Association of trypanolytic ApoL1 variants with kidney disease in African Americans

Genes, environment, and African ancestry in cardiometabolic disorders

The past two decades have been characterized by a substantial global increase in cardiometabolic diseases, but the prevalence and incidence of these diseases and related traits differ across populations. African ancestry populations are among the most affected yet least included in research. Populations of African descent manifest significant genetic and environmental diversity and this under-representation is a missed opportunity for discovery and could exacerbate existing health disparities and curtail equitable implementation of precision medicine. Here, we discuss cardiometabolic diseases and traits in the context of African descent populations, including both genetic and environmental contributors and emphasizing novel discoveries. We also review new initiatives to include more individuals of African descent in genomics to address current gaps in the field.

Clinical and pathological features of omicron variant of SARS-CoV-2-associated kidney injury

Kidney injury is common in patients with Coronavirus Disease-19 (COVID-19), which is related to poor prognosis. We aim to summarize the clinical features, athological types, and prognosis of COVID-19 associated kidney injury caused by the Omicron strain. In this study, 46 patients with Omicron-associated kidney injury were included, 38 of whom performed renal biopsy. Patients were divided into two groups: group A for patients with onset of kidney injury after SARS-CoV-2 infection; group B for patients with pre-existing kidney disease who experienced aggravation of renal insufficiency after SARS-CoV-2 infection. The clinical, pathological, and prognostic characteristics of the patients were observed. Acute kidney injury (AKI) (35%) was the most common clinical manifestation in group A. Patients in group B mainly presented with chronic kidney disease (CKD) (55%) and nephrotic syndrome (NS) (40%). The pathological type was mainly IgA nephropathy (IgAN) (39% in group A and 45% in group B). Among all of them, one case presenting with thrombotic microangiopathy had worse kidney function at biopsy time. Mean serum C3 levels were 1.2 ± 0.5 and 1.0 ± 0.2 g/L in group A and group B, respectively. In renal tissues, C3 deposits were observed in 71.1% of patients. 11.8% (n = 2) patients experienced deterioration of renal function after treatment, but no patients developed to end-stage renal disease. In our single-center study in China, the main clinical manifestations were AKI, CKD, and NS, while the main pathological type was IgAN. Compared with previous strains of SARS-CoV-2, patients with the Omicron infection had a favorable prognosis.

Uterine leiomyomata and keloids fibrosis origins: a mini-review of fibroproliferative diseases

Diseases such as uterine leiomyomata (fibroids and benign tumors of the uterus) and keloids (raised scars) may share common etiology. Fibroids and keloids can co-occur in individuals, and both are highly heritable, suggesting they may share common genetic risk factors. Fibroproliferative diseases are common and characterized by scarring and overgrowth of connective tissue, impacting multiple organ systems. These conditions both have racial disparities in prevalence, with the highest prevalence observed among individuals of African ancestry. Several fibroproliferative diseases are more severe and common in populations of sub-Saharan Africa. This mini-review aims to provide a broad overview of the current knowledge of the evolutionary origins and causes of fibroproliferative diseases. We also discuss current hypotheses proposing that the increased prevalence of these diseases in African-derived populations is due to the selection for profibrotic alleles that are protective against helminth infections and provide examples from knowledge of uterine fibroid and keloid research.

Hypoxia and renal fibrosis

Renal fibrosis is the final stage of most progressive kidney diseases. Chronic kidney disease (CKD) is associated with high comorbidity and mortality. Thus, preventing fibrosis and thereby preserving kidney function increases the quality of life and prolongs the survival of patients with CKD. Many processes such as inflammation or metabolic stress modulate the progression of kidney fibrosis. Hypoxia has also been implicated in the pathogenesis of renal fibrosis, and oxygen sensing in the kidney is of outstanding importance for the body. The dysregulation of oxygen sensing in the diseased kidney is best exemplified by the loss of stimulation of erythropoietin production from interstitial cells in the fibrotic kidney despite anemia. Furthermore, hypoxia is present in acute or chronic kidney diseases and may affect all cell types present in the kidney including tubular and glomerular cells as well as resident immune cells. Pro- and antifibrotic effects of the transcription factors hypoxia-inducible factors 1 and 2 have been described in a plethora of animal models of acute and chronic kidney diseases, but recent advances in sequencing technologies now allow for novel and deeper insights into the role of hypoxia and its cell type-specific effects on the progression of renal fibrosis, especially in humans. Here, we review existing literature on how hypoxia impacts the development and progression of renal fibrosis.

A translational perspective towards clinical AI fairness

Artificial intelligence (AI) has demonstrated the ability to extract insights from data, but the fairness of such data-driven insights remains a concern in high-stakes fields. Despite extensive developments, issues of AI fairness in clinical contexts have not been adequately addressed. A fair model is normally expected to perform equally across subgroups defined by sensitive variables (e.g., age, gender/sex, race/ethnicity, socio-economic status, etc.). Various fairness measurements have been developed to detect differences between subgroups as evidence of bias, and bias mitigation methods are designed to reduce the differences detected. This perspective of fairness, however, is misaligned with some key considerations in clinical contexts. The set of sensitive variables used in healthcare applications must be carefully examined for relevance and justified by clear clinical motivations. In addition, clinical AI fairness should closely investigate the ethical implications of fairness measurements (e.g., potential conflicts between group- and individual-level fairness) to select suitable and objective metrics. Generally defining AI fairness as "equality" is not necessarily reasonable in clinical settings, as differences may have clinical justifications and do not indicate biases. Instead, "equity" would be an appropriate objective of clinical AI fairness. Moreover, clinical feedback is essential to developing fair and well-performing AI models, and efforts should be made to actively involve clinicians in the process. The adaptation of AI fairness towards healthcare is not self-evident due to misalignments between technical developments and clinical considerations. Multidisciplinary collaboration between AI researchers, clinicians, and ethicists is necessary to bridge the gap and translate AI fairness into real-life benefits.

Association between APOL1 risk variants and the occurrence of sepsis in Black patients hospitalized with infections: a retrospective cohort study

Background

Two risk variants in the apolipoprotein L1 gene ( APOL1 ) have been associated with increased susceptibility to sepsis in Black patients. However, it remains unclear whether APOL1 high-risk genotypes are associated with occurrence of either sepsis or sepsis-related phenotypes in patients hospitalized with infections, independent of their association with pre-existing severe renal disease.

Methods

A retrospective cohort study of 2,242 Black patients hospitalized with infections. We assessed whether carriage of APOL1 high-risk genotypes was associated with the risk of sepsis and sepsis-related phenotypes in patients hospitalized with infections. The primary outcome was sepsis; secondary outcomes were short-term mortality and organ failure related to sepsis.

Results

Of 2,242 Black patients hospitalized with infections, 565 developed sepsis. Patients with high-risk APOL1 genotypes had a significantly increased risk of sepsis (odds ratio [OR]=1.29 [95% CI, 1.00-1.67; p=0.047]); however, this association was not significant after adjustment for pre-existing severe renal disease (OR=1.14 [95% CI, 0.88-1.48; p=0.33]), nor after exclusion of those patients with pre-existing severe renal disease (OR=0.99 [95% CI, 0.70-1.39; p=0.95]. APOL1 high-risk genotypes were significantly associated with the renal dysfunction component of the Sepsis-3 criteria (OR=1.64 [95% CI, 1.21-2.22; p=0.001], but not with other sepsis-related organ dysfunction or short-term mortality. The association between high-risk APOL1 genotypes and sepsis-related renal dysfunction was markedly attenuated by adjusting for pre-existing severe renal disease (OR=1.36 [95% CI, 1.00-1.86; p=0.05]) and was nullified after exclusion of patients with pre-existing severe renal disease (OR=1.16 [95% CI, 0.74-1.81; p=0.52]).

Conclusion

APOL1 high-risk genotypes were associated with an increased risk of sepsis; however, this increased risk was attributable predominantly to pre-existing severe renal disease.

