterin pretreatment led to significant reduction of IRI-related parenchymal damage enabling recipient survival. These results show a striking superiority of tetrahydrobiopterin in preventing lethal IRI compared with related compounds and suggest nitric oxide synthases as treatment target.

Pretreatment with cobalt protoporphyrin protects against acute pancreatitis in rats

AIM: To investigate the protective effect of cobalt protoporphyrin (CoPP) against acute pancreatitis (AP) in rats and to explore possible mechanisms involved.

METHODS: Ninety Sprague-Dawley rats were randomly divided into three groups (n = 30 for each group): sham operation (SO) group, AP group, CoPP group. At 6, 12, and 24 h after AP induction, pancreatic pathological changes and serum levels of amylase, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) were detected and compared among different groups. The expression of heme oxygenase-1 (HO-1) mRNA in peripheral blood mononuclear cells (PMBCs) and pancreatic tissue were measured by real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS: At 6, 12, and 24 h after the surgical procedure, rats of the AP and CoPP groups showed typical histopathological changes of AP. The pathological score of pancreatic tissue (24 h: 9.13 ± 1.02, 9.42 ± 0.87 vs 0.00 ± 0.00, both P < 0.01) and serum levels of serum amylase, TNF-α, and IL-6 (24 h: 8 991.7 U/L ± 911.54 U/L, 8 298.0 U/L ± 1 015.67 U/L vs 819.1 U/L ± 177.81 U/L; 157.84 ng/L ± 19.72 ng/L, 142.09 ng/L ± 22.6 ng/L vs 25.71 ng/L ± 0.84 ng/L; 552.92 ng/L ± 72.96 ng/L, 511.03 ng/L ± 57.76 ng/L vs 89.51 ng/L ± 14.73 ng/L, all P < 0.01) in the AP and CoPP groups were significantly elevated compared with the SO group. Pretreatment with CoPP up-regulated the expression of HO-1 mRNA in PBMCs and pancreatic tissue (24 h: 2.795 ± 0.282, 5.174 ± 0.631 vs 0.780 ± 0.105; 16.436 ± 2.219, 28.902 ± 3.791 vs 5.604 ± 0.988, all P < 0.05). Compared with the AP group, at 6 and 12 h after AP induction, the CoPP group had significantly alleviated pathological alterations, and lower pathological score, serum levels of amylase, TNF-α and IL-6 (t = 5.08, 3.74; t = 4.38, 5.32; t = 6.19, 5.03; t = 4.92, 3.65, all P < 0.01).

CONCLUSION: Pretreatment with CoPP can modulate inflammatory reaction and decrease pancreatic injury in AP rats via mechanisms that may be closely related to up-regulation of HO-1 expression to inhibit cytokine production.

In vivo assessment of the hepatic microcirculation after mesenterico-portal bypass (REX-shunt) using orthogonal polarization spectral imaging

BACKGROUND

Extrahepatic portal vein thrombosis, not associated with cirrhosis or tumours, is the second most frequent cause of portal hypertension worldwide. Especially in children, anatomic mesenterico-portal interposition (REX-shunt) has become an established treatment. The changes in hepatic microcirculation after reperfusion of the shunt have not been investigated so far.

AIMS

This study investigates the hepatic microcirculation before and after REX-shunt interposition using orthogonal polarization spectral imaging (OPS).

PATIENTS AND METHODS

Since 2004, three consecutive patients with extrahepatic portal vein thrombosis underwent REX-shunt interposition. We measured the hepatic microcirculation by OPS before and directly after REX-shunt reperfusion and analysed the capillary vessel diameter, red blood cell velocity, functional capillary density and volumetric blood flow. Furthermore, we compared our values with the physiological values of the hepatic microcirculation defined previously by other investigators.

RESULTS

All shunts showed an excellent function in the follow-up investigations. The intra-individual microcirculatory analysis revealed a reduction in the red blood cell velocity after shunt reperfusion in particular.

CONCLUSIONS

Our results provide preliminary evidence for the reversal of the hepatic arterial buffer response following the restoration of the portal venous blood flow. This may be a short-term effect because of the restored portal venous blood flow.

