Quantitative evaluation of histological features in "time-zero" liver allograft biopsies as predictors of rejection or graft failure: receiver-operating characteristic analysis application

Extracellular Vesicles as Drug Delivery Systems in Organ Transplantation: The Next Frontier

Extracellular vesicles are lipid bilayer-delimited nanoparticles excreted into the extracellular space by all cells. They carry a cargo rich in proteins, lipids and DNA, as well as a full complement of RNA species, which they deliver to recipient cells to induce downstream signalling, and they play a key role in many physiological and pathological processes. There is evidence that native and hybrid EVs may be used as effective drug delivery systems, with their intrinsic ability to protect and deliver a functional cargo by utilising endogenous cellular mechanisms making them attractive as therapeutics. Organ transplantation is the gold standard for treatment for suitable patients with end-stage organ failure. However, significant challenges still remain in organ transplantation; prevention of graft rejection requires heavy immunosuppression and the lack of donor organs results in a failure to meet demand, as manifested by growing waiting lists. Pre-clinical studies have demonstrated the ability of EVs to prevent rejection in transplantation and mitigate ischemia reperfusion injury in several disease models. The findings of this work have made clinical translation of EVs possible, with several clinical trials actively recruiting patients. However, there is much to be uncovered, and it is essential to understand the mechanisms behind the therapeutic benefits of EVs. Machine perfusion of isolated organs provides an unparalleled platform for the investigation of EV biology and the testing of the pharmacokinetic and pharmacodynamic properties of EVs. This review classifies EVs and their biogenesis routes, and discusses the isolation and characterisation methods adopted by the international EV research community, before delving into what is known about EVs as drug delivery systems and why organ transplantation represents an ideal platform for their development as drug delivery systems.

Ischemia-reperfusion injury and its relationship with early allograft dysfunction in liver transplant patients

Ischemia-reperfusion injury (IRI) is believed to contribute to graft dysfunction after liver transplantation (LT). However, studies on IRI and the impact of early allograft dysfunction (EAD) in IRI grafts are limited. Histological IRI was graded in 506 grafts from patients who had undergone LT and classified based on IRI severity (no, minimal, mild, moderate, and severe). Of the 506 grafts, 87.4% had IRI (no: 12.6%, minimal: 38.1%, mild: 35.4%, moderate: 13.0%, and severe: 0.8%). IRI severity correlated with the incidence of EAD and graft survival at 6 months. Longer cold/warm ischemia time, recipient/donor hypertension, and having a male donor were identified as independent risk factors for moderate to severe IRI. Among 70 grafts with moderate to severe IRI, 42.9% of grafts developed EAD, and grafts with EAD had significantly inferior survival compared to grafts without EAD. Longer cold ischemia time and large droplet macrovesicular steatosis (≥20%) were identified as independent risk factors for EAD. Our study demonstrated that increased IRI severity was correlated with inferior short-term graft outcomes. Careful consideration of IRI risk factors during donor-recipient matching may assist in optimizing graft utilization and LT outcomes. Furthermore, identification of risk factors of IRI-associated EAD may guide patient management and possible timely graft replacement.

Intrahepatic Microdialysis for Monitoring of Metabolic Markers to Detect Rejection Early After Liver Transplantation

OBJECTIVES

The clinical and biochemical manifestations of acute rejection after liver transplantation are nonspecific, and a liver biopsy is often needed to verify the diagnosis. This may delay treatment. The aim of this study was to evaluate whether monitoring of intrahepatic glucose, lactate, pyruvate, and glycerol by microdialysis can be used to predict rejection early after liver transplantation.

METHODS

Seventy-one patients undergoing liver transplantation were included in the study. The patients were monitored using microdialysis for up to 6 days postoperatively. Patients who developed acute rejection within 1 month were identified according to standard protocol. Area under the curve (AUC) was calculated for 12-hour intervals for glucose, lactate, pyruvate, glycerol, and lactate/pyruvate ratio. Patients with and without rejection were compared with respect to these parameters, as well as standard liver blood investigations and time-zero biopsies.

