Validating human and mouse tissues commonly used in atherosclerosis research with coronary and aortic reference tissue: similarities but profound differences in disease initiation and plaque stability

Objective

Characterization of the atherosclerotic process fully relies on histological evaluation and staging through a consensus grading system. So far, a head-to-head comparison of atherosclerotic process in experimental models and tissue resources commonly applied in atherosclerosis research with the actual human atherosclerotic process is missing.

Material and Methods

Aspects of the atherosclerotic process present in established murine atherosclerosis models and human carotid endarterectomy specimen were systematically graded using the modified American Heart Association histological classification (Virmani classification). Aspects were aligned with the atherosclerotic process observed in human coronary artery and aortic atherosclerosis reference tissues that were available through biobanks based on human tissue/organ donor material.

Results

Apart from absent intraplaque hemorrhages in aortic lesions, the histological characteristics of the different stages of human coronary and aortic atherosclerosis are similar. Carotid endarterectomy samples all represent end-stage "fibrous calcified plaque" lesions, although secondary, progressive, and vulnerable lesions with gross morphologies similar to coronary/aortic lesions occasionally present along the primary lesions. For the murine lesions, clear histological parallels were observed for the intermediate lesion types ("pathological intimal thickening," and "early fibroatheroma"). However, none of the murine lesions studied progressed to an equivalent of late fibroatheroma or beyond. Notable contrasts were observed for disease initiation: whereas disease initiation in humans is characterized by a mesenchymal cell influx in the intima, the earliest murine lesions are exclusively intimal, with subendothelial accumulation foam cells. A mesenchymal (and medial) response are absent. In fact, it is concluded that the stage of "adaptive intimal thickening" is absent in all mouse models included in this study.

Conclusions

The Virmani classification for coronary atherosclerosis can be applied for systematically grading experimental and clinical atherosclerosis. Application of this histological grading tool shows clear parallels for intermediate human and murine atherosclerotic lesions. However, clear contrasts are observed for disease initiation, and late stage atherosclerotic lesions. Carotid endarterectomy all represent end-stage fibrous calcified plaque lesions, although secondary earlier lesions may present in a subset of samples.

Quality assessment of donor liver procurement surgery using an unadjusted CUSUM prediction model. A practical nationwide evaluation

BACKGROUND

The aim of this study was to analyze the value of the unadjusted CUSUM graph of liver surgical injury and discard rates in organ procurement in the Netherlands.

METHODS

Unadjusted CUSUM graphs were plotted for surgical injury (C event) and discard rate (C2 event) from procured livers accepted for transplantation for each local procurement team compared with the total national cohort. The average incidence for each outcome was used as benchmark based on procurement quality forms (Sep 2010-Oct 2018). The data from the five Dutch procuring teams were blind-coded.

RESULTS

The C and C2 event rate were 17% and 1.9%, respectively (n = 1265). A total of 12 CUSUM charts were plotted for the national cohort and the five local teams. National CUSUM charts showed an overlapping "alarm signal." This overlapping signal for both C and C2, albeit a different time period, was only found in one local team. The other CUSUM alarm signal went off for two separate local teams, but only for C events or C2 events respectively, and at different points in time. The other remaining CUSUM charts showed no alarm signaling.

CONCLUSION

The unadjusted CUSUM chart is a simple and effective monitoring tool in following performance quality of organ procurement for liver transplantation. Both national and local recorded CUSUMs are useful to see the implication of national and local effects on organ procurement injury. Both procurement injury and organ discard are equally important in this analysis and need to be separately CUSUM charted.

Study protocol for a multicentre nationwide prospective cohort study to investigate the natural course and clinical outcome in benign liver tumours and cysts in the Netherlands: the BELIVER study

INTRODUCTION

Benign liver tumours and cysts (BLTCs) comprise a heterogeneous group of cystic and solid lesions, including hepatic haemangioma, focal nodular hyperplasia and hepatocellular adenoma. Some BLTCs, for example, (large) hepatocellular adenoma, are at risk of complications. Incidence of malignant degeneration or haemorrhage is low in most other BLTCs. Nevertheless, the diagnosis BLTC may carry a substantial burden and patients may be symptomatic, necessitating treatment. The indications for interventions remain matter of debate. The primary study aim is to investigate patient-reported outcomes (PROs) of patients with BLTCs, with special regards to the influence of invasive treatment as compared with the natural course of the disease.

METHODS AND ANALYSIS

A nationwide observational cohort study of patients with BLTC will be performed between October 2021 and October 2026, the minimal follow-up will be 2 years. During surveillance, a questionnaire regarding symptoms and their impact will be sent to participants on a biannual basis and more often in case of invasive intervention. The questionnaire was previously developed based on PROs considered relevant to patients with BLTCs and their caregivers. Most questionnaires will be administered by computerised adaptive testing through the Patient-Reported Outcomes Measurement Information System. Data, such as treatment outcomes, will be extracted from electronic patient files. Multivariable analysis will be performed to identify patient and tumour characteristics associated with significant improvement in PROs or a complicated postoperative course.

ETHICS AND DISSEMINATION

The study was assessed by the Medical Ethics Committee of the University Medical Center Groningen and the Amsterdam UMC. Local consultants will provide information and informed consent will be asked of all patients. Results will be published in a peer-reviewed journal.

STUDY REGISTRATION

NL8231-10 December 2019; Netherlands Trial Register.

Donor characteristics and their impact on kidney transplantation outcomes: Results from two nationwide instrumental variable analyses based on outcomes of donor kidney pairs accepted for transplantation

BACKGROUND

Donor-characteristics and donor characteristics-based decision algorithms are being progressively used in the decision process whether or not to accept an available donor kidney graft for transplantation. While this may improve outcomes, the performance characteristics of the algorithms remains moderate. To estimate the impact of donor factors of grafts accepted for transplantation on transplant outcomes, and to test whether implementation of donor-characteristics-based algorithms in clinical decision-making is justified, we applied an instrumental variable analysis to outcomes for kidney donor pairs transplanted in different individuals.

METHODS

This analysis used (dis)congruent outcomes of kidney donor pairs as an instrument and was based on national transplantation registry data for all donor kidney pairs transplanted in separate individuals in the Netherlands (1990-2018, 2,845 donor pairs), and the United Kingdom (UK, 2000-2018, 11,450 pairs). Incident early graft loss (EGL) was used as the primary discriminatory factor. It was reasoned that a scenario with a dominant impact of donor variables on transplantation outcomes would result in high concordance of EGL in both recipients, whilst dominance of asymmetrical outcomes could indicate a more complex scenario, involving an interaction of donor, procedural and recipient factors.

FINDINGS

Incidences of congruent EGL (Netherlands: 1·2%, UK: 0·7%) were slightly lower than the arithmetical (stochastic) incidences, suggesting that once a graft has been accepted for transplantation, donor factors minimally contribute to incident EGL. A long-term impact of donor factors was explored by comparing outcomes for functional grafts from donor pairs with asymmetrical vs. symmetrical outcomes. Recipient survival was similar for both groups, but a slightly compromised graft survival was observed for grafts with asymmetrical outcomes in the UK cohort: (10-years Hazard Ratio for graft loss: 1·18 [1·03-1·35] p<0·018); and 5 years eGFR (48·6 [48·3-49·0] vs. 46·0 [44·5-47·6] ml/min in the symmetrical outcome group, p<0·001).

INTERPRETATION

Our results suggest that donor factors for kidney grafts deemed acceptable for transplantation impact minimally on transplantation outcomes. A strong reliance on donor factors and/or donor-characteristics-based decision algorithms could result in unjustified rejection of grafts. Future efforts to optimize transplant outcomes should focus on a better understanding of the recipient factors underlying transplant outcomes.

FUNDING

None.

Circumventing the Crabtree effect in cell culture: A systematic review

Metabolic reprogramming and mitochondrial dysfunction are central elements in a broad variety of physiological and pathological processes. While cell culture established itself as a versatile technique for the elaboration of physiology and disease, studying metabolism using standard cell culture protocols is profoundly interfered by the Crabtree effect. This phenomenon refers to the adaptation of cultured cells to a glycolytic phenotype, away from oxidative phosphorylation in glucose-containing medium, and questions the applicability of cell culture in certain fields of research. In this systematic review we aim to provide a comprehensive overview and critical appraisal of strategies reported to circumvent the Crabtree effect.

Donor diabetes mellitus is a risk factor for diminished outcome after liver transplantation: a nationwide retrospective cohort study

With the growing incidence of diabetes mellitus (DM), an increasing number of organ donors with DM can be expected. We sought to investigate the association between donor DM with early post‐transplant outcomes. From a national cohort of adult liver transplant recipients (1996–2016), all recipients transplanted with a liver from a DM donor (n = 69) were matched 1:2 with recipients of livers from non‐DM donors (n = 138). The primary end‐point included early post‐transplant outcome, such as the incidence of primary nonfunction (PNF), hepatic artery thrombosis (HAT), and 90‐day graft survival. Cox regression analysis was used to analyze the impact of donor DM on graft failure. PNF was observed in 5.8% of grafts from DM donors versus 2.9% of non‐DM donor grafts (P = 0.31). Recipients of grafts derived from DM donors had a higher incidence of HAT (8.7% vs. 2.2%, P = 0.03) and decreased 90‐day graft survival (88.4% [70.9–91.1] vs. 96.4% [89.6–97.8], P = 0.03) compared to recipients of grafts from non‐DM donors. The adjusted hazard ratio for donor DM on graft survival was 2.21 (1.08–4.53, P = 0.03). In conclusion, donor DM is associated with diminished outcome early after liver transplantation. The increased incidence of HAT after transplantation of livers from DM donors requires further research.

