Liver Transplantation: The Last Ten Years

Biomarkers in Solid Organ Transplantation

After more than 6 decades of clinical practice, the transplant community continues to research noninvasive biomarkers of solid organ injury to help improve patient care. In this review, we discuss the clinical usefulness of selective biomarkers and how they are processed at the laboratory. In addition, we organize these biomarkers based on specific aims and introduce innovative markers currently under investigation.

Microdialysis monitoring of liver grafts by metabolic parameters, cytokine production, and complement activation

INTRODUCTION

The outcome of liver transplantation is steadily improving. Still there is need for earlier detection of complications like hepatic artery thrombosis and rejection. The aim of this study was to explore whether microdialysis with a 100-kDa cutoff filter could be used to monitor local inflammation after liver transplantation.

METHODS

Twenty patients undergoing liver transplantations were observed for 1 week posttransplant. Microdialysis catheters were introduced in each liver lobe subcutaneously and metabolic parameters (glucose, pyruvate, glycerol, and lactate), cytokines (interleukin [IL]-6, IL-8, monocyte chemottractic protein-1, and inducible protein [IP]-10), and complement activation (C5a) were measured.

RESULTS

Fourteen patients experienced an uneventful course, judged clinically by ultrasound Doppler and by metabolic markers including lactate and the ischemia indicator lactate-to-pyruvate ratio. All patients with uneventful course had a consistent rise in IP-10 from 200 to 3000 pg/mL after transplantation, whereas the other cytokines stayed low. Two patients with rejection showed a selective increase in IL-8 and C5a, starting 2 to 4 days before alanine transferase increased, reaching 10- to 50-fold increase compared with baseline levels, and decreased rapidly after start of antirejection therapy. C5a concentration was substantially increased in these two patients at the time of transplantation. A third patient developed a hepatic artery thrombosis and rejection and showed a rapid rise in intrahepatic lactate and a complex inflammatory pattern.

CONCLUSION

Microdialysis using a 100-kDa filter is a promising way of monitoring the inflammatory reaction after liver transplantation. Increase in IP-10 reflects a normal pathophysiologic response posttransplant, whereas IL-8 and C5a were increased only in patients with rejection.

The Concept of Quality of Life in Organ Transplantation

The goal of organ transplantation is not only to ensure the survival of individuals with end-stage heart, lung, liver, kidney, pancreas, and small bowel diseases, but also to offer patients the health they enjoyed before the disease, achieving a good balance between the functional efficacy of the graft and the patient's psychological and physical integrity. Quality of life (QoL) assessments are used to evaluate the physical, psychological, and social domains of health, seen as distinct areas that are influenced by a person's experiences, beliefs, expectations, and perceptions, and QoL is emerging as a new medical indicator in transplantation medicine too.

Quality of life following organ transplantation

Organ transplantation is a procedure that can save and prolong the life of individuals with end-stage heart, lung, liver, kidney, pancreas and small bowel diseases. The goal of transplantation is not only to ensure their survival, but also to offer patients the sort of health they enjoyed before the disease, achieving a good balance between the functional efficacy of the graft and the patient's psychological and physical integrity. Quality of life (QoL) assessments are used to evaluate the physical, psychological and social domains of health, seen as distinct areas that are influenced by a person's experiences, beliefs, expectations and perceptions, and QoL is emerging as a new medical indicator in transplantation medicine too. This review considers changes in overall QoL after organ transplantation, paying special attention to living donor transplantation, pediatric transplantation and particular aspects of QoL after surgery, e.g. sexual function, pregnancy, schooling, sport and work.

Post-liver transplant obesity and diabetes

PURPOSE OF REVIEW

Post-liver transplant patients present a vast array of metabolic changes in the early and late phase which impact on their morbidity and mortality. The development of obesity and diabetes in these patients has been widely described in the literature with several hypotheses suggested: liver donor, nutritional and metabolic state, and immunosuppressive drugs.

RECENT FINDINGS

Most that is known about the development of these metabolic derangements has been attributed to the drugs used, especially the corticosteroids. When these have been used in higher doses for longer periods to treat rejection, the incidence of diabetes and obesity seems to be higher. However cyclosporine and to a lesser extent tacrolimus are also related to these alterations.

