Regulatory T cells effectively downregulate the autoimmune anti-MPO response and ameliorate anti-MPO induced glomerulonephritis in mice.

Regulation of autoreactive cells is key for both prevention and amelioration of autoimmune disease. A better understanding of the key cell population(s) responsible for downregulation of autoreactive cells would provide necessary foundational insight for cellular-based therapies in autoimmune disease. Utilizing a mouse model of anti-myeloperoxidase (MPO) glomerulonephritis, we sought to understand which immune cells contribute to downregulation of the anti-MPO autoimmune response. MPO-/- mice were immunized with whole MPO to induce an anti-MPO response. Anti-MPO splenocytes were then transferred into recipient mice (Rag2-/- mice or WT mice). Anti-MPO titers were followed over time. After anti-MPO splenocyte transfer, WT mice are able to downregulate the anti-MPO response while anti-MPO titers persist in Rag2-/- recipients. Reconstitution with WT splenocytes into Rag2-/- recipients prior to anti-MPO splenocyte transfer enabled mice to downregulate the anti-MPO immune response. Therefore, wildtype splenocytes contain a cellular population that is capable of downregulating the autoimmune response. Through splenocyte transfer, antibody depletion experiments, and purified cell population transfers, we confirmed that the regulatory T cell (Treg) population is responsible for the downregulation of the anti-MPO autoimmune response. Further investigation revealed that functional Tregs from WT mice are capable of downregulating anti-MPO antibody production and ameliorate anti-MPO induced glomerulonephritis. These data underscore the importance of functional Tregs for control of autoimmune responses and prevention of end-organ damage due to autoimmunity.

Association of Obesity With Kidney and Cardiac Outcomes Among Patients With Glomerular Disease: Findings From the Cure Glomerulonephropathy Network.

RATIONALE & OBJECTIVE: The influence of obesity on cardiorenal outcomes in individuals with glomerular disease is incompletely known. This study examined the association between obesity and kidney and cardiovascular outcomes in children and adults with glomerular kidney disease. STUDY DESIGN: Prospective, multicenter, observational study. SETTING & PARTICIPANTS: Participants in the Cure Glomerulonephropathy Network (CureGN) who were≥5 years of age at enrollment. EXPOSURE: Adult body mass index (BMI) groups: 20-24 (healthy) versus 25-34 (overweight/class 1 obesity) versus≥35 (class 2-3 obesity); and pediatric BMI percentiles: 5th-84th (healthy) versus 85th-94th (overweight) versus≥95th (obese). OUTCOME: A composite kidney outcome (40% estimated glomerular filtration rate [eGFR] decline or kidney failure) and a composite cardiovascular outcome (myocardial infarction, stroke, heart failure, or death). ANALYTICAL APPROACH: Time to composite primary outcomes by BMI strata were estimated using Kaplan-Meier analysis. The adjusted associations between BMI and outcomes were estimated using Cox proportional hazards analysis. RESULTS: The study included 2,301 participants (1,548 adults and 753 children). The incidence of the primary kidney end point was 90.8 per 1,000 person-years in adults with class 2-3 obesity, compared with 58.0 in normal weight comparators. In the univariable analysis, class 2-3 obesity was associated with the primary kidney outcome only in adults (HR, 1.6 [95% CI, 1.1-2.2], P=0.006) compared with the healthy weight groups. In the multivariable adjusted analysis, class 2-3 obesity did not remain significant among adults when controlling for baseline eGFR and proteinuria. Adults with class 2-3 obesity had an incidence of 19.7 cardiovascular events per 1,000 person-years and greater cardiovascular risk (HR, 3.9 [95% CI, 1.4-10.7], P=0.009) in the fully adjusted model. LIMITATIONS: BMI is an imperfect indicator of adiposity. Residual confounding may exist from socioeconomic factors. CONCLUSIONS: Among adult patients in CureGN, class 2-3 obesity is associated with cardiovascular but not kidney outcomes when adjusted for potential confounding factors. PLAIN-LANGUAGE SUMMARY: Obesity is a risk factor for adverse heart and kidney outcomes in patients with chronic kidney disease, but whether it is associated with these outcomes in patients with glomerulonephropathy is not known. This study used existing data from a large sample of adults and children with glomerular diseases to address this question. The findings suggest that obesity increases the risk of cardiovascular but not kidney disease events in adult patients with glomerular disease.