RESULTS

The lactate/pyruvate ratio was higher at 0 to 12 hours in the group with rejection as compared to the group without rejection. Glucose was lower in the group with rejection at 24 to 48 hours. Also, the intrahepatic lactate levels at 48 to 72 hours and pyruvate levels at 60 to 72 hours after liver transplantation, were higher in the rejection group. The lactate/pyruvate ratio at 0 to 12 hours and lactate at 60 to 72 hours were two independent risk factors for rejection within the first month after liver transplantation. No significant differences in glycerol levels could be detected between the two patient groups.

CONCLUSIONS

Microdialysis monitoring following liver transplantation may be useful in the detection of the metabolic events that precede rejection. The metabolic patterns detected by microdialysis early after transplantation indicate a possible relation between primary ischemia-reperfusion injury and the development of rejection. Identifying these patterns may help to identify patients at risk for the development of acute rejection and may help select those who may benefit from higher dose of immunosuppression early after liver transplantation.

Vertical interval between hepatic segment of inferior vena cava and right atrium predicts intraoperative blood loss during hemi-hepatectomy

BACKGROUND

Intraoperative bleeding is a major issue for hepatic surgeons because large intraoperative blood loss causes poor patient outcome. The aim of this study was to identify predictors of intraoperative bleeding during hemi-hepatectomy. Methods This study enrolled 45 living donors for liver transplantation (cohort 1) and 44 patients with various conditions (cohort 2) who underwent hemi-hepatectomy at Ehime University Hospital between January 2010 and March 2019 (Approval number: 1810024). The gap between the ventral horizontal line of the inferior vena cava (IVC) confluent with the right atrium (RA) and the dorsal horizontal line of the hepatic segment of the IVC (IVC-RA gap) was determined from preoperative images. Cardiopulmonary and liver functions were investigated as potential predictors of intraoperative estimated blood loss (iEBL). Results The IVC-RA gap positively correlated with iEBL in cohorts 1 and 2 (r = 0.453, P = 0.002 and r = 0.443, P = 0.003, respectively), and multivariate analysis selected the IVC-RA gap as an independent predictor of iEBL >400 ml in cohorts 1 and 2 (odds ratios 1.177 and 1.115; 95% confidence intervals 1.041-1.330 and 1.007-1.234; P = 0.009 and P = 0.036, respectively). Conclusions The IVC-RA gap is a novel and simple predictor of iEBL.

Combined Flush With Histidine-Tryptophan-Ketoglutarate and University of Wisconsin Solutions in Liver Transplantation: Preliminary Results

INTRODUCTION

Ischemia reperfusion injury (IRI) is the main cause of early allograft dysfunction (EAD) and subsequent primary allograft failure (PAF).

OBJECTIVES

The purpose of this study is to compare IRI, EAD, and PAF in liver transplantation in a cohort of patients perfused with histidine-tryptophan-ketoglutarate (HTK) solution and University of Wisconsin (UW) solution versus HTK alone.

METHODS

A randomized trial was performed to compare outcomes in liver recipients who underwent transplantation surgery in the University Regional Hospital of Malaga, Spain. Forty patients were randomized to two groups. Primary endpoints included IRI, EAD, PAF, re-intervention, acute cellular rejection, retransplantation, arterial complications, and biliary complications at postoperative day 90.

RESULTS

Postoperative glutamic oxaloacetic transaminase (1869.15 ± 1559.75 UI/L vs. 953.15 ± 777.27 UI/L; P = .004) and glutamic pyruvic transaminase (1333.60 ± 1115.49 U/L vs. 721.70 ± 725.02 U/L; P = .023) were significantly higher in patients perfused with HTK alone. A clear tendency was observed in recipients perfused with HTK alone to present moderate to severe IRI (7 patients in the HTK + UW solution group vs. 15 patients in the HTK-alone solution group; P = .06), EAD (0 patients in the HTK + UW solution group vs. 0 patients in the HTK-alone solution group; P = .76), and PAF (3 patients in the HTK + UW solution group vs. 8 patients in the HTK-alone solution group; P = .15).

CONCLUSIONS

Initial perfusion with HTK solution followed by UW solution in liver transplantation improves early liver function as compared to perfusion with HTK alone.

