The longitudinal relationship between patient-reported outcomes and clinical characteristics among patients with focal segmental glomerulosclerosis in the Nephrotic Syndrome Study Network

Epidemiology and burden of focal segmental glomerulosclerosis among United States Veterans: An analysis of Veteran's Affairs data

INTRODUCTION

Focal segmental glomerulosclerosis (FSGS) is a rare glomerular disease that can lead to reduced kidney function and kidney failure (KF). The objective of this study was to describe the epidemiology, characteristics, clinical outcomes, healthcare resource utilization, and costs associated with focal segmental glomerulosclerosis (FSGS) in United States (US) veterans.

METHODS

This retrospective cohort study included patients in the National Veterans Affairs Health Care Network with ≥2 FSGS-associated diagnostic codes that were 30-180 days apart (October 1999-February 2021). Annual FSGS incidence and prevalence per 1,000,000 US veterans were calculated. Patient and disease characteristics as of the index date (date of first FSGS diagnosis) and baseline (6-months pre-index) comorbidities were described. Kaplan-Meier analyses were used to assess overall survival and time from index to KF or death, dialysis, and kidney transplant. Post-index medication use, HRU, and direct healthcare costs were summarized.

RESULTS

The study included 2,515 veterans with FSGS who were followed for an average of 8.9 years. The mean age was 57.5 years, most patients were male (94.6%), and the most common comorbidity was hypertension (87.0%). The mean annual incidence and prevalence of FSGS during 2000-2020 were 19.6 and 164.7 per million veterans, respectively. Approximately half (51.5%) died during follow-up (median time: 11.6 years) and 76.9% had kidney failure (4.1 years). Overall, 43.3% underwent dialysis and 5.8% had a kidney transplant. During follow-up, statins and calcium channel blockers were commonly used (81.9% and 75.1%). During the first year post-index, 40% had an inpatient admission and 33% visited the emergency room; mean total healthcare cost per patient in the analysis was $36,543.

CONCLUSIONS

Among US veterans, FSGS is associated with considerable clinical and economic burdens. Better treatments for FSGS are needed to slow kidney disease progression, improve patient outcomes, and reduce the burden.

Cardiovascular, Kidney Failure, and All-Cause Mortality Events in Patients with FSGS in a US Real-World Database

Key Points

In our patients with FSGS, elevated proteinuria and progression to kidney failure (KF) were associated with a higher risk of cardiovascular disease/all-cause mortality events. In addition, elevated pre-KF proteinuria was associated with KF/all-cause mortality events. CKD stage, nephrotic syndrome, and cardiovascular disease event rates, as well as the incremental costs of these events, were high.

Background

FSGS leads to proteinuria and progressive decline in GFR, which correlates with kidney failure (KF) and increased cardiovascular risk. The purpose of this study was to estimate the effects of proteinuria on KF status/all-cause mortality and cardiovascular disease (CVD) events/all-cause mortality, as well as the relationship between progression to KF and occurrence of CVD/mortality events among adult patients (18 years or older) with FSGS.

Methods

This was an observational, retrospective cohort study utilizing Optum deidentified Market Clarity Data and proprietary Natural Language Processing data. The study period was from January 1, 2007, through March 31, 2021, with patients in the overall cohort being identified from July 1, 2007, through March 31, 2021. The index date was the first FSGS ICD-10 diagnosis code or FSGS-related natural language processing term within the identification period.

Results

Elevated proteinuria >1.5 and ≥3.5 g/g increased the risk of KF/all-cause mortality (adjusted hazard ratio [HR] [95% confidence interval (CI)], 2.34 [1.99 to 2.74] and 2.44 [2.09 to 2.84], respectively) and CVD/all-cause mortality (adjusted HR [95% CI], 2.11 [1.38 to 3.22] and 2.27 [1.44 to 3.58], respectively). Progression to KF was also associated with a higher risk of CVD/all-cause mortality (adjusted HR [95% CI], 3.04 [2.66 to 3.48]).

Conclusions

A significant proportion of patients with FSGS experience KF and CVD events. Elevated proteinuria and progression to KF were associated with a higher risk of CVD/all-cause mortality events, and elevated pre-KF proteinuria was associated with progression to KF/all-cause mortality events. Treatments that meaningfully reduce proteinuria and slow the decline in GFR have the potential to reduce the risk of CVD, KF, and early mortality in patients with FSGS.