Infections Following Kidney Transplantation After Exposure to Immunosuppression for Treatment of Glomerulonephritis.

RATIONALE & OBJECTIVE: Kidney transplant patients with glomerulonephritis (GN) as their native disease commonly have received pretransplant immunosuppression (PTI). This may contribute to the immunosuppression burden potentially increasing the risk for infections after transplantation. STUDY DESIGN: Single-center, retrospective cohort study. SETTING & PARTICIPANTS: Recipients of a kidney transplant from January 2005 until May 2020 at a tertiary care university teaching hospital. EXPOSURE: Patients with GN as their native kidney disease who received PTI for treatment of GN (n=184) were compared with nondiabetic recipients of kidney transplants who did not receive PTI (n = 579). OUTCOME: First occurrence after transplantation of an infection outcome, either viral (BK or cytomegalovirus [CMV] infection) or bacterial. ANALYTICAL APPROACH: Cox regression analysis adjusted for age at transplant, sex, race, donor type, year of transplant surgery, dialysis vintage, receipt of T-cell depleting induction, and CMV transplant status. RESULTS: Over a median follow-up period of 5.7 years, patients with GN PTI were not at an increased risk for developing any first viral infection compared with controls (adjusted HR [AHR] 0.69 [95% CI, 0.52-0.91]) nor at increased risk for specific viral infections: BK infection 19.6% vs 26.3% (AHR 0.72 [95% CI, 0.50-1.05]) or CMV infection, 24.5% vs 29.0% (AHR, 0.76 [95% CI, 0.54-1.07]), respectively. There was also no increased risk of developing a first bacterial infection: 54.5% vs 57.5% (AHR, 0.90 [95% CI, 0.71-1.13]). These findings of no increased risk for infection were independent of the type of PTI used (cyclophosphamide, rituximab, mycophenolate mofetil, or calcineurin inhibitor) or the type of T-cell depleting induction therapy (alemtuzumab or antithymocyte globulin) administered. LIMITATIONS: Single-center study, no data on methylprednisone use for PTI, unmeasured confounding. CONCLUSIONS: Use of PTI for the treatment of GN was not associated with an increased risk of viral (BK or CMV) or bacterial infection after transplantation. Additional surveillance for infection after transplantation for patients who received PTI may not be necessary. PLAIN-LANGUAGE SUMMARY: Many kidney transplant patients have glomerular disease as the cause of kidney failure. These patients may be exposed to immunosuppression before transplantation, which could increase the risk for infections after receipt of a transplanted kidney. We identified kidney transplant recipients at a university teaching hospital who received immunosuppression before transplant for the treatment of glomerular kidney disease. We examined their risk for infection after transplantation by comparing it with the risk among transplant patients who were not exposed to immunosuppression before transplant. We observed no increased risk for infection after exposure to prior immunosuppression. Therefore, patients exposed to significant amounts of immunosuppression before transplantation may not require special surveillance or medication adjustment for fear of infection after their receipt of a kidney transplant.

Malignancy risk in kidney transplant recipients exposed to immunosuppression pre-transplant for the treatment of glomerulonephritis.

BACKGROUND: Kidney transplant patients with glomerulonephritis (GN) as their native disease may receive significant amounts of pre-transplant immunosuppression (PTI), which could increase the risk for development of malignancy post-transplant. METHODS: We conducted a single-center, retrospective study of kidney transplant recipients from January 2005 until May 2020. Patients with GN as their native kidney disease who received PTI for treatment of GN (n = 184) were compared with a control cohort (n = 579) of non-diabetic, non-PTI-receiving kidney transplant patients. We calculated hazard ratios (HR) with 95% confidence intervals (95% CI) for outcomes of first occurrence of solid or hematologic malignancy, non-melanoma skin cancer (NMSC) and post-transplant lymphoproliferative disorder (PTLD). RESULTS: Over a median follow-up of 5.7 years, PTI for GN was associated with significantly increased risk for malignancy compared with controls [13.0%  vs 9.7%, respectively; adjusted HR 1.82 (95% CI 1.10-3.00)], but not for NMSC [10.3% vs 11.4%, respectively; adjusted HR 1.09 (95% CI 0.64-1.83)] or PTLD [3.3% vs 3.1%, respectively; adjusted HR 1.02 (95% CI 0.40-2.61)]. The risk for malignancy was significantly increased in those who received cyclophosphamide [HR 2.59 (95% CI 1.48-4.55)] or rituximab [HR 3.82 (95% CI 1.69-8.65)] pre-transplant, and particularly in those who received both cyclophosphamide and rituximab, but not for calcineurin inhibitors or mycophenolate. CONCLUSION: The use of PTI for treatment of GN, especially cyclophosphamide or even with rituximab, is associated with increased risk for development of solid or hematologic malignancy post-transplant. These data highlight potential risks with treatment of GN and underscore the importance of post-transplant malignancy surveillance in this patient population.