SUMMARY

As long-term survival improves in liver transplant patients, cardiovascular complications associated with dyslipidemia, obesity, and diabetes are emerging as risk factors for late morbidity and mortality. Therefore, it is important to assess the potential risk factors related to these complications, in order to prevent or decrease their incidence. From what has been seen, immunossupressive drugs seem to be the greatest risk factor for the development of metabolic derangements in post-transplantation patients. However other risk factors might also be involved, such as non-healthy eating habits and lack of exercise. The latter can be preventable if counseling policies are targeted at these patients in the pre-transplantation phase and continued after the operation.

Reduction in energy expenditure after liver transplantation

After successful liver transplantation (LTx), excessive weight gain is common among recipients. This rapid change in body morphology has been attributed to immunosuppressive regimens. The liver's role as a metabolic sensor and its autonomic innervation are pivotal in relaying humoral and neural information to the hypothalamus, where ingestive behavior is determined and has largely been ignored. We examined and assessed the contribution of drugs, energy intake, and energy expenditure on weight gain after LTx. Twenty-three patients were followed up at 3-mo intervals after LTx. Energy expenditure was measured by indirect calorimetry and dietary intake by diet diaries, and body composition was assessed with anthropometry and multifrequency bioelectrical impedance analysis. Cumulative drug doses were calculated, and associations between body composition and immunosuppressive regimens and energy expenditure were examined. Nine months after LTx, 20 of 23 (87%) recipients were overweight or obese, despite three-fourths of this cohort being on weight-reduction regimens. After LTx, a decrease in measured energy expenditure was observed (60.3 +/- 1.6 kJ/kg of body cell mass pre-LTx versus 53.7 +/- 2.2 kJ/kg of body cell mass after 9 mo; P < 0.05). Multiple stepwise regression analysis showed that, when adjusted for body weight, the strongest predictor of fat mass at 9 mo after LTx was resting energy expenditure. Weight gain after LTx is not predicted by immunosuppressive drug dosage. The strong association between weight gain and energy economy might be a consequence of the loss of hepatic metabolic integration and accelerated further by increased energy intake. Effective management of weight gain will not be achieved until the mechanisms involved in altered energy homeostasis are elucidated.

Amino acids in rinse effluents as a predictor of graft function after transplantation of fatty livers in rats

There are too few reliable markers by which one can predict future function of a liver before implantation. Consequently, the purpose of this study was to test the hypothesis that amino acids in rinse-effluents could predict transplant outcome in marginal fatty livers from rats. Amino acids were measured in the rinse effluent from the livers immediately after harvest and graft preparation or cold storage. Amino acids in the effluent were twice as high in ethanol-treated animals compared to those in nonfatty controls. Ethanol-treated fatty livers survived for no longer than 7 days after transplantation while 83% of nonfatty controls survived (P < 0.05). In subsequent studies, the cold-storage time was decreased to 6 h to determine whether failing fatty livers released more amino acid than grafts that would function normally. There was a significant increase in amino acids in the effluent of fatty grafts compared to controls. Moreover, the sum of the four selected amino acids (alanine, valine, histidine, leucine) was lower than 23 nmol/g liver in functional livers, whereas failing grafts had totals significantly higher than 25 nmol/g liver. The sum of the four amino acids correlated well with 24 h post-transplant serum AST levels (r = 0.78, P < 0.0001). So we can conclude that amino acid release can serve as a useful marker of graft viability and reliably predicts survival.

Optimal timing of liver transplantation for primary biliary cirrhosis

In 1989, we reported on the efficacy of liver transplantation in primary biliary cirrhosis (PBC) by demonstrating that the actual patient survival following transplantation was significantly better than without transplantation as predicted by a mathematical survival model ("Mayo natural history model"). Our aim in this investigation was to determine an optimal time to perform liver transplantation in PBC. One hundred forty-three patients with PBC undergoing liver transplantation were followed prospectively. Disease severity was measured immediately before transplantation by a summary score ("risk score") used in the Mayo natural history model, namely age, bilirubin, albumin, prothrombin time, and the presence or absence of edema. Proportional hazards analyses were performed assessing patient survival following transplantation. The influence of disease severity immediately pretransplantation on resource utilization for liver transplantation was assessed. Compared with our report in 1989, liver transplantation was performed at an earlier stage of disease (e.g., median risk score: 7.5 vs. 8.3; P < .01). Following transplantation, patient survival probabilities at 1, 2, and 5 years were 93%, 90%, and 88%, respectively. In the proportional hazards analysis, the risk of death following transplantation remained low until reaching a risk score of 7.8. In contrast, risk scores greater than 7.8 were associated with a progressively increased mortality. Resource utilization measured by the days in the intensive care unit (ICU) and hospital and the requirement for intraoperative blood transfusions was significantly greater in recipients who had higher risk scores before transplantation. Our data suggest that an optimal timing for liver transplantation, as determined by patient survival and resource utilization, appears to be at a risk score around 7.8 in patients with PBC.