Association of mental health-related patient reported outcomes with blood pressure in adults and children with primary proteinuric glomerulopathies

INTRODUCTION

The prevalence of mental health disorders including anxiety and depression is increasing and is linked to hypertension in healthy individuals. However, the relationship of psychosocial patient-reported outcomes on blood pressure (BP) in primary proteinuric glomerulopathies is not well characterized. This study explored longitudinal relationships between psychosocial patient-reported outcomes and BP status among individuals with proteinuric glomerulopathies.

METHODS

An observational cohort study was performed using data from 745 adults and children enrolled in the Nephrotic Syndrome Study Network (NEPTUNE). General Estimating Equations for linear regression and binary logistic analysis for odds ratios were performed to analyze relationships between the exposures, longitudinal Patient-Reported Outcome Measurement Information System (PROMIS) measures and BP and hypertension status as outcomes.

RESULTS

In adults, more anxiety was longitudinally associated with higher systolic and hypertensive BP. In children, fatigue was longitudinally associated with increased odds of hypertensive BP regardless of the PROMIS report method. More stress, anxiety, and depression were longitudinally associated with higher systolic BP index, higher diastolic BP index, and increased odds of hypertensive BP index in children with parent-proxy patient-reported outcomes.

DISCUSSION/CONCLUSION

Chronically poor psychosocial patient-reported outcomes may be significantly associated with higher BP and hypertension in adults and children with primary proteinuric glomerulopathies. This interaction appears strong in children but should be interpreted with caution, as multiple confounders related to glomerular disease may influence both mental health and BP independently. That said, access to mental health resources may help control BP, and proper disease and BP management may improve overall mental health.

Preparation and Rationale for a Patient-Centered Clinical Outcome Assessment Set of Fluid Overload for Drug Development in Nephrotic Syndrome

Introduction

Fluid overload is a source of substantial morbidity for adults and children with nephrotic syndrome (NS). Preparation and Rationale for a Fluid Overload in Nephrotic Syndrome Clinical Outcomes Assessment Set for Drug Development (Prepare-NS, 5UG3FD007308) was funded by the US Food and Drug Administration to develop a core set of patient-reported and observer-reported (for young children) outcome measures of fluid overload for use in pharmaceutical trials across the lifespan.

Methods

The Prepare-NS study team developed the proposed context of use with input from stakeholders. We conducted a scoping review to assess the available literature on relevant patient- and observer-reported measures and performed secondary analyses of existing qualitative and quantitative data.

Results

The outcome set will aim to serve individuals 2 years of age and older with primary NS conditions (specifically focal segmental glomerulosclerosis, minimal change disease, IgM nephropathy, membranous nephropathy, and childhood-onset NS not biopsied). The existing literature describing patient-reported outcomes in NS largely relies on nonspecific measures of health-related quality of life; fluid overload has been associated with lower scores on these measures.

Conclusion

To address the gap in measure availability and fluid overload content, the Prepare-NS team has launched a set of qualitative studies for concept elicitation from the population of interest to inform development of new measures. The resulting measures subsequently will undergo psychometric evaluation and validation in a survey study.

Patient-Reported Outcomes Over 24 Months in Pediatric CKD: Findings From the MyKidneyHealth Cohort Study

RATIONALE & OBJECTIVE

The lived experience of children with chronic kidney disease (CKD) is poorly characterized. We examined the associations between patient-reported outcome (PRO) scores measuring their fatigue, sleep health, psychological distress, family relationships, and global health with clinical outcomes over time in children, adolescents, and younger adults with CKD and investigated how the PRO scores of this group compare with those of other children, adolescents, and younger adults.

STUDY DESIGN

Prospective cohort study.

SETTING & PARTICIPANTS

212 children, adolescentss, and adults aged 8 to 21 years with CKD and their parents recruited from 16 nephrology programs across North America.

PREDICTORS

CKD stage, disease etiology, and sociodemographic and clinical variables.

OUTCOME

PRO scores over 2 years.

ANALYTICAL APPROACH

We compared PRO scores in the CKD sample with a nationally representative general pediatric population (ages 8 to 17 years). Change of PROs over time and association of sociodemographic and clinical variables with PROs were assessed using multivariable regression models.