Results of an explorative clinical evaluation suggest immediate and persistent post-reperfusion metabolic paralysis drives kidney ischemia reperfusion injury

Delayed graft function is the manifestation of ischemia reperfusion injury in the context of kidney transplantation. While hundreds of interventions successfully reduce ischemia reperfusion injury in experimental models, all clinical interventions have failed. This explorative clinical evaluation examined possible metabolic origins of clinical ischemia reperfusion injury combining data from 18 pre- and post-reperfusion tissue biopsies with 36 sequential arteriovenous blood samplings over the graft in three study groups. These groups included living and deceased donor grafts with and without delayed graft function. Group allocation was based on clinical outcome. Magic angle NMR was used for tissue analysis and mass spectrometry-based platforms were used for plasma analysis. All kidneys were functional at one-year. Integration of metabolomic data identified a discriminatory profile to recognize future delayed graft function. This profile was characterized by post-reperfusion ATP/GTP catabolism (significantly impaired phosphocreatine recovery and significant persistent (hypo)xanthine production) and significant ongoing tissue damage. Failing high-energy phosphate recovery occurred despite activated glycolysis, fatty-acid oxidation, glutaminolysis and autophagia, and related to a defect at the level of the oxoglutarate dehydrogenase complex in the Krebs cycle. Clinical delayed graft function due to ischemia reperfusion injury associated with a post-reperfusion metabolic collapse. Thus, efforts to quench delayed graft function due to ischemia reperfusion injury should focus on conserving metabolic competence, either by preserving the integrity of the Krebs cycle and/or by recruiting metabolic salvage pathways.

Postponed or immediate drainage of infected necrotizing pancreatitis (POINTER trial): study protocol for a randomized controlled trial

Background

Infected necrosis complicates 10% of all acute pancreatitis episodes and is associated with 15–20% mortality. The current standard treatment for infected necrotizing pancreatitis is the step-up approach (catheter drainage, followed, if necessary, by minimally invasive necrosectomy). Catheter drainage is preferably postponed until the stage of walled-off necrosis, which usually takes 4 weeks. This delay stems from the time when open necrosectomy was the standard. It is unclear whether such delay is needed for catheter drainage or whether earlier intervention could actually be beneficial in the current step-up approach. The POINTER trial investigates if immediate catheter drainage in patients with infected necrotizing pancreatitis is superior to the current practice of postponed intervention.

Methods

POINTER is a randomized controlled multicenter superiority trial. All patients with necrotizing pancreatitis are screened for eligibility. In total, 104 adult patients with (suspected) infected necrotizing pancreatitis will be randomized to immediate (within 24 h) catheter drainage or current standard care involving postponed catheter drainage. Necrosectomy, if necessary, is preferably postponed until the stage of walled-off necrosis, in both treatment arms. The primary outcome is the Comprehensive Complication Index (CCI), which covers all complications between randomization and 6-month follow up. Secondary outcomes include mortality, complications, number of (repeat) interventions, hospital and intensive care unit (ICU) lengths of stay, quality-adjusted life years (QALYs) and direct and indirect costs. Standard follow-up is at 3 and 6 months after randomization.

Discussion

The POINTER trial investigates if immediate catheter drainage in infected necrotizing pancreatitis reduces the composite endpoint of complications, as compared with the current standard treatment strategy involving delay of intervention until the stage of walled-off necrosis.

Trial registration

ISRCTN, 33682933. Registered on 6 August 2015. Retrospectively registered.

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3315-6) contains supplementary material, which is available to authorized users.

Superiority of Step-up Approach vs Open Necrosectomy in Long-term Follow-up of Patients With Necrotizing Pancreatitis

BACKGROUND & AIMS

In a 2010 randomized trial (the PANTER trial), a surgical step-up approach for infected necrotizing pancreatitis was found to reduce the composite endpoint of death or major complications compared with open necrosectomy; 35% of patients were successfully treated with simple catheter drainage only. There is concern, however, that minimally invasive treatment increases the need for reinterventions for residual peripancreatic necrotic collections and other complications during the long term. We therefore performed a long-term follow-up study.

METHODS

We reevaluated all the 73 patients (of the 88 patients randomly assigned to groups) who were still alive after the index admission, at a mean 86 months (±11 months) of follow-up. We collected data on all clinical and health care resource utilization endpoints through this follow-up period. The primary endpoint was death or major complications (the same as for the PANTER trial). We also measured exocrine insufficiency, quality of life (using the Short Form-36 and EuroQol 5 dimensions forms), and Izbicki pain scores.

RESULTS

From index admission to long-term follow-up, 19 patients (44%) died or had major complications in the step-up group compared with 33 patients (73%) in the open-necrosectomy group (P = .005). Significantly lower proportions of patients in the step-up group had incisional hernias (23% vs 53%; P = .004), pancreatic exocrine insufficiency (29% vs 56%; P = .03), or endocrine insufficiency (40% vs 64%; P = .05). There were no significant differences between groups in proportions of patients requiring additional drainage procedures (11% vs 13%; P = .99) or pancreatic surgery (11% vs 5%; P = .43), or in recurrent acute pancreatitis, chronic pancreatitis, Izbicki pain scores, or medical costs. Quality of life increased during follow-up without a significant difference between groups.

CONCLUSIONS

In an analysis of long-term outcomes of trial participants, we found the step-up approach for necrotizing pancreatitis to be superior to open necrosectomy, without increased risk of reinterventions.

Retrospective study on detection, treatment, and clinical outcome of graft thrombosis following pancreas transplantation

Complete graft thrombosis is the leading cause of early graft loss following pancreas transplantation. Partial thrombosis is usually subclinical and discovered on routine imaging. Treatment options may vary in such cases. We describe the incidence and relevance of partial graft thrombosis in a large transplant center. All consecutive pancreas transplantation at our center (2004–2015) were included in this study. Radiological follow‐up, type and quantity of thrombosis prophylaxis, complications and, graft and patient survival were collected. Partial thrombosis and follow‐up were also studied. All 230 pancreas transplantations were included in the analysis. Computed tomography was performed in most cases (89.1%). Early graft failure occurred in 23 patients (13/23 due to graft thrombosis, 3/23 bleeding, 1/23 anastomotic leakage, 6/23 secondary to antibody mediated rejection). There was evidence of partial thrombosis in 59 cases (26%), of which the majority was treated with heparin and a vitamin K antagonist with graft preservation in 57/59 patients (97%). Thrombosis is the leading cause of early graft loss following pancreas transplantation. Computed tomography allows for early detection of partial thrombosis, which is usually subclinical. Partial graft thrombosis occurs in about 25% of all cases. In this series, treatment with anticoagulant therapy (heparin and vitamin K antagonist) resulted in graft preservation in almost all cases.

Qualitative evaluation of coronary atherosclerosis in a large cohort of young and middle-aged Dutch tissue donors implies that coronary thrombo-embolic manifestations are stochastic

Background and aims

With the intention to gain support for the hypothesis that incident ischemic complications of atherosclerotic disease involve a stochastic aspect, we performed a histological, qualitative evaluation of the epidemiology of coronary atherosclerotic disease in a cohort of aortic valve donors.

Patients and methods

Donors (n = 695, median age 54, range 11–65 years) were dichotomized into a non-cardiovascular (non-CVD) and a cardiovascular disease death (CVD) group. Consecutive 5 mm proximal left coronary artery segments were Movat stained, and the atherosclerotic burden for each segment was graded (revised AHA-classification).

Results

Non-CVD and CVD groups showed steep increase of atherosclerosis severity beyond the age of 40, resulting in an endemic presence of advanced atherosclerosis in men over 40 and women over 50 years. In fact, only 19% of the non-CVD and 6% of the CVD donors over 40 years were classified with a normal LCA or a so called non-progressive lesion type. Fibrous calcified plaques (FCP), the consolidated remnants of earlier ruptured lesions, dominated in both non-CVD and CVD donors. Estimates of the atherosclerosis burden (i.e. average lesion grade, proportion of FCPs, and average number of FCPs per cross-section) were all higher in the CVD group (p<1.10⁻¹⁶, p<0.0001, and p<0.05, respectively).

Conclusions

Dominance of consolidated FCP lesions in males over 40 and females over 50 years, show that plaque ruptures in the left coronary artery are common. However, the majority of these ruptures remain asymptomatic. This implies that the atherosclerotic process is repetitive. A relative difference in disease burden between CVD and non-CVD donors supports the concept that complications of atherosclerotic disease involve a stochastic element.

