Liver and Kidney Transplantation: A Half-Century Historical Perspective

Demographic Trends in Liver Transplant Survivors After 3 Decades of Program Implementation: The Impact of Cohort and Period Effects on Life Expectancy

Background

Demographic analyses may reveal current patterns of change in the outcomes of rapidly developing medical procedures because they incorporate the period perspective.

Methods

We analyzed the changes in size, age structure, and hospitalizations in the population of liver transplantation (LT) survivors in our center during the last 30 y (n = 1114 patients) and generated projections, including life expectancy (LE), considering cohort and period effects. Life tables were used to project the complete LE (overall 1990-2020 experience), the cohort LE (according to the decade of surgery: 1990-2000, 2000-2010, and 2010-2020), and the period LE (current 2015-2020 experience).

Results

The population of LT recipients in follow-up continued to experience progressive growth and aging since 1990 (492 patients [41.9% >65 y] in 2020), and the magnitude of these phenomena may double in the next 30 y. However, the number of admissions and days of admission has been decreasing. The complete LE at LT was 12.4 y, whereas the period LE was 15.8 y. The cohort LE (limited to 10 y) was 5.3, 6.3, and 7.3 y for the 1990-2000, 2000-2010, and 2010-2020 cohorts, respectively.

Conclusions

The target population of our medical care after LT is growing and aging. The prevalence of both of these phenomena is expected to increase in the coming years and is associated with a current improvement in LE. However, the hospitalization burden associated with LT survivors is declining. The period effect should be considered for generating up-to-date information on these current trends, which are crucial when designing health policies for LT survivors.

Clinical Research in Renal Transplantation: A Bibliometric Perspective on a Half-century of Innovation and Progress

BACKGROUND

Groundbreaking biomedical research has transformed renal transplantation (RT) into a widespread clinical procedure that represents the mainstay of treatment for end-stage kidney failure today. Here, we aimed to provide a comprehensive bibliometric perspective on the last half-century of innovation in clinical RT.

METHODS

The Web of Science Core Collection was used for a comprehensive screening yielding 123 303 research items during a 50-y period (January 1973-October 2022). The final data set of the 200 most-cited articles was selected on the basis of a citation-based strategy aiming to minimize bias.

RESULTS

Studies on clinical and immunological outcomes (n = 63 and 48), registry-based epi research (n = 38), and randomized controlled trials (n = 35) dominated the data set. Lead US authors have signed 110 of 200 articles. The overall level of evidence was high, with 84% of level1 and -2 reports. Highest numbers of these articles were published in New England Journal of Medicine , Transplantation , and American Journal of Transplantation. Increasing trend was observed in the number of female authors in the postmillennial era (26% versus 7%).

CONCLUSIONS

This study highlights important trends in RT research of the past half-century. This bibliometric perspective identifies the most intensively researched areas and shift of research interests over time; however, it also describes important imbalances in distribution of academic prolificacy based on topic, geographical aspects, and gender.

The role of efferocytosis and transplant rejection: Strategies in promoting transplantation tolerance using apoptotic cell therapy and/or synthetic particles

Recently, efforts have been made to recognize the precise reason(s) for transplant failure and the process of rejection utilizing the molecular signature. Most transplant recipients do not appreciate the unknown length of survival of allogeneic grafts with the existing standard of care. Two noteworthy immunological pathways occur during allogeneic transplant rejection. A nonspecific innate immune response predominates in the early stages of the immune reaction, and allogeneic antigens initiate a donor-specific adaptive reaction. Though the adaptive response is the major cause of allograft rejection, earlier pro-inflammatory responses that are part of the innate immune response are also regarded as significant in graft loss. The onset of the innate and adaptive immune response causes chronic and acute transplant rejection. Currently employed immunosuppressive medications have shown little or no influence on chronic rejection and, as a result, on overall long-term transplant survival. Furthermore, long-term pharmaceutical immunosuppression is associated with side effects, toxicity, and an increased risk of developing diseases, both infectious and metabolic. As a result, there is a need for the development of innovative donor-specific immunosuppressive medications to regulate the allorecognition pathways that induce graft loss and to reduce the side effects of immunosuppression. Efferocytosis is an immunomodulatory mechanism with fast and efficient clearance of apoptotic cells (ACs). As such, AC therapy strategies have been suggested to limit transplant-related sequelae. Efferocytosis-based medicines/treatments can also decrease the use of immunosuppressive drugs and have no detrimental side effects. Thus, this review aims to investigate the impact of efferocytosis on transplant rejection/tolerance and identify approaches using AC clearance to increase transplant viability.