RESULTS

For all time points, 84% of the parents and 77% of the children, adolescents, and younger adults completed PRO surveys . The baseline PRO scores for the participants with CKD revealed a higher burden of fatigue, sleep-related impairment, psychological distress, impaired global health, and poorer family relationships compared with the general pediatric population, with median score differences≥1 SD for fatigue and global health. The baseline PRO scores did not differ by CKD stage or glomerular versus nonglomerular etiology. Over 2 years, PROs were stable with a<1-point annual change on average on each measure and intraclass correlation coefficients ranging from 0.53 to 0.79, indicating high stability. Hospitalization and parent-reported sleep problems were associated with worse fatigue, psychological health, and global health scores (all P<0.04).

LIMITATIONS

We were unable to assess responsiveness to change with dialysis or transplant.

CONCLUSIONS

Children with CKD experience a high yet stable burden of impairment across numerous PRO measures, especially fatigue and global health, independent of disease severity. These findings underscore the importance of assessing PROs, including fatigue and sleep measures, in this vulnerable population.

PLAIN-LANGUAGE SUMMARY

Children with chronic kidney disease (CKD) have many treatment demands and experience many systemic effects. How CKD impacts the daily life of a child is poorly understood. We surveyed 212 children, adolescents, and younger adults with CKD and their parents over 24 months to assess the participants' well-being over time. Among children, adolescents, and younger adults with CKD we found a very high and persistent burden of psychological distress that did not differ by degree of CKD or type of kidney disease. The participants with CKD endorsed greater impairment in fatigue and global health compared with healthy children, adolescents, and younger adults, and parent-reported sleep problems were associated with poorer patient-reported outcome (PRO) scores across all domains. These findings emphasize the importance of including PRO measures, including fatigue and sleep measures, into routine clinical care to optimize the lived experience of children with CKD.

Enabling flourishing: novel approaches in palliative medicine for children with advanced kidney disease

PURPOSE OF REVIEW

Paediatric kidney disease results in considerable burden on children and their families. Paediatric palliative care is a holistic, family-centred care approach intended to enable flourishing and address the many impediments to life participation which advanced kidney disease can impose. To date, palliative care resources have been underutilized in paediatric nephrology. This review will highlight recent literature targeting the engagement and life participation of children with advanced kidney disease through implementation of novel palliative care approaches and propose directions for future research.

RECENT FINDINGS

Children with advanced kidney disease and their families highly value incorporation of their perspectives, particularly on life participation, within care plan development; but what it means to participate in life can be variable, and clinicians need improved tools to ascertain and incorporate these perspectives. Novel palliative care interventions developed for application in comparable disease states offer potential opportunities for paediatric nephrologists to support this goal.

SUMMARY

Children with advanced kidney disease and their families will benefit from incorporation of their perspectives and values, facilitated by palliative interventions.

CureGN-Diabetes Study: Rationale, Design, and Methods of a Prospective Observational Study of Glomerular Disease Patients with Diabetes

Glomerular diseases (GDs) represent the third leading cause of end-stage kidney disease (ESKD) in the US Diabetes was excluded from the CureGN Study, an NIH/NIDDK-sponsored observational cohort study of four leading primary GDs: IgA nephropathy (IgAN), membranous nephropathy (MN), focal segmental glomerulosclerosis (FSGS), and minimal change disease (MCD). CureGN-Diabetes, an ancillary study to CureGN, seeks to understand how diabetes influences the diagnosis, treatment, and outcomes of GD. It is a multicenter, prospective cohort study, targeting an enrollment of 300 adults with prevalent type 1 or type 2 diabetes and MCD, FSGS, MN, or IgAN, with first kidney biopsy obtained within 5 years of enrollment in 80% (20% allowed if biopsy after 2010). CureGN and Transformative Research in DiabEtic NephropaThy (TRIDENT) provide comparator cohorts. Retrospective and prospective clinical data and patient-reported outcomes are obtained. Blood and urine specimens are collected at study visits annually. Kidney biopsy reports and digital images are obtained, and standardized pathologic evaluations performed. Light microscopy images are uploaded to the NIH pathology repository. Outcomes include relapse and remission rates, changes in proteinuria and estimated glomerular filtration rate, infections, cardiovascular events, malignancy, ESKD, and death. Multiple analytical approaches will be used leveraging the baseline and longitudinal data to compare disease presentation and progression across subgroups of interest. With 300 patients and an average of 3 years of follow-up, the study has 80% power to detect a HR of 1.4-1.8 for time to complete remission of proteinuria, a rate ratio for hospitalizations of 1.18-1.56 and difference in eGFR slope of 6.0-8.6 mL/min/year between two groups of 300 participants each. CureGN-Diabetes will enhance our understanding of diabetes as a modifying factor of the pathology and outcomes of GDs and support studies to identify disease mechanisms and improve patient outcomes in this understudied patient population.