Gentle in situ liver manipulation during organ harvest decreases survival after rat liver transplantation: role of Kupffer cells

BACKGROUND

The etiology of primary graft nonfunction and dysfunction is unknown but most likely involves Kupffer cell-dependent reperfusion injury. However, the donor operation and surgical technique may also have an effect on the outcome after transplantation. Because liver manipulation during harvest cannot be prevented completely with standard procedures, its effect on survival was assessed here.

METHODS

Donor livers were harvested from female Sprague-Dawley rats (200-230 g). Briefly, after minimal dissection during the first 12 min, livers were either manipulated gently or left alone for 13 subsequent minutes. At 25 min, all livers were perfused with cold University of Wisconsin solution via the portal vein, and transplantation was performed after cold storage (1 hr). In some rats, Kupffer cells were destroyed with gadolinium chloride or inactivated with dietary glycine before harvest. Survival, proteolytic activity in the rinse effluent, serum transaminases, trypan blue distribution to index microcirculation, and histology were compared.

RESULTS

In the nonmanipulated group, survival was 100% after transplantation; however, gentle manipulation decreased survival by 70%. Further, manipulation elevated transaminases fivefold and caused about 200% necrosis. At harvest, proteolytic activity and the time for trypan blue to distribute homogeneously were elevated three- to eightfold by manipulation. Gadolinium chloride and glycine prevented the effects of manipulation on all parameters studied.

CONCLUSION

These data indicate for the first time that brief, gentle manipulation of the donor liver has a marked detrimental effect on survival by priming or activating Kupffer cells. This may represent an important early event in pathogenesis, because Kupffer cells play an important role in primary graft nonfunction.

Hormonal responsiveness of hepatocytes after hypothermic preservation in University of Wisconsin solution

The hormonal responsiveness of freshly isolated rat hepatocytes was compared to that of a) cold-preserved isolated hepatocytes and b) hepatocytes isolated from cold-preserved whole liver. Cold-preserved hepatocytes and cells isolated from cold-preserved whole liver increased phosphorylase alpha activity in response to norepinephrine (plus propranolol), vasopressin, angiotensin II and glucagon. However, the maximal response to these agents was smaller than that of freshly isolated hepatocytes. Basal phosphorylase alpha activity was increased in cold-preserved hepatocytes. Similarly, cold preservation decreased the accumulation of cyclic AMP induced by glucagon and the effects of norepinephrine (plus propranolol), vasopressin and angiotensin II on the production of inositol phosphates. Basal levels of cyclic AMP were similar in the three conditions studied but basal production of [3H]IP2 plus [3H]IP3 was increased in cold-preserved hepatocytes. There was a very small effect of beta-adrenergic activation on phosphorylase activity and a small accumulation of cyclic AMP in response to isoproterenol in the conditions studied.

A statewide, population-based, time series analysis of access to liver transplantation

While the number of patients listed for liver transplant has increased, the pool of donor organs has remained constant. Questions have arisen regarding equitable access to organs. The purpose of this study was to analyze factors associated with access to liver transplantation (LT) using a large, population-based, hospital discharge database. The primary hypothesis was that a variety of factors other than medical need could be associated with access to LT. The rate of LT was defined as the number of liver transplants per admission for liver disease. The data sources were selected to allow a population-based, time-series analysis of all patients admitted with liver disease and those receiving liver transplants in all 157 nonfederal hospitals in North Carolina from 1988 to 1993. The hypotheses of this study were that age, gender, payment source, type of liver disease, distance from the transplant center, and rural county of residence were associated with patients' likelihood of access to LT. During the six years studied, 56,803 patients were admitted with liver disease and 126 underwent liver transplantation (LT). The rate of LT increased from 0.07% to 0.27%. Age, gender, source of payment, type of liver disease, rural county of residence, and distance of residence from the transplant center were associated with rates of transplantation. In the multivariate model, source of payment appeared to have the strongest association with the likelihood of LT. These findings raise important questions associated with equitable access to health care, need for physician education, and transplant center regionalization.