Kidney disease characteristics, prevalence, and risk factors in León, Nicaragua: a population-based study.

BACKGROUND: CKD of unknown etiology (CKDu) disproportionately affects young people in Central America who lack traditional CKD risk factors (diabetes and hypertension) and has instead been variably linked to heat stress, occupational and environmental exposures, nephrotoxic medications, and/or genetic susceptibility. This study aimed to estimate the prevalence of CKD and identify risk factors for traditional CKD and CKDu in Nicaragua. METHODS: Surveys and assessment for CKD markers in urine and serum were performed in 15-59 year olds in households of the León municipality of Nicaragua. The survey included questions on demographics, health behaviors, occupation, and medical history. Participants with CKD were subdivided into traditional CKD and suspected CKDu based on history of diabetes, hypertension, or other specified conditions. A multinomial logistic regression model was used to identify factors associated with traditional CKD and suspected CKDu, compared to the non-CKD reference group. RESULTS: In 1795 study participants, CKD prevalence was 8.6%. Prevalence in males was twofold higher than females (12% vs 6%). Of those with CKD, 35% had suspected CKDu. Both traditional CKD and CKDu were associated with male sex and increasing age. Traditional CKD was associated with a family history of CKD, history of urinary tract infections, and lower socioeconomic status, while CKDu was associated with drinking well water and a lower body mass index. CONCLUSIONS: Both traditional CKD and CKDu are significant burdens in this region. Our study supports previous hypotheses of CKDu etiology and emphasizes the importance of CKD screening.

Immunological Interaction of HLA-DPB1 and Proteinase 3 in ANCA Vasculitis is Associated with Clinical Disease Activity.

BACKGROUND: PR3-ANCA vasculitis has a genetic association with HLA-DPB1. We explored immunologic and clinical features related to the interaction of HLA-DPB1*04:01 with a strongly binding PR3 peptide epitope (PR3225-239). METHODS: Patients with ANCA vasculitis with active disease and disease in remission were followed longitudinally. Peripheral blood mononuclear cells from patients and healthy controls with HLA-DPB1*04:01 were tested for HLA-DPB1*04:01 expression and interaction with a PR3 peptide identified via in silico and in vitro assays. Tetramers (HLA/peptide multimers) identified autoreactive T cells in vitro. RESULTS: The HLA-DPB1*04:01 genotype was associated with risk of relapse in PR3-ANCA (HR for relapse 2.06; 95% CI, 1.01 to 4.20) but not in myeloperoxidase (MPO)-ANCA or the combined cohort. In silico predictions of HLA and PR3 peptide interactions demonstrated strong affinity between ATRLFPDFFTRVALY (PR3225-239) and HLA-DPB1*04:01 that was confirmed by in vitro competitive binding studies. The interaction was tested in ex vivo flow cytometry studies of labeled peptide and HLA-DPB1*04:01-expressing cells. We demonstrated PR3225-239 specific autoreactive T cells using synthetic HLA multimers (tetramers). Patients in long-term remission off therapy had autoantigenic peptide and HLA interaction comparable to that of healthy volunteers. CONCLUSIONS: The risk allele HLA-DPB1*04:01 has been associated with PR3-ANCA, but its immunopathologic role was unclear. These studies demonstrate that HLA-DPB1*04:01 and PR3225-239 initiate an immune response. Autoreactive T cells specifically recognized PR3225-239 presented by HLA-DPB1*04:01. Although larger studies should validate these findings, the pathobiology may explain the observed increased risk of relapse in our cohort. Moreover, lack of HLA and autoantigen interaction observed during long-term remission signals immunologic nonresponsiveness.