Decoding the Mechanism behind the Pathogenesis of the Focal Segmental Glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) is a chronic glomerular disease associated with podocyte injury which is named after the pathologic features of the kidney. The aim of this study is to decode the key changes in gene expression and regulatory network involved in the formation of FSGS. Integrated network analysis included Gene Expression Omnibus (GEO) datasets to identify differentially expressed genes (DEGs) between FSGS patients and healthy donors. Bioinformatics analysis was used to identify the roles of the DEGs and included the development of protein-protein interaction (PPI) networks, Gene Ontology (GO), and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses, and the key modules were assured. The expression levels of DEGs were validated using the additional dataset. Eventually, transcription factors and ceRNA networks were established to illuminate the regulatory relationships in the formation of FSGS. 1130 DEGs including 475 upregulated genes and 655 downregulated genes with functional enrichment analysis were determined. Further analysis uncovered that the validated hub genes were defined as candidate genes, including Complement C3a Receptor 1 (C3AR1), C-C Motif Chemokine Receptor 1(CCR1), C-X3-C Motif Chemokine Ligand 1 (CX3CL1), Melatonin Receptor 1A (MTNR1A), and Purinergic Receptor P2Y13 (P2RY13). More importantly, we identified transcription factors and mRNA-miRNA-lncRNA regulatory networks associated with the candidate genes. The candidate genes and regulatory networks discovered in this study can help to comprehend the molecular mechanism of FSGS and supply potential targets for the diagnosis and therapy of FSGS.

Non-disease specific patient-reported outcome measures of health-related quality of life in juvenile idiopathic arthritis: a systematic review of current research and practice

Juvenile idiopathic arthritis (JIA), as a chronic condition, is associated with symptoms negatively impacting health-related quality of life (HRQL). Regarding growing interest in the implementation of the patient-reported outcome measures (PROMs), we aimed to review the non-disease specific PROMs addressing HRQL assessment, potentially useful in the clinical care of JIA and daily practice. A systematic literature search was conducted using MEDLINE/PubMed, Google Scholar, Scopus and Embase databases (1990 to 2021), with a focus on the recent 5-years period. Entry keywords included the terms: “children”, “adolescents”, “JIA”, “chronic diseases”, “HRQL”, “PROMs” and wordings for the specific tools. Several available PROMs intended to measure HRQL, non-specific to JIA, were identified. The presented outcomes differed in psychometric properties, yet all were feasible in assessing HRQL in healthy children and those with chronic diseases. Both EQ-5D-Y and PedsQL have already been tested in JIA, showing relevant reliability, validity, and similar efficiency as disease-specific measurements. For PROMIS® PGH-7 and PGH-7 + 2, such validation and cross-cultural adaptation need to be performed. Considering the future directions in pediatric rheumatology, the large-scale implementation of PROMIS® PGH-7 and PGH-7 + 2 in JIA offers a particularly valuable opportunity. The PROMs reflect the patient perception of the chronic disease and allow to understand child’s opinions. The PROMs may provide an important element of the holistic medical care of patients with JIA and a standardized tool for clinical outcomes, monitoring disease severity and response to treatment.

Patient-Reported Outcomes in Children With Chronic Kidney Disease

Patient-reported outcomes (PROs) are quantitative assessments of a patient's perspective on their health and are derived directly from the patient, as opposed to clinician interpretation. PROs can serve as unique tools to improve health care providers' understanding of the patient's daily lived experience and highlight salient domains that are specific to children with chronic kidney disease (CKD). As such, PROs fill an important gap in achieving optimal health and well-being for children with CKD. However, several knowledge gaps remain in the implementation of PROs within both the clinical and research realms. This review provides a broad overview of PRO development, implementation for children with CKD, and highlights future directions and challenges.

Re-transplantation in pediatric patients with failure of primary transplant due to recurrent focal segmental glomerulosclerosis: A pediatric nephrology research consortium study

INTRODUCTION

Recurrent focal and segmental glomerulosclerosis (FSGS) in kidney transplant recipients is associated with lower graft survival and increased morbidity. There are limited data to guide the decision to re-transplant patients with transplant failure due to FSGS recurrence. We aimed to evaluate outcomes in patients re-transplanted after having initial graft failure due to recurrent FSGS and to study physician attitudes and practice patterns.

METHODS

Retrospective data from 10 centers were collected on 20 patients transplanted between January 1997 and September 2018. A survey was sent to nephrologist members of the Pediatric Nephrology Research Consortium.