Perspective review on solid-organ transplant: needs in point-of-care optical biomarkers

Solid-organ transplant is one of the most complex areas of modern medicine involving surgery. There are challenging opportunities in solid-organ transplant, specifically regarding the deficiencies in pathology workflow or gaps in pathology support, which may await alleviations or even de novo solutions, by means of point-of-care, or point-of-procedure optical biomarkers. Focusing the discussions of pathology workflow on donor liver assessment, we analyze the undermet need for intraoperative, real-time, and nondestructive assessment of the donor injuries (such as fibrosis, steatosis, and necrosis) that are the most significant predictors of post-transplant viability. We also identify an unmet need for real-time and nondestructive characterization of ischemia or irreversible injuries to the donor liver, earlier than appearing on morphological histology examined with light microscopy. Point-of-procedure laparoscopic optical biomarkers of liver injuries and tissue ischemia may also facilitate post-transplant management that is currently difficult for or devoid of pathological consultation due to lack of tools. The potential and pitfalls of point-of-procedure optical biomarkers for liver assessment are exemplified in breadth for steatosis. The more general and overarching challenges of point-of-procedure optical biomarkers for liver transplant pathology, including the shielding effect of the liver capsule that was quantitated only recently, are projected. The technological and presentational benchmarks that a candidate technology of point-of-procedure optical biomarkers for transplant pathology must demonstrate to motivate clinical translation are also foreseen.

Analysis of ischemia/reperfusion injury in time-zero biopsies predicts liver allograft outcomes

Ischemia/reperfusion injury (IRI) that develops after liver implantation may prejudice long-term graft survival, but it remains poorly understood. Here we correlate the severity of IRIs that were determined by histological grading of time-zero biopsies sampled after graft revascularization with patient and graft outcomes. Time-zero biopsies of 476 liver transplants performed at our center between 2000 and 2010 were graded as follows: nil (10.5%), mild (58.8%), moderate (26.1%), and severe (4.6%). Severe IRI was associated with donor age, donation after circulatory death, prolonged cold ischemia time, and liver steatosis, but it was also associated with increased rates of primary nonfunction (9.1%) and retransplantation within 90 days (22.7%). Longer term outcomes in the severe IRI group were also poor, with 1-year graft and patient survival rates of only 55% and 68%, respectively (cf. 90% and 93% for the remainder). Severe IRI on the time-zero biopsy was, in a multivariate analysis, an independent determinant of 1-year graft survival and was a better predictor of 1-year graft loss than liver steatosis, early graft dysfunction syndrome, and high first-week alanine aminotransferase with a positive predictive value of 45%. Time-zero biopsies predict adverse clinical outcomes after liver transplantation, and severe IRI upon biopsy signals the likely need for early retransplantation.

Biomarkers to assess graft quality during conventional and machine preservation in liver transplantation

A global rising organ shortage necessitates the use of extended criteria donors (ECD) for liver transplantation (LT). However, poor preservation and extensive ischemic injury of ECD grafts have been recognized as important factors associated with primary non-function, early allograft dysfunction, and biliary complications after LT. In order to prevent for these ischemia-related complications, machine perfusion (MP) has gained interest as a technique to optimize preservation of grafts and to provide the opportunity to assess graft quality by screening for extensive ischemic injury. For this purpose, however, objective surrogate biomarkers are required which can be easily determined at time of graft preservation and the various techniques of MP. This review provides an overview and evaluation of biomarkers that have been investigated for the assessment of graft quality and viability testing during different types of MP. Moreover, studies regarding conventional graft preservation by static cold storage (SCS) were screened to identify biomarkers that correlated with either allograft dysfunction or biliary complications after LT and which could potentially be applied as predictive markers during MP. The pros and cons of the different biomaterials that are available for biomarker research during graft preservation are discussed, accompanied with suggestions for future research. Though many studies are currently still in the experimental setting or of low evidence level due to small cohort sizes, the biomarkers presented in this review provide a useful handle to monitor recovery of ECD grafts during clinical MP in the near future.

Approach to Intraoperative Consultation for Donor Liver Biopsies

Context.— As demand for organs to treat end-stage liver disease increases, donor livers once deemed only marginally suitable for donation are being considered for transplantation. Pathologists are increasingly being asked to evaluate these livers for acceptability. This article provides guidelines for frozen section evaluation of livers for transplantation.

Objective.— This article concentrates on the histopathologic features of transplant suitability with appropriate clinicopathologic correlation for the practicing pathologist. Recommendations for proper handling and sampling of tissue are discussed. Relative and absolute contraindications as well as artifacts and benign conditions are emphasized.