Necroptosis in Solid Organ Transplantation: A Literature Overview

Ischemia-reperfusion injury (IRI) is encountered in various stages during solid organ transplantation (SOT). IRI is known to be a multifactorial inflammatory condition involving hypoxia, metabolic stress, leukocyte extravasation, cellular death (including apoptosis, necrosis and necroptosis) and an activation of immune response. Although the cycle of sterile inflammation during IRI is consistent among different organs, the underlying mechanisms are poorly understood. Receptor-interacting protein kinase 3 (RIPK3) and mixed-lineage kinase domain-like pseudokinase (MLKL) are thought to be crucial in the implementation of necroptosis. Moreover, apart from “silent” apoptotic death, necrosis also causes sterile inflammation—necroinflammation, which is triggered by various damage-associated molecular patterns (DAMPs). Those DAMPs activate the innate immune system, causing local and systemic inflammatory responses, which can result in graft failure. In this overview we summarize knowledge on mechanisms of sterile inflammation processes during SOT with special focus on necroptosis and IRI and discuss protective strategies.

Complications and safety of the transplanted organ after upper extremity surgery in patients receiving immunosuppressant therapy after solid organ transplantation

PURPOSE

The purpose of this study was to evaluate the complications and safety of transplanted organs after upper extremity surgery in patients taking immunosuppressants after solid organ transplantation (SOT).

METHODS

Seventy-two transplant recipients underwent 99 upper extremity surgeries while on immunosuppressants after SOT at our institution between January 2009 and December 2018. We retrospectively reviewed the clinical data of these patients, including their demographic information and data related to the SOT and upper extremity surgery.

RESULTS

Trigger/tendon release (n = 31, 31.3%) was the most frequently performed upper extremity surgery, followed by incision and drainage for an infection (n = 16, 16.2%). Post-operative complications occurred after ten upper extremity operative procedures (10.1%), among which uncontrolled infection after surgery for an infection (n = 4) was the most common. According to the Clavien-Dindo classification, the complications of three surgical procedures were grade I, three were grade II, and four were grade III, and all were treatable. The occurrence rate of the complications was not significantly different between emergent and elective surgery. All transplanted organ-specific indicators did not worsen significantly after emergent or elective upper extremity surgery.

CONCLUSIONS

Since the function of the transplanted organ was well-preserved after emergent or elective upper extremity surgery, common upper extremity procedures do not seem to be a worrisome practice for SOT patients. However, when treating hand and upper extremity infections in SOT patients, surgeons should explain the possible need for multiple operations  and the high complication rate.

A Review of the Current State of Liver Transplantation Disparities

Equity in access is one of the core goals of the Organ Procurement and Transplant Network (OPTN). However, disparities in liver transplantation have been described since the passage of the National Organ Transplant Act, which established OPTN in the 1980s. During the past few decades, several efforts have been made by the United Network for Organ Sharing (UNOS) to address disparities in liver transplantation with notable improvements in many areas. Nonetheless, disparities have persisted across insurance type, sex, race/ethnicity, geographic area, and age. African Americans have lower rates of referral to transplant centers, females have lower rates of transplantation from the liver waiting list than males, and public insurance is associated with worse posttransplant outcomes than private insurance. In addition, pediatric candidates and older adults have a disadvantage on the liver transplant waiting list, and there are widespread regional disparities in transplantation. Given the large degree of inequity in liver transplantation, there is a tremendous need for studies to propose and model policy changes that may make the liver transplant system more just and equitable.

History of organ transplantation and the development of key immunosuppressants

The history of organ transplantation is limited to the last century. To overcome the barrier of the host immune system, which results in transplant rejection, the pioneers of transplantation achieved their first success by performing a kidney transplantation between identical twins. This achievement led the transplant clinicians to perform transplantations with immunological barriers present. Strategies such as whole-body irradiation combined with steroids yielded success in kidney transplantation between non-identical twins and siblings. However, owing to the toxicity related to irradiation, the paradigm shifted to the use of immunosuppressants. Azathioprine, steroids, and anti-lymphocyte globulin became the first multiple immunosuppressive regimens. With the introduction of cyclosporine, the 1-year survival rate increased by more than 80%. Cyclosporine, azathioprine, and steroids became the new standard maintenance regimens until the introduction of tacrolimus and mycophenolate mofetil, which replaced cyclosporine and azathioprine, respectively. The most recent change in immunosuppressants was the development of monoclonal antibodies with specific binding sites, such as CD20 (rituximab) and CD25 (basiliximab). With the innovation of molecular engineering and new insights into the costimulatory pathways, new molecules are under investigation in the field of transplantation.

