Apolipoprotein L1: role in the evaluation of kidney transplant donors

Expanding Opportunities for Living Donation: Recommendations From the 2023 Santander Summit to Ensure Donor Protections, Informed Decision Making, and Equitable Access

A strategic vision toward global convergence in transplantation must encourage and remove barriers to living organ donation and transplantation. Here, we discuss deliberations of a working group of the 2023 Santander Summit charged with formulating recommendations for the safe expansion of living donor kidney transplantation and living donor liver transplantation worldwide. Living donor kidney transplantation has grown to be the preferred treatment for advanced kidney failure. Living donor liver transplantation emerged more recently as a strategy to reduce waitlist mortality, with adoption influenced by cultural factors, regional policies, clinical team experience, and the maturity of regional deceased donor transplant systems. Barriers to living donor transplantation span domains of education, infrastructure, risk assessment/risk communication, and financial burden to donors. Paired donor exchange is a growing option for overcoming incompatibilities to transplantation but is variably used across and within countries. Effectively expanding access to living donor transplantation requires multifaceted strategies, including improved education and outreach, and measures to enhance efficiency, transparency, and shared decision making in donor candidate evaluation. Efforts toward global dissemination and vigilant oversight of best practices and international standards for the assessment, informed consent, approval, and monitoring of living donors are needed. Fostering greater participation in paired exchange requires eliminating disincentives and logistical obstacles for transplant programs and patients, and establishing an ethical and legal framework grounded in World Health Organization Guiding Principles. Sharing of best practices from successful countries and programs to jurisdictions with emerging practices is vital to safely expand the practice of living donation worldwide and bring the field together globally.

APOL1 Kidney Risk Variants and Long-Term Kidney Function in Healthy Middle-Aged Black Individuals: The Atherosclerosis Risk in Communities (ARIC) Study

Rationale & Objective

The effect of apolipoprotein L1(APOL1) genotype on future risk of kidney disease among middle-aged individuals with good kidney function is not well established.

Study Design

Longitudinal cohort study.

Setting & Participants

In total, 5,886 healthy individuals (45-64 years old) enrolled in the Atherosclerosis Risk in Communities study with creatinine-based estimated glomerular filtration rate ≥ 80 mL/min who would be suitable kidney donors.

Exposures

Race and APOL1 genotype.

Outcomes

Creatinine- and cystatin C-based estimated glomerular filtration rate (eGFRcr-cys) using the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) 2021 equation, urinary albumin-creatinine ratio (UACR), proportion with chronic kidney disease (CKD) 3a or worse, end-stage kidney disease (ESKD), and death.

Analytical Approach

Participants grouped based on race and APOL1 genotype. Compared eGFRcr-cys and UACR across groups. Multinomial logistic regression models were used compare odds of CKD. Kaplan-Meier survival curves were created to compare rates of ESKD and death at last follow-up.

Results

There were 5,075 Whites (86%), 701 Blacks carrying the low-risk APOL1 genotype (12%), and 110 Blacks carrying the high-risk APOL1 genotype (2%). The mean age at baseline was 53 ± 6 years. At 10 years, White participants had lower eGFRcr-cys than low-risk and high-risk groups (89 ± 16 vs 91 ± 16 and 92 ± 15 mL/min/1.73 m2, respectively; P < 0.001). At 25 years, White participants continued to have lower eGFRcr-cys than the low-risk group (70 ± 18 vs 72 ± 19 mL/min/1.73 m2; P < 0.001) but not compared with the high-risk APOL1 genotype (67±23 mL/min/1.73 m2). There was no difference in UACR among groups at 10 and 25 years (P = 0.87 and 0.91, respectively). The odds of developing CKD stage 3a or worse were not different between low-risk and high-risk APOL1 group in both unadjusted and adjusted models (P = 0.26 and P = 0.39, respectively). At last follow-up, <5% developed ESKD, and 45% of individuals either died or reached ESKD with no difference in outcomes between the groups.

Limitations

Low ascertainment because of death and long follow-up.

Conclusions

Among middle-aged individuals, APOL1 genotype does not appear to be a major driver of future risk of kidney disease.

Evaluating ApoL1 Genetic Testing Policy Options for Transplant Centers: A Delphi Consensus Panel Project with Stakeholders

BACKGROUND

Apolipoprotein L1 (ApoL1) variants G1 and G2 are associated with a higher risk of kidney disease. ApoL1 risk variants are predominantly seen in individuals with sub-Saharan African ancestry. In most transplant centers, potential organ donors are being selectively genetically tested for ApoL1 risk variants. Transplant programs have highly variable ApoL1 testing practices and need guidance on essential ApoL1 clinical policy questions.