CRIPTO promotes an aggressive tumour phenotype and resistance to treatment in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related death worldwide. Despite increasing treatment options for this disease, prognosis remains poor. CRIPTO (TDGF1) protein is expressed at high levels in several human tumours and promotes oncogenic phenotype. Its expression has been correlated to poor prognosis in HCC. In this study, we aimed to elucidate the basis for the effects of CRIPTO in HCC. We investigated CRIPTO expression levels in three cohorts of clinical cirrhotic and HCC specimens. We addressed the role of CRIPTO in hepatic tumourigenesis using Cre-loxP-controlled lentiviral vectors expressing CRIPTO in cell line-derived xenografts. Responses to standard treatments (sorafenib, doxorubicin) were assessed directly on xenograft-derived ex vivo tumour slices. CRIPTO-overexpressing patient-derived xenografts were established and used for ex vivo drug response assays. The effects of sorafenib and doxorubicin treatment in combination with a CRIPTO pathway inhibitor were tested in ex vivo cultures of xenograft models and 3D cultures. CRIPTO protein was found highly expressed in human cirrhosis and hepatocellular carcinoma specimens but not in those of healthy participants. Stable overexpression of CRIPTO in human HepG2 cells caused epithelial-to-mesenchymal transition, increased expression of cancer stem cell markers, and enhanced cell proliferation and migration. HepG2-CRIPTO cells formed tumours when injected into immune-compromised mice, whereas HepG2 cells lacking stable CRIPTO overexpression did not. High-level CRIPTO expression in xenograft models was associated with resistance to sorafenib, which could be modulated using a CRIPTO pathway inhibitor in ex vivo tumour slices. Our data suggest that a subgroup of CRIPTO-expressing HCC patients may benefit from a combinatorial treatment scheme and that sorafenib resistance may be circumvented by inhibition of the CRIPTO pathway. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

No indications for platelet activation in acute clinical myocardial or renal ischemia/reperfusion injury

The pathophysiology of ischemia/reperfusion (I/R) injury is complex and poorly understood. Animal studies imply platelet activation as an initiator of the inflammatory response upon reperfusion. However, it remains unclear whether and how these results translate to clinical I/R. This study evaluates putative platelet activation in the context of two forms of clinical I/R (heart valve surgery with aortic-cross clamping, n = 39 and kidney transplantation, n = 34). The technique of sequential selective arteriovenous (AV) measurements over the reperfused organs was applied to exclude the influence of systemic changes occurring during surgery while simultaneously maximizing sensitivity. Platelet activation and degranulation was evaluated by assessing the expression levels of established markers, i.e. RANTES (Regulated on Activation, Normal T Cell Expressed and Secreted), β-thromboglobulin (β-TG), platelet-derived growth factor (PDGF)-BB and CXCL8 (known as interleukin-8), and by employing an in-vitro assay that specifically tests for platelet excitability. Moreover, a histological analysis was performed by means of CD41 staining. Results show stable RANTES, β-TG, PDGF-BB and CXCL8 AV-concentrations within the first half hour over the reperfused organs, suggesting that myocardial and renal I/R are not associated with platelet activation. Results from the platelet excitability assay were in line with these findings and indicated reduced and stable platelet excitability following renal and myocardial reperfusion, respectively. Histological analysis yield evidence of platelet marginalization in the reperfused organs. In conclusion, results from this study do not support a role for platelet activation in early phases of clinical I/R injury.

The hypoxanthine-xanthine oxidase axis is not involved in the initial phase of clinical transplantation-related ischemia-reperfusion injury

The hypoxanthine-xanthine oxidase (XO) axis is considered to be a key driver of transplantation-related ischemia-reperfusion (I/R) injury. Whereas interference with this axis effectively quenches I/R injury in preclinical models, there is limited efficacy of XO inhibitors in clinical trials. In this context, we considered clinical evaluation of a role for the hypoxanthine-XO axis in human I/R to be relevant. Patients undergoing renal allograft transplantation were included (n = 40) and classified based on duration of ischemia (short, intermediate, and prolonged). Purine metabolites excreted by the reperfused kidney (arteriovenous differences) were analyzed by the ultra performance liquid chromatography-tandem mass spectrometer (UPLCMS/MS) method and tissue XO activity was assessed by in situ enzymography. We confirmed progressive hypoxanthine accumulation (P < 0.006) during ischemia, using kidney transplantation as a clinical model of I/R. Yet, arteriovenous concentration differences of uric acid and in situ enzymography of XO did not indicate significant XO activity in ischemic and reperfused kidney grafts. Furthermore, we tested a putative association between hypoxanthine accumulation and renal oxidative stress by assessing renal malondialdehyde and isoprostane levels and allantoin formation during the reperfusion period. Absent release of these markers is not consistent with an association between ischemic hypoxanthine accumulation and postreperfusion oxidative stress. On basis of these data for the human kidney we hypothesize that the role for the hypoxanthine-XO axis in clinical I/R injury is less than commonly thought, and as such the data provide an explanation for the apparent limited clinical efficacy of XO inhibitors.

Professionalization of surgical abdominal organ recovery leading to an increase in pancreatic allografts accepted for transplantation in the Netherlands: a serial analysis

Professional abdominal organ recovery with certification has been mandatory in the Netherlands since 2010. This study analyses the effects of certification (January 2010-September 2015) on pancreas transplantation and compares it to an era before certification (February 2002-May 2008) for surgical injuries and the number of pancreases transplanted. A total of 264 cases were analysed. Eighty-four recovered pancreases (31.8%) with surgically injuries were encountered. Forty-six of those were surgically salvaged for transplantation, resulting in a total of 226 (85.6%) being transplanted. It was found that certified surgeons recovered grafts from older donors (36.8 vs. 33.3; P = 0.021), more often from donation after circulatory death (DCD) donors (18% vs. 0%; P < 0.001) and had less surgical injuries (21.6% vs. 41.0%; P < 0.001). Certification (OR: 0.285; P < 0.001) and surgeons from a pancreas transplant centre (OR: 0.420; P = 0.002) were independent risk factors for surgical organ injury. Predictors for proceeding to the actual pancreas transplantation were a recovering surgeon from a pancreas transplantation centre (OR: 3.230; P = 0.003), certification (OR: 3.750; P = 0.004), donation after brain death (DBD) (OR: 8.313; P = 0.002) and donor body mass index (BMI) (OR: 0.851; P = 0.023). It is concluded that certification in abdominal organ recovery will limit the number of surgical injuries in pancreas grafts which will translate in more pancreases available for transplantation.

Histological evaluation disqualifies IMT and calcification scores as surrogates for grading coronary and aortic atherosclerosis

BACKGROUND/OBJECTIVES

Carotid intimal media thickness (IMT) and coronary calcium scores (CCS) are thought to reflect atherosclerotic burden. The validity of this assumption for IMT is challenged by recent meta-analyses; for CCS by absence of a relationship between negative scores, and freedom of future events. As such, we considered evaluation of the relationship between tissue IMT and CCS, and extend of atherosclerotic disease relevant.

METHODS

Analyses were performed on donor aortas obtained during renal graft procurement, and on coronary arteries collected during heart valve procurement for tissue donation. Movat pentachrome and Hematoxylin staining was performed, and the degree of atherosclerosis histologically graded. IMT and presence of calcium deposits were quantified on graded tissue sections.

RESULTS

304 aortas and 185 coronary arteries covering the full atherosclerotic spectrum were evaluated. Aortas and coronaries showed similar relationships between tissue IMT and degree of atherosclerosis, with gradual increase in tissue IMT during earlier phases of atherosclerosis (r=0.68 and r=0.30, P<0.00001 for aorta and coronaries respectively), followed by plateauing of the curve in intermediate and advanced stages. Results for tissue IMT reveal high variability, resulting in wide confidence intervals. Results for CCS are similar for aorta and coronaries, with calcium depositions limited to advanced lesions.

CONCLUSIONS

Histological IMT measurements for the aorta and coronaries show large variations around the trend and plateauing of, and possibly reductions in IMT in late stage atherosclerotic disease. These observations for the aorta and coronaries may (partly) explain the limited benefit of including carotid IMT in risk prediction algorithms.

Succinate Accumulation and Ischemia-Reperfusion Injury: Of Mice but Not Men, a Study in Renal Ischemia-Reperfusion

A recent seminal paper implicated ischemia-related succinate accumulation followed by succinate-driven reactive oxygen species formation as a key driver of ischemia-reperfusion injury. Although the data show that the mechanism is universal for all organs tested (kidney, liver, heart, and brain), a remaining question is to what extent these observations in mice translate to humans. We showed in this study that succinate accumulation is not a universal event during ischemia and does not occur during renal graft procurement; in fact, tissue succinate content progressively decreased with increasing graft ischemia time (p < 0.007). Contrasting responses were also found with respect to mitochondrial susceptibility toward ischemia and reperfusion, with rodent mitochondria robustly resistant toward warm ischemia but human and pig mitochondria highly susceptible to warm ischemia (p < 0.05). These observations suggest that succinate-driven reactive oxygen formation does not occur in the context of kidney transplantation. Moreover, absent allantoin release from the reperfused grafts suggests minimal oxidative stress during clinical reperfusion.

The dorsal pancreatic artery in pancreas procurement and transplantation: anatomical considerations and potential implications

AIM

Organ procurement errors account for almost 20% of discarded pancreatic allografts. For this reason, the anatomical significance of the dorsal pancreatic artery (DPA) was reviewed.

METHODS

A strategy on dealing with an often overlooked DPA is evaluated.

RESULTS

The DPA provides together with the splenic artery the main blood supply to the pancreatic tail. Three different arterial variations have been described. In the rare instances when the DPA arises from the common hepatic artery or the celiac trunk, instead of the splenic origin, the DPA can easily be overlooked by surgeons not familiar with this artery. This may result in an unintentional damage to the pancreatic tail blood supply. If unrecognized during the back-table inspection, it could potentially jeopardize the pancreatic graft after reperfusion. When a cut DPA is encountered during inspection, efforts should be attempted to revascularize the graft, especially if there is no backflow from the splenic artery as sign of absent collateral circulation.

CONCLUSION

The DPA may play a more prominent role in the vascularization of pancreas transplants than currently assumed. Better understanding of the vascular anatomy may lead to improved results in pancreas transplantation.