Missed opportunities for organ donation in patients with intracranial haemorrhage at the emergency department: A single-centre study

Background:

The demand for transplantable organs has increased in Singapore. However, organ donation has been consistently lower than international standards. Donation after brain death (DBD) most commonly follows intracranial haemorrhage (ICH).

Objective:

Our aim was to identify missed opportunities for organ donation among those who presented to the Emergency Department (ED) and died following ICH.

Methods:

A retrospective study was carried out for all cases of ICH presenting to the ED from 1 January 2013 to 31 December 2017. The patients’ medical records were reviewed for identification of potential donors and actualisation of organ donation.

Results:

There were 615 cases of ICH, with a mortality rate of 6.0%. Among those who died, 28 (75.7%) died in the Intensive Care Unit (ICU) and nine (24.3%) patients had withdrawal of care in the ED. Thirty patients (81.1%) were potential donors but organ donation was actualised in only three (8.1%) patients. Thirteen organs, as well as heart valves and iliac vessels were retrieved from the organ donors for transplantation.

Conclusion:

There were missed opportunities for organ donation. EDs have an important role to play in the national organ donation programme by identifying potential donors for organ donation and considering admitting these patients to ICU to facilitate organ donation.

Infections in Transplantation: Introduction and Overview

Over the last 70 years, a steady growth in population of patients with severe and mostly iatrogenically induced immune suppression while undergoing myeloablative antineoplastic therapy and blood- and marrow-derived stem cell or solid organ transplantation has resulted in a near-explosive growth of opportunistic infections. Furthermore, the advent and now common use of biologic immunosuppressive drugs are given to an increasing number of patients prior to transplantation or for treatment of complications arising during the posttransplant period such as graft-versus-host disease, lymphoproliferative disorders, opportunistic malignancies, cancer recurrences, and rejection of solid organ allograft. These and other recent therapeutic advances in transplantation procedures continue to be fraught with prolonged and often unpredictable period of drug-induced immune dysregulation. The emergence and spread of difficult-to-treat opportunistic bacterial, viral, fungal, and parasitic diseases in transplant population have evolved under the influence of environmental-, host-, disease-, and treatment-specific variance. A diligent diagnostic adjudication is of utmost importance in a population with known proclivity for atypical disease presentation. Inaccurate diagnosis may result in inappropriate and ineffective empiric therapy that may worsen patients’ morbidity and heighten the risk for further complications and death. Advancement in understanding the immunopathogenesis of infectious diseases, hosts’ immunologic vulnerability for infections, emerging molecular diagnostic paradigms, deciphering potential therapeutic impact of immune modulation by existing and new antimicrobial drugs, and active research and development in mitigation strategies to promote immune recovery and immune preservation are encouraging developments in optimizing care for patients in need for lifesaving transplantation procedures.

Solid organ transplantation in the 21st century

Solid organ transplantation (SOT) has emerged from an experimental approach in the 20th century to now being an established and practical definitive treatment option for patients with end-organ dysfunction. The evolution of SOT has seen the field progress rapidly over the past few decades with incorporation of a variety of solid organs-liver, kidney, pancreas, heart, and lung-into the donor pool. New advancements in surgical technique have allowed for more efficient and refined multi-organ procurements with minimal complications and decreased ischemic injury events. Additionally, immunosuppression therapy has also seen advancements with the expansion of immunosuppressive protocols to dampen the host immune response and improve short and long-term graft survival. However, the field of SOT faces new barriers, most importantly the expanding demand for SOT that is outpacing the current supply. Allocation protocols have been developed in an attempt to address these concerns. Other avenues for SOT are also being explored to increase the donor pool, including split-liver donor transplants, islet cell implantation for pancreas transplants, and xenotransplantation. The future of SOT is bright with exciting new research being explored to overcome current obstacles.