METHODS

We conducted a Delphi consensus panel focused on ApoL1 clinical policy questions, including who gets tested, who decides whether testing occurs, how test results are shared, who receives test results, and how test results are used. A total of 27 panelists across seven stakeholder groups participated: living kidney donors ( n =4), deceased donor family members ( n =3), recipients of a deceased donor kidney ( n =4), recipients of a living donor kidney ( n =4), nephrologists ( n =4), transplant surgeons ( n =4), and genetic counselors ( n =4). Nineteen panelists (70%) identified as Black. The Delphi panel process involved two rounds of educational webinars and three rounds of surveys administered to panelists, who were asked to indicate whether they support, could live with, or oppose each policy option.

RESULTS

The panel reached consensus on one or more acceptable policy options for each clinical policy question; panelists supported 18 policy options and opposed 15. Key elements of consensus include the following: ask potential donors about African ancestry rather than race; make testing decisions only after discussion with donors; encourage disclosure of test results to blood relatives and organ recipients but do not require it; use test results to inform decision making, but never for unilateral decisions by transplant programs.

CONCLUSIONS

The panel generally supported policy options involving discussion and shared decision making among patients, donors, and family stakeholders. There was general opposition to unilateral decision making and prohibiting donation altogether.

Apolipoprotein L1 Opinions of African American Living Kidney Donors, Kidney Transplant Patients, and Nonpatients

INTRODUCTION

The discovery of apolipoprotein L1 (ApoL1) has raised important ethical and clinical questions about genetic testing in the context of living and deceased kidney donation. Largely missing from this discussion are the perspectives of those African Americans (AA) most likely to be impacted by ApoL1 testing.

METHODS

We surveyed 331 AA potential and former living kidney donors (LKDs), kidney transplant candidates and recipients, and nonpatients at three United States transplant programs about their ApoL1 testing attitudes.

RESULTS

Overall, 72% felt that transplant programs should offer ApoL1 testing to AA potential LKDs. If a potential LKD has the high-risk genotype, 79% felt that the LKD should be allowed to make their own donation decision or participate in shared decision-making with transplant doctors. More than half of the potential LKDs (58%) would undergo ApoL1 testing and 81% of former LKDs would take the test now if offered. Most transplant candidates expressed a low likelihood of accepting a kidney from a LKD (79%) or a deceased donor (67%) with the high-risk genotype.

CONCLUSIONS

There is strong support among LKDs and transplant patients for ApoL1 testing when evaluating potential kidney donors of African ancestry. Inclusion of AA stakeholders in developing guidelines and educational programs for ApoL1 testing is critical.

Evaluation of Genetic Kidney Diseases in Living Donor Kidney Transplantation: Towards Precision Genomic Medicine in Donor Risk Assessment

Purpose of Review

To provide a comprehensive update on the role of genetic testing for the evaluation of kidney transplant recipient and living donor candidates.

Recent Findings

The evaluation of candidates for living donor transplantation and their potential donors occurs within an ever-changing landscape impacted by new evidence and risk assessment techniques. Criteria that were once considered contraindications to living kidney donation are now viewed as standard of care, while new tools identify novel risk markers that were unrecognized in past decades. Recent work suggests that nearly 10% of a cohort of patients with chronic/end-stage kidney disease had an identifiable genetic etiology, many whose original cause of renal disease was either unknown or misdiagnosed. Some also had an incidentally found genetic variant, unrelated to their nephropathy, but medically actionable. These patterns illustrate the substantial potential for genetic testing to better guide the selection of living donors and recipients, but guidance on the proper application and interpretation of novel technologies is in its infancy. In this review, we examine the utility of genetic testing in various kidney conditions, and discuss risks and unresolved challenges. Suggested algorithms in the context of related and unrelated donation are offered.

Summary

Genetic testing is a rapidly evolving strategy for the evaluation of candidates for living donor transplantation and their potential donors that has potential to improve risk assessment and optimize the safety of donation.

Disparities in Deceased Organ Donor Research Authorization: Experience at One Organ Procurement Organization and Call for National Conversations

Introduction

Research with deceased donor organs can provide an important platform for studying interventions to improve organ use and outcomes after authorization from the next-of-kin (NOK) or before death by the decedent (i.e., first-person authorization [FPA]). To date, information on authorization rates across donor subgroups is lacking.

Methods

We performed a retrospective chart review of all 690 deceased organ donors from January 2017 to December 2019 at a midsized Midwestern organ procurement organization (OPO). Multivariable logistic regression was used to assess associations between donor factors and research decline (adjusted odds ratio [aOR], 95% confidence interval [CI]).