Systematic Evaluation of the Cellular Innate Immune Response During the Process of Human Atherosclerosis

Background

The concept of innate immunity is well recognized within the spectrum of atherosclerosis, which is primarily dictated by macrophages. Although current insights to this process are largely based on murine models, there are fundamental differences in the atherosclerotic microenvironment and associated inflammatory response relative to humans. In this light, we characterized the cellular aspects of innate immune response in normal, nonprogressive, and progressive human atherosclerotic plaques.

Methods and Results

A systematic analysis of innate immune response was performed on 110 well‐characterized human perirenal aortic plaques with immunostaining for specific macrophage subtypes (M1 and M2 lineage) and their activation markers, neopterin and human leukocyte antigen–antigen D related (HLA‐DR), together with dendritic cells (DCs), natural killer (NK) cells, mast cells, neutrophils, and eosinophils. Normal aortae were devoid of low‐density lipoprotein, macrophages, DCs, NK cells, mast cells, eosinophils, and neutrophils. Early, atherosclerotic lesions exhibited heterogeneous populations of (CD68⁺) macrophages, whereby 25% were double positive “M1” (CD68⁺/ inducible nitric oxide synthase [iNOS]⁺/CD163⁻), 13% “M2” double positive (CD68⁺/iNOS⁻/CD163⁺), and 17% triple positive for (M1) iNOS (M2)/CD163 and CD68, with the remaining (≈40%) only stained for CD68. Progressive fibroatheromatous lesions, including vulnerable plaques, showed increasing numbers of NK cells and fascin‐positive cells mainly localized to the media and adventitia whereas the M1/M2 ratio and level of macrophage activation (HLA‐DR and neopterin) remained unchanged. On the contrary, stabilized (fibrotic) plaques showed a marked reduction in macrophages and cell activation with a concomitant decrease in NK cells, DCs, and neutrophils.

Conclusions

Macrophage “M1” and “M2” subsets, together with fascin‐positive DCs, are strongly associated with progressive and vulnerable atherosclerotic disease of human aorta. The observations here support a more complex theory of macrophage heterogeneity than the existing paradigm predicated on murine data and further indicate the involvement of (poorly defined) macrophage subtypes or greater dynamic range of macrophage plasticity than previously considered.

Same-admission versus interval cholecystectomy for mild gallstone pancreatitis (PONCHO): a multicentre randomised controlled trial

BACKGROUND

In patients with mild gallstone pancreatitis, cholecystectomy during the same hospital admission might reduce the risk of recurrent gallstone-related complications, compared with the more commonly used strategy of interval cholecystectomy. However, evidence to support same-admission cholecystectomy is poor, and concerns exist about an increased risk of cholecystectomy-related complications with this approach. In this study, we aimed to compare same-admission and interval cholecystectomy, with the hypothesis that same-admission cholecystectomy would reduce the risk of recurrent gallstone-related complications without increasing the difficulty of surgery.

METHODS

For this multicentre, parallel-group, assessor-masked, randomised controlled superiority trial, inpatients recovering from mild gallstone pancreatitis at 23 hospitals in the Netherlands (with hospital discharge foreseen within 48 h) were assessed for eligibility. Adult patients (aged ≥18 years) were eligible for randomisation if they had a serum C-reactive protein concentration less than 100 mg/L, no need for opioid analgesics, and could tolerate a normal oral diet. Patients with American Society of Anesthesiologists (ASA) class III physical status who were older than 75 years of age, all ASA class IV patients, those with chronic pancreatitis, and those with ongoing alcohol misuse were excluded. A central study coordinator randomly assigned eligible patients (1:1) by computer-based randomisation, with varying block sizes of two and four patients, to cholecystectomy within 3 days of randomisation (same-admission cholecystectomy) or to discharge and cholecystectomy 25-30 days after randomisation (interval cholecystectomy). Randomisation was stratified by centre and by whether or not endoscopic sphincterotomy had been done. Neither investigators nor participants were masked to group assignment. The primary endpoint was a composite of readmission for recurrent gallstone-related complications (pancreatitis, cholangitis, cholecystitis, choledocholithiasis needing endoscopic intervention, or gallstone colic) or mortality within 6 months after randomisation, analysed by intention to treat. The trial was designed to reduce the incidence of the primary endpoint from 8% in the interval group to 1% in the same-admission group. Safety endpoints included bile duct leakage and other complications necessitating re-intervention. This trial is registered with Current Controlled Trials, number ISRCTN72764151, and is complete.

FINDINGS

Between Dec 22, 2010, and Aug 19, 2013, 266 inpatients from 23 hospitals in the Netherlands were randomly assigned to interval cholecystectomy (n=137) or same-admission cholecystectomy (n=129). One patient from each group was excluded from the final analyses, because of an incorrect diagnosis of pancreatitis in one patient (in the interval group) and discontinued follow-up in the other (in the same-admission group). The primary endpoint occurred in 23 (17%) of 136 patients in the interval group and in six (5%) of 128 patients in the same-admission group (risk ratio 0·28, 95% CI 0·12-0·66; p=0·002). Safety endpoints occurred in four patients: one case of bile duct leakage and one case of postoperative bleeding in each group. All of these were serious adverse events and were judged to be treatment related, but none led to death.

INTERPRETATION

Compared with interval cholecystectomy, same-admission cholecystectomy reduced the rate of recurrent gallstone-related complications in patients with mild gallstone pancreatitis, with a very low risk of cholecystectomy-related complications.

FUNDING

Dutch Digestive Disease Foundation.

A change in inflammatory footprint precedes plaque instability: a systematic evaluation of cellular aspects of the adaptive immune response in human atherosclerosis

Background

Experimental studies characterize adaptive immune response as a critical factor in the progression and complications of atherosclerosis. Yet, it is unclear whether these observations translate to the human situation. This study systematically evaluates cellular components of the adaptive immune response in a biobank of human aortas covering the full spectrum of atherosclerotic disease.

Methods and Results

A systematic analysis was performed on 114 well‐characterized perirenal aortic specimens with immunostaining for T‐cell subsets (CD3/4/8/45RA/45RO/FoxP3) and the Th1/non‐Th1/Th17 ratio (CD4⁺T‐bet⁺/CD4⁺T‐bet⁻/CD4⁺/interleukin‐17⁺ double staining). CD20 and CD138 were used to identify B cells and plasma cells, while B‐cell maturation was evaluated by AID/CD21 staining and expression of lymphoid homeostatic CXCL13. Scattered CD4 and CD8 cells with a T memory subtype were found in normal aorta and early, nonprogressive lesions. The total number of T cells increases in progressive atherosclerotic lesions (≈1:5 CD4/CD8 T‐cell ratio). A further increase in medial and adventitial T cells is found upon progression to vulnerable lesions.

This critical stage is further hallmarked by de novo formation of adventitial lymphoidlike structures containing B cells and plasma cells, a process accompanied by transient expression of CXCL13. A dramatic reduction of T‐cell subsets, disappearance of lymphoid structures, and loss of CXCL13 expression characterize postruptured lesions. FoxP3 and Th17 T cells were minimally present throughout the atherosclerotic process.

Conclusions

Transient CXCL13 expression, restricted presence of B cells in human atherosclerosis, along with formation of nonfunctional extranodal lymphoid structures in the phase preceding plaque rupture, indicates a “critical” change in the inflammatory footprint before and during plaque destabilization.

Early versus on-demand nasoenteric tube feeding in acute pancreatitis

BACKGROUND

Early enteral feeding through a nasoenteric feeding tube is often used in patients with severe acute pancreatitis to prevent gut-derived infections, but evidence to support this strategy is limited. We conducted a multicenter, randomized trial comparing early nasoenteric tube feeding with an oral diet at 72 hours after presentation to the emergency department in patients with acute pancreatitis.

METHODS

We enrolled patients with acute pancreatitis who were at high risk for complications on the basis of an Acute Physiology and Chronic Health Evaluation II score of 8 or higher (on a scale of 0 to 71, with higher scores indicating more severe disease), an Imrie or modified Glasgow score of 3 or higher (on a scale of 0 to 8, with higher scores indicating more severe disease), or a serum C-reactive protein level of more than 150 mg per liter. Patients were randomly assigned to nasoenteric tube feeding within 24 hours after randomization (early group) or to an oral diet initiated 72 hours after presentation (on-demand group), with tube feeding provided if the oral diet was not tolerated. The primary end point was a composite of major infection (infected pancreatic necrosis, bacteremia, or pneumonia) or death during 6 months of follow-up.

RESULTS

A total of 208 patients were enrolled at 19 Dutch hospitals. The primary end point occurred in 30 of 101 patients (30%) in the early group and in 28 of 104 (27%) in the on-demand group (risk ratio, 1.07; 95% confidence interval, 0.79 to 1.44; P=0.76). There were no significant differences between the early group and the on-demand group in the rate of major infection (25% and 26%, respectively; P=0.87) or death (11% and 7%, respectively; P=0.33). In the on-demand group, 72 patients (69%) tolerated an oral diet and did not require tube feeding.

CONCLUSIONS

This trial did not show the superiority of early nasoenteric tube feeding, as compared with an oral diet after 72 hours, in reducing the rate of infection or death in patients with acute pancreatitis at high risk for complications. (Funded by the Netherlands Organization for Health Research and Development and others; PYTHON Current Controlled Trials number, ISRCTN18170985.).

Abstract 168: Splice Variants of Tissue Factor Determine the Coagulant State of Endothelial Cells and Modulate Vascular Stabilization/Regression

Introduction: Recruitment of pericytes (PC), critical to microvascular maturation, requires deposition of basement membrane proteins such as von Willebrand factor (vWF). Loss of PCs ultimately leads to vessel regression and rarefaction.