Data Sources.— Sources include a compilation of the authors' experiences in academic and community liver transplantation centers. In addition, relevant medical literature was reviewed, as well as Web sites specializing in organ transplantation, such as Transplant Pathology Internet Services and the Organ Procurement and Transplantation Network.

Conclusions.— Malignancy and extensive necrosis in the liver are absolute contraindications to transplantation. Evaluation of macrosteatosis, fibrosis, hepatitis, and necrosis depends on the severity of disease and correlation with the clinical situation. Donor age of greater than 60 years does not preclude transplantation. Artifacts and benign conditions need to be understood to prevent wastage of precious organs and to ensure that an appropriate organ is provided for the recipient.

Prediction of graft dysfunction based on extended criteria donors in the model for end-stage liver disease score era

BACKGROUND

To explain the influence of recipient status combined with the accumulation of extended criteria donor (ECD) variables on the appearance of severe ischemia-reperfusion injury and graft survival in a model for end-stage liver disease (MELD)-based system, we analyzed our most recent consecutive liver transplantations (LTs), dividing them into two periods: 400 LTs (1992-2002; pre-MELD era) and 275 LTs (2002-2007; post-MELD era).

METHODS

Primary dysfunction (PD) was defined as primary graft failure that required emergency retransplantation or as initial poor function. Donor variables were included in a regression model to assess the probability of PD.

RESULTS

Donor age, macrovesicular steatosis more than 30%, and cold ischemia time were associated with allograft dysfunction. Mean probability of PD was 14.8%, 19.2%, 27.5%, and 37.4% for ECD 0, 1, 2, and more than or equal to 3, respectively (P=0.003). Distribution of no-mild, moderate, and severe ischemia-reperfusion injuries among MELD categories was 72.53%, 24.17%, and 3.30% (MELD group=12-19); 56.52%, 36.96%, and 6.5% (MELD group=20-28); and 23.91%, 54.35%, and 21.74% (MELD group >or=29), respectively (P=0.043). The development of PD according to ECD variables was 18.8%, 18.1%, 28.0%, and 35.3% for ECD 0, 1, 2, and more than or equal to 3, respectively (P=0.047). These variables were independent predictors of PD (Cox proportional regression model): ECD 2 (relative risk [RR]=1.59; 95% confidence interval [CI]=1.25-1.62), ECD 3 (RR=2.74; 95% CI=2.38-3.13), MELD 21 to 30 (RR=1.89; 95% CI=1.32-2.06), and MELD more than or equal to 30 (RR=3.38; 95% CI=2.43-3.86). Graft survival decreased, whereas MELD and the number of ECD variables increased.

CONCLUSION

The combination of three or more ECD variables and an MELD more than or equal to 29 is the worst scenario for graft success after LT.

Intrahepatic complement activation, sinusoidal endothelial injury, and lactic acidosis are associated with initial poor function of the liver after transplantation

BACKGROUND

Changes in glucose metabolism in the liver during transplantation have been recently described using microdialysis. Here, these findings are correlated with histopathologic, immunohistochemical, and ultrastructural changes in liver.

METHODS

Microdialysis catheters were inserted into 15 human livers, which were perfused with isotonic solution, and samples of perfusate were analyzed before harvest, after storage, and after reperfusion. At each stage Menghini needle biopsy samples were taken and each studied using light and electron microscopy.

RESULTS

Six livers showed serum biochemical evidence of initial poor function. These livers had significantly more staining for complement fragment 4d (C4d) of both lobular and periportal hepatocytes. C4d-positive hepatocytes were also found in the liver during cold storage (3 of 15). These periportal hepatocytes also showed evidence of necrosis and were found to have intracellular neutrophils. Hepatocyte rounding in zone III, necrosis, and C4d staining in recipient were also significantly correlated with the degree of lactic acidosis during this phase. Intrahepatic lactic acidosis at all time points was significantly associated with sinusoidal endothelial cell injury after reperfusion. There were no correlations between glucose, pyruvate, and glycerol levels and histopathologic changes in the liver.