Funding

This study was supported by R01GM120523 (Q.F.), R01HL163854 (Q.F.), R35GM131770 (C.M.S.), HL133786 (W.Q.W.), and Vanderbilt Faculty Research Scholar Fund (Q.F.). The dataset(s) used for the analyses described were obtained from Vanderbilt University Medical Center's BioVU which is supported by institutional funding, the 1S10RR025141-01 instrumentation award, and by the CTSA grant UL1TR0004from NCATS/NIH. Additional funding provided by the NIH through grants P50GM115305 and U19HL065962. The authors wish to acknowledge the expert technical support of the VANTAGE and VANGARD core facilities, supported in part by the Vanderbilt-Ingram Cancer Center (P30 CA068485) and Vanderbilt Vision Center (P30 EY08126).The funders had no role in design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Genome-wide meta-analysis identifies new candidate genes for sickle cell disease nephropathy

Sickle cell disease nephropathy (SCDN), a common SCD complication, is strongly associated with mortality. Polygenic risk scores calculated from recent transethnic meta-analyses of urinary albumin-to-creatinine ratio and estimated glomerular filtration rate (eGFR) trended toward association with proteinuria and eGFR in SCD but the model fit was poor (R2 < 0.01), suggesting that there are likely unique genetic risk factors for SCDN. Therefore, we performed genome-wide association studies (GWAS) for 2 critical manifestations of SCDN, proteinuria and decreased eGFR, in 2 well-characterized adult SCD cohorts, representing, to the best of our knowledge, the largest SCDN sample to date. Meta-analysis identified 6 genome-wide significant associations (false discovery rate, q ≤ 0.05): 3 for proteinuria (CRYL1, VWF, and ADAMTS7) and 3 for eGFR (LRP1B, linc02288, and FPGT-TNNI3K/TNNI3K). These associations are independent of APOL1 risk and represent novel SCDN loci, many with evidence for regulatory function. Moreover, GWAS SNPs in CRYL1, VWF, ADAMTS7, and linc02288 are associated with gene expression in kidney and pathways important to both renal function and SCD biology, supporting the hypothesis that SCDN pathophysiology is distinct from other forms of kidney disease. Together, these findings provide new targets for functional follow-up that could be tested prospectively and potentially used to identify patients with SCD who are at risk, before onset of kidney dysfunction.

Demographics and treatment of patients with primary nephrotic syndrome in Japan using a national registry of clinical personal records

The nationwide clinical features of Japanese patients with primary nephrotic syndrome (NS), including minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS), or membranous nephropathy (MN), have not yet been reported. We collected the clinical personal records of patients with primary NS between 2015 and 2018 from the national registry organized by the Japanese Ministry of Health, Labour, and Welfare. Overall, the demographics, chronic kidney disease classification based on glomerular filtration rate and albuminuria, and treatment of 6036 patients were collected: 3394 (56.2%) with MCD, 677 (11.2%) with FSGS, 1455 (24.1%) with MN, and 510 (8.5%) with others. MN patients were older than MCD and FSGS patients (67 vs. 42 and 47 years, respectively). Steroid-dependent NS or frequently relapsing NS was found in 70.2%, 40.5%, and 24.6%, whereas steroid-resistant NS was found in 6.4%, 36.0%, and 37.9% of patients in the MCD, FSGS, and MN, respectively. The present oral prednisolone use (mean dose, mg/day) was 87.2% (21.2), 80.9% (20.0), and 77.5% (18.8) of patients in the MCD, FSGS, and MN, respectively. The national registry of clinical personal records of primary NS could provide an informative insight into the characteristics, clinical features, and treatment approaches for patients with primary NS in Japan.

Management of Type 2 Diabetes Mellitus and Kidney Failure in People with HIV-Infection in Africa: Current Status and a Call to Action

There is an increasing global burden of diabetes mellitus (DM) and chronic kidney disease (CKD), coupled with a high burden of people with HIV (PWH). Due to an increased lifespan on ART, PWH are now at risk of developing non-communicable diseases, including DM. Africa has the greatest burden of HIV infection and will experience the greatest increase in prevalence of DM over the next two decades. In addition, there is a rising number of people with CKD and progression to kidney failure. Therefore, there is an urgent need for the early identification and management of all 3 diseases to prevent disease progression and complications. This is particularly important in Africa for people with CKD where there is restricted or no access to dialysis and/or transplantation. This review focuses on the epidemiology and pathophysiology of the interaction between HIV infection and DM and the impact that these diseases have on the development and progression of CKD. Finally, it also aims to review the data on the management, which stems from the growing burden of all three diseases.

Nonpodocyte Roles of APOL1 Variants: An Evolving Paradigm

Since the seminal discovery of the trypanolytic, exonic variants in apolipoprotein L1 (APOL1) and their association with kidney disease in individuals of recent African ancestry, a wide body of research has emerged offering key insights into the mechanisms of disease. Importantly, the podocyte has become a focal point for our understanding of how risk genotype leads to disease, with activation of putative signaling pathways within the podocyte identified as playing a causal role in podocytopathy, FSGS, and progressive renal failure. However, the complete mechanism of genotype-to-phenotype progression remains incompletely understood in APOL1-risk individuals. An emerging body of evidence reports more than podocyte-intrinsic expression of APOL1 risk variants is needed for disease to manifest. This article reviews the seminal data and reports which placed the podocyte at the center of our understanding of APOL1-FSGS, as well as the evident shortcomings of this podocentric paradigm. We examine existing evidence for environmental and genetic factors that may influence disease, drawing from both clinical data and APOL1's fundamental role as an immune response gene. We also review the current body of data for APOL1's impact on nonpodocyte cells, including endothelial cells, the placenta, and immune cells in both a transplant and native setting. Finally, we discuss the implications of these emerging data and how the paradigm of disease might evolve as a result.

Applying an evolutionary mismatch framework to understand disease susceptibility

Noncommunicable diseases (NCDs) are on the rise worldwide. Obesity, cardiovascular disease, and type 2 diabetes are among a long list of "lifestyle" diseases that were rare throughout human history but are now common. The evolutionary mismatch hypothesis posits that humans evolved in environments that radically differ from those we currently experience; consequently, traits that were once advantageous may now be "mismatched" and disease causing. At the genetic level, this hypothesis predicts that loci with a history of selection will exhibit "genotype by environment" (GxE) interactions, with different health effects in "ancestral" versus "modern" environments. To identify such loci, we advocate for combining genomic tools in partnership with subsistence-level groups experiencing rapid lifestyle change. In these populations, comparisons of individuals falling on opposite extremes of the "matched" to "mismatched" spectrum are uniquely possible. More broadly, the work we propose will inform our understanding of environmental and genetic risk factors for NCDs across diverse ancestries and cultures.

Retaining Race in Chronic Kidney Disease Diagnosis and Treatment

The best overall measure of kidney function is glomerular filtration rate (GFR) as commonly estimated from serum creatinine concentrations (eGFRcr) using formulas that correct for the higher average creatinine concentrations in Blacks. After two decades of use, these formulas have come under scrutiny for estimating GFR differently in Blacks and non-Blacks. Discussions of whether to include race (Black vs. non-Black) in the calculation of eGFRcr fail to acknowledge that the original race-based eGFRcr provided the same CKD treatment recommendations for Blacks and non-Blacks based on directly (exogenously) measured GFR. Nevertheless, the National Kidney Foundation and the American Society of Nephrology Task Force on Reassessing the Inclusion of Race in Diagnosing Kidney Disease removed race in CKD treatment guidelines and pushed for the immediate adoption of a race-free eGFRcr formula by physicians and clinical laboratories. This formula is projected to negate CKD in 5.51 million White and other non-Black adults and reclassify CKD to less severe stages in another 4.59 million non-Blacks, in order to expand treatment eligibility to 434,000 Blacks not previously diagnosed and to 584,000 Blacks previously diagnosed with less severe CKD. This review examines: 1) the validity of the arguments for removing the original race correction, and 2) the performance of the proposed replacement formula. Excluding race in the derivation of eGFRcr changed the statistical bias from +3.7 to -3.6 ml/min/1.73m2 in Blacks and from +0.5 to +3.9 in non-Blacks, i.e., promoting CKD diagnosis in Blacks at the cost of restricting diagnosis in non-Blacks. By doing so, the revised eGFRcr greatly exaggerates the purported racial disparity in CKD burden. Claims that the revised formulas identify heretofore undiagnosed CKD in Blacks are not supported when studies that used kidney failure replacement therapy and mortality are interpreted as proxies for baseline CKD. Alternatively, a race-stratified eGFRcr (i.e., separate equations for Blacks and non-Blacks) would provide the least biased eGFRcr for both Blacks and non-Blacks and the best medical treatment for all patients.

