Lupus nephritis is a potentially fatal autoimmune disease for which the current treatment is ineffective and often toxic. To develop mechanistic hypotheses of disease, we analyzed kidney samples from patients with lupus nephritis and from healthy control subjects using single-cell RNA sequencing. Our analysis revealed 21 subsets of leukocytes active in disease, including multiple populations of myeloid cells, T cells, natural killer cells and B cells that demonstrated both pro-inflammatory responses and inflammation-resolving responses. We found evidence of local activation of B cells correlated with an age-associated B-cell signature and evidence of progressive stages of monocyte differentiation within the kidney. A clear interferon response was observed in most cells. Two chemokine receptors, CXCR4 and CX3CR1 , were broadly expressed, implying a potentially central role in cell trafficking. Gene expression of immune cells in urine and kidney was highly correlated, which would suggest that urine might serve as a surrogate for kidney biopsies.

Heart failure is a common consequence of CKD, and it portends high risk for mortality. However, among patients without known heart failure, the associations of different stages of estimated GFR (eGFR) with changes in cardiac structure and function are not well described. Here, we performed a cross-sectional analysis to study these associations among 3487 participants of the Chronic Renal Insufficiency Cohort Study. We estimated GFR using cystatin C. The prevalence of left ventricular hypertrophy (LVH) assessed by echocardiography was 32%, 48%, 57%, and 75% for eGFR categories $60, 45-59, 30-44, and ,30 ml/ min per 1.73 m 2 , respectively. In fully adjusted multivariable analyses, subjects with eGFR levels of ,30 ml/ min per 1.73 m 2 had twofold higher odds of LVH (OR=2.20, 95% CI=1.40-3.40; P,0.001) relative to subjects with eGFR$60 ml/min per 1.73 m 2 . This reduction in kidney function also significantly associated with abnormal LV geometry but not diastolic or systolic dysfunction. An eGFR of 30-44 ml/min per 1.73 m 2 also significantly associated with LVH and abnormal LV geometry compared with eGFR$60 ml/min per 1.73 m 2 . In summary, in this large CKD cohort, reduced kidney function associated with abnormal cardiac structure. We did not detect significant associations between kidney function and systolic or diastolic function after adjusting for potential confounding variables.

Introduction: Much of the higher risk for end-stage kidney disease (ESKD) in African American individuals relates to ancestry-specific variation in the apolipoprotein L1 gene (APOL1). Relative to kidneys from European American deceased-donors, kidneys from African American deceased-donors have shorter allograft survival and African American living-kidney donors more often develop ESKD. The National Institutes of Health (NIH)-sponsored APOL1 Long-term Kidney Transplantation Outcomes Network (APOLLO) is prospectively assessing kidney allograft survival from donors with recent African ancestry based on donor and recipient APOL1 genotypes. Methods: APOLLO will evaluate outcomes from 2614 deceased kidney donor-recipient pairs, as well as additional living-kidney donor-recipient pairs and unpaired deceased-donor kidneys. Results: The United Network for Organ Sharing (UNOS), Association of Organ Procurement Organizations, American Society of Transplantation, American Society for Histocompatibility and Immunogenetics, and nearly all U.S. kidney transplant programs, organ procurement organizations (OPOs), and histocompatibility laboratories are participating in this observational study. APOLLO employs a central institutional review board (cIRB) and maintains voluntary partnerships with OPOs and histocompatibility laboratories. A Community Advisory Council composed of African American individuals with a personal or family history of kidney disease has advised the NIH Project Office and Steering Committee since inception. UNOS is providing data for outcome analyses. Conclusion: This article describes unique aspects of the protocol, design, and performance of APOLLO. Results will guide use of APOL1 genotypic data to improve the assessment of quality in deceased-donor kidneys and could increase numbers of transplanted kidneys, reduce rates of discard, and improve the safety of living-kidney donation.