RESULTS

Mean patient age (years) was 9.8 ± 4.8 at first transplant and 15.9 ± 4.9 at re-transplantation. Pre-transplant plasmapheresis was used in 1 (5.3%) primary transplant vs. 7 (38.9%) re-transplants (p = .03). Nephrotic syndrome recurred in 14 patients (70%) after re-transplantation and was severe in 21.1% vs. 64.7% after first transplant (p = .04). Graft survival was significantly higher in the second transplant (p .009) with 70% having functioning grafts at a median of 25.2 months. Thirty-one physicians from 21 centers completed the survey, 94% indicated they would re-transplant such patients, 44.4% preferred a minimum waiting period before re-transplantation, 36.4% preferred living donors, and 22.2% indicated having protocols for re-transplantation at their centers.

CONCLUSIONS

Consideration for re-transplantation is high among pediatric nephrologists. Pre-transplant plasmapheresis was more frequent in re-transplanted patients. Nephrotic syndrome recurrence was less severe, with better graft survival. More data and a larger population are necessary to further evaluate outcome determinants and best practices in this special population.

A Retrospective Study of Clinical and Economic Burden of Focal Segmental Glomerulosclerosis (FSGS) in the United States

Introduction

Information on the economic burden of focal segmental glomerulosclerosis (FSGS) is sparse. This study characterized health care resource utilization (HCRU) and costs in patients with FSGS, and evaluated the impact of nephrotic range proteinuria on these outcomes.

Methods

This retrospective, observational cohort study used administrative claims data from the Optum Clinformatics Data Mart Database from October 2015 to December 2019. Patients with FSGS (n = 844; first claim = index event) between April 2016 and December 2018 were matched on index date, age, sex, and race to non-FSGS controls (n = 1688). FSGS nephrotic range (urine protein/creatinine ratio >3000 mg/g or albumin/creatinine ratio >2000 mg/g) and non-nephrotic subpopulations were identified. Baseline comorbidities, 12-month post-index all-cause HCRU and costs (per patient per year [PPPY]), and immunosuppressant prescriptions were compared between matched cohorts and between FSGS subpopulations.

Results

Comorbidity burden was higher in FSGS. Of 308 patients with available urine protein/creatinine ratio/albumin/creatinine ratio results, 36.4% were in nephrotic range. All-cause HCRU was higher in FSGS across resource categories (all P < 0.0001); 50.6% of FSGS and 23.3% of controls were prescribed glucocorticoids (P < 0.0001). Mean total medical costs were higher in FSGS ($59,753 vs. $8431 PPPY; P < 0.0001), driven by outpatient costs. Nephrotic range proteinuria was associated with higher all-cause inpatient, outpatient, and prescription costs versus nonnephrotic patients (all P < 0.0001), resulting in higher total costs ($70,481 vs. $36,099 PPPY; P < 0.0001).

Conclusions

FSGS is associated with significant clinical and economic burdens; the presence of nephrotic range proteinuria increased the economic burden. New treatment modalities are needed to reduce proteinuria, help improve patient outcomes, and reduce HCRU and associated costs.

Evaluation of PROMIS Preference Scoring System (PROPr) in Patients Undergoing Hemodialysis or Kidney Transplant

BACKGROUND AND OBJECTIVES

A preference-based health utility score (PROPr) can be calculated using Patient-Reported Outcomes Measurement Information System domain scores. We assessed the construct validity of PROPr among patients treated with KRT (hemodialysis or kidney transplant).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We performed a secondary analysis of data collected in multicenter, cross-sectional studies of adults treated with KRT, recruited between April 2016 to March 2020 in Toronto, Canada. All participants provided informed consent. The outcome was the PROPr score. Coadministered outcome variables included the Short-Form Six-Domain (SF-6D) and EuroQol Five-Domain Five-Level (EQ-5D-5L) scores. Socioeconomic and clinical variables included age, sex, diabetes, eGFR, serum albumin, hemoglobin, KRT, and Charlson Comorbidity Index. Construct validity was assessed through correlations between PROPr and SF-6D or EQ-5D-5L, and associations between PROPr and other exposure variables. Health-condition impact estimates (coefficients for health conditions compared with a referent category, e.g., dialysis versus kidney transplant) were calculated using multivariable linear regression.