HIV and Associated TB: A Lethal Association for Kidney Health?

Human immunodeficiency virus (HIV) and tuberculosis (TB) are the leading infectious causes of death globally. The combined brunt of these diseases is experienced mainly in low-income and lower-middle-income countries. HIV/TB have devastating effects on the kidneys, leading to accelerated decline of kidney function as well as mortality. Managing the triad of TB/HIV and kidney disease is challenging. We discuss the epidemiology of HIV/TB coinfection and the kidney and the key mechanisms of kidney disease including genetic susceptibility. The clinical presentation and pathology, as well as the challenges of diagnosing CKD in these patients, also are discussed. The strategies to prevent and manage HIV/TB-related kidney disease such as proper assessment, avoiding nephrotoxic regimens, drug dose adjustments, kidney function monitoring, avoidance of drug-drug interactions, and other interventions are explored. We also briefly discuss the complexities around HIV/TB patients on dialysis and kidney transplantation. HIV/TB coinfection presents an increased risk for kidney-related morbidity and mortality; patients with this triad need to be given special consideration for future research and management.

Our Experience with SARS-CoV-2 Infection and Acute Kidney Injury: Results from a Single-Center Retrospective Observational Study

BACKGROUND

Renal failure in COVID-19 patients is reportedly related to multiple factors such as a direct SARS-CoV-2 cytopathic effect, cytokine storm, the association of pulmonary and/or cardiovascular lesions, the presence of thrombotic microangiopathy, endothelial damage, or the use of potentially nephrotoxic medications.

METHODS

We retrospectively analyzed 466 cases of SARS-CoV-2 infection, comparing 233 patients with acute kidney injury (AKI) with 233 patients without AKI in terms of their demographic characteristics, comorbidities, clinical background, laboratory investigations, time of AKI onset, therapy, and outcomes after using univariate analysis and a CART decision-tree approach. The latter was constructed in a reverse manner, starting from the top with the root and branching out until the splitting ceased, interconnecting all the predictors to predict the overall outcome (AKI vs. non-AKI).

RESULTS

There was a statistically significant difference between the clinical form distribution in the two groups, with fewer mild (2 vs. 5) and moderate (54 vs. 133) cases in the AKI group than in the non-AKI group and more severe and critical patients in the AKI cohort (116 vs. 92 and 60 vs. 3). There were four deaths (1.71%) in the non-AKI group and 120 deaths in the AKI group (51.5%) (p-value < 0.001). We noted statistically significant differences between the two study groups in relation to different tissue lesions (LDH), particularly at the pulmonary (CT severity score), hepatic (AST, ALT), and muscular levels (Creatine kinase). In addition, an exacerbated procoagulant and inflammatory profile in the study group was observed. The CART algorithm approach yielded decision paths that helped sort the risk of AKI progression into three categories: the low-risk category (0-40%), the medium-risk category (40-80%), and the high-risk category (>80%). It recognized specific inflammatory and renal biomarker profiles with particular cut-off points for procalcitonin, ferritin, LDH, creatinine, initial urea, and creatinine levels as important predictive factors of AKI outcomes (93.3% overall performance).

CONCLUSIONS

Our study revealed the association between particular risk factors and AKI progression in COVID-19 patients. Diabetes, dyspnea on admission, the need for supplemental oxygen, and admission to the intensive care unit all had a crucial role in producing unfavorable outcomes, with a death rate of more than 50%. Necessary imaging studies (CT scan severity score) and changes in specific biomarker levels (ferritin and C-reactive protein levels) were also noted. These factors should be further investigated in conjunction with the pathophysiological mechanisms of AKI progression in COVID-19 patients.

Strong protective effect of the APOL1 p.N264K variant against G2-associated focal segmental glomerulosclerosis and kidney disease

Black Americans have a significantly higher risk of developing chronic kidney disease (CKD), especially focal segmental glomerulosclerosis (FSGS), than European Americans. Two coding variants (G1 and G2) in the APOL1 gene play a major role in this disparity. While 13% of Black Americans carry the high-risk recessive genotypes, only a fraction of these individuals develops FSGS or kidney failure, indicating the involvement of additional disease modifiers. Here, we show that the presence of the APOL1 p.N264K missense variant, when co-inherited with the G2 APOL1 risk allele, substantially reduces the penetrance of the G1G2 and G2G2 high-risk genotypes by rendering these genotypes low-risk. These results align with prior functional evidence showing that the p.N264K variant reduces the toxicity of the APOL1 high-risk alleles. These findings have important implications for our understanding of the mechanisms of APOL1 -associated nephropathy, as well as for the clinical management of individuals with high-risk genotypes that include the G2 allele.

Develop and Validate a Risk Score in Predicting Renal Failure in Focal Segmental Glomerulosclerosis

Introduction

The aim of this study was to develop and validate a risk score (RS) for end-stage kidney disease (ESKD) in patients with focal segmental glomerulosclerosis (FSGS).

Methods

Patient with biopsy-proven FSGS was enrolled. All the patients were allocated 1:1 to the two groups according to their baseline gender, age, and baseline creatinine level by using a stratified randomization method. ESKD was the primary endpoint.

Results

We recruited 359 FSGS patients, and 177 subjects were assigned to group 1 and 182 to group 2. The clinicopathological variables were similar between two groups. There were 23 (13%) subjects reached to ESKD in group 1 and 22 (12.1%) in group 2. By multivariate Cox regression analyses, we established RS 1 and RS 2 in groups 1 and 2, respectively. RS 1 consists of five parameters including lower eGFR, higher urine protein, MAP, IgG level, and tubulointerstitial lesion (TIL) score; RS 2 also consists of five predictors including lower C3, higher MAP, IgG level, hemoglobin, and TIL score. RS 1 and RS 2 were cross-validated between these two groups, showing RS 1 had better performance in predicting 5-year ESKD in group 1 (c statics, 0.86 [0.74-0.98] vs. 0.82 [0.69-0.95]) and group 2 (c statics, 0.91 [0.83-0.99] vs. 0.89 [0.79-0.99]) compared to RS 2. We then stratified the risk factors into four groups, and Kaplan-Meier survival curve revealed that patients progressed to ESKD increased as risk levels increased.

Conclusions

A predictive model incorporated clinicopathological feature was developed and validated for the prediction of ESKD in FSGS patients.

Implementation and Feasibility of Clinical Genome Sequencing Embedded Into the Outpatient Nephrology Care for Patients With Proteinuric Kidney Disease

Introduction

The diagnosis and management of proteinuric kidney diseases such as focal segmental glomerulosclerosis (FSGS) are challenging. Genetics holds the promise to improve clinical decision making for these diseases; however, it is often performed too late to enable timely clinical action and it is not implemented within routine outpatient nephrology visits.

Methods

We sought to test the implementation and feasibility of clinical rapid genome sequencing (GS) in guiding decision making in patients with proteinuric kidney disease in real-time and embedded in the outpatient nephrology setting.