Pattern of liver, kidney, heart, and intestine allograft rejection in different mouse strain combinations

With advances in microsurgery and molecular biology, the mouse model for organ transplantation has become increasingly popular. However, knowledge about these models is limited, as only a small number of centers have experience with murine models. In this study, we compared the rejection pattern after liver, kidney, heart, and small bowel transplantation in the three different mouse strain combinations: (1) C57BL/6 (H2b)-->BALB/c (H2d), (2) BALB/c (H2d)-->CBA (H2k), and (3) C57BL/6-->C3H/HeN (H2k). Our study demonstrated that mouse allograft survival varies depending on the organ graft and on the donor-recipient strain combinations. The majority of liver allografts were spontaneously accepted despite complete MHC disparity. A mixed pattern of acute rejection and acceptance occurred in kidney recipients depending on the donor-recipient strain combination. All the heart grafts developed rejection and all the intestinal grafts were rapidly rejected with no spontaneous acceptance. The criteria for rejection, the potential applications, and the limitations of each model are discussed. The models described in this article provide a number of useful choices for organ transplantation research.

Effects of liver transplantation and resection on lipid parameters: a longitudinal study

BACKGROUND

The liver plays a vital role in the production and clearance of a large number of lipoproteins and is an important determinant of the plasma levels of various lipids including cholesterol, as well as apoproteins such as apoprotein (a).

METHODS

To explore the role of the liver in the regulation of lipids and apoprotein concentrations, a serial prospective study measuring lipid parameters and apoprotein (a) levels over 6 months was performed in individuals undergoing hepatic resection for isolated hepatic metastases, transplantation for end-stage liver disease and in individuals undergoing colorectal surgery for malignancy.

RESULTS

In the group with hepatic resection, there was a rapid decrease in total, high density lipoprotein (HDL) and low density lipoprotein (LDL) cholesterol in the immediate postoperative period. However, these changes could be explained by fasting and surgical intervention as a similar phenomenon was observed in the control subjects. In patients undergoing liver transplantation, total cholesterol decreased over the the immediate postoperative period but had fully recovered by day 40. Apoprotein (a) was low pre-operatively, remained low over the first week but had risen by day 10. Apoprotein (a) at day 40 correlated with the apoprotein (a) level of the donor (r = 0.80, P < 0.01) but not of the recipient's pre-operative level and this correlation persisted 6 months after hepatic transplantation.

CONCLUSIONS

The liver has a large reserve and is able to maintain lipoprotein production and removal despite greater than 50% removal. The major cause of reduced plasma lipid concentrations in the postoperative period relates to other factors such as fasting and handling of the gut during surgery. In liver transplantation, apoprotein (a) levels resemble those of the donor within 2 weeks of organ donation, consistent with the liver being the major site of production of this apoprotein.

Corticosteroid withdrawal after liver transplantation

BACKGROUND

Long-term side effects of corticosteroids (CSs) result in > major morbidity for recipients of orthotopic liver transplants (OLT). We instituted a program of CS withdrawal among OLT recipients to quantify the contribution of CS to adverse clinical sequelae and to determine whether long-term CS administration is necessary to avoid rejection.

METHODS

Recipients who had normal allograft function on CS, cyclosporine, and azathioprine more than 1 year after OLT were offered CS withdrawal during 12 to 22 weeks. Patients underwent routine clinical monitoring and laboratory studies. Continuous variables were compared by paired t test analysis.

RESULTS

CSs were discontinued in 51 recipients; 45 (88%) of 51 patients remain steroid-free after a mean follow-up of 13.8 months (range, 4 to 36). CS therapy was reinstituted in 6 patients who had abnormal transaminase levels during routine follow-up. Among the patients who remain off CS, there were no significant changes in blood pressure, transaminase, alkaline phosphatase, bilirubin, or glucose levels during the study period. Mean number of blood pressure medications decreased from 0.7 +/- 0.1 to 0.4 +/- 0.1 (p = 0.007). Cholesterol decreased from 217 +/- 8 mg/dl on CS to 204 +/- 9 mg/dl at 1 month (p = 0.0001), 183 +/- 10 mg/dl at 3 months (p = 0.0001), 198 +/- 8 mg/dl at 6 months (p = 0.04), 213 +/- 11 mg/dl at 12 months (p = 0.01), 209 mg/dl +/- 16 at 18 months (p = 0.02), and 183 +/- 19 mg/dl at 24 months (p = 0.2) off CS. Weight loss occurred in 88% of patients and averaged 9.5 pounds.

CONCLUSIONS

CS therapy can be successfully withdrawn without precipitating rejection in liver transplant recipients who have stable graft function 1 year after OLT. The incidence and severity of hypertension and hypercholesterolemia are reduced in patients whose CSs have been withdrawn.