RESULTS

The mean (SD) age of the 524 participants was 57 (17) years, 58% were male, and 45% were White. Median (interquartile range) score was 0.39 (0.24-0.58) for PROPr, 0.69 (0.58-0.86) for SF-6D, and 0.85 (0.70-0.91) for EQ-5D-5L. Large correlations were observed between PROPr versus SF-6D (0.79; 95% confidence interval [95% CI], 0.76 to 0.82) and EQ-5D-5L (0.71; 95% CI, 0.66 to 0.75). Both PROPr and the other utility indices demonstrated health-condition impact in the expected direction. For example, the estimate for PROPr was -0.17 (95% CI, -0.13 to -0.21) for dialysis (versus kidney transplant), -0.05 (95% CI, -0.11 to 0.01; P=0.08) for kidney transplant recipients with an eGFR of <45 versus ≥45 ml/min per 1.73 m², and -0.28 (95% CI, -0.22 to -0.33) for moderate/severe versus no/mild depressive symptoms.

CONCLUSIONS

Our results support the validity of PROPr among patients treated with KRT.

Health-Related Quality of Life in Focal Segmental Glomerular Sclerosis and Minimal Change Disease: A Qualitative Study of Children and Adults to Inform Patient-Reported Outcomes

RATIONALE & OBJECTIVE

Assessment of how patients feel and function is needed for clinical care and research for focal segmental glomerulosclerosis (FSGS) and minimal change disease (MCD). The objective of this study was to develop a patient-reported outcome assessment appropriate for use in children and adults with FSGS and MCD.

STUDY DESIGN

Qualitative study using semi-structured interviews.

SETTING & PARTICIPANTS

48 semi-structured interviews with children aged 8 to 17 years (n = 11) and adults (n = 10) with FSGS and children aged 8 to 17 (n = 11) and adults (n = 16) with MCD recruited from 3 academic medical centers.

ANALYTICAL APPROACH

Latent content analysis.

RESULTS

FSGS and MCD have a pervasive and comparable impact on physical, social, and mental health-related quality of life regardless of age or diagnosis. Physical symptoms of swelling, fatigue, and pain were articulated by most participants. Disease management was also a frequent topic of discussion; participants described their experiences with medication and associated side effects, as well as lifestyle changes made to manage their disease (ie, dietary changes and frequent medical appointments). These discussions often identified a profound impact on physical abilities and life participation. In many instances, participants described the negative impact these symptoms had on their mood and sense of self, with most participants reporting feelings of anxiety.

LIMITATIONS

Participants were primarily non-Hispanic White and English speaking, which may limit generalizability.

CONCLUSIONS

Our results suggest that there are commonalities to the FSGS-MCD patient experience of health-related quality of life that will enable the generation of a disease-specific FSGS-MCD patient-reported outcomes instrument for use in children and adults. The development of this tool is intended to facilitate better care and support clinical research for these individuals.

Sex and kidney ACE2 expression in primary focal segmental glomerulosclerosis: A NEPTUNE study

Background

Angiotensin-converting enzyme 2 (ACE2) has been implicated in the pathogenesis of experimental kidney disease. ACE2 is on the X chromosome, and in mice, deletion of ACE2 leads to the development of focal segmental glomerulosclerosis (FSGS). The relationship between sex and renal ACE2 expression in humans with kidney disease is a gap in current knowledge.

Methods

We studied renal tubulointerstitial microarray data and clinical variables from subjects with FSGS enrolled in the Nephrotic Syndrome Study Network (NEPTUNE) study. We compared relationships between ACE2 expression and age, estimated glomerular filtration rate (eGFR), urinary albumin to creatinine ratio (UACR), interstitial fibrosis, tubular atrophy, and genes implicated in inflammation and fibrosis in male and female subjects.

Results

ACE2 mRNA expression was lower in the tubulointerstitium of males compared to females (P = 0.0026). Multiple linear regression analysis showed that ACE2 expression was related to sex and eGFR but not to age or treatment with renin angiotensin system blockade. ACE2 expression is also related to interstitial fibrosis, and tubular atrophy, in males but not in females. Genes involved in inflammation (CCL2 and TNF) correlated with ACE2 expression in males (TNF: r = -0.65, P < 0.0001; CCL2: r = -0.60, P < 0.0001) but not in females. TGFB1, a gene implicated in fibrosis correlated with ACE2 in both sexes.

Conclusions

Sex is an important determinant of ACE2 expression in the tubulointerstitium of the kidney in FSGS. Sex also influences the relationships between ACE2, kidney fibrosis, and expression of genes involved in kidney inflammation.