The economic impact of preservation time in cadaveric liver transplantation

Future Economics of Liver Transplantation: A 20-Year Cost Modeling Forecast and the Prospect of Bioengineering Autologous Liver Grafts

During the past 20 years liver transplantation has become the definitive treatment for most severe types of liver failure and hepatocellular carcinoma, in both children and adults. In the U.S., roughly 16,000 individuals are on the liver transplant waiting list. Only 38% of them will receive a transplant due to the organ shortage. This paper explores another option: bioengineering an autologous liver graft. We developed a 20-year model projecting future demand for liver transplants, along with costs based on current technology. We compared these cost projections against projected costs to bioengineer autologous liver grafts. The model was divided into: 1) the epidemiology model forecasting the number of wait-listed patients, operated patients and postoperative patients; and 2) the treatment model forecasting costs (pre-transplant-related costs; transplant (admission)-related costs; and 10-year post-transplant-related costs) during the simulation period. The patient population was categorized using the Model for End-Stage Liver Disease score. The number of patients on the waiting list was projected to increase 23% over 20 years while the weighted average treatment costs in the pre-liver transplantation phase were forecast to increase 83% in Year 20. Projected demand for livers will increase 10% in 10 years and 23% in 20 years. Total costs of liver transplantation are forecast to increase 33% in 10 years and 81% in 20 years. By comparison, the projected cost to bioengineer autologous liver grafts is $9.7M based on current catalog prices for iPS-derived liver cells. The model projects a persistent increase in need and cost of donor livers over the next 20 years that’s constrained by a limited supply of donor livers. The number of patients who die while on the waiting list will reflect this ever-growing disparity. Currently, bioengineering autologous liver grafts is cost prohibitive. However, costs will decline rapidly with the introduction of new manufacturing strategies and economies of scale.

Liver retransplantation for adult recipients

Living donor liver graft can be used for the first or second liver transplantation. The timing of retransplantation also should be stratified as 2 types according to the reoperation timing. Combination of these two classifications results in 6 types of living donor liver transplantation (LDLT)-associated retransplantation. However, late retransplantation to LDLT might have not been performed in most LDLT programs, thus other 4 types of LDLT-associated retransplantation can be taken into account. The most typical type of LDLT-associated retransplantation might be early living donor-to-deceased donor retransplantation. For early living donor-to-living donor retransplantation, its eligibility criteria might be similar to those of early living donor-to-deceased donor retransplantation. For early deceased donor-to-living donor retransplantation, its indications are exactly the same to those for aforementioned living donor-to-living donor retransplantation. Late deceased donor retransplantation after initial LDLT has the same indication for ordinary late deceased donor retransplantation.

Economic burden of hepatitis C-associated diseases in the United States

There are approximately 100 drugs in development to treat hepatitis C. Over the next decade, a number of new therapies will become available. A good understanding of the cost of hepatitis C sequelae is important for assessing the value of new treatments. The objective of this study was to assess the economic burden data sources for hepatitis C in the United States. A systematic literature search was conducted to identify studies reporting the costs of hepatitis C sequelae in the United States. Over 400 references were identified, of which 50 were pertinent. The costs were compiled and adjusted to 2010 constant US dollars using the medical component of the consumer price index (CPI). The cost of liver transplants was estimated at $201 110 ($178 760-$223 460), hepatocellular carcinoma (HCC) at $23 755-$44 200, variceal haemorrhage at $25 595, compensated cirrhosis at $585-$1110, refractory ascites at $24 755, hepatic encephalopathy at $16 430, sensitive ascites at $2450, moderate chronic hepatitis C at $155, and mild chronic hepatitis C at $145 per year per person. All studies were traced back to a handful of publications in the 1990s, which have provided the basis for all sequelae-based cost estimates to date. Hepatitis C imposes a high economic burden. Most cost analysis is more than 10 years old, and more research is required to update the sequelae costs associated with HCV infection.

Hepatic ischemia reperfusion injury and calcium overload

Hepatic ischemia reperfusion injury is a common pathophysiologic process, whose basic mechanism is related to intracellular calcium overload. Calcium overload is related to cell membrane cranny, Na⁺/Ca²⁺ exchanger, the decreased activity of Ca²⁺-ATPase, mitochondrial dysfuncsion and oxygen free radicals. The prophylaxis and treatment options of calcium overload include: ATP-sensitive K⁺ channel openers, anesthesia, calcium channel entry blockers, mitochondrial permeability transition inhibitors, heme oxygenase 1 and so on.