Donor pretreatment with tetrahydrobiopterin saves pancreatic isografts from ischemia reperfusion injury in a mouse model

Depletion of the nitric oxide synthase cofactor tetrahydrobiopterin (H4B) during ischemia and reperfusion is associated with severe graft pancreatitis. Since clinically feasible approaches to prevent ischemia reperfusion injury (IRI) by H4B-substitution are missing we investigated its therapeutic potential in a murine pancreas transplantation model using different treatment regimens. Grafts were subjected to 16 h cold ischemia time (CIT) and different treatment regimens: no treatment, 160 μM H4B to perfusion solution, H4B 50 mg/kg prior to reperfusion and H4B 50 mg/kg before recovery of organs. Nontransplanted animals served as controls. Recipient survival and endocrine graft function were assessed. Graft microcirculation was analyzed 2 h after reperfusion by intravital fluorescence microscopy. Parenchymal damage was assessed by histology and nitrotyrosine immunohistochemistry, H4B tissue levels by high pressure liquid chromatography (HPLC). Compared to nontransplanted controls prolonged CIT resulted in significant microcirculatory deterioration. Different efficacy according to route and timing of administration could be observed. Only donor pretreatment with H4B resulted in almost completely abrogated IRI-related damage showing graft microcirculation comparable to nontransplanted controls and restored intragraft H4B levels, resulting in significant reduction of parenchymal damage (p < 0.002) and improved survival and endocrine function (p = 0.0002 each). H4B donor pretreatment abrogates ischemia-induced parenchymal damage and represents a promising strategy to prevent IRI following pancreas transplantation.

[Long-term therapy with propofol has no impact on microcirculation in medical intensive care patients]

BACKGROUND

Microcirculation has become a major focus of research in critical care medicine due to its growing clinical relevance detecting changes in organ perfusion at an early stage. A negative impact of propofol infusion on microcirculation during short-term anesthesia was described recently. The influence of long-term sedation with propofol on microflow of critical care patients is still unclear.

PATIENTS AND METHODS

Microflow was analyzed using sidestream darkfield microscopy of sublingual mucosa in 28 patients of whom eleven received continuous infusion of propofol. According to current guidelines, microflow was recorded digitally. Quantitative analysis was performed offline in a semiquantitative way (0: no flow; 1: intermittent flow; 2: sluggish flow; 3: continuous flow).

RESULTS

Good microflow rates were detected in sublingual vessels (10-100 microm) in hemodynamically stable, medical intensive care patients. In the majority of cases, continuous flow profiles were recorded. There was no difference in flow rates between patients with and without propofol therapy.

CONCLUSION

In hemodynamically stable intensive care patients, long-term therapy with propofol did not affect sublingual microflow in this small cohort. However, intensive care physicians should keep such possible interactions in mind avoiding administration of these substances in patients with manifested shock. The effects of propofol in hemodynamically impaired patients should be evaluated in further studies.

Protective role of heme oxygenase-1 in pancreatic microcirculatory dysfunction after ischemia/reperfusion in rats

OBJECTIVES

Microcirculatory derangements caused by ischemia and reperfusion (I/R) play a pivotal role in acute and graft pancreatitis. The inducible enzyme heme oxygenase 1 (HO-1) has been shown to decrease I/R injury by modulation of capillary perfusion in other organs. It was the aim of this study to evaluate the effect of HO-1 induction on pancreatic microcirculation after I/R.

METHODS

Rats were randomized into 4 groups: (1) sham controls; (2) 1-hour ischemia and 2-hour reperfusion (I/R); (3) I/R + cobalt protoporphyrin (CoPP), an HO-1 inducer; and (4) I/R + CoPP + tin protoporphyrin, an HO inhibitor. Functional capillary density (FCD) and leukocyte endothelium interaction were analyzed using intravital microscopy during reperfusion. Expression of HO-1 mRNA, HO-1 protein, and HO activity were assessed by Northern blot, Western blot, and an HO activity assay.

RESULTS

Functional capillary density decreased significantly in the I/R group as compared with sham controls. Cobalt protoporphyrin treatment increased FCD to control values. In contrast, HO inhibition in CoPP-pretreated animals lowered FCD and increased leukocyte endothelium interaction significantly. Cobalt protoporphyrin administration increased HO-1 mRNA, protein, and HO activity, whereas activity of the enzyme was reduced after injection of tin protoporphyrin.

CONCLUSIONS

Heme oxygenase 1 plays a beneficial role in pancreatic microcirculatory derangements after I/R. This could be of therapeutic relevance after pancreas transplantation and other forms of postischemic pancreatitis.

