Can controlled non-heart-beating donors provide a solution to the organ shortage?

Donations After Circulatory Death in Liver Transplant

The supply of liver grafts for treatment of end-stage liver disease continues to fall short of ongoing demands. Currently, most liver transplants originate from donations after brain death. Enhanced utilization of the present resources is prudent to address the needs of the population. Donation after circulatory or cardiac death is a mechanism whereby the availability of organs can be expanded. Donations after circulatory death pose unique challenges given their exposure to warm ischemia. Technical principles of donations after circulatory death procurement and pertinent studies investigating patient outcomes, graft outcomes, and complications are highlighted in this review. We also review associated risk factors to suggest potential avenues to achieve improved outcomes and reduced complications. Future considerations and alternative techniques of organ preservation are discussed, which may suggest novel strategies to enhance preservation and donor expansion through the use of marginal donors. Ultimately, without effective measures to bolster organ supply, donations after circulatory death should remain a consideration; however, an understanding of inherent risks and limitations is necessary.

How important is donor age in liver transplantation?

The age of liver donors has been increasing in the past several years because of a donor shortage. In the United States, 33% of donors are age 50 years or older, as are more than 50% in some European countries. The impact of donor age on liver transplantation (LT) has been analyzed in several studies with contradictory conclusions. Nevertheless, recent analyses of the largest databases demonstrate that having an older donor is a risk factor for graft failure. Donor age is included as a risk factor in the more relevant graft survival scores, such as the Donor Risk Index, donor age and Model for End-stage Liver Disease, Survival Outcomes Following Liver Transplantation, and the Balance of Risk. The use of old donors is related to an increased rate of biliary complications and hepatitis C virus-related graft failure. Although liver function does not seem to be significantly affected by age, the incidence of several liver diseases increases with age, and the capacity of the liver to manage or overcome liver diseases or external injuries decreases. In this paper, the importance of age in LT outcomes, the role of donor age as a risk factor, and the influence of aging on liver regeneration are reviewed.

The bile duct in donation after cardiac death donor liver transplant

PURPOSE OF REVIEW

This review considers the biliary complications associated with liver transplantation using donation after cardiac death (DCD) donor grafts.

RECENT FINDINGS

The increasing use of DCD liver grafts with their increased incidence of biliary complications is discussed. The ethics of this greater use is briefly analysed. Recent animal and human study evidence to support the peribiliary vascular plexus' role in ischaemic cholangiopathy is reviewed. Recent advances in in-vivo and ex-vivo perfusion are explored. In particular, the latest theories regarding perfusion's peribiliary plexus preserving effects and the mechanism by which biliary regeneration may be promoted as a consequence are discussed.

SUMMARY

This article explores the need for DCD liver graft use and the associated biliary complications. The current theories regarding the cause of DCD biliary complications are reviewed, as are the current strategies to reduce them.

Safety evaluation of stem cells used for clinical cell therapy in chronic liver diseases; with emphasize on biochemical markers

There are several issues to be considered to reduce the risk of rejection and minimize side effects associated with liver cell transplantation in chronic liver diseases. The source and the condition of stem cell proliferation and differentiation ex vivo and the transplantation protocols are important safety considerations for cell based therapy. The biochemical and molecular markers are important tools for safety evaluation of different processes of cell expansion and transplantation. Studies show that hepatocytes differentiated from adult and embryonic stem cells exhibit biochemical and metabolic properties resembling mature hepatocytes. Therefore these assays can help to assess the biological and metabolic performance of hepatocytes and progenitor stem cells. The assays also help in testing the contribution of transplanted hepatocytes in improving the repair and function of damaged liver in the recipient. Here we review the biochemical and metabolic markers, which are implicated in evaluation of safety issues of stem cells used for therapeutic purposes in chronic liver diseases and regeneration of damaged liver. We also highlight application of biochemical tests for assessment of liver cell transplantation.

Human hepatocyte transplantation overview

The interest in hepatocyte transplantation has been growing continuously in recent years and this treatment may represent an alternative clinical approach for patients with acute liver failure and liver-based metabolic disorders. This chapter presents an overview of liver cell transplantation, from the basic research to human experience. It summarizes the pre-clinical studies and present status of clinical hepatocyte transplantation and identifies some possible areas of future research in this area.