Kidney thrombotic microangiopathy in lupus nephritis: Impact on treatment and prognosis.

INTRODUCTION: Lupus nephritis (LN) may present with thrombotic microangiopathy (TMA) on kidney biopsy, the impact of which on outcomes is unclear. This study examined the prognostic importance of LN with TMA on kidney biopsy, including response to therapy and long-term outcomes. METHODS: We conducted a single-center, retrospective study of all cases of LN with concomitant TMA on kidney biopsy in the Glomerular Disease Collaborative Network database. Controls were individuals with LN without TMA matched to cases based on demographic and clinical variables. Outcomes were remission at 6- and 12-months, end-stage kidney disease (ESKD) and death. Logistic regression and Cox proportional hazards models were used to ascertain the risks for outcomes, with adjustment for serum creatinine and proteinuria. RESULTS: There were 17 cases and 28 controls. Cases had higher creatinine, higher proteinuria and greater chronicity on biopsy at baseline compared to controls. The rates of remission at 6-months and 12-months were similar between cases and controls (6-months 53.9% vs 46.4%, adjusted OR 2.54, 95% CI 0.48, 13.37; 12-months 53.9% vs 50.0%, adjusted OR 2.95, 95% CI 0.44, 19.78). Cases were at greater risk for ESKD in univariate analysis (HR 3.77; 95% CI 1.24, 11.41) but not when adjusting for serum creatinine and proteinuria (HR 2.20; 95% CI 0.63, 7.71). There was no significant difference in the risk of death between cases and controls. CONCLUSION: Lupus nephritis with renal TMA likely responds to therapy similarly to those without TMA; risk for ESKD is not significantly increased, although the influence of renal function and proteinuria in larger samples is needed.

Podocyte density is reduced in kidney allografts with high-risk APOL1 genotypes at transplantation.

Variants in apolipoprotein L1 (APOL1) gene are associated with nondiabetic kidney diseases in black subjects and reduced kidney transplant graft survival. Living and deceased black kidney donors (n = 107) were genotyped for APOL1 variants. To determine whether allografts from high-risk APOL1 donors have reduced podocyte densities contributing to allograft failure, we morphometrically estimated podocyte number, glomerular volume, and podocyte density. We compared allograft loss and eGFR trajectories stratified by APOL1 high-risk and low-risk genotypes. Demographic characteristics were similar in high-risk (n = 16) and low-risk (n = 91) donors. Podocyte density was significantly lower in high-risk than low-risk donors (108 ± 26 vs 127 ± 40 podocytes/106 um3 , P = .03). Kaplan-Meier graft survival (high-risk 61% vs. low-risk 91%, p-value = 0.049) and multivariable Cox models (hazard ratio = 2.6; 95% CI, 0.9-7.8) revealed higher graft loss in recipients of APOL1 high-risk allografts over 48 months. More rapid eGFR decline was seen in recipients of high-risk APOL1 allografts (P < .001). At 60 months, eGFR was 27 vs. 51 mL/min/1.73 min2 in recipients of APOL1 high-risk vs low-risk kidney allografts, respectively. Kidneys from high-risk APOL1 donors had worse outcomes versus low-risk APOL1 genotypes. Lower podocyte density in kidneys from high-risk APOL1 donors may increase susceptibility to CKD from subsequent stresses in both the recipients and donors.

ANCA autoantigen gene expression highlights neutrophil heterogeneity where expression in normal-density neutrophils correlates with ANCA-induced activation.