Results

We enrolled 10 children or young adults with biopsy-proven FSGS (9 cases) or minimal change disease (1 case). The mean age at enrollment was 16.2 years (range 2-30). The workflow did not require referral to external genetics clinics but was conducted entirely during the nephrology standard-of-care appointments. The total turn-around-time from enrollment to return-of-results and clinical decision averaged 21.8 days (12.4 for GS), which is well within a time frame that allows clinically relevant treatment decisions. A monogenic or APOL1-related form of kidney disease was diagnosed in 5 of 10 patients. The genetic findings resulted in a rectified diagnosis in 6 patients. Both positive and negative GS findings determined a change in pharmacological treatment. In 3 patients, the results were instrumental for transplant evaluation, donor selection, and the immunosuppressive treatment. All patients and families received genetic counseling.

Conclusion

Clinical GS is feasible and can be implemented in real-time in the outpatient care to help guiding clinical management. Additional studies are needed to confirm the cost-effectiveness and broader utility of clinical GS across the phenotypic and demographic spectrum of kidney diseases.

CMV-associated collapsing focal segmental glomerulosclerosis after kidney transplant in a pediatric patient

BACKGROUND

Cytomegalovirus (CMV) is a significant cause of morbidity among immunocompromised patients who have undergone kidney transplantation and is known to rarely induce collapsing focal segmental glomerulosclerosis (FSGS) among adults.

METHODS

We present the first reported case of CMV-induced collapsing FSGS in a pediatric patient after kidney transplant.

RESULTS

Our patient underwent a deceased donor kidney transplant due to end-stage renal disease secondary to lupus nephritis. Approximately 4 months after transplantation, he developed signs of worsening kidney function in the setting of CMV viremia and was found to have collapsing features of FSGS on kidney transplant biopsy. He was managed with a prompt escalation of antiviral therapy along with a reduction of immunosuppression and recovered without significant complication. At follow-up, he continued to have undetectable CMV titers, creatinine within normal limits, and no significant proteinuria.

CONCLUSION

This report demonstrates CMV as a cause of collapsing FSGS and should be considered among pediatric transplant recipients who present with acute kidney injury, as should early assessment of APOL1 genetic status in both donor and recipient.

HIV-associated nephropathy in children: challenges in a resource-limited setting

HIV infection remains one of the leading causes of morbidity and mortality worldwide, especially in children living in resource-limited settings. Although the World Health Organization (WHO) recently recommended antiretroviral therapy (ART) initiation upon diagnosis regardless of the number of CD4, ART access remains limited, especially in children living in sub-Saharan Africa (SSA). HIV-infected children who do not receive appropriate ART are at increased risk of developing HIV-associated nephropathy (HIVAN). Although due to genetic susceptibility, SSA is recognized to be the epicenter of HIVAN, limited information is available regarding the burden of HIVAN in children living in Africa. The present review discusses the information available to date on the prevalence, pathogenesis, risk factors, diagnosis, and management of HIVAN in children, focusing on related challenges in a resource-limited setting.

Glomerular hyperfiltration: part 2-clinical significance in children

Glomerular hyperfiltration (GHF) is a phenomenon that can occur in various clinical conditions affecting the kidneys such as sickle cell disease, diabetes mellitus, autosomal dominant polycystic kidney disease, and solitary functioning kidney. Yet, the pathophysiological mechanisms vary from one disease to another and are not well understood. More so, it has been demonstrated that GHF may occur at the single-nephron in some clinical conditions while in others at the whole-kidney level. In this review, we explore the pathophysiological mechanisms of GHF in relation to various clinical conditions in the pediatric population. In addition, we discuss the role and mechanism of action of important factors such as gender, low birth weight, and race in the pathogenesis of GHF. Finally, in this current review, we further highlight the consequences of GHF in the progression of kidney disease.

Inaxaplin for the treatment of APOL1-associated kidney disease

Chronic kidney disease (CKD) is highly prevalent World-Wide and it is an important cause of morbidity and mortality. In 2010, variants in apolipoprotein type 1 (APOL1) gene was identified as a major risk factor for higher prevalence of CKD in individuals of African ancestry. The mechanisms by which toxic gain of function APOL1 variants cause disease are the subjects of current investigations, and there is currently no effective targeted therapy for APOL1 associated kidney disease. Egbuna and others recently reported that an orally administered small molecule compound inaxaplin (VX-147) that binds APOL1 may be useful in the treatment of APOL1 associated kidney disease. This is a groundbreaking study, if confirmed in randomized control studies it may turn out to be one of the major advances in the therapy of proteinuric CKD this decade, and may also represent precision therapy for addressing health disparity in CKD. However, there is a need for a larger randomized control studies with stable eGFR and complete remission of proteinuria as end point, such studies should also be carried out in a more geographically diverse population.

Multi-ancestry GWAS analysis identifies two novel loci associated with diabetic eye disease and highlights APOL1 as a high risk locus in patients with diabetic macular edema

Diabetic retinopathy (DR) is a common complication of diabetes. Approximately 20% of DR patients have diabetic macular edema (DME) characterized by fluid leakage into the retina. There is a genetic component to DR and DME risk, but few replicable loci. Because not all DR cases have DME, we focused on DME to increase power, and conducted a multi-ancestry GWAS to assess DME risk in a total of 1,502 DME patients and 5,603 non-DME controls in discovery and replication datasets. Two loci reached GWAS significance (p<5x10-8). The strongest association was rs2239785, (K150E) in APOL1. The second finding was rs10402468, which co-localized to PLVAP and ANKLE1 in vascular / endothelium tissues. We conducted multiple sensitivity analyses to establish that the associations were specific to DME status and did not reflect diabetes status or other diabetic complications. Here we report two novel loci for risk of DME which replicated in multiple clinical trial and biobank derived datasets. One of these loci, containing the gene APOL1, is a risk factor in African American DME and DKD patients, indicating that this locus plays a broader role in diabetic complications for multiple ancestries. Trial Registration: NCT00473330, NCT00473382, NCT03622580, NCT03622593, NCT04108156.

The genetic and phenotypic correlates of mtDNA copy number in a multi-ancestry cohort

Mitochondrial DNA copy number (mtCN) is often treated as a proxy for mitochondrial (dys-) function and disease risk. Pathological changes in mtCN are common symptoms of rare mitochondrial disorders, but reported associations between mtCN and common diseases vary across studies. To understand the biology of mtCN, we carried out genome- and phenome-wide association studies of mtCN in 30,666 individuals from the Penn Medicine BioBank (PMBB)-a diverse cohort of largely African and European ancestry. We estimated mtCN in peripheral blood using exome sequence data, taking cell composition into account. We replicated known genetic associations of mtCN in the PMBB and found that their effects are highly correlated between individuals of European and African ancestry. However, the heritability of mtCN was much higher among individuals of largely African ancestry ( h 2 = 0.3 ) compared with European ancestry individuals( h 2 = 0.1 ) . Admixture mapping suggests that there are undiscovered variants underlying mtCN that are differentiated in frequency between individuals with African and European ancestry. We show that mtCN is associated with many health-related phenotypes. We discovered robust associations between mtDNA copy number and diseases of metabolically active tissues, such as cardiovascular disease and liver damage, that were consistent across African and European ancestry individuals. Other associations, such as epilepsy and prostate cancer, were only discovered in either individuals with European or African ancestry but not both. We show that mtCN-phenotype associations can be sensitive to blood cell composition and environmental modifiers, explaining why such associations are inconsistent across studies. Thus, mtCN-phenotype associations must be interpreted with care.