Cost of liver transplantation: a systematic review and meta-analysis comparing the United States with other OECD countries

Large cost variations of liver transplantation are reported. The aim of this study was to assess cost differences of liver transplantation and clinical follow-up between the United States and other Organization for Economic Cooperation and Development (OECD) countries. Eight electronic databases were searched, and 2,000 citations published after 1990 with more than 10 transplantations, and with original cost data, were identified. A total of 30 articles included 5,975 liver transplantations. Meta-analysis was used to derive a combined mean using a random-effects model to test for heterogeneity between studies. Estimated mean cost of a U.S. liver transplantation was US$163,438 (US$145,277-181,598) compared to US$103,548 (US$85,514-121,582) for other OECD countries. Patient characteristics, disease characteristics, quality of the health care provider, and methodology could not explain this cost difference. Health system characteristics differed between the U.S. and other OECD countries. Cost differences in liver transplantation between these two groups may be largely explained by health system characteristics.

2-APB protects against liver ischemia-reperfusion injury by reducing cellular and mitochondrial calcium uptake

Ischemia-reperfusion (I/R) injury is a commonly encountered clinical problem in liver surgery and transplantation. The pathogenesis of I/R injury is multifactorial, but mitochondrial Ca(2+) overload plays a central role. We have previously defined a novel pathway for mitochondrial Ca(2+) handling and now further characterize this pathway and investigate a novel Ca(2+)-channel inhibitor, 2-aminoethoxydiphenyl borate (2-APB), for preventing hepatic I/R injury. The effect of 2-APB on cellular and mitochondrial Ca(2+) uptake was evaluated in vitro by using (45)Ca(2+). Subsequently, 2-APB (2 mg/kg) or vehicle was injected into the portal vein of anesthetized rats either before or following 1 h of inflow occlusion to 70% of the liver. After 3 h of reperfusion, liver injury was assessed enzymatically and histologically. Hep G2 cells transfected with green fluorescent protein-tagged cytochrome c were used to evaluate mitochondrial permeability. 2-APB dose-dependently blocked Ca(2+) uptake in isolated liver mitochondria and reduced cellular Ca(2+) accumulation in Hep G2 cells. In vivo I/R increased liver enzymes 10-fold, and 2-APB prevented this when administered pre- or postischemia. 2-APB significantly reduced cellular damage determined by hematoxylin and eosin and terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling staining of liver tissue. In vitro I/R caused a dissociation between cytochrome c and mitochondria in Hep G2 cells that was prevented by administration of 2-APB. These data further establish the role of cellular Ca(2+) uptake and subsequent mitochondrial Ca(2+) overload in I/R injury and identify 2-APB as a novel pharmacological inhibitor of liver I/R injury even when administered following a prolonged ischemic insult.

Consequences of eliminating HLA-B in deceased donor kidney allocation to increase minority transplantation

HLA matching contributes to the disparity in Caucasian compared to minority kidney transplantation. HLA-B locus matching was eliminated from kidney allocation to shift a projected 166 organs from Caucasians to minorities annually. This study estimated the economic and quality-of-life impact of this policy. Cost-effectiveness analysis was performed using a Markov model. Data from the United States Renal Data System (USRDS) were used to estimate race-specific outcomes, patient and graft survival, quality-adjusted life years (QALYs) and medical costs in U.S. dollars. The greatest benefit is expected in African Americans, with expected savings of US 7.5 million dollars and 243 QALYs. Smaller cost and QALY benefits are seen in other minority groups. In Caucasians, a loss of 7.0 million dollars and a decrease of 967 QALYs are expected with the shift of organs. Overall, this policy is expected to save US 5400 dollars for each QALY that is lost. The same increase in minority transplantation would be expected from increasing Caucasian donation rates by 5.5%, or African-American donation by 29.0%, each producing large cost savings and QALY gains. Policies to increase minority transplants by increasing donation rates may prove more cost effective than the elimination of HLA-B matching from deceased donor kidney allocation.

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.

Predicting outcome after liver transplantation: utility of the model for end-stage liver disease and a newly derived discrimination function

BACKGROUND

The Model for End-Stage Liver Disease (MELD) has been found to accurately predict pretransplant mortality and is a valuable system for ranking patients in greatest need of liver transplantation. It is unknown whether a higher MELD score also predicts decreased posttransplant survival.

METHODS

We examined a cohort of patients from the United Network for Organ Sharing (UNOS) database for whom the critical pretransplant recipient values needed to calculate the MELD score were available (international normalized ratio of prothrombin time, total bilirubin, and creatinine). In these 2,565 patients, we analyzed whether the MELD score predicted graft and patient survival and length of posttransplant hospitalization.

RESULTS

In contrast with its ability to predict survival in patients with chronic liver disease awaiting liver transplant, the MELD score was found to be poor at predicting posttransplant outcome except for patients with the highest 20% of MELD scores. We developed a model with four variables not included in MELD that had greater ability to predict 3-month posttransplant patient survival, with a c-statistic of 0.65, compared with 0.54 for the pretransplant MELD score. These pretransplant variables were recipient age, mechanical ventilation, dialysis, and retransplantation. Recipients with any two of the three latter variables showed a markedly diminished posttransplant survival rate.