Recent advances in understanding and managing infectious diseases in solid organ transplant recipients

Background: Undergoing solid organ transplantation (SOT) exposes the recipient to various infectious risks, including possible transmission of pathogen by the transplanted organ, post-surgical infections, reactivation of latent pathogens, or novel infections. Recent advances: In the last few years, the emergence of Zika virus has raised concerns in the transplant community. Few cases have been described in SOT patients, and these were associated mainly with moderate disease and favorable outcome; the notable exception is a recent case of fatal meningo-encephalopathy in a heart transplant recipient. Because of the advances in treating hepatitis C, several teams recently started to use organs from hepatitis C-positive donors. The worldwide increasing incidence of multidrug-resistant pathogens, as well as the increasing incidence of Clostridioidesdifficile infection, is of particular concern in SOT patients. In the field of mycology, the main recent therapeutic advance is the availability of isavuconazole for the treatment of invasive aspergillosis and mucormycosis. This drug has the advantage of minimal interaction with calcineurin inhibitors. Regarding the viral reactivations occurring after transplant, cytomegalovirus (CMV) infection is still a significant issue in SOT patients. The management of resistant CMV remains particularly difficult. The approval of letermovir, albeit in bone marrow transplantation, and the therapeutic trial of maribavir bring a ray of hope. Another advancement in management of post-transplant infections is the development of in vitro tests evaluating pathogen-specific immune response, such as immunodiagnostics for CMV and, more recently, tests for monitoring immunity against BK virus. Conclusion: The increasing number of organ transplantations, the use of newer immunosuppressive drugs, and high-risk donors continue to define the landscape of transplant infectious diseases in the current era.

Evolving Trends in Racial Disparities for Peri-Operative Outcomes with the New Kidney Allocation System (KAS) Implementation

INTRODUCTION

To improve kidney transplant allocation equitability, a new Kidney Allocation System (KAS) was implemented December 4, 2014. The purpose of this study was to determine if the impact of KAS on peri-operative outcomes differed by recipient race/ethnicity.

METHODS

This was a time series analysis using data aggregated in monthly intervals from October 2012 through September 2015 using the University HealthSystem Consortium (UHC). This includes national data aggregated at the center level of all US kidney transplant centers that participate in the UHC (416 centers). Segmented regression with interaction terms was used to determine the impact of KAS on outcomes and differences by race/ethnicity.

RESULTS

A total of 28,809 deceased donor kidney transplants were included with 25 months of pre-KAS data and 10 months of post-KAS data. After KAS implementation, the estimated transplant rate per month decreased significantly for Caucasians by 17.6 cases per month (p = 0.0001), and increased significantly for AAs by 37.8 (p = 0.0001), Hispanics by 16.3 (p = 0.0001), and other races by 8.2 cases per month (p = 0.0001). Delayed graft function, 7- and 14-day readmissions significantly increased after KAS, which did not differ by race. Hispanics saw a 7.7% decrease in ICU admissions after KAS, which differed as compared to other racial/ethnic cohorts (p = 0.0026). Costs of kidney transplantation increased significantly after KAS in all groups except Hispanics. Mortality, length of stay, in-hospital complications, and 30-day readmissions were not significantly impacted by KAS, also not differing by race/ethnicity.

CONCLUSION

KAS had substantial impact on transplant rates by race/ethnicity. KAS also led to increased costs, readmissions, and delayed graft function (DGF) across all racial/ethnic groups. The impact of KAS on ICU cases solely within Hispanics requires further investigation into potential etiologies.

Association of Clinical Events With Everolimus Exposure in Kidney Transplant Patients Receiving Low Doses of Tacrolimus

A key objective in the use of immunosuppression after kidney transplantation is to attain the optimal balance between efficacy and safety. In a phase 3b, multicenter, randomized, open-label, noninferiority study, the incidences of clinical events, renal dysfunction, and adverse events (AEs) were analyzed at 12 months in 309 de novo renal transplant recipients receiving everolimus (EVR), low-dose tacrolimus (LTac), and prednisone. Cox proportional hazard regression modeling was used to estimate the probability of clinical events at specified combinations of time-normalized EVR and Tac trough concentrations. At 12 months, the highest incidence of treated biopsy-proven acute rejection (tBPAR) and graft loss occurred most often in patients with EVR trough concentration <3 ng/mL (64.7% and 10.5%, respectively). At 1 month and 12 months, increasing EVR levels were associated with fewer tBPAR events (both p < 0.0001). Low estimated glomerular filtration rate (eGFR) and decreased eGFR occurred more often in patients with lower EVR and higher Tac levels. AEs were most often observed in patients with EVR levels <3 ng/mL. This study supports maintaining an EVR trough concentration of 3-8 ng/mL, when combined with LTac, to achieve balanced efficacy and safety in renal transplant recipients.

TRIAL REGISTRATION

NCT01025817.