Hypothesis: Splice variants of tissue factor (TF) stabilize the vasculature by supporting EC-PC interactions.

Results: We determined that alternatively spliced TF (asTF) resides in Weibel Palade bodies (WPB) of ECs. Overexpression of KLF-2 enhanced asTF protein levels in WPBs. In confluent EC monolayers, asTF was deposited into the extracellular matrix (ECM). In assays employing vascular plexus remodelling on 3D-basement membrane and purified recombinant asTF or full-length TF (flTF), only asTF improved EC-PC interactions. At sites of low KLF-2 expression (low or turbulent flow), total TF mRNA was diminished, leading to low asTF expression. However, upon EC activation by TNFα, total TF mRNA levels rapidly increased and TF protein expression shifted from the ECM-deposited asTF to luminally expressed flTF. Interestingly, flTF-driven EC conversion to a procoagulant state was associated with the release of vWF and asTF from WPBs, depleting the intracellular depots from these proteins. Immunohistochemical staining of kidney specimens of human living donors confirmed that asTF was present at high levels in WPBs of microvascular endothelium. Moreover, after 45 minutes of reperfusion of the transplanted kidney, asTF- and vWF-staining was markedly reduced, consistent with their release from WPB following an inflammatory insult.

Conclusion: We show for the first time that quiescent, KLF-2 expressing ECs predominantly generate non-coagulant asTF, which is stored in WPBs and serves to stabilize the microvasculature by supporting EC-PC interactions. In contrast, in low-flow zones or sites with disturbed flow (e.g. at bifurcations), KLF-2 is downregulated, leading to decreased production of asTF and impaired stabilization of the vasculature. During inflammation, acute perturbation of ECs (e.g. exposure to TNFα) is associated with downregulation of KLF-2 and a post-transcriptionally regulated increase in the production of flTF, resulting in a pro-coagulant phenotype and loss of EC-PC interactions.

Silencing of miRNA-126 in kidney ischemia reperfusion is associated with elevated SDF-1 levels and mobilization of Sca-1+/Lin- progenitor cells

Integrity of the capillary network in the kidney is essential in the recovery from ischemia/ reperfusion injury (IRI), a phenomenon central to kidney transplantation and acute kidney injury. MicroRNA- 126 (miR-126) is known to be important in maintaining vascular homeostasis by facilitating vascular regeneration and modulating the mobilization of vascular progenitor cells. Stromal cell-derived factor 1 (SDF-1), important in the mobilization of vascular progenitor cells, is a direct target of miR-126 and modulation of miR-126 was previously shown to affect the number of circulating Sca-1(+)/Lin(-) vascular progenitor cells in a mouse model for hind limb ischemia. Here, we assessed the in vivo contribution of miR-126 to progenitor cell mobilization and kidney function following IRI in mice. A three day follow up of blood urea levels following kidney IRI demonstrated that systemic antagomir silencing of miR-126 did not impact the loss or subsequent restoration of kidney function. However, whole kidney lysates displayed elevated gene expression levels of Sdf-1, Vegf-A and eNOS after IRI as a result of systemic silencing of miR-126. Furthermore, FACS-analysis on whole blood three days after surgery revealed a marked up regulation of the number of circulating Sca-1(+)/Lin(-) progenitor cells in the antagomir-126 treated mice, in an ischemia dependent manner. Our data indicate that silencing of miR-126 can enhance renal expression of Sdf-1 after IRI, leading to the mobilization of vascular progenitor cells into the circulation.

Transluminal endoscopic step-up approach versus minimally invasive surgical step-up approach in patients with infected necrotising pancreatitis (TENSION trial): design and rationale of a randomised controlled multicenter trial [ISRCTN09186711]

Background

Infected necrotising pancreatitis is a potentially lethal disease that nearly always requires intervention. Traditionally, primary open necrosectomy has been the treatment of choice. In recent years, the surgical step-up approach, consisting of percutaneous catheter drainage followed, if necessary, by (minimally invasive) surgical necrosectomy has become the standard of care. A promising minimally invasive alternative is the endoscopic transluminal step-up approach. This approach consists of endoscopic transluminal drainage followed, if necessary, by endoscopic transluminal necrosectomy. We hypothesise that the less invasive endoscopic step-up approach is superior to the surgical step-up approach in terms of clinical and economic outcomes.

Methods/Design

The TENSION trial is a randomised controlled, parallel-group superiority multicenter trial. Patients with (suspected) infected necrotising pancreatitis with an indication for intervention and in whom both treatment modalities are deemed possible, will be randomised to either an endoscopic transluminal or a surgical step-up approach. During a 4 year study period, 98 patients will be enrolled from 24 hospitals of the Dutch Pancreatitis Study Group. The primary endpoint is a composite of death and major complications within 6 months following randomisation. Secondary endpoints include complications such as pancreaticocutaneous fistula, exocrine or endocrine pancreatic insufficiency, need for additional radiological, endoscopic or surgical intervention, the need for necrosectomy after drainage, the number of (re-)interventions, quality of life, and total direct and indirect costs.

Discussion

The TENSION trial will answer the question whether an endoscopic step-up approach reduces the combined primary endpoint of death and major complications, as well as hospital stay and related costs compared with a surgical step-up approach in patients with infected necrotising pancreatitis.

Recipient's genetic R702W NOD2 variant is associated with an increased risk of bacterial infections after orthotopic liver transplantation

Introduction

Orthotopic liver transplantation (OLT) is accompanied by a significant postoperative infection risk. Immunosuppression to prevent rejection increases the susceptibility to infections, mainly by impairing the adaptive immune system. Genetic polymorphisms in the lectin complement pathway of the donor have recently been identified as important risk determinants of clinically significant bacterial infection (CSI) after OLT. Another genetic factor involved in innate immunity is NOD2, which was reported to be associated with increased risk of spontaneous bacterial peritonitis in cirrhotic patients.

Methods

We assessed association of three genetic NOD2 variants (R702W, G908R and 3020insC) with increased risk of CSI after OLT. 288 OLT recipient-donor pairs from two tertiary referral centers were genotyped for the three NOD2 variants. The probability of CSI in relation to NOD2 gene variants was determined with cumulative incidence curves and log-rank analysis.

Results

The R702W NOD2 variant in the recipient was associated with CSI after OLT. Eight out of 15 (53.3%) individuals with a mutated genotype compared to 80/273 (29.3%) with wild type genotype developed CSI (p=0.027, univariate cox regression), illustrated by a higher frequency of CSI after OLT over time (p=0.0003, log rank analysis). Multivariate analysis (including the donor lectin complement pathway profile) showed independence of this R702W NOD2 association from other risk factors (HR 2.0; p=0.04). The other NOD2 variants, G908R and 3020insC, in the recipient were not associated with CSI. There was no association with CSI after OLT for any of the NOD2 variants in the donor.

Conclusion

The mutated NOD2 R702W genotype in the recipient is independently associated with an increased risk of bacterial infections after liver transplantation, indicating a predisposing role for this genetic factor impairing the recipient’s innate immune system.

Autologous bone marrow-derived mesenchymal stromal cells for the treatment of allograft rejection after renal transplantation: results of a phase I study

Despite excellent short-term results, long-term survival of transplanted kidneys has not improved accordingly. Although alloimmune responses and calcineurin inhibitor-related nephrotoxicity have been identified as main drivers of fibrosis, no effective treatment options have emerged. In this perspective, mesenchymal stromal cells (MSCs) are an interesting candidate because of their immunosuppressive and regenerative properties. Of importance, no other clinical studies have investigated their effects in allograft rejection and fibrosis. We performed a safety and feasibility study in kidney allograft recipients to whom two intravenous infusions (1 million cells per kilogram) of autologous bone marrow (BM) MSCs were given, when a protocol renal biopsy at 4 weeks or 6 months showed signs of rejection and/or an increase in interstitial fibrosis/tubular atrophy (IF/TA). Six patients received MSC infusions. Clinical and immune monitoring was performed up to 24 weeks after MSC infusions. MSCs fulfilled the release criteria, infusions were well-tolerated, and no treatment-related serious adverse events were reported. In two recipients with allograft rejection, we had a clinical indication to perform surveillance biopsies and are able to report on the potential effects of MSCs in rejection. Although maintenance immunosuppression remained unaltered, there was a resolution of tubulitis without IF/TA in both patients. Additionally, three patients developed an opportunistic viral infection, and five of the six patients displayed a donor-specific downregulation of the peripheral blood mononuclear cell proliferation assay, not reported in patients without MSC treatment. Autologous BM MSC treatment in transplant recipients with subclinical rejection and IF/TA is clinically feasible and safe, and the findings are suggestive of systemic immunosuppression.

Pancreatitis of biliary origin, optimal timing of cholecystectomy (PONCHO trial): study protocol for a randomized controlled trial

Background

After an initial attack of biliary pancreatitis, cholecystectomy minimizes the risk of recurrent biliary pancreatitis and other gallstone-related complications. Guidelines advocate performing cholecystectomy within 2 to 4 weeks after discharge for mild biliary pancreatitis. During this waiting period, the patient is at risk of recurrent biliary events. In current clinical practice, surgeons usually postpone cholecystectomy for 6 weeks due to a perceived risk of a more difficult dissection in the early days following pancreatitis and for logistical reasons. We hypothesize that early laparoscopic cholecystectomy minimizes the risk of recurrent biliary pancreatitis or other complications of gallstone disease in patients with mild biliary pancreatitis without increasing the difficulty of dissection and the surgical complication rate compared with interval laparoscopic cholecystectomy.