ANCA vasculitis is an autoimmune disease with increased expression of the autoantigen genes, myeloperoxidase (MPO) and proteinase 3 (PRTN3), but the origin and significance of expression is less distinct. To clarify this, we measured MPO and PRTN3 messenger RNA in monocytes, normal-density neutrophils, and in enriched leukocytes from peripheral blood mononuclear cells. Increased autoantigen gene expression was detected in normal-density neutrophils and enriched leukocytes from patients during active disease compared to healthy individuals, with the largest difference in enriched leukocytes. RNA-seq of enriched leukocytes comparing active-remission pairs identified a gene signature for low-density neutrophils. Cell sorting revealed low-density neutrophils contained mature and immature neutrophils depending on the presence or absence of CD10. Both populations contributed to autoantigen expression but the frequency of immature cells in low-density neutrophils did not correlate with low-density neutrophil MPO or PRTN3 expression. Low-density neutrophils were refractory to MPO-ANCA induced oxidative burst, suggesting an alternative role for low-density neutrophils in ANCA vasculitis pathogenesis. In contrast, normal-density neutrophils were activated by MPO-ANCA and monoclonal anti-PR3 antibody. Normal-density neutrophil activation correlated with MPO and PRTN3 mRNA. Increased autoantigen gene expression originating from the mature low-density and normal-density neutrophils suggests transcriptional dysregulation is a hallmark of ANCA vasculitis. Thus, the correlation between autoantigen gene expression and antibody-mediated normal-density neutrophil activation connects autoantigen gene expression with disease pathogenesis.

Restricted myeloperoxidase epitopes drive the adaptive immune response in MPO-ANCA vasculitis.

BACKGROUND: Treatment of autoimmune diseases has relied on broad immunosuppression. Knowledge of specific interactions between human leukocyte antigen (HLA), the autoantigen, and effector immune cells, provides the foundation for antigen-specific therapies. These studies investigated the role of HLA, specific myeloperoxidase (MPO) epitopes, CD4+ T cells, and ANCA specificity in shaping the immune response in patients with anti-neutrophil cytoplasmic autoantibody (ANCA) vasculitis. METHODS: HLA sequence-based typing identified enriched alleles in our patient population (HLA-DPB1*04:01 and HLA-DRB4*01:01), while in silico and in vitro binding studies confirmed binding between HLA and specific MPO epitopes. Class II tetramers with MPO peptides were utilized to detect autoreactive CD4+ T cells. TCR sequencing was performed to determine the clonality of T cell populations. Longitudinal peptide ELISAs assessed the temporal nature of anti-MPO447-461 antibodies. Solvent accessibility combined with chemical modification determined the buried regions of MPO. RESULTS: We identified a restricted region of MPO that was recognized by both CD4+ T cells and ANCA. The autoreactive T cell population contained CD4+CD25intermediateCD45RO+ memory T cells and secreted IL-17A. T cell receptor (TCR) sequencing demonstrated that autoreactive CD4+ T cells had significantly less TCR diversity when compared to naïve and memory T cells, indicating clonal expansion. The anti-MPO447-461 autoantibody response was detectable at onset of disease in some patients and correlated with disease activity in others. This region of MPO that is targeted by both T cells and antibodies is not accessible to solvent or chemical modification, indicating these epitopes are buried. CONCLUSIONS: These observations reveal interactions between restricted MPO epitopes and the adaptive immune system within ANCA vasculitis that may inform new antigen-specific therapies in autoimmune disease while providing insight into immunopathogenesis.

Proteinase-3 and myeloperoxidase serotype in relation to demographic factors and geographic distribution in anti-neutrophil cytoplasmic antibody-associated glomerulonephritis.

Background: In anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis, antigen specificity varies between myeloperoxidase (MPO) and proteinase 3 (PR3). This has been reported to vary in relation to age, gender, geography and extrarenal manifestations. However, studies are difficult to compare as criteria for inclusion vary. The aim of this study was to investigate the relationship between ANCA serotype, latitude, ultraviolet (UV) radiation levels, age, gender and renal function at diagnosis in a large study with uniform inclusion criteria. Methods: Patients with biopsy-proven ANCA-associated glomerulonephritis were identified from regional or nationwide registries in 14 centres in Norway, Sweden, the UK, the Czech Republic, Croatia, Italy and the USA during the period 2000-13. UV radiation levels for 2000-13 in Europe were obtained from the Swedish Meteorological and Hydrological Institute. Results: A total of 1408 patients (45.2% PR3-ANCA) were included in the study. In univariable analysis, PR3-ANCA was significantly associated with male gender {odds ratio [OR] 2.12 [95% confidence interval (CI) 1.71-2.62]}, younger age [OR per year 0.97 (95% CI 0.96-0.98)] and higher glomerular filtration rate [OR per mL/min 1.01 (95% CI 1.01-1.02); P < 0.001] at diagnosis but not with latitude or UV radiation. In multivariable logistic regression analysis, latitude and UV radiation also became significant, with higher odds for PR3-ANCA positivity at northern latitudes/lower UV radiation levels. However, the latitudinal difference in MPO:PR3 ratio is smaller than differences previously reported concerning microscopic polyangiitis and granulomatosis with polyangiitis. Conclusions: The ratio between PR3-ANCA and MPO-ANCA varies in glomerulonephritis with respect to age, gender, renal function and geographic latitude/UV radiation levels.