DISCUSSION

In the patients studied, the degree of C4d staining correlated with initial poor function and was associated with intrahepatic lactic acidosis in the donor during cold storage and after reperfusion. Complement activity in the liver during cold storage may be after in situ activation. Intrahepatic lactic acidosis is associated with sinusoidal endothelial cell and hepatocyte injury. The role of intrahepatic neutrophils is uncertain and could possibly be in response to cell necrosis.

Differentially Expressed Genes in Postperfusion Biopsies Predict Early Graft Dysfunction After Liver Transplantation

BACKGROUND

Preservation induced injury is a major contributing factor to early graft dysfunction in liver allograft recipients. We hypothesized that changes in gene expression represent the earliest indicator of ischemia/reperfusion-related injuries measurable in the graft and could be used as prognostic marker for the occurrence of graft-related complications.

METHODS

We studied the expression of 67 genes, known to play a role in acute inflammatory processes by real-time polymerase chain reaction in 59 postperfusion biopsies. The level of expression was correlated with the occurrence of graft-related complications.

RESULTS

We identified six genes that were significantly correlated with the occurrence of early graft dysfunction (Spearman test, two-tailed; P<0.05). High C-reactive protein (CRP) gene expression levels correlated significantly with the need of therapeutic interventions due to graft-related complications (P=0,011). Furthermore, five genes related to vascular endothelial cell physiology (CTGF, WWP2, CD274, VEGF. and its receptor FLT1) showed significantly reduced expression in the postperfusion biopsies of patients with need of therapeutic interventions due to graft-related complications in the first month (P<0.05). Using a risk score based on the expression of these five genes, complications could be predicted with 96% sensitivity (ROC analysis, specificity: 74%, positive predictive value: 72%, negative predictive value: 96%).

CONCLUSION

Quantitative gene expression analysis in postperfusion biopsies may be a valuable tool to prospectively identify patients at risk for early clinical allograft dysfunction after liver transplantation.

Ischemic preconditioning in deceased donor liver transplantation: a prospective randomized clinical trial of safety and efficacy

Ischemic preconditioning (IPC) has the potential to decrease graft injury and morbidity after liver transplantation. We prospectively investigated the safety and efficacy of 5 minutes of IPC induced by hilar clamping in local deceased donor livers randomized 1:1 to standard (STD) recovery (N = 28) or IPC (N = 34). Safety was assessed by measurement of heart rate, blood pressure, and visual inspection of abdominal organs during recovery, and efficacy by recipient aminotransferases (aspartate aminotransferase [AST] and alanine aminotransferase [ALT], both measured in U/L), total bilirubin, and international normalized ratio of prothrombin time (INR) after transplantation. IPC performed soon after laparotomy did not cause hemodynamic instability or visceral congestion. Recipient median AST, median ALT, and mean INR, in STD vs. IPC were as follows: day 1 AST 696 vs. 841 U/L; day 3 AST 183 vs. 183 U/L; day 1 ALT 444 vs. 764 U/L; day 3 ALT 421 vs. 463 U/L; day 1 INR 1.7 +/- .4 vs. 2.0 +/- .8; and day 3 INR 1.3 +/- .2 vs. 1.4 +/- .3; all P > .05. No instances of nonfunction occurred. The 6-month graft and patient survival STD vs. IPC were 82 vs. 91% and median hospital stay was 10 vs. 8 days; both P > .05. In conclusion, deceased donor livers tolerated 5 minutes of hilar clamping well, but IPC did not decrease graft injury. Further trials with longer periods of preconditioning such as 10 minutes are needed.

DNA methylation profiling of cervical squamous intraepithelial lesions using liquid-based cytology specimens: an approach that utilizes receiver-operating characteristic analysis

BACKGROUND

Cervical carcinoma is a common malignancy among women worldwide, and its pathogenesis is related causally to human papillomavirus infection. The progression from precursor squamous intraepithelial lesions to cervical carcinoma requires additional genetic and epigenetic alterations that have not been characterized fully. The authors examined aberrant promoter methylation of multiple tumor suppressor genes in precursor squamous intraepithelial lesions.

METHODS

A multiplex, nested, methylation-specific polymerase chain reaction approach was used to examine promoter methylation of 15 tumor suppressor genes in high-grade squamous intraepithelial lesions (HSIL, n = 11), low-grade squamous intraepithelial lesions (LSIL, n = 17), and negative tissues (n = 11) from liquid-based cytology samples. The area under the receiver-operating characteristic (ROC) curve was determined for individual methylated tumor suppressor genes and for gene combinations to evaluate test performance for the ability of methylation profiles to distinguish HSIL cytology samples from combined LSIL/negative cytology samples.