Remote preconditioning reduces microcirculatory disorders in pancreatic ischemia/reperfusion injury

OBJECTIVES

Remote preconditioning (RPC) can protect from ischemia/reperfusion injury (IRI). We investigated the influence of RPC in pancreatic IRI.

METHODS

Wistar rats were randomized to 2 hours of ischemia and 2 hours of reperfusion of a pancreatic tail segment with or without 15 minutes of infrarenal ischemia 60 minutes before IRI. Microcirculatory measurements before ischemia and 1 and 2 hours after reperfusion included functional capillary density and leukocyte adherence in postcapillary venules, quantified by intravital fluorescence microscopy. Histology and tissue myeloperoxidase activity were further parameters of pancreatic injury.

RESULTS

Remote preconditioning caused an improvement of microcirculation (functional capillary density: 1 hour after reperfusion, 460 +/- 13 vs 350 +/- 9 cm/cm2; 2 hours after reperfusion, 437 +/- 13 vs 295 +/- 13 cm/cm2; P < 0.01) and reduced inflammatory tissue response (leukocyte adherence in postcapillary venules: 2 hours after reperfusion, 155 +/- 55 vs 748 +/- 187 cells/mm2; P < 0.01). Histology was significantly better in preconditioned animals (IR, 8.1+/- 1.3 score points; RPC, 6.2 +/- 1.3 score points; P < 0.05). The difference in myeloperoxidase activity was not significant (ischemia/reperfusion [IR], 105 +/- 72; RPC, 245 +/- 209 mU x min(-1) x mg(ti)(-1); P = 0.13).

CONCLUSIONS

With our dynamic functional microcirculatory measurements, we could demonstrate that RPC is a feasible method to reduce experimental pancreatic IRI. This was seen in an attenuation of nutritive tissue perfusion and a reduction of inflammatory tissue response and a lower histological damage. Because it is easy to perform before organ harvest, RPC could be a step to improve organ procurement in pancreas transplantation. Clinical studies are the next step to evaluate RPC in pancreas transplantation.

Simultaneous pancreas--kidney transplantation: to anticoagulate or not? Is that a question?

Pancreas graft loss due to venous thrombosis is the leading non-immunological cause for graft failure following kidney-pancreas transplantation. Thromboelastography (TEG)-directed anticoagulation protocol has shown that approximately one-third of the patients undergoing pancreas transplantation require therapeutic anticoagulation to prevent the occurrence of graft thrombosis. This article presents the argument for individualised anticoagulation in these patients based on their TEG tracings and suggests the use of TEG in patients undergoing pancreas transplantation.

In vivo Visualization of Early Microcirculatory Changes following Ischemia/Reperfusion Injury in Human Kidney Transplantation

To determine whether microcirculatory changes following ischemia/reperfusion (I/R) may serve as predictors for subsequent graft dysfunction, we used noninvasive orthogonal polarization spectral (OPS) imaging to directly visualize and quantify cortical kidney microcirculation. In a total of 13 combined kidney/pancreas recipients, following reperfusion (5/30 min) microcirculatory parameters such as capillary diameter, functional capillary density (FCD) and red-blood-cell velocity (V(RBC)) of the renal graft were analyzed. From these parameters, a heterogeneity index (HI) and volumetric capillary blood flow (vCBF) were calculated. In addition, the extent of graft injury was determined by daily analysis of serum creatinine, blood urea nitrogen, C-reactive protein and systemic leukocyte count for 7 days post-transplant. At early reperfusion, a heterogeneous perfusion pattern with oscillating flow and scattered microvascular thrombosis of peritubular capillaries, resembling a 'no reflow', was observed. FCD was constant throughout the entire reperfusion period, whereas HI, capillary diameters, V(RBC) and vCBF increased. The latter showed a significant positive correlation with creatinine changes between days 1 and 3. So far our finding of a positive correlation of early microvascular changes (vCBF) and clinical parameters (creatinine) indicate a possible therapeutic implication of OPS imaging to predict early I/R-induced renal graft dysfunction.

Influence of glutamine on pancreatic blood flow and apoptosis of pancreatic acinar in rats with severe acute pancreatitis

OBJECTIVE

To investigate the role of glutamine on splanchnic blood flow, apoptosis of pancreatic acinar and the underlying mechanism in rats with severe acute pancreatitis.