State of the art in childhood nephrotic syndrome: concrete discoveries and unmet needs

Nephrotic syndrome (NS) is a clinical entity characterized by proteinuria, hypoalbuminemia, and peripheral edema. NS affects about 2-7 per 100,000 children aged below 18 years old yearly and is classified, based on the response to drugs, into steroid sensitive (SSNS), steroid dependent, (SDNS), multidrug dependent (MDNS), and multidrug resistant (MRNS). Forms of NS that are more difficult to treat are associated with a worse outcome with respect to renal function. In particular, MRNS commonly progresses to end stage renal failure requiring renal transplantation, with recurrence of the original disease in half of the cases. Histological presentations of NS may vary from minimal glomerular lesions (MCD) to focal segmental glomerulosclerosis (FSGS) and, of relevance, the histological patterns do not correlate with the response to treatments. Moreover, around half of MRNS cases are secondary to causative pathogenic variants in genes involved in maintaining the glomerular structure. The pathogenesis of NS is still poorly understood and therapeutic approaches are mostly based on clinical experience. Understanding of pathogenetic mechanisms of NS is one of the 'unmet needs' in nephrology and represents a significant challenge for the scientific community. The scope of the present review includes exploring relevant findings, identifying unmet needs, and reviewing therapeutic developments that characterize NS in the last decades. The main aim is to provide a basis for new perspectives and mechanistic studies in NS.

INTERPRETING GENERATIVE ADVERSARIAL NETWORKS TO INFER NATURAL SELECTION FROM GENETIC DATA

Understanding natural selection in humans and other species is a major focus for the use of machine learning in population genetics. Existing methods rely on computationally intensive simulated training data. Unlike efficient neutral coalescent simulations for demographic inference, realistic simulations of selection typically requires slow forward simulations. Because there are many possible modes of selection, a high dimensional parameter space must be explored, with no guarantee that the simulated models are close to the real processes. Mismatches between simulated training data and real test data can lead to incorrect inference. Finally, it is difficult to interpret trained neural networks, leading to a lack of understanding about what features contribute to classification. Here we develop a new approach to detect selection that requires relatively few selection simulations during training. We use a Generative Adversarial Network (GAN) trained to simulate realistic neutral data. The resulting GAN consists of a generator (fitted demographic model) and a discriminator (convolutional neural network). For a genomic region, the discriminator predicts whether it is "real" or "fake" in the sense that it could have been simulated by the generator. As the "real" training data includes regions that experienced selection and the generator cannot produce such regions, regions with a high probability of being real are likely to have experienced selection. To further incentivize this behavior, we "fine-tune" the discriminator with a small number of selection simulations. We show that this approach has high power to detect selection in simulations, and that it finds regions under selection identified by state-of-the art population genetic methods in three human populations. Finally, we show how to interpret the trained networks by clustering hidden units of the discriminator based on their correlation patterns with known summary statistics. In summary, our approach is a novel, efficient, and powerful way to use machine learning to detect natural selection.

Hiding in plain sight: genetics of childhood steroid-resistant nephrotic syndrome in Sub-Saharan Africa

Steroid-resistant nephrotic syndrome (SRNS) is the most severe form of childhood nephrotic syndrome with an increased risk of progression to chronic kidney disease stage 5. Research endeavors to date have identified more than 80 genes that are associated with SRNS. Most of these genes regulate the structure and function of the podocyte, the visceral epithelial cells of the glomerulus. Although individuals of African ancestry have the highest prevalence of SRNS, especially those from Sub-Saharan Africa (SSA), with rates as high as 30-40% of all cases of nephrotic syndrome, studies focusing on the characterization and understanding of the genetic basis of SRNS in the region are negligible compared with Europe and North America. Therefore, it remains unclear if some of the variants in SRNS genes that are deemed pathogenic for SRNS are truly disease causing, and if the leading causes of monogenic nephrotic syndrome in other populations are the same for children in SSA with SRNS. Other implications of this lack of genetic data for SRNS in the region include the exclusion of children from the region from clinical trials aimed at identifying potential novel therapeutic agents for this severe form of nephrotic syndrome. This review underlines a need for concerted efforts to advance the genetic basis of SRNS in children in SSA. Such endeavors will complement global efforts at understanding the genetic basis of nephrotic syndrome.

[Unexpected diagnosis of nephronopthisis in the genetic study of hypertension due to histological diagnosis of benign nephroangioesclerosis evolved in a young caucasian patient]

We present the case of a young Caucasian patient with renal disease of unclear cause, with a final diagnosis of advanced benign nephroangiosclerosis established by renal biopsy. Due to the possibility of having hypertension in pediatric age (without study or treatment), with the renal biopsy findings, the genetic study showed polymorphisms risk in the APOL1 and MYH9, and also an unexpected diagnosis of a complete deletion of the NPHP1 gene in homozygosis, associated with the development of nephronophthisis. In conclusion, this case illustrates the importance of carrying out a genetic study in youngs patients with renal disease unclear cause, even having a histological diagnosis of nephroangiosclerosis.

Glomerulonephritis: immunopathogenesis and immunotherapy

'Glomerulonephritis' (GN) is a term used to describe a group of heterogeneous immune-mediated disorders characterized by inflammation of the filtration units of the kidney (the glomeruli). These disorders are currently classified largely on the basis of histopathological lesion patterns, but these patterns do not align well with their diverse pathological mechanisms and hence do not inform optimal therapy. Instead, we propose grouping GN disorders into five categories according to their immunopathogenesis: infection-related GN, autoimmune GN, alloimmune GN, autoinflammatory GN and monoclonal gammopathy-related GN. This categorization can inform the appropriate treatment; for example, infection control for infection-related GN, suppression of adaptive immunity for autoimmune GN and alloimmune GN, inhibition of single cytokines or complement factors for autoinflammatory GN arising from inborn errors in innate immunity, and plasma cell clone-directed or B cell clone-directed therapy for monoclonal gammopathies. Here we present the immunopathogenesis of GN and immunotherapies in use and in development and discuss how an immunopathogenesis-based GN classification can focus research, and improve patient management and teaching.

Clinical Course of Adult FSGS and Minimal Change Disease in North American and Japanese Cohorts

Key Points

Data from different geographical regions highlighted the differences in clinical manifestations and treatment response of adult FSGS/minimal change disease. There were shared factors that were associated with treatment response across the cohorts: FSGS, higher BP, and lower eGFR. Recognizing geographical difference allows us better understanding of disease biology, risk prediction, and design of future clinical trials.

Background

Regional differences in presentation and clinical course of nephrotic syndrome (NS) have not been studied well because few studies directly compared the data from different intercontinental regions.

Methods

We included adult nephrotic patients with FSGS and minimal change disease (MCD) who received immunosuppressive therapy (IST) in a North American (Nephrotic Syndrome Study Network [NEPTUNE], N =89) or Japanese (Nagoya Kidney Disease Registry [N-KDR], N =288) cohort. Baseline characteristics and rates of complete remission (CR) were compared. Factors associated with time to CR were evaluated by Cox regression models.

Results

NEPTUNE participants had more FSGS (53.9 versus 17.0%) and family history of kidney disease (35.2 versus 3.2%). N-KDR participants were older (median 56 versus 43 years) and demonstrated greater levels of urine protein creatinine ratio (7.73 versus 6.65) and hypoalbuminemia (1.6 versus 2.2 mg/dl). N-KDR participants showed higher proportion of CR (overall: 89.2 versus 62.9%; FSGS: 67.3 versus 43.7%; MCD: 93.7 versus 85.4%). A multivariable model showed that FSGS (versus MCD: hazard ratio [HR], 0.28; 95% confidence interval [CI], 0.20 to 0.41), systolic BP (per 10 mm Hg: HR, 0.93; 95% CI, 0.86 to 0.99), and eGFR (per 10 ml/min per 1.73 m2: HR, 1.16; 95% CI, 1.09 to 1.24) were associated with time to CR. There were significant interactions in patient age (P = 0.004) and eGFR (P = 0.001) between the cohorts.

Conclusions

The North American cohort had more FSGS and more frequent family history. Japanese patients showed more severe NS with better response to IST. FSGS, hypertension, and lower eGFR were shared predictors of poor treatment response. Identifying shared and unique features across geographically diverse populations may help uncover biologically relevant subgroups, improve prediction of disease course, and better design future multinational clinical trials.