RESULTS

Aberrant promoter methylation of DAPK1 and IGSF4 occurred at a high frequency in HSIL samples and was absent in LSIL and negative samples. There was a significant trend toward increased methylation with the increased severity of lesions, and the mean number of methylated genes was significantly higher in HSIL samples compared with LSIL and negative samples. Using the area under the ROC curve as a measure of test performance, the methylation of IGSF4 and DAPK1 had areas that were significantly greater than 0.5; thus, each had the ability to distinguish HSIL samples from combined LSIL/negative samples. The areas under the curve for the best two-gene combination (IGSF4/DAPK1) and the best three-gene combination (IGSF4/DAPK1/HIC1) were not statistically different from the best individual tumor suppressor gene (IGSF4) in distinguishing HSIL samples from combined LSIL/negative samples.

CONCLUSIONS

Aberrant promoter methylation of tumor suppressor genes is an epigenetic alteration that occurs during neoplastic progression to cervical carcinoma. The methylation status of multiple tumor suppressor genes can be evaluated using ROC analysis to determine methylation profiles that can distinguish HSIL samples from combined LSIL/negative samples.

Preservation injury patterns in liver transplantation associated with poor prognosis

Preservation injury (PI) is defined as hepatic dysfunction that occurs within 10 days of liver transplantation (OLT) but spontaneously resolves. However, we noted two new patterns: one characterized by histologic evidence of preservation injury that occurs at later than 10 days post-OLT (late PI), and a second, of persistent charge in liver biopsies > 10 days post-OLT (persistent PI). To characterize these new patterns, we performed a retrospective study of patients who underwent liver biopsies for hepatic dysfunction post-OLT from September 1993 to March 1998. The outcome of the 61 patients with preservation injury on liver biopsy after OLT was followed until the last clinic visit or death. Thirty patients had early PI, 16 patients had persistent preservation injury and 15 patients, late onset preservation injury. There were no significant differences in the age (P =.28), sex (P =.77), follow-up time (P =.78), cold ischemia (P =.3), or warm ischemia time (P =.16) between these groups. There was also no significant association between early preservation injury or persistent preservation injury with the development of acute or chronic rejection (P =.19). The overall survival rates at 1, 3, and 5 years was 52%, 45%, and 45%, respectively. There was no significant difference in survival between early, persistent, and late PI patterns (P =.59), although there was a trend toward better survival for patients with early preservation injury. The survival of OLT patients with persistent or late preservation injury is poor and should prompt consideration for retransplantation.

Donors with cardiac arrest: improved organ recovery but no preconditioning benefit in liver allografts

BACKGROUND

Historically, organ recovery rates in donors with cardiac arrest (CA) have been low, presumably from hemodynamic instability. We hypothesized that donor resuscitation has improved hemodynamic stability and organ recovery in CA donors, and that CA triggers ischemic preconditioning (IP) in liver grafts.

METHODS

A total of 131 donor pairs with and without CA were matched in age, gender, and year of recovery. Hemodynamic stability was determined by vasopressor use. Abdominal and thoracic organs recovered and livers transplanted were compared between the groups. Liver graft function, injury, and IP benefit were examined by comparing liver chemistries after transplantation and postperfusion biopsies between recipients of grafts from both groups (n=40 each).

RESULTS

Hemodynamic stability was similar in both groups, but recovery of thoracic organs was significantly lower in CA versus non-CA donors (35 vs. 53%, P<0.01). On the other hand, recovery rates of three or more abdominal organs from CA donors approached those of non-CA donors (77 vs. 87%, not significant). Although significantly fewer livers were transplanted from CA donors (69 vs. 85%, P<0.01), posttransplantation graft function and injury parameters were similar between the two groups, and CA did not appear to trigger IP.

CONCLUSION

Compared with historical data, cardiovascular stability and abdominal organ recovery rates have improved considerably in CA donors. Liver grafts from CA donors function similarly to grafts from non-CA donors with no IP from CA. Our data support the increased use of livers and other organs from donors with CA.