Results

Electronic records for all 690 deceased donors were reviewed. Of these, 659 (95.5%) yielded at least one transplanted organ. Overall, research was declined in 10.8% of donations. Compared to White donors, research decline was higher for Black (16.0% vs. 8.9%; aOR, 1.87; 95% CI, 1.03-3.40; P = 0.04) and other non-White donors (24.0% vs. 8.9%; aOR, 4.21; 95% CI, 1.02-17.39; P = 0.05). Unadjusted research decline trended higher for Hispanic donors versus non-Hispanic donors (23.1% vs. 10.5%; P = 0.14). Compared to donors age <40 years, research decline trended higher for donors age ≥65 years (16.7% vs. 11.8%; aOR, 4.87; 95% CI, 1.12-21.05; P = 0.03), whereas research decline was 55% lower when donors provided FPA (7.3% vs 15.0%; aOR, 0.45; 95% CI, 0.27-0.76; P = 0.003).

Conclusions

Deceased donor research authorization decline is higher for Black, other non-White, and older donors, but lower when the descendent provides FPA. Identification of disparities in research authorization may stimulate educational strategies to reduce barriers to scientific investigations directed at optimizing the outcomes of organ donation.

A Roadmap for Innovation to Advance Transplant Access and Outcomes: A Position Statement From the National Kidney Foundation

Over the past 65 years, kidney transplantation has evolved into the optimal treatment for patients with kidney failure, dramatically reducing suffering through improved survival and quality of life. However, access to transplant is still limited by organ supply, opportunities for transplant are inequitably distributed, and lifelong transplant survival remains elusive. To address these persistent needs, the National Kidney Foundation convened an expert panel to define an agenda for future research. The key priorities identified by the panel center on the needs to develop and evaluate strategies to expand living donation, improve waitlist management and transplant readiness, maximize use of available deceased donor organs, and extend allograft longevity. Strategies targeting the critical goal of decreasing organ discard that warrant research investment include educating patients and clinicians about potential benefits of accepting nonstandard organs, use of novel organ assessment technologies and real-time decision support, and approaches to preserve and resuscitate allografts before implantation. The development of personalized strategies to reduce the burden of lifelong immunosuppression and support "one transplant for life" was also identified as a vital priority. The panel noted the specific goal of improving transplant access and graft survival for children with kidney failure. This ambitious agenda will focus research investment to promote greater equity and efficiency in access to transplantation, and help sustain long-term benefits of the gift of life for more patients in need.

Apolipoprotein L1 and mechanisms of kidney disease susceptibility

PURPOSE OF REVIEW

Allelic variants in the gene for apolipoprotein L1 (APOL1), found only in individuals of African ancestry, explain a majority of the excess risk of kidney disease in African Americans. However, a clear understanding how the disease-associated APOL1 variants cause kidney injury and the identity of environmental stressors that trigger the injury process have not been determined.

RECENT FINDINGS

Basic mechanistic studies of APOL1 biochemistry and cell biology, bolstered by new antibody reagents and inducible pluripotent stem cell-derived cell systems, have focused on the cytotoxic effect of the risk variants when APOL1 gene expression is induced. Since the APOL1 variants evolved to alter a key protein-protein interaction with the trypanosome serum resistance-associated protein, additional studies have begun to address differences in APOL1 interactions with other proteins expressed in podocytes, including new observations that APOL1 variants may alter podocyte cytoskeleton dynamics.

SUMMARY

A unified mechanism of pathogenesis for the various APOL1 nephropathies still remains unclear and controversial. As ongoing studies have consistently implicated the pathogenic gain-of-function effects of the variant proteins, novel therapeutic development inhibiting the synthesis or function of APOL1 proteins is moving toward clinical trials.

Using race to estimate glomerular filtration and its impact in kidney transplantation

Since direct measurement of glomerular filtration rate (GFR) is time-consuming and more expensive, estimated GFR (eGFR) based on measured laboratory values is widely used to determine kidney function. Commonly used formulae to calculate eGFR are dependent on variables, which include filtration markers like serum creatinine and patient characteristics including race. Medical algorithms which utilize race are increasingly being scrutinized, as race is recognized to be a social construct rather than a biologic one. eGFR calculations have important implications for kidney transplantation, both in the listing of candidates as well as in the evaluation of potential kidney donors. This review considers the specific implications of race-based eGFR calculations on recipient evaluation and on decisions related to living kidney donation. We suggest a potential policy solution to ensure that racial and ethnic minority patients are not disadvantaged by eGFR as a result of current calculation methods.