Diagnosis of Chronic Kidney Disease and Assessing Glomerular Filtration Rate

Chronic kidney disease (CKD) is a silent progressive disease. It is diagnosed by assessing filtration and markers of kidney damage such as albuminuria. The diagnosis of CKD should include not only assessing the glomerular filtration rate (GFR) and albuminuria but also the cause. The CKD care plan should include documentation of the trajectory and prognosis. The use of a combination of serum cystatin C and creatinine concentration offers a more accurate estimation of GFR. Social determinants of health are important to address as part of the diagnosis because they contribute to CKD disparities.

Perturbations in podocyte transcriptome and biological pathways induced by FSGS associated circulating factors

Background

Focal segmental glomerulosclerosis (FSGS) is frequently associated with heavy proteinuria and progressive renal failure requiring dialysis or kidney transplantation. However, primary FSGS also has a ~40% risk of recurrence of disease in the transplanted kidney (rFSGS). Multiple circulating factors have been identified to contribute to the pathogenesis of primary and rFSGS including soluble urokinase-type plasminogen activator receptor (suPAR) and patient-derived CD40 autoantibody (CD40autoAb). However, the downstream effector pathways specific to individual factors require further study. The tumor necrosis factor, TNF pathway activation by one or more circulating factors present in the sera of patients with FSGS has been supported by multiple studies.

Methods

A human in vitro model was used to study podocyte injury measured as the loss of actin stress fibers. Anti-CD40 autoantibody was isolated from FSGS patients (recurrent and non-recurrent) and control patients with ESRD due to non-FSGS related causes. Two novel human antibodies-anti-uPAR (2G10) and anti-CD40 antibody (Bristol Meyer Squibb, 986090) were tested for their ability to rescue podocyte injury. Podocytes treated with patient derived antibody were transcriptionally profiled using whole human genome microarray.

Results

Here we show that podocyte injury caused by sera from FSGS patients is mediated by CD40 and suPAR and can be blocked by human anti-uPAR and anti-CD40 antibodies. Transcriptomic studies to compare the molecules and pathways activated in response to CD40 autoantibody from rFSGS patients (rFSGS/CD40autoAb) and suPAR, identified unique inflammatory pathways associated with FSGS injury.

Conclusions

We identified several novel and previously described genes associated with FSGS progression. Targeted blockade of suPAR and CD40 pathways with novel human antibodies showed inhibition of podocyte injury in FSGS.

Diversity and Scale: Genetic Architecture of 2,068 Traits in the VA Million Veteran Program

Genome-wide association studies (GWAS) have underrepresented individuals from non-European populations, impeding progress in characterizing the genetic architecture and consequences of health and disease traits. To address this, we present a population-stratified phenome-wide GWAS followed by a multi-population meta-analysis for 2,068 traits derived from electronic health records of 635,969 participants in the Million Veteran Program (MVP), a longitudinal cohort study of diverse U.S. Veterans genetically similar to the respective African (121,177), Admixed American (59,048), East Asian (6,702), and European (449,042) superpopulations defined by the 1000 Genomes Project. We identified 38,270 independent variants associating with one or more traits at experiment-wide P < 4.6 × 10 - 11 significance; fine-mapping 6,318 signals identified from 613 traits to single-variant resolution. Among these, a third (2,069) of the associations were found only among participants genetically similar to non-European reference populations, demonstrating the importance of expanding diversity in genetic studies. Our work provides a comprehensive atlas of phenome-wide genetic associations for future studies dissecting the architecture of complex traits in diverse populations.

APOL1 promotes endothelial cell activation beyond the glomerulus

Apolipoprotein L1 (APOL1) high-risk genotypes are associated with increased risk of chronic kidney disease (CKD) in people of West African ancestry. Given the importance of endothelial cells (ECs) in CKD, we hypothesized that APOL1 high-risk genotypes may contribute to disease via EC-intrinsic activation and dysfunction. Single cell RNA sequencing (scRNA-seq) analysis of the Kidney Precision Medicine Project dataset revealed APOL1 expression in ECs from various renal vascular compartments. Utilizing two public transcriptomic datasets of kidney tissue from African Americans with CKD and a dataset of APOL1-expressing transgenic mice, we identified an EC activation signature; specifically, increased intercellular adhesion molecule 1 (ICAM-1) expression and enrichment in leukocyte migration pathways. In vitro, APOL1 expression in ECs derived from genetically modified human induced pluripotent stem cells and glomerular ECs triggered changes in ICAM-1 and platelet endothelial cell adhesion molecule 1 (PECAM-1) leading to an increase in monocyte attachment. Overall, our data suggest the involvement of APOL1 as an inducer of EC activation in multiple renal vascular beds with potential effects beyond the glomerular vasculature.

The metabolic effects of APOL1 in humans

Harboring apolipoprotein L1 (APOL1) variants coded by the G1 or G2 alleles of the APOL1 gene increases the risk for collapsing glomerulopathy, focal segmental glomerulosclerosis, albuminuria, chronic kidney disease, and accelerated kidney function decline towards end-stage kidney disease. However, most subjects carrying APOL1 variants do not develop the kidney phenotype unless a second clinical condition adds to the genotype, indicating that modifying factors modulate the genotype-phenotype correlation. Subjects with an APOL1 high-risk genotype are more likely to develop essential hypertension or obesity, suggesting that carriers of APOL1 risk variants experience more pronounced insulin resistance compared to noncarriers. Likewise, arterionephrosclerosis (the pathological correlate of hypertension-associated nephropathy) and glomerulomegaly take place among carriers of APOL1 risk variants, and these pathological changes are also present in conditions associated with insulin resistance, such as essential hypertension, aging, and diabetes. Insulin resistance may contribute to the clinical features associated with the APOL1 high-risk genotype. Unlike carriers of wild-type APOL1, bearers of APOL1 variants show impaired formation of lipid droplets, which may contribute to inducing insulin resistance. Nascent lipid droplets normally detach from the endoplasmic reticulum into the cytoplasm, although the proteins that enable this process remain to be fully defined. Wild-type APOL1 is located in the lipid droplet, whereas mutated APOL1 remains sited at the endoplasmic reticulum, suggesting that normal APOL1 may participate in lipid droplet biogenesis. The defective formation of lipid droplets is associated with insulin resistance, which in turn may modulate the clinical phenotype present in carriers of APOL1 risk variants.

HDL and chronic kidney disease

Low HDL-cholesterol (HDL-C) concentrations are a typical trait of the dyslipidemia associated with chronic kidney disease (CKD). In this condition, plasma HDLs are characterized by alterations in structure and function, and these particles can lose their atheroprotective functions, e.g., the ability to promote cholesterol efflux from peripheral cells, anti-oxidant and anti-inflammatory proprieties and they can even become dysfunctional, i.e., exactly damaging. The reduction in plasma HDL-C levels appears to be the only lipid alteration clearly linked to the progression of renal disease in CKD patients. The association between the HDL system and CKD development and progression is also supported by the presence of genetic kidney alterations linked to HDL metabolism, including mutations in the APOA1, APOE, APOL and LCAT genes. Among these, renal disease associated with LCAT deficiency is well characterized and lipid abnormalities detected in LCAT deficiency carriers mirror the ones observed in CKD patients, being present also in acquired LCAT deficiency. This review summarizes the major alterations in HDL structure and function in CKD and how genetic alterations in HDL metabolism can be linked to kidney dysfunction. Finally, the possibility of targeting the HDL system as possible strategy to slow CKD progression is reviewed.