Pharmacokinetic determinants of cisplatin-induced subclinical kidney injury in oncology patients.

PURPOSE: The ability to predict and detect clinical and subclinical nephrotoxicity early in the course of therapy has the potential to improve long-term outcomes in cancer patients receiving cisplatin chemotherapy. Pharmacokinetic parameters could serve as predictors of cisplatin-induced nephrotoxicity. METHODS: Participants [n = 13] were treated with a 1-h cisplatin infusion [30-75 mg/m2]. Blood was collected pre-dose and up to 6 h post-dose. Urinary biomarkers [KIM-1, calbindin, clusterin, GST-pi, ß2M, albumin, NGAL, osteopontin, clusterin, MCP-1, cystatin C, and TFF3] were measured at baseline, days 3 and 10. Total and unbound platinum concentrations were measured using ICP/MS. Noncompartmental analysis was performed, and correlation and regression analyses evaluated the relationships between platinum pharmacokinetics and nephrotoxicity. RESULTS: Peak platinum urinary concentrations correlated with urinary levels of KIM-1, calbindin, clusterin, GST-pi, ß2M, albumin, NGAL, osteopontin, clusterin, cystatin C, and TFF3 at day 10. Unbound platinum plasma concentrations at 2 h also correlated with urinary clusterin, ß2M, cystatin C, NGAL, osteopontin, and TFF3 at day 3. Regression analyses suggested 2-h total plasma platinum concentrations greater than 2000 ng/ml, and peak urinary platinum concentrations above 24,000 ng/ml may serve as potential approximations for elevated risk of nephrotoxicity. Platinum area under the plasma concentration time curve was associated with serum creatinine and estimated glomerular filtration rate. CONCLUSIONS: Peak plasma and urinary platinum concentrations and pharmacokinetic parameters were associated with risk of subclinical cisplatin-induced kidney injury as assessed using novel urinary biomarkers. Future studies will examine these relationships in larger clinical populations of cisplatin-induced acute kidney injury.

Intravenous pulse methylprednisolone for induction of remission in severe ANCA associated Vasculitis: a multi-center retrospective cohort study.

BACKGROUND: Intravenous pulse methylprednisolone (MP) is commonly included in the management of severe ANCA associated vasculitis (AAV) despite limited evidence of benefit. We aimed to evaluate outcomes in patients who had, or had not received MP, along with standard therapy for remission induction in severe AAV. METHODS: We retrospectively studied 114 consecutive patients from five centres in Europe and the United States with a new diagnosis of severe AAV (creatinine > 500 µmol/L or dialysis dependency) and that received standard therapy (plasma exchange, cyclophosphamide and high-dose oral corticosteroids) for remission induction with or without pulse MP between 2000 and 2013. We evaluated survival, renal recovery, relapses, and adverse events over the first 12 months. RESULTS: Fifty-two patients received pulse MP in addition to standard therapy compared to 62 patients that did not. There was no difference in survival, renal recovery or relapses. Treatment with MP associated with higher risk of infection during the first 3 months (hazard ratio (HR) 2.7, 95%CI [1.4-5.3], p = 0.004) and higher incidence of diabetes (HR 6.33 [1.94-20.63], p = 0.002), after adjustment for confounding factors. CONCLUSIONS: The results of this study suggest that addition of pulse intravenous MP to standard therapy for remission induction in severe AAV may not confer clinical benefit and may be associated with more episodes of infection and higher incidence of diabetes.

Segmental Sclerosis and Extracapillary Hypercellularity Predict Diabetic ESRD.