Segmental liver transplantation from non-heart beating donors--an early experience with implications for the future

We report our experience of pediatric liver transplantation with partial grafts from non-heart beating donors (NHBD). Controlled donors less than 40 years of age with a warm ischemia time (WI) of less than 30 min were considered for pediatric recipients. Death was declared 5 min after asystole. A super-rapid recovery technique with aortic and portal perfusion was utilized. Mean donor age was 29 years and WI 14.6 min (range 11-18). Seven children, mean age 4.9 years (0.7-11), median weight 20 kg (8.4-53) received NHBD segmental liver grafts. Diagnoses included seronegative hepatitis, neonatal sclerosing cholangitis, familial intrahepatic cholestasis, hepatoblastoma, primary hyperoxaluria and factor VII deficiency (n=2). The grafts included four reduced and one split left lateral segments, one left lobe and one right auxiliary graft. Mean cold ischemia was 7.3 h (6.2-8.8). Complications included one pleural effusion and one biliary collection drained percutaneously. At 20 months (10-36) follow-up all children are alive and well with functioning grafts. Donation after cardiac death is a significant source of liver grafts for adults and children with careful donor selection and short cold ischemic times.

Isolation of hepatocytes from livers from non-heart-beating donors for cell transplantation

One of the limitations to hepatocyte transplantation is the restricted availability of donor liver tissue. The aim of this study was to evaluate livers from non-heart-beating donors (NHBDs) as a source of hepatocytes for cell transplantation. A total of 20 livers/segments obtained from NHBD were perfused under good manufacturing practices using a standard collagenase digestion method. The donor liver median warm ischemia time was 15 minutes (range, 11-40 minutes), and cold ischemia time was 13 hours (range, 6-30 hours) prior to cell isolation. The cell viability of the hepatocytes obtained was 52% (1-81%), with a yield of 2.2 x 10(6)(0.2-29.7 x 10(6)) cells per gram of tissue. There was a significant negative correlation between hepatocyte viability and length of both warm ischemia (r = -0.544, P = 0.013) and cold ischemia (r = -0.510, P = 0.022). Preliminary experiments were performed on the viability testing of NHBD livers based on digestion of needle biopsies with collagenase and assessment of the hepatocytes produced. Two of the NHBD cell preparations, which had been cryopreserved, were used as part of a series of cell infusions for hepatocyte transplantation. A 3.5-yr-old girl with Crigler-Najjar syndrome type I received 9.7 x 10(8) NHBD hepatocytes (viability on thawing, 65%), and a 4-month-old boy with inherited clotting factor VII deficiency received 5.0 x 10(8) hepatocytes (viability, 57%). In conclusion, hepatocytes suitable for cell transplantation can be obtained from NHBD livers. Higher viability values may be obtained if both warm and cold ischemia times of donor liver can be reduced prior to processing.

The effects of cryopreservation on human hepatocytes obtained from different sources of liver tissue

Successful cryopreservation of human hepatocytes is important to establish hepatocyte banks for clinical use or in vitro research. The availability of donor tissue from unused liver segments/lobes and non-heart-beating donors (NHBD) has provided newer sources of hepatocytes. The quality of hepatocytes at the time of cryopreservation is important as cells isolated from liver tissue of borderline quality may not withstand the stresses associated with cryopreservation and subsequent thawing. Human hepatocytes were cryopreserved after isolation from mainly donor tissues (n = 40). In vitro assessment of the viability and function of the fresh and thawed cryopreserved hepatocytes was performed. Viability, attachment efficiency, enzyme activity, and albumin production of hepatocytes were all significantly decreased, and LDH leakage significantly increased, on thawing after cryopreservation. The viability of cryopreserved hepatocytes isolated from tissue rejected for orthotopic liver transplantation (36 +/- 15%) was significantly lower than those isolated from tissue where part was used for liver transplantation (47 +/- 14%, p = 0.002), but there were no significant differences in functional parameters. The viability of cryopreserved hepatocytes isolated from NHBD tissue (29 +/- 9%, p = 0.001) and from steatotic donor tissue (35 +/- 11%, p = 0.019) was significantly lower than those isolated from normal donor tissue (49 +/- 14%). There was no difference in functional parameters, except for albumin production of hepatocytes from NHBD tissue (2.9 +/- 1.0 microg/h/mg protein) being significantly lower than those from normal donor tissue (4.8 +/- 2.8 microg/h/mg protein, p = 0.03). The viability and attachment efficiency of cryopreserved hepatocytes isolated from liver tissue from resections for tumors was significantly higher, and the LDH leakage significantly lower, than those isolated from all donor tissue. Hepatocytes isolated from NHBD and steatotic tissue were more vulnerable to the effects of cryopreservation. Further research is required to improve hepatocyte isolation and cryopreservation protocols for different types of liver tissue.

Critical Care Pharmacy in Donor Management

Significant systemic changes occur following neurologic insult and subsequent brain death. If left untreated, the hemodynamic instability and neuroendocrine alterations that ensue may significantly affect the quality of the donor organs, and contribute to posttransplant allograft dysfunction. A number of pharmacologic interventions are often implemented in an attempt to stabilize donor hemodynamics and optimize organ perfusion, thereby increasing the number and quality of cadaveric donor organs available for transplantation. This review provides a summary of these interventions, with an emphasis placed on hormonal resuscitation, which involves utilizing such agents as thyroxin, vasopressin, insulin, and corticosteroids.