Early recurrence of focal segmental glomerulosclerosis in a kidney transplant recipient with APOL1 one risk variant

Apolipoprotein 1 (APOL1) risk variants (G1 and G2) are associated with focal segmental glomerulosclerosis (FSGS) in patients of African ancestry. The prevalence of APOL1 two risk variants is lower in Hispanics and very rare in European and Asian populations. APOL1 two risk variants in donor kidneys is associated with recipient kidney graft loss, however the effect of recipient risk variant in the kidney transplant outcome is unclear. Here, we present a late adolescent male with FSGS and end stage renal disease with one APOL1 risk variant (G2) who had immediate recurrence of FSGS in the post-KT period. There was an excellent response to few sessions of plasmapheresis and Rituximab with no further recurrence of FSGS in the 1 year follow-up period. It needs to be seen whether the recipient APOL1 single risk variant causes increased susceptibility to kidney graft loss on a long run via recurrent or de novo pathologies.

Genetic and epigenetic background of diabetic kidney disease

Diabetic kidney disease (DKD) is a severe diabetic complication that affects up to half of the individuals with diabetes. Elevated blood glucose levels are a key underlying cause of DKD, but DKD is a complex multifactorial disease, which takes years to develop. Family studies have shown that inherited factors also contribute to the risk of the disease. During the last decade, genome-wide association studies (GWASs) have emerged as a powerful tool to identify genetic risk factors for DKD. In recent years, the GWASs have acquired larger number of participants, leading to increased statistical power to detect more genetic risk factors. In addition, whole-exome and whole-genome sequencing studies are emerging, aiming to identify rare genetic risk factors for DKD, as well as epigenome-wide association studies, investigating DNA methylation in relation to DKD. This article aims to review the identified genetic and epigenetic risk factors for DKD.

Implementation of a culturally competent APOL1 genetic testing programme into living donor evaluation: A two-site, non-randomised, pre-post trial design

INTRODUCTION

While living donor (LD) kidney transplantation is the optimal treatment for patients with kidney failure, LDs assume a higher risk of future kidney failure themselves. LDs of African ancestry have an even greater risk of kidney failure post-donation than White LDs. Because evidence suggests that Apolipoprotein L1 (APOL1) risk variants contribute to this greater risk, transplant nephrologists are increasingly using APOL1 genetic testing to evaluate LD candidates of African ancestry. However, nephrologists do not consistently perform genetic counselling with LD candidates about APOL1 due to a lack of knowledge and skill in counselling. Without proper counselling, APOL1 testing will magnify LD candidates' decisional conflict about donating, jeopardising their informed consent. Given cultural concerns about genetic testing among people of African ancestry, protecting LD candidates' safety is essential to improve informed decisions about donating. Clinical 'chatbots', mobile apps that provide genetic information to patients, can improve informed treatment decisions. No chatbot on APOL1 is available and no nephrologist training programmes are available to provide culturally competent counselling to LDs about APOL1. Given the shortage of genetic counsellors, increasing nephrologists' genetic literacy is critical to integrating genetic testing into practice.

METHODS AND ANALYSIS

Using a non-randomised, pre-post trial design in two transplant centres (Chicago, IL, and Washington, DC), we will evaluate the effectiveness of culturally competent APOL1 testing, chatbot and counselling on LD candidates' decisional conflict about donating, preparedness for decision-making, willingness to donate and satisfaction with informed consent and longitudinally evaluate the implementation of this intervention into clinical practice using the Reach, Effectiveness, Adoption, Implementation and Maintenance framework.

ETHICS AND DISSEMINATION

This study will create a model for APOL1 testing of LDs of African ancestry, which can be implemented nationally via implementation science approaches. APOL1 will serve as a model for integrating culturally competent genetic testing into transplant and other practices to improve informed consent. This study involves human participants and was approved by Northwestern University IRB (STU00214038). Participants gave informed consent to participate in the study before taking part.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04910867. Registered 8 May 2021, https://register.

CLINICALTRIALS

gov/prs/app/action/SelectProtocol?sid=S000AWZ6&selectaction=Edit&uid=U0001PPF&ts=7&cx=-8jv7m2 ClinicalTrials.gov Identifier: NCT04999436. Registered 5 November 2021, https://register.

CLINICALTRIALS

gov/prs/app/action/SelectProtocol?sid=S000AYWW&selectaction=Edit&uid=U0001PPF&ts=11&cx=9tny7v.

FSGS and COVID-19 in Non-African American Patients

Collapsing Focal Segmental Glomerulosclerosis (FSGS) has been reported relatively frequently in African American (AA) patients with coronavirus disease 2019 (COVID-19), and it is associated almost always with Apolipoprotein L gen 1 (APOL1) high-risk variants. We reviewed the published literature from April 2020 to November 2022 searching for non-African American (non-AA) patients with FSGS associated with COVID-19 (eight White patients, six Hispanic patients, three Asian patients, one Indian patient, and one Asian Indian patient). The following histologic patterns were found: collapsing (n=11), not otherwise specified (n=5), tip (n=2), and perihilar (n=1). Fifteen of the 19 patients had AKI. The APOL1 genotype was reported in only six of the 19 non-AA patients. Three of them (two Hispanic patients and one White patient) with collapsing FSGS had high-risk APOL1 variants. The other three patients (two White patients and one Hispanic patient with the collapsing variant, tip variant, and not otherwise specified) had low-risk APOL1 variants. Among 53 African American patients with collapsing FSGS associated with COVID-19, 48 had high-risk APOL1 variants and five had low-risk APOL1 variants. We conclude that in non-AA patients, FSGS is a rare complication of COVID-19. FSGS associated with COVID-19 can occur rarely with low-risk APOL1 variants in non-AA and AA patients. Non-AA patients reported to be associated with high-risk APOL1 variants possibly reflect inaccuracy of self-reported race with AA admixture because of unknown ancestry. Given the importance of APOL1 in the pathogenesis of FSGS associated with viral infection and to avoid racial bias, it seems appropriate that APOL1 testing be considered in patients with FSGS associated with COVID-19, regardless of self-reported race.

Collapsing glomerulopathy: unraveling varied pathogeneses

PURPOSE OF REVIEW

Collapsing glomerulopathy presents clinically with nephrotic syndrome and rapid progressive loss of kidney function. Animal models and patient studies have uncovered numerous clinical and genetic conditions associated with collapsing glomerulopathy, as well as putative mechanisms, which will be reviewed here.

RECENT FINDINGS

Collapsing glomerulopathy is classified pathologically as a variant of focal and segmental glomerulosclerosis (FSGS). As such, most research efforts have focused on the causative role of podocyte injury in driving the disease. However, studies have also shown that injury to the glomerular endothelium or interruption of the podocyte-glomerular endothelial cell signaling axis can also cause collapsing glomerulopathy. Furthermore, emerging technologies are now enabling exploration of diverse molecular pathways that can precipitate collapsing glomerulopathy using biopsies from patients with the disease.

SUMMARY

Since its original description in the 1980s, collapsing glomerulopathy has been the subject of intense study, and these efforts have uncovered numerous insights into potential disease mechanisms. Newer technologies will enable profiling of the intra-patient and inter-patient variability in collapsing glomerulopathy mechanisms directly in patient biopsies, which will improve the diagnosis and classification of collapsing glomerulopathy.

Clinical and Genetic Characteristics of CKD Patients with High-Risk APOL1 Genotypes

SIGNIFICANCE STATEMENT

APOL1 high-risk genotypes confer a significant risk of kidney disease, but variability in patient outcomes suggests the presence of modifiers of the APOL1 effect. We show that a diverse population of CKD patients with high-risk APOL1 genotypes have an increased lifetime risk of kidney failure and higher eGFR decline rates, with a graded risk among specific high-risk genotypes. CKD patients with high-risk APOL1 genotypes have a lower diagnostic yield for monogenic kidney disease. Exome sequencing revealed enrichment of rare missense variants within the inflammasome pathway modifying the effect of APOL1 risk genotypes, which may explain some clinical heterogeneity.

BACKGROUND

APOL1 genotype has significant effects on kidney disease development and progression that vary among specific causes of kidney disease, suggesting the presence of effect modifiers.