Methods/Design

PONCHO is a randomized controlled, parallel-group, assessor-blinded, superiority multicenter trial. Patients are randomly allocated to undergo early laparoscopic cholecystectomy, within 72 hours after randomization, or interval laparoscopic cholecystectomy, 25 to 30 days after randomization. During a 30-month period, 266 patients will be enrolled from 18 hospitals of the Dutch Pancreatitis Study Group. The primary endpoint is a composite endpoint of mortality and acute re-admissions for biliary events (that is, recurrent biliary pancreatitis, acute cholecystitis, symptomatic/obstructive choledocholithiasis requiring endoscopic retrograde cholangiopancreaticography including cholangitis (with/without endoscopic sphincterotomy), and uncomplicated biliary colics) occurring within 6 months following randomization. Secondary endpoints include the individual endpoints of the composite endpoint, surgical and other complications, technical difficulty of cholecystectomy and costs.

Discussion

The PONCHO trial is designed to show that early laparoscopic cholecystectomy (within 72 hours) reduces the combined endpoint of mortality and re-admissions for biliary events as compared with interval laparoscopic cholecystectomy (between 25 and 30 days) after recovery of a first episode of mild biliary pancreatitis.

Trial registration

Current Controlled Trials: ISRCTN72764151

Visualizing TGF-β and BMP signaling in human atherosclerosis: a histological evaluation based on Smad activation

BACKGROUND

The TGF-β superfamily members transforming growth factor-β (TGF-β/Activin) and bone morphogenetic proteins (BMP) have been implicated in the pathogenesis of atherosclerosis. However, their role in human disease remains controversial. In this study we used Smad phosphorylation as a read out for TGF-β and BMP signaling during the initiation, progression and (de)stabilization of human atherosclerotic disease.

MATERIAL AND METHODS

A systematic analysis was performed in 114 peri-renal aortic patches (stained with Movat Pentachrome, H&E, pSmad2, pSmad1,5,8 and PAI-1) covering the entire atherosclerotic spectrum (van Dijk, 2010). Immunostaining against T-cells (CD3) and monocytes and macrophages (CD68) was used to explore a putative association between TGF-β and BMP signaling and vascular inflammation.

RESULTS

Smad phosphorylation was present within the normal arterial wall in approximately 10% of the endothelial cells and intimal smooth muscle cells. A significant increase in pSmad2 and pSmad1,5,8 positivity was found in non-progressive lesions (>50% positivity). No further increase or decrease was found in the progressive atherosclerotic lesions, vulnerable and stabilized lesions. No association was found between TGF-β and BMP signaling and CD3 and CD68 expression, nor cap thickness.

CONCLUSION

Activation of the TGF-β and BMP pathways is an early event in atherosclerotic lesion formation. No significant relationships were found between Smad phosphorylation and vessel wall inflammation or plaque vulnerability.

A conservative and minimally invasive approach to necrotizing pancreatitis improves outcome

BACKGROUND & AIMS

Treatment of patients with necrotizing pancreatitis has become more conservative and less invasive, but there are few data from prospective studies to support the efficacy of this change. We performed a prospective multicenter study of treatment outcomes among patients with necrotizing pancreatitis.

METHODS

We collected data from 639 consecutive patients with necrotizing pancreatitis, from 2004 to 2008, treated at 21 Dutch hospitals. Data were analyzed for disease severity, interventions (radiologic, endoscopic, surgical), and outcome.

RESULTS

Overall mortality was 15% (n=93). Organ failure occurred in 240 patients (38%), with 35% mortality. Treatment was conservative in 397 patients (62%), with 7% mortality. An intervention was performed in 242 patients (38%), with 27% mortality; this included early emergency laparotomy in 32 patients (5%), with 78% mortality. Patients with longer times between admission and intervention had lower mortality: 0 to 14 days, 56%; 14 to 29 days, 26%; and >29 days, 15% (P<.001). A total of 208 patients (33%) received interventions for infected necrosis, with 19% mortality. Catheter drainage was most often performed as the first intervention (63% of cases), without additional necrosectomy in 35% of patients. Primary catheter drainage had fewer complications than primary necrosectomy (42% vs 64%, P=.003). Patients with pancreatic parenchymal necrosis (n=324), compared with patients with only peripancreatic necrosis (n=315), had a higher risk of organ failure (50% vs 24%, P<.001) and mortality (20% vs 9%, P<.001).

CONCLUSIONS

Approximately 62% of patients with necrotizing pancreatitis can be treated without an intervention and with low mortality. In patients with infected necrosis, delayed intervention and catheter drainage as first treatment improves outcome.

Mannose-binding lectin and ficolin-2 gene polymorphisms predispose to cytomegalovirus (re)infection after orthotopic liver transplantation

BACKGROUND & AIMS

The lectin pathway of complement activation is a crucial effector cascade of the innate immune response to pathogens. Cytomegalovirus (CMV) infection occurs frequently in immunocompromised patients after orthotopic liver transplantation (OLT). Single-nucleotide polymorphisms (SNPs) in the lectin pathway genes determine their liver-derived protein level and functional activity. We examined the association between these SNPs and the risk for CMV infection in OLT.

METHODS

OLT patients (n = 295) were genotyped for recipient and donor SNPs in mannose-binding lectin (MBL2), Ficolin-2 (FCN2) and MBL-associated serine protease (MASP2) genes.

RESULTS

Combined analysis of independently associated variant MBL2 [HR 1.65, p<0.02] and wild-type FCN2 [1.85; p<0.02] SNPs in the donor liver showed an increased risk of CMV infection for either and both risk genotypes [HR 2.02 and HR 3.26, respectively, p = 0.004], especially in CMV Donor-/Recipient+ (D-/R+) patients [HR 4.7 and HR 10.0, respectively, p = 0.01]. A genetic donor-recipient mismatch for MBL2 and FCN2 increased the CMV risk independently, also combined [HR 5.35; p<0.001], particularly in CMV D-/R+ patients [HR 16.6; p = 0.009]. Multivariate Cox analysis showed a consistent stepwise increase in CMV infection risk with the gene profile of the donor [up to HR 2.77; p<0.005] and the combined MBL2 and FCN2 donor-recipient mismatch profile [up to HR 4.57; p<0.001], independent from donor-recipient CMV serostatus, also at higher CMV (re)infection cut-off values.

CONCLUSIONS

MBL2 and FCN2 risk alleles of donor liver and recipient constitute independent risk factors for CMV infection after OLT. Patients with these risk genes probably need intensified CMV monitoring and anti-viral therapy.

Timing of cholecystectomy after mild biliary pancreatitis

Background

The aim of the study was to evaluate recurrent biliary events as a consequence of delay in cholecystectomy following mild biliary pancreatitis.

Methods

Between 2004 and 2007, patients with acute pancreatitis were registered prospectively in 15 Dutch hospitals. Patients with mild biliary pancreatitis were candidates for cholecystectomy. Recurrent biliary events requiring admission before and after cholecystectomy, and after endoscopic sphincterotomy (ES), were evaluated.

Results

Of 308 patients with mild biliary pancreatitis, 267 were candidates for cholecystectomy. Eighteen patients underwent cholecystectomy during the initial admission, leaving 249 potential candidates for cholecystectomy after discharge. Cholecystectomy was performed after a median of 6 weeks in 188 patients (75·5 per cent). Before cholecystectomy, 34 patients (13·7 per cent) were readmitted for biliary events, including 24 with recurrent biliary pancreatitis. ES was performed in 108 patients during the initial admission. Eight (7·4 per cent) of these patients suffered from biliary events after ES and before cholecystectomy, compared with 26 (18·4 per cent) of 141 patients who did not have ES (risk ratio 0·51, 95 per cent confidence interval 0·27 to 0·94; P = 0·015). Following cholecystectomy, eight (3·9 per cent) of 206 patients developed biliary events after a median of 31 weeks. Only 142 (53·2 per cent) of 267 patients were treated in accordance with the Dutch guideline, which recommends cholecystectomy or ES during the index admission or within 3 weeks thereafter.

Conclusion

A delay in cholecystectomy after mild biliary pancreatitis carries a substantial risk of recurrent biliary events. ES reduces the risk of recurrent pancreatitis but not of other biliary events.

Pancreatitis, very early compared with normal start of enteral feeding (PYTHON trial): design and rationale of a randomised controlled multicenter trial

BACKGROUND

In predicted severe acute pancreatitis, infections have a negative effect on clinical outcome. A start of enteral nutrition (EN) within 24 hours of onset may reduce the number of infections as compared to the current practice of starting an oral diet and EN if necessary at 3-4 days after admission.

METHODS/DESIGN

The PYTHON trial is a randomised controlled, parallel-group, superiority multicenter trial. Patients with predicted severe acute pancreatitis (Imrie-score ≥ 3 or APACHE-II score ≥ 8 or CRP > 150 mg/L) will be randomised to EN within 24 hours or an oral diet and EN if necessary, after 72 hours after hospital admission.During a 3-year period, 208 patients will be enrolled from 20 hospitals of the Dutch Pancreatitis Study Group. The primary endpoint is a composite of mortality or infections (bacteraemia, infected pancreatic or peripancreatic necrosis, pneumonia) during hospital stay or within 6 months following randomisation. Secondary endpoints include other major morbidity (e.g. new onset organ failure, need for intervention), intolerance of enteral feeding and total costs from a societal perspective.

DISCUSSION

The PYTHON trial is designed to show that a very early (< 24 h) start of EN reduces the combined endpoint of mortality or infections as compared to the current practice of an oral diet and EN if necessary at around 72 hours after admission for predicted severe acute pancreatitis.