Pathogenetic markers of diabetic kidney disease (DKD) progression to ESRD are lacking. We characterized the prognostic value of histologic findings in DKD for time to ESRD in native kidney specimens from biopsies performed from 1995 to 2011 with diabetic glomerulosclerosis as the only glomerular disease diagnosis (n=109). Biopsy specimens were analyzed according to standard methods, including determination of diabetic nephropathy class, as defined by the Renal Pathology Society. Clinical data were extracted from electronic medical records. We used competing risk models, with death as the competing risk, to estimate subdistribution hazard ratios (HRs) for ESRD. All multivariable models included age, sex, black race, baseline eGFR, and baseline proteinuria. Pathologic characteristics achieving P<0.1 were added into successively complex models. ESRD occurred in 56% of patients, and 26% of patients died before reaching ESRD. In univariate analyses, diabetic nephropathy class was not statistically significant in predicting time to ESRD. The final multivariable model (n=106) showed a borderline association between mild mesangial expansion and decreased risk for ESRD (subdistribution HR, 0.64; 95% confidence interval, 0.40 to 1.00). Poor prognostic factors in the final model included segmental sclerosis and extracapillary hypercellularity (subdistribution HR, 2.04; 95% confidence interval, 1.36 to 3.05; and subdistribution HR, 2.21; 95% confidence interval, 1.19 to 4.11, respectively). In conclusion, we identified segmental sclerosis and extracapillary hypercellularity as novel, poor prognostic indicators of time from DKD to ESRD. Whether these indicators represent a distinct pathogenetic phenotype of DKD will require a large study with a broad spectrum of disease severity.

Glomerular disease frequencies by race, sex and region: results from the International Kidney Biopsy Survey.

Background: Large-scale studies comparing glomerular disease frequencies across continents are lacking. Methods: We surveyed 29 nephropathology laboratories in four continents using a standardized data collection form. We obtained recent consecutive kidney biopsy diagnosis frequencies at each center and summary demographics for each diagnosis. This report focuses on glomerular disease frequencies by region and race/ethnicity. Results: Among 42 603 glomerular disease diagnoses reported (median age 47 years, 52% male, 57% white), from a total of 60 340 diagnoses, glomerular disease subtype frequencies differed considerably by continent. Diabetic glomerulosclerosis (GS; 19.1%) and focal segmental glomerulosclerosis (FSGS; 19.1%) predominated in North America; lupus nephritis (38.1%) and FSGS (15.8%) predominated in Latin America; IgA nephropathy (IgAN; 22.1%) and FSGS (14.9%) predominated in Europe; and IgAN (39.5%) and lupus nephritis (16.8%) predominated in Asia. After stratifying by race, diabetic GS (17.4% versus 4.3%, P < 0.001) and FSGS (17.3% versus 11.8%, P < 0.001) were more, and lupus nephritis less (15.8% versus 45.6%, P < 0.001), frequent among Latinos in North versus Latin America; FSGS was more (13.1% versus 7.1%, P < 0.001), and IgAN less (27.4% versus 40.5%, P < 0.001), frequent among Asians in North America versus Asia; and FSGS (18.9% versus 13.5%, P < 0.001) and diabetic GS (18.7% versus 6.5%, P < 0.001) were more, and IgAN less (14.4% versus 25.4%, P < 0.001), frequent among whites in North America versus Europe. Conclusions: We determined that glomerular disease frequencies differed by continent, even among patients of similar race/ethnicity. Regional environmental and lifestyle factors, and local biopsy policies, might influence glomerular disease epidemiology independently of race/ethnicity.

Gene-Specific DNA Methylation Changes Predict Remission in Patients with ANCA-Associated Vasculitis.

ANCA-associated vasculitis is an autoimmune condition characterized by vascular inflammation and organ damage. Pharmacologically induced remission of this condition is complicated by relapses. Potential triggers of relapse are immunologic challenges and environmental insults, both of which associate with changes in epigenetic silencing modifications. Altered histone modifications implicated in gene silencing associate with aberrant autoantigen expression. To establish a link between DNA methylation, a model epigenetic gene silencing modification, and autoantigen gene expression and disease status in ANCA-associated vasculitis, we measured gene-specific DNA methylation of the autoantigen genes myeloperoxidase (MPO) and proteinase 3 (PRTN3) in leukocytes of patients with ANCA-associated vasculitis observed longitudinally (n=82) and of healthy controls (n=32). Patients with active disease demonstrated hypomethylation of MPO and PRTN3 and increased expression of the autoantigens; in remission, DNA methylation generally increased. Longitudinal analysis revealed that patients with ANCA-associated vasculitis could be divided into two groups, on the basis of whether DNA methylation increased or decreased from active disease to remission. In patients with increased DNA methylation, MPO and PRTN3 expression correlated with DNA methylation. Kaplan-Meier estimate of relapse revealed patients with increased DNA methylation at the PRTN3 promoter had a significantly greater probability of a relapse-free period (P<0.001), independent of ANCA serotype. Patients with decreased DNA methylation at the PRTN3 promoter had a greater risk of relapse (hazard ratio, 4.55; 95% confidence interval, 2.09 to 9.91). Thus, changes in the DNA methylation status of the PRTN3 promoter may predict the likelihood of stable remission and explain autoantigen gene regulation.