METHODS

We assessed the risk of kidney failure and the eGFR decline rate in patients with CKD carrying high-risk ( N =239) and genetically matched low-risk ( N =1187) APOL1 genotypes. Exome sequencing revealed monogenic kidney diseases. Exome-wide association studies and gene-based and gene set-based collapsing analyses evaluated genetic modifiers of the effect of APOL1 genotype on CKD.

RESULTS

Compared with genetic ancestry-matched patients with CKD with low-risk APOL1 genotypes, those with high-risk APOL1 genotypes had a higher risk of kidney failure (Hazard Ratio [HR]=1.58), a higher decline in eGFR (6.55 versus 3.63 ml/min/1.73 m 2 /yr), and were younger at time of kidney failure (45.1 versus 53.6 years), with the G1/G1 genotype demonstrating the highest risk. The rate for monogenic kidney disorders was lower among patients with CKD with high-risk APOL1 genotypes (2.5%) compared with those with low-risk genotypes (6.7%). Gene set analysis identified an enrichment of rare missense variants in the inflammasome pathway in individuals with high-risk APOL1 genotypes and CKD (odds ratio=1.90).

CONCLUSIONS

In this genetically matched cohort, high-risk APOL1 genotypes were associated with an increased risk of kidney failure and eGFR decline rate, with a graded risk between specific high-risk genotypes and a lower rate of monogenic kidney disease. Rare missense variants in the inflammasome pathway may act as genetic modifiers of APOL1 effect on kidney disease.

Dietary Patterns, Apolipoprotein L1 Risk Genotypes, and CKD Outcomes Among Black Adults in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) Cohort Study

Rationale & Objective

Dietary factors may impact inflammation and interferon production, which could influence phenotypic expression of Apolipoprotein1 (APOL1) genotypes. We investigated whether associations of dietary patterns with kidney outcomes differed by APOL1 genotypes.

Study Design

Prospective cohort.

Settings & Participants

5,640 Black participants in the Reasons for Geographic and Racial Differences in Stroke (REGARDS).

Exposures

Five dietary patterns derived from food frequency questionnaires: Convenience foods, Southern, Sweets and Fats, Plant-based, and Alcohol/Salads.

Outcomes

Incident chronic kidney disease (CKD), CKD progression, and kidney failure. Incident CKD was defined as a change in estimated glomerular filtration rate (eGFR) to <60 mL/min/1.73 m2 accompanied by a ≥25% decline from baseline eGFR or development of kidney failure among those with baseline eGFR ≥60 mL/1.73 m2 body surface area. CKD progression was defined as a composite of 40% reduction in eGFR from baseline or development of kidney failure in the subset of participants who had serum creatinine levels at baseline and completed a second in-home visit/follow-up visit.

Analytical Approach

We examined associations of dietary pattern quartiles with incident CKD (n=4,188), CKD progression (n=5,640), and kidney failure (n=5,640). We tested for statistical interaction between dietary patterns and APOL1 genotypes for CKD outcomes and explored stratified analyses by APOL1 genotypes.

Results

Among 5,640 Black REGARDS participants, mean age was 64 years (standard deviation = 9), 35% were male, and 682 (12.1%) had high-risk APOL1 genotypes. Highest versus lowest quartiles (Q4 vs Q1) of Southern dietary pattern were associated with higher adjusted odds of CKD progression (OR, 1.28; 95% CI, 1.01-1.63) but not incident CKD (OR, 0.92; 95% CI, 0.74-1.14) or kidney failure (HR, 1.48; 95% CI, 0.90-2.44). No other dietary patterns showed significant associations with CKD. There were no statistically significant interactions between APOL1 genotypes and dietary patterns. Stratified analysis showed no consistent associations across genotypes, although Q3 and Q4 versus Q1 of Plant-based and Southern patterns were associated with lower odds of CKD progression among APOL1 high- but not low-risk genotypes.

Limitations

Included overlapping dietary patterns based on a single time point and multiple testing.

Conclusions

In Black REGARDS participants, Southern dietary pattern was associated with increased risk of CKD progression. Analyses stratified by APOL1 genotypes suggest associations may differ by genetic background, but these findings require confirmation in other cohorts.

Regulated cell death pathways in kidney disease

Disorders of cell number that result from an imbalance between the death of parenchymal cells and the proliferation or recruitment of maladaptive cells contributes to the pathogenesis of kidney disease. Acute kidney injury can result from an acute loss of kidney epithelial cells. In chronic kidney disease, loss of kidney epithelial cells leads to glomerulosclerosis and tubular atrophy, whereas interstitial inflammation and fibrosis result from an excess of leukocytes and myofibroblasts. Other conditions, such as acquired cystic disease and kidney cancer, are characterized by excess numbers of cyst wall and malignant cells, respectively. Cell death modalities act to clear unwanted cells, but disproportionate responses can contribute to the detrimental loss of kidney cells. Indeed, pathways of regulated cell death - including apoptosis and necrosis - have emerged as central events in the pathogenesis of various kidney diseases that may be amenable to therapeutic intervention. Modes of regulated necrosis, such as ferroptosis, necroptosis and pyroptosis may cause kidney injury directly or through the recruitment of immune cells and stimulation of inflammatory responses. Importantly, multiple layers of interconnections exist between different modalities of regulated cell death, including shared triggers, molecular components and protective mechanisms.

A non-muscle myosin heavy chain 9 genetic variant is associated with graft failure following kidney transplantation

BACKGROUND

Despite current matching efforts to identify optimal donor-recipient pairs for kidney transplantation, alloimmunity remains a major source of late transplant failure. Additional genetic parameters in donor-recipient matching could help improve longterm outcomes. Here, we studied the impact of a non-muscle myosin heavy chain 9 gene (MYH9) polymorphism on allograft failure.

METHODS

We conducted an observational cohort study, analyzing the DNA of 1,271 kidney donor-recipient transplant pairs from a single academic hospital for the MYH9 rs11089788 C>A polymorphism. The associations of the MYH9 genotype with risk of graft failure, biopsy-proven acute rejection (BPAR), and delayed graft function (DGF) were estimated.

RESULTS

A trend was seen in the association between the MYH9 polymorphism in the recipient and graft failure (recessive model, p = 0.056), but not for the MYH9 polymorphism in the donor. The AA-genotype MYH9 polymorphism in recipients was associated with higher risk of DGF (p = 0.03) and BPAR (p = 0.021), although significance was lost after adjusting for covariates (p = 0.15 and p = 0.10, respectively). The combined presence of the MYH9 polymorphism in donor-recipient pairs was associated with poor long-term kidney allograft survival (p = 0.04), in which recipients with an AA genotype receiving a graft with an AA genotype had the worst outcomes. After adjustment, this combined genotype remained significantly associated with 15-year death-censored kidney graft survival (hazard ratio, 1.68; 95% confidence interval, 1.05-2.70; p = 0.03).

CONCLUSION

Our results reveal that recipients with an AA-genotype MYH9 polymorphism receiving a donor kidney with an AA genotype have significantly elevated risk of graft failure after kidney transplantation.

Genetic evaluation of living kidney donor candidates: A review and recommendations for best practices

The growing accessibility and falling costs of genetic sequencing techniques has expanded the utilization of genetic testing in clinical practice. For living kidney donation, genetic evaluation has been increasingly used to identify genetic kidney disease in potential candidates, especially in those of younger ages. However, genetic testing on asymptomatic living kidney donors remains fraught with many challenges and uncertainties. Not all transplant practitioners are aware of the limitations of genetic testing, are comfortable with selecting testing methods, comprehending test results, or providing counsel, and many do not have access to a renal genetic counselor or a clinical geneticist. Although genetic testing can be a valuable tool in living kidney donor evaluation, its overall benefit in donor evaluation has not been demonstrated and it can also lead to confusion, inappropriate donor exclusion, or misleading reassurance. Until more published data become available, this practice resource should provide guidance for centers and transplant practitioners on the responsible use of genetic testing in the evaluation of living kidney donor candidates.