TRIAL REGISTRATION

ISRCTN: ISRCTN18170985.

Lectin complement pathway gene profile of donor and recipient determine the risk of bacterial infections after orthotopic liver transplantation

Infectious complications after orthotopic liver transplantation (OLT) are a major clinical problem. The lectin pathway of complement activation is liver-derived and a crucial effector of the innate immune defense against pathogens. Polymorphisms in lectin pathway genes determine their functional activity. We assessed the relationship between these polymorphic genes and clinically significant bacterial infections, i.e., sepsis, pneumonia, and intra-abdominal infection, and mortality within the first year after OLT, in relation to major risk factors in two cohorts from different transplant centers. Single-nucleotide polymorphisms in the mannose-binding lectin gene (MBL2), the ficolin-2 gene (FCN2), and the MBL-associated serine protease gene (MASP2) of recipients and donors were determined. Recipients receiving a donor liver in the principal cohort with polymorphisms in all three components i.e., MBL2 (XA/O; O/O), FCN2+6359T, and MASP2+371A, had a cumulative risk of an infection of 75% as compared to 18% with wild-type donor livers (P = 0.002), an observation confirmed in the second cohort (P = 0.04). In addition, a genetic (mis)match between donor and recipient conferred a two-fold higher infection risk for each separate gene. Multivariate Cox analysis revealed a stepwise increase in infection risk with the lectin pathway gene profile of the donor (hazard ratio = 4.52; P = 8.1 x 10(-6)) and the donor-recipient (mis)match genotype (hazard ratio = 6.41; P = 1.9 x 10(-7)), independent from the other risk factors sex and antibiotic prophylaxis (hazard ratio > 1.7 and P < 0.02). Moreover, patients with a lectin pathway gene polymorphism and infection had a six-fold higher mortality (P = 0.9 x 10(-8)), of which 80% was infection-related.

CONCLUSION

Donor and recipient gene polymorphisms in the lectin complement pathway are major determinants of the risk of clinically significant bacterial infection and mortality after OLT.

A step-up approach or open necrosectomy for necrotizing pancreatitis

BACKGROUND

Necrotizing pancreatitis with infected necrotic tissue is associated with a high rate of complications and death. Standard treatment is open necrosectomy. The outcome may be improved by a minimally invasive step-up approach.

METHODS

In this multicenter study, we randomly assigned 88 patients with necrotizing pancreatitis and suspected or confirmed infected necrotic tissue to undergo primary open necrosectomy or a step-up approach to treatment. The step-up approach consisted of percutaneous drainage followed, if necessary, by minimally invasive retroperitoneal necrosectomy. The primary end point was a composite of major complications (new-onset multiple-organ failure or multiple systemic complications, perforation of a visceral organ or enterocutaneous fistula, or bleeding) or death.

RESULTS

The primary end point occurred in 31 of 45 patients (69%) assigned to open necrosectomy and in 17 of 43 patients (40%) assigned to the step-up approach (risk ratio with the step-up approach, 0.57; 95% confidence interval, 0.38 to 0.87; P=0.006). Of the patients assigned to the step-up approach, 35% were treated with percutaneous drainage only. New-onset multiple-organ failure occurred less often in patients assigned to the step-up approach than in those assigned to open necrosectomy (12% vs. 40%, P=0.002). The rate of death did not differ significantly between groups (19% vs. 16%, P=0.70). Patients assigned to the step-up approach had a lower rate of incisional hernias (7% vs. 24%, P=0.03) and new-onset diabetes (16% vs. 38%, P=0.02).

CONCLUSIONS

A minimally invasive step-up approach, as compared with open necrosectomy, reduced the rate of the composite end point of major complications or death among patients with necrotizing pancreatitis and infected necrotic tissue. (Current Controlled Trials number, ISRCTN13975868.)

Timing and impact of infections in acute pancreatitis

BACKGROUND

Although infected necrosis is an established cause of death in acute pancreatitis, the impact of bacteraemia and pneumonia is less certain.

METHODS

This was a cohort study of 731 patients with a primary episode of acute pancreatitis in 2004-2007, including 296 patients involved in a randomized controlled trial to investigate the value of probiotic treatment in severe pancreatitis. Time of onset of bacteraemia, pneumonia, infected pancreatic necrosis, persistent organ failure and death were recorded.

RESULTS

The initial infection in 173 patients was diagnosed a median of 8 (interquartile range 3-20) days after admission (infected necrosis, median day 26; bacteraemia/pneumonia, median day 7). Eighty per cent of 61 patients who died had an infection. In 154 patients with pancreatic parenchymal necrosis, bacteraemia was associated with increased risk of infected necrosis (65 versus 37.9 per cent; P = 0.002). In 98 patients with infected necrosis, bacteraemia was associated with higher mortality (40 versus 16 per cent; P = 0.014). In multivariable analysis, persistent organ failure (odds ratio (OR) 18.0), bacteraemia (OR 3.4) and age (OR 1.1) were associated with death.

CONCLUSION

Infections occur early in acute pancreatitis, and have a significant impact on mortality, especially bacteraemia. Prophylactic strategies should focus on early intervention.

Accumulation of autoreactive effector T cells and allo-specific regulatory T cells in the pancreas allograft of a type 1 diabetic recipient

AIMS/HYPOTHESIS

Simultaneous kidney-pancreas transplantation is an established treatment for patients with type 1 diabetes and end-stage renal failure, even though restored beta cell function may become affected by recurrent islet autoimmunity or graft rejection. We characterised infiltrating lymphocytes isolated from a pancreatic graft with normal endocrine function in a kidney-pancreas recipient with type 1 diabetes.

METHODS

The pancreas graft was removed due to recurrent graft pancreatitis of unknown cause. Pancreas-infiltrating lymphocytes and peripheral blood mononuclear cells (PBMC) were isolated and characterised phenotypically and functionally.

RESULTS

Compared with PBMC, pancreas-infiltrating lymphocytes exhibited a distinct activation/memory phenotype and T cell receptor profile that were indicative of selective infiltration of the pancreas. Islet autoreactive CD8(+) T cells could be detected in the pancreas and were increased in frequency compared with PBMC. Additionally, an augmentation of CD8(+) CD28(-) regulatory T cells was observed in the pancreas; these induced expression of the inhibitory receptor immunoglobulin-like transcript-3 on antigen-presenting cells in a donor HLA class I-specific manner.

CONCLUSIONS/INTERPRETATION

These data demonstrate the simultaneous presence of regulatory and effector T cells in the pancreas allograft of a recipient with type 1 diabetes. They also indicate that circulating islet autoreactive T cells may reflect immunological processes in pancreatic tissue, even though their frequency in the periphery may lead to underestimation of their presence in the pancreas. Additional specificities were also present in the pancreas that were undetectable in the circulation.

Feasibility of minimally invasive approaches in patients with infected necrotizing pancreatitis

Background

Minimally invasive procedures to treat infected necrotizing pancreatitis (INP) are gaining popularity. The proportion of patients suitable for this approach remains unknown.

Methods

Preoperative computed tomography (CT) scans were reviewed from 106 consecutive patients who had surgery for INP between 2000 and 2003 in 11 Dutch hospitals. Collections related to the pancreas were classified according to their distance from the left abdominal wall. Five radiologists judged ‘accessibility’ for drain placement and the likelihood that there was a fluid component that would drain (‘drainability’). Agreement between radiologists was determined.

Results

CT scans of 80 (75 per cent) patients were available (59 men; age range 29–80 years). The median interval between hospital admission and preoperative CT scan was 20 days. In 55 (69 per cent) patients, the lateral border of the collection was less than 5 cm from the left abdominal wall. Placement of a drain was deemed feasible in 67 (84 (range 77–89) per cent) patients; mean(s.d.) kappa 0·428(0·096). In 45 (56 per cent) patients, a drain could be placed through the left retroperitoneum. In 43 (54 (range 49–82) per cent) patients, collections were judged to contain a drainable fluid component. Interobserver agreement on ‘drainability’ was poor, mean(s.d.) kappa 0·289(0·101).

Conclusion

Most peripancreatic collections in INP were considered accessible to a minimally invasive approach.

Porcine islet cells of Langerhans are destroyed by human complement and not by antibody-dependent cell-mediated mechanisms

In the near future, xenotransplantation of porcine islets of Langerhans might be an alternative in the treatment of patients with diabetes mellitus. However, xenotransplantation of islets of Langerhans in large animals has been shown to result in an exceedingly short graft survival, which suggests that a humoral immune response might play a major role in islet demise. This study was performed to assess binding human preformed antibodies to isolated porcine islet cells (PIC) and to determine the lysis of PIC using human sera in complement-mediated cytotoxicity (CMC) and antibody-dependent cell-mediated cytotoxicity (ADCC) assays. Ten Dutch Landrace pigs were used for the isolation of PIC. Sera from 30 healthy blood donors (1/10 diluted) were used in a 51Cr release assay to assess CMC. Heat-inactivated normal human sera and fresh sera from patients with agammaglobulinemia were used as controls. Binding of human IgM IgG, and IgA antibodies to PIC was tested in an ELISA using isotype-specific secondary monoclonal antibodies ADCC was tested in a 51Cr release assay using normal human sera and sera from newly diagnosed type I diabetics with peripheral blood mononuclear cells as effector cells and PIC as targets. It was found that PIC were recognized by human IgM and IgG preformed antibodies and that fresh human sera had strong CMC activity inducing a percentage-specific PIC lysis of 61 +/- 10% (mean +/- SD) within 60 min. Agammaglobulinemic sera killed 42 +/- 12% of PIC. No significant cytotoxic activity was found in ADCC assays using normal sera or sera from diabetic patients. These results show that all tested human sera lyse PIC via CMC, even in the absence of human antibodies, as concluded from the use of agammaglobulinemic sera. In pig-to-human transplantation, islets may be hyperacutely rejected by antibody-dependent and antibody-independent activation of complement and not by antibody-dependent cell-mediated mechanisms.