Pharmacogenomic Variants May Influence the Urinary Excretion of Novel Kidney Injury Biomarkers in Patients Receiving Cisplatin.

Nephrotoxicity is a dose limiting side effect associated with the use of cisplatin in the treatment of solid tumors. The degree of nephrotoxicity is dictated by the selective accumulation of cisplatin in renal tubule cells due to: (1) uptake by organic cation transporter 2 (OCT2) and copper transporter 1 (CTR1); (2) metabolism by glutathione S-transferases (GSTs) and γ-glutamyltransferase 1 (GGT1); and (3) efflux by multidrug resistance-associated protein 2 (MRP2) and multidrug and toxin extrusion protein 1 (MATE1). The purpose of this study was to determine the significance of single nucleotide polymorphisms that regulate the expression and function of transporters and metabolism genes implicated in development of acute kidney injury (AKI) in cisplatin treated patients. Changes in the kidney function were assessed using novel urinary protein biomarkers and traditional markers. Genotyping was conducted by the QuantStudio 12K Flex Real-Time PCR System using a custom open array chip with metabolism, transport, and transcription factor polymorphisms of interest to cisplatin disposition and toxicity. Traditional and novel biomarker assays for kidney toxicity were assessed for differences according to genotype by ANOVA. Allele and genotype frequencies were determined based on Caucasian population frequencies. The polymorphisms rs596881 (SLC22A2/OCT2), and rs12686377 and rs7851395 (SLC31A1/CTR1) were associated with renoprotection and maintenance of estimated glomerular filtration rate (eGFR). Polymorphisms in SLC22A2/OCT2, SLC31A1/CTRI, SLC47A1/MATE1, ABCC2/MRP2, and GSTP1 were significantly associated with increases in the urinary excretion of novel AKI biomarkers: KIM-1, TFF3, MCP1, NGAL, clusterin, cystatin C, and calbindin. Knowledge concerning which genotypes in drug transporters are associated with cisplatin-induced nephrotoxicity may help to identify at-risk patients and initiate strategies, such as using lower or fractionated cisplatin doses or avoiding cisplatin altogether, in order to prevent AKI.

Patients with primary membranous nephropathy are at high risk of cardiovascular events.

Here we conducted a retrospective study to examine the risk of cardiovascular events (CVEs) relative to that of end-stage renal disease (ESRD) in patients with primary membranous nephropathy, in a discovery cohort of 404 patients. The cumulative incidence of CVEs was estimated in the setting of the competing risk of ESRD with risk factors for CVEs assessed by multivariable survival analysis. The observed cumulative incidences of CVEs were 4.4%, 5.4%, 8.2%, and 8.8% at 1, 2, 3, and 5 years respectively in the primary membranous nephropathy cohort. In the first 2 years after diagnosis, the risk for CVEs was similar to that of ESRD in the entire cohort, but exceeded it among patients with preserved renal function. Accounting for traditional risk factors and renal function, the severity of nephrosis at the time of the event (hazard ratio 2.1, 95% confidence interval 1.1 to 4.3) was a significant independent risk factor of CVEs. The incidence and risk factors of CVEs were affirmed in an external validation cohort of 557 patients with primary membranous nephropathy. Thus early in the course of disease, patients with primary membranous nephropathy have an increased risk of CVEs commensurate to, or exceeding that of ESRD. Hence, reduction of CVEs should be considered as a therapeutic outcome measure and focus of intervention in primary membranous nephropathy.