METHODS

Forty-eight rats were randomized into two groups: the glutamine group (n = 24) and the severe acute pancreatitis group (n = 24). Jejunotomy was performed in all rats: the glutamine group also received glutamine, and the severe acute pancreatitis group received normal saline. Each group was then subdivided into three subgroups of eight rats each, with the rats be killed at 12, 24 and 36 h after the operation, respectively. A control group underwent sham operation (n = 8). The regional pancreatic microvascular blood flow was measured by Doppler ultrasound. The blood flow of the portal vein, splenic artery and superior mesenteric artery were also recorded. Apoptosis of pancreatic acinar cells was evaluated by TUNEL method.

RESULTS

The regional pancreatic microvascular blood flow (KHz) decreased significantly in the severe acute pancreatitis group (P < 0.01), and continued to decrease after 24 h (vs. 12 h, P < 0.01). The blood flow of the portal vein, splenic artery and superior mesenteric artery also decreased in the severe acute pancreatitis group. The glutamine group showed increased regional pancreatic microvascular blood flows, as well as increased blood flow of the portal vein, splenic artery and superior mesenteric artery (vs. the severe acute pancreatitis group, P < 0.01). The apoptotic index of pancreatic acinar in the glutamine group was higher than in the severe acute pancreatitis group (P < 0.01), and both were much higher than that in the control group (P < 0.01).

CONCLUSIONS

Enteral administration of glutamine increased the splanchnic blood flow in severe acute pancreatitis rats. The apoptotic index of pancreatic acinar was negatively correlated with the severity of the disease. The interrelation between glutamine and apoptosis in severe acute pancreatitis is worthy of further investigation.

Single-shot antithrombin in human pancreas-kidney transplantation: reduction of reperfusion pancreatitis and prevention of graft thrombosis*

Reperfusion pancreatitis and graft thrombosis often induce early graft loss in simultaneous pancreas-kidney (SPK) transplantation. Antithrombin (AT) is a coagulatory inhibitor with pleiotropic activities that reduces experimental ischemia/reperfusion injury. This study retrospectively analyses prophylactic high-dose AT application in patients with first SPK. In an university transplantation center, 53 consecutive patients with SPK were studied without randomization. In one group, 3000 IU of AT was given intravenously before pancreatic reperfusion (AT, n = 24). Patients receiving standard therapy including postoperative AT supplementation (controls, n = 29) served as controls. Daily blood sampling was performed as a part of the clinical routine during four postoperative days. There were no differences in demographic and laboratory parameters [donor/recipient age, ischemia time, perfusion solution, body weight, mismatches] between both groups. Baseline creatinine values were lower in the control group versus AT group (P < 0.05). Coagulatory parameters and bleeding incidence were not influenced by AT, while incidence of graft thrombosis was reduced (control: 7/29; AT: 4/24; relative reduction of risk: -33%; P < 0.05). Single-shot AT application during SPK modulated serum lipase activity on postoperative days 2 and 3, and minimized risk for graft thromboses without increasing perioperative bleeding. This new concept should deserve testing in a prospective clinical trial.

Ciclosporin aggravates tissue damage in ischemia reperfusion-induced acute pancreatitis

OBJECTIVES

Ischemia reperfusion (I/R)-associated early graft pancreatitis is a major complication after pancreas transplantation. The influence of immunosuppressants on graft pancreatitis remains unclear. The aim of this study was to evaluate ciclosporin and tacrolimus in experimental pancreatic I/R.

METHODS

Moderate pancreatitis was induced in rats by I/R injury. Animals were assigned to 4 groups: (1) control without I/R, (2) I/R without therapy, (3) I/R + ciclosporin, or (4) I/R + tacrolimus. After 24 hours, pancreatic damage was evaluated by amylase, endothelin 1, thromboxane A2, and histology. Additionally, microcirculation was evaluated 12 hours after reperfusion by intravital microscopy.

RESULTS

I/R significantly increased amylase compared with controls, with maximum levels after ciclosporin treatment. Histology showed comparable tissue injury in control and tacrolimus-treated animals. Ciclosporin-treated animals developed significantly (P < 0.05) more inflammation and necrosis compared with the other groups. Erythrocyte velocity evaluated by intravital microscopy was reduced in all animals after I/R. This was significantly pronounced after ciclosporin application. There was a significant increase of adherent leukocytes and platelets in ciclosporin-treated animals compared with both other groups.

CONCLUSIONS

Tacrolimus does not negatively influence I/R-induced pancreatitis, whereas ciclosporin aggravates pancreatic tissue damage after I/R. These effects should be evaluated in the clinical setting of pancreas transplantation.