Human complement activation via the alternative pathway on porcine endothelium initiated by IgA antibodies

The role of the classical pathway (CP) and the alternative pathway (AP) of complement activation in hyperacute xenograft rejection remains a matter of considerable debate. In addition, it is unknown whether IgG and IgA antibodies activate complement, although these antibodies have been found in hyperacutely rejected xenografts. This study was initiated to assess a possible role of the AP of complement activation in a pig-to-human transplantation model using fresh human sera and isolated antibodies with cultured porcine endothelial cells (PEC) as targets. IgM, IgG, monomeric IgA, and dimeric IgA (dIgA) antibodies with reactivity toward PEC as determined by ELISA were isolated from pooled normal human sera. Serum from patients with agammaglobulinemia was used as a source of human complement. C3 and C4 deposition on nonfixed PEC during CP (1% serum) or AP activation (10% serum with MgEGTA) was analyzed using an ELISA. Complement-mediated PEC lysis was tested in a 51Cr release assay. Using normal human sera as the source of antibodies and complement, C3 and C4 deposition was already found after 10 min of incubation in the CP, whereas an increasing amount of C3 was found in the AP. During AP activation, no C4 deposition was observed, indicating that CP activation did not contribute to the observed AP-mediated C3 deposition. Moreover, dIgA antibodies caused deposition of C3 and not C4. Purified IgM and dIgA antibodies (1 mg/ml) in the presence of 10% agammaglobulinemic serum showed a mean specific PEC lysis of 31% and 28%, respectively. Agammaglobulinemic serum alone or with IgG or monomeric IgA antibodies had no detectable lytic activity. In conclusion, dIgA antibodies might play an additional role in pig-to-human xenograft rejection by activating human complement via the AP.

Antibody-dependent cell-mediated cytotoxicity against porcine endothelium induced by a majority of human sera

Preformed natural antibodies seem to play a predominant role in hyperacute xenograft rejection. The potential of these antibodies in antibody-dependent cell-mediated rejection has not been elucidated, yet. This study was performed to assess a possible role of human antibodies in antibody-dependent cell-mediated cytotoxicity (ADCC) in pig to human transplantation using cultured porcine endothelial cells (PEC). Sera from 100 healthy blood donors were used to determine their ability to lyse PEC in a 51Cr release assay using human PBMC as effector cells. To reveal the underlying mechanism of the observed lysis, binding of human IgM, IgA, and IgG (IgG1, IgG2, IgG3, and IgG4) antibodies and F(ab')2 fragments to PEC was studied. Sixty-four percent of the sera showed a positive ADCC with 12-56% specific lysis of PEC using 1/16 diluted serum. Blocking of FcRIII (CD16) on effector cells did prevent PEC lysis. Most sera contained IgM, IgG, and IgA antibodies to PEC. IgG F(ab')2 fragments isolated from these sera specifically recognized PEC antigens without displaying ADCC activity. With regard to IgG subclass distribution of these antibodies, all sera contained IgG antibodies reacting with PEC, whereas most sera showed binding of IgG1 or IgG3 antibodies to PEC. No binding of IgG4 antibodies to PEC was found. Binding of total IgG, IgG1, IgG2, or IgG3 antibodies to PEC was not directly correlated with serum cytotoxicity. In conclusion, most human sera have the ability to lyse PEC through non-complement-fixing IgG antibodies via binding to FcRIII (CD16) on killer cells. Thus, human IgG antibodies may contribute to porcine xenograft rejection. The in vivo consequences of the predominant recognition of PEC antigens by IgG2 and IgA antibodies remain to be studied.

Islet cell hormone release immediately after human pancreatic transplantation. A marker of tissue damage associated with cold ischemia

Pancreatic graft procurement, preservation, and transplantation surgery may result in damage to and loss of the integrity of endocrine cells and consequently in leakage of cell products into the insular vascular capillaries. Thus, the amount of alpha-, beta-, and pancreatic polypeptide (PP) cell products released into the vascular space of the recipient immediately after graft reperfusion may reflect islet cell injury. To test this hypothesis, we assessed glucagon, PP, C-peptide, and insulin levels in a prospective study of 22 consecutive renal-pancreatic transplantations. Transplantation-related parameters were used to account for differences in hormone release. Five grafts were preserved using Euro-Collins preservation fluid and 17 grafts were preserved using University of Wisconsin solution (UW). The first sign of a reinstalled physiological axis was the decrease of the blood glucose concentration after a median duration of 40 min (range 5-90 min) and the association of the recipient's ambient blood glucose levels with insulin release between 25 and 180 min after reperfusion. The delay period before a fall in blood glucose was observed correlated with cold ischemia time (rs = 0.73, P < 0.001, n = 21). An immediate and marked increase in plasma levels of glucagon (from 180 +/- 18 to 585 +/- 99 ng/L, mean +/- SEM), PP (from 57 +/- 8 to 122 +/- 13 pmol/L), C-peptide (from < 0.06 +/- 0.02 to 5.43 +/- 0.63 nmol/L), and insulin (from 0.15 +/- 0.21 to 2.05 +/- 0.26 nmol/L) was observed. C-peptide release correlated with glucagon (r = 0.76, P < 0.001) and PP (r = 0.60, P < 0.01). The hormone release was compared with computed tomography scans that were performed in the immediate postoperative period in 15 UW-preserved allografts. The diameter of the pancreatic head was increased and ranged from 4.5 to 7.7 cm (mean 6.2 cm). Peroperative C-peptide release significantly correlated with morphological graft changes reflected by the pancreatic head diameter (r = 0.58, P = 0.02). In a stepwise multiple regression analysis, cold ischemia time was a significant factor for the release of PP (r2 = 0.18, P = 0.049) and C-peptide (r2 = 0.35, P = 0.004). We suggest that peroperative hormone release reflects endocrine tissue damage. Furthermore, cold ischemia time may jeopardize the pancreatic allograft after relatively short preservation times, even when UW is used.

The role of early baseline computed tomography in the interpretation of morphological changes after kidney-pancreas transplantation

In a prospective study, 17 early baseline computed tomography (CT) scans were obtained 2 or 3 days after simultaneous kidney-pancreas transplantation. Morphological changes and their relevance to the early detection of graft rejection and complications were evaluated. The pancreatic grafts were enlarged and showed signs of mild pancreatitis. Serial scans obtained during the first renal graft rejection episode were compared with the baseline CT scans (n = 7). They showed a significant increase in pancreatic graft size in the case of biopsy-proven severe renal graft rejection (P = 0.008). Normally functioning pancreatic allografts showed a 15%-40% decrease in size 1-6 months after transplantation. We conclude that the morphological changes observed early after transplantation are compatible with mild pancreatitis, which may contribute to the development of pancreatic graft thrombosis. There is an increase in the number of morphological changes during severe rejection, yet enlarged pancreatic grafts appear to recover from transplantation-related damage and regain their normal size without signs of atrophy.

Pancreatic graft survival after arterial thrombosis in simultaneous renal-pancreatic transplantation

Vascular thrombosis following pancreas transplantation is one of the main causes of early graft loss. Successful thrombectomy after pancreatic graft thrombosis has not been reported yet. A patient with arterial graft thrombosis in whom the graft survived after thrombectomy is described. Different varieties of pancreatic graft thrombosis are discussed.

Transmural inhomogeneity of extracellular [K+] and pH and myocardial energy metabolism in the isolated rat heart during acute global ischemia; dependence on gaseous environment

We investigated in the isolated rat heart the influence of the gas surrounding the globally ischemic heart on transmural inhomogeneity of energy metabolism, extracellular K+ accumulation, and change of extracellular pH. Hearts were made ischemic in 100% N2 (N2-ischemia), 100% O2 (O2-ischemia) or 100% CO2 (CO2-ischemia). We measured: 1) Midmural, subepicardial, and epicardial changes of extracellular [K+] and pH during successive 6-min periods of global ischemia, and 2) content of creatinephosphate (CrP) in consecutive tissue sections of 100 microns, from the subepicardium after 10 min of ischemia. A) During O2-ischemia both extracellular [K+] and change of pH in the subepicardium are significantly less than in the midmyocardium. During N2-ischemia only minor differences exist in [K+] and pH between the subepicardium and the midmyocardium. During CO2-ischemia midmural and subepicardial [K+] are similar to those during N2-ischemia. The midmural change of pH resembles that during N2-ischemia; subepicardial change of pH, however, was slightly larger. Midmural changes in [K+] and pH were not influenced by the nature of the surrounding gas. B) After 10 min of O2-ischemia a gradient of tissue content of CrP extends from the epicardium (CrP about 30 mumoles/g dry weight) to a distance of about 1000 microns (CrP 1 mumoles/g dry weight). In N2- and CO2-ischemia a CrP gradient is absent; CrP is appreciably less than 1 mumoles/g dry weight at any distances from the epicardium. C) We conclude that diffusion of O2 into the myocardium and of CO2 from the myocardium affects transmural gradients of [K+], pH, and energy metabolism during ischemia. Local availability of O2 increases the capacity of the ischemic tissue to generate high energy phosphates and mitigates ischemia-induced changes of transsarcolemmal ion gradients.