Background and objectives Elevations in N-terminal pro-B-type natriuretic peptide and high-sensitivity troponin T are associated with poor cardiovascular outcomes. Whether elevations in these cardiac biomarkers are associated with decline in kidney function was evaluated.Design, setting, participants, & measurements N-terminal pro-B-type natriuretic peptide and troponin T were measured at baseline in 3752 participants free of heart failure in the Cardiovascular Health Study. eGFR was determined from the Chronic Kidney Disease Epidemiology Collaboration equation using serum cystatin C. Rapid decline in kidney function was defined as decline in serum cystatin C eGFR$30%, and incident CKD was defined as the onset of serum cystatin C eGFR,60 among those without CKD at baseline (n=2786). Cox regression models were used to examine the associations of each biomarker with kidney function decline adjusting for demographics, baseline serum cystatin C eGFR, diabetes, and other CKD risk factors.Results In total, 503 participants had rapid decline in serum cystatin C eGFR over a mean follow-up time of 6.41 (1.81) years, and 685 participants developed incident CKD over a mean follow-up time of 6.41 (1.74) years. Participants in the highest quartile of N-terminal pro-B-type natriuretic peptide (.237 pg/ml) had an 67% higher risk of rapid decline and 38% higher adjusted risk of incident CKD compared with participants in the lowest quartile (adjusted hazard ratio for serum cystatin C eGFR rapid decline, 1.67; 95% confidence interval, 1.25 to 2.23; hazard ratio for incident CKD, 1.38; 95% confidence interval, 1.08 to 1.76). Participants in the highest category of troponin T (.10.58 pg/ml) had 80% greater risk of rapid decline compared with participants in the lowest category (adjusted hazard ratio, 1.80; 95% confidence interval, 1.35 to 2.40). The association of troponin T with incident CKD was not statistically significant (hazard ratio, 1.17; 95% confidence interval, 0.92 to 1.50).Conclusions Elevated N-terminal pro-B-type natriuretic peptide and troponin T are associated with rapid decline of kidney function and incident CKD. Additional studies are needed to evaluate the mechanisms that may explain this association.

BACKGROUND The study of novel urinary biomarkers of acute kidney injury has expanded exponentially. Effective interpretation of data and meaningful comparisons between studies require awareness of factors that can adversely affect measurement. We examined how variations in short-term storage and processing might affect measurement of urine biomarkers. STUDY DESIGN Cross-sectional, prospective. SETTING & PARTICIPANTS Hospitalized patients from two sites: Yale New Haven Hospital (n= 52) and University of California, San Francisco Medical Center (n=36) PREDICTORS We tested the impact of 3 urine processing conditions on these biomarkers: a) centrifugation and storage at 4°C for 48 hours before freezing at −80°C, b) centrifugation and storage at 25°C for 48 hours before freezing at −80°C, and c) uncentrifuged samples immediately frozen at −80°C. OUTCOMES Urine concentration of five biomarkers: neutrophil gelatinase-associated lipocalin (NGAL), interleukin 18 (IL-18), kidney injury molecule 1 (KIM-1), liver-type fatty acid–binding protein (L-FABP) and cystatin C MEASUREMENTS We measured urine biomarkers by an established ELISA method. Biomarker values were log-transformed, and agreement with a reference standard of immediate centrifugation and storage at −80°C was compared using concordance correlation coefficients (CCCs). RESULTS Neither storing samples at 4°C for 48 hours nor centrifugation had a significant effect on measured levels, with CCCs above 0.9 for all biomarkers tested. For samples stored at 25°C for 48 hours, excellent CCC values (>0.9) were also noted between the test sample and the reference standard for NGAL, cystatin C, L-FABP and KIM-1. However, the CCC for IL-18 between samples stored at 25°C for 48 hours and the reference standard was 0.81 (95% CI, 0.66–0.96). Limitations No comparisons to fresh “unfrozen” samples, no evaluation of the effect of protease inhibitors. CONCLUSIONS All candidate markers tested using the specified assays showed high stability with both short-term storage at 4°C and without centrifugation prior to freezing. For optimal fidelity, urine for IL-18 measurement should not be stored at 25°C before long-term storage or analysis.