CONCLUSIONS

The MELD score is a relatively poor predictor of posttransplant outcome. In contrast, a model based on four pretransplant variables (recipient age, mechanical ventilation, dialysis, and retransplantation) had a better ability to predict outcome. Our results support the use of MELD for liver allocation and indicate that statistical modeling, such as reported in this article, can be used to identify futile cases in which expected outcome is too poor to justify transplantation.

Reversed activity of mitochondrial adenine nucleotide translocator in ischemia-reperfusion

BACKGROUND

Graft dysfunction as a result of preservation injury remains a major clinical problem in liver transplantation. This is related in part to accumulation of mitochondrial calcium. In an attempt to sustain cell and mitochondrial integrity during ischemia, intramitochondrial F(0)F(1) adenosine triphosphate (ATP) synthase reverses its activity and hydrolyzes ATP to maintain the mitochondrial transmembrane potential (mdeltapsi). It is not known how cytoplasmic ATP becomes available for hydrolysis by this enzyme. The authors hypothesized that mitochondrial adenine nucleotide translocator (ANT) reverses its activity during ischemia, making cytoplasmic ATP available for hydrolysis by F(0)F(1) ATP synthase.

METHODS

Rat livers were perfused with cold University of Wisconsin solution at 4 degrees C (39.2 degrees F)through the portal vein and processed immediately or after 24 hr of cold storage. Mitochondria were separated by differential centrifugation. ATP-dependent mitochondrial calcium-45 (45Ca)2+ uptake was determined after incubation with ATP (5 mM) or adenosine diphosphate (ADP) (5 mM) with or without 15 microM of bongkrekic acid (BA), an ANT blocker; the nonhydrolyzable analog of ATP (adenosine 5'-beta,gamma-imidotriphosphate [AMP-PNP]) served as the negative control. All measurements were performed in triplicate. Student t test, P<0.05 was taken as significant.

RESULTS

Inhibition of ANT by BA prevents mitochondrial Ca2+ accumulation in the presence of ATP and high 45Ca2+ concentrations, and increased extramitochondrial 45Ca2+ stimulated mitochondrial 45Ca2+ uptake in the presence of ATP but not ADP, AMP-PNP, or BA.

CONCLUSIONS

These data demonstrate that ANT plays an important role in mitochondrial Ca2+ uptake under ischemic conditions by reversing its activity and allowing transport of extramitochondrial ATP into the matrix for hydrolysis by reversed F(0)F(1) ATP synthase.

Altered ATP-dependent mitochondrial Ca2+ uptake in cold ischemia is attenuated by ruthenium red

BACKGROUND

Graft dysfunction as a result of preservation injury remains a major clinical problem in liver transplantation. This is related in part to accumulation of mitochondrial calcium (Ca(2+)), which has been linked to activation of proapoptotic factors. We hypothesized that cold ischemia increases mitochondrial Ca(2+) uptake in a concentration dependent fashion and that ruthenium red (RR) will attenuate these changes by inhibiting the mitochondrial Ca(2+) uniporter.

METHODS

Rat livers perfused with cold University of Wisconsin (UW) solution (4 degrees C) with or without RR (10 microM) via the portal vein (n = 3 per group) were processed immediately (no ischemia) or after 24 h cold-storage (24 h cold ischemia). Mitochondria were separated by differential centrifugation, and adenosine triphosphate (ATP)-dependent (45)Ca(2+) uptake was determined in the presence of ATP (5 mM), adenosine diphosphate (ADP), or adenosine 5'-beta,gamma-imidotriphosphate (AMP-PNP); variable concentrations of extramitochondrial (45)Ca(2+) were used. All measurements were performed in triplicate. Student's t test with P < 0.05 was taken as significant.

RESULTS

Our data demonstrate the following: 1) ATP-dependent (45)Ca(2+) uptake in mitochondria separated from livers following 24 h of cold ischemia in UW alone was higher than in mitochondria isolated from non-ischemic livers; the increased uptake was dependent on the concentration of (45)Ca(2+) in the incubation buffer. 2) There was no difference in ATP-dependent (45)Ca(2+) uptake between nonischemic mitochondria and those separated from livers stored in UW-RR for 24 h. 3) (45)Ca(2+) uptake in mitochondria from livers subjected to 24 h of cold ischemia in UW-RR was significantly lower compared to those from livers stored in UW alone when (45)Ca(2+) concentrations were greater than 1 microM.

CONCLUSION

1) Cold ischemia affects mitochondrial Ca(2+) handling, especially when it is challenged by high extramitochondrial Ca(2+) concentrations. 2) The addition of RR in preservation solution attenuates the effects of cold ischemia on mitochondrial Ca(2+) handling. 3) Inhibition of mitochondrial Ca(2+) uniporter with RR protects mitochondria from Ca(2+) overload at high Ca(2+) concentrations. These findings may offer a potentially effective strategy for prevention of ischemia-reperfusion injury in liver transplantation.