Defining Glomerular Disease in Mechanistic Terms: Implementing an Integrative Biology Approach in Nephrology

Advances in biomedical research allow for the capture of an unprecedented level of genetic, molecular, and clinical information from large patient cohorts, where the quest for precision medicine can be pursued. An overarching goal of precision medicine is to integrate the large–scale genetic and molecular data with deep phenotypic information to identify a new mechanistic disease classification. This classification can ideally be used to meet the clinical goal of the right medication for the right patient at the right time. Glomerular disease presents a formidable challenge for precision medicine. Patients present with similar signs and symptoms, which cross the current disease categories. The diseases are grouped by shared histopathologic features, but individual patients have dramatic variability in presentation, progression, and response to therapy, reflecting the underlying biologic heterogeneity within each glomerular disease category. Despite the clinical challenge, glomerular disease has several unique advantages to building multilayered datasets connecting genetic, molecular, and structural information needed to address the goals of precision medicine in this population. Kidney biopsy tissue, obtained during routine clinical care, provides a direct window into the molecular mechanisms active in the affected organ. In addition, urine is a biofluid ideally suited for repeated measurement from the diseased organ as a liquid biopsy with potential to reflect the dynamic state of renal tissue. In our review, current approaches for large–scale data generation and integration along the genotype-phenotype continuum in glomerular disease will be summarized. Several successful examples of this integrative biology approach within glomerular disease will be highlighted along with an outlook on how achieving a mechanistic disease classification could help to shape glomerular disease research and care in the future

Comparison and evaluation of lupus nephritis response criteria in lupus activity indices and clinical trials

Abstract Systemic lupus erythematosus (SLE) is a systemic autoimmune disease with diverse manifestations. Although the approval of new therapies includes only one agent in 50 years, a number of promising new drugs are in development. Lupus nephritis is a dreaded complication of SLE as it is associated with significant morbidity and mortality. Advancing the treatment of lupus nephritis requires well-designed clinical trials and this can be challenging in SLE. The major obstacles involve identifying the correct population of patients to enroll and ensuring that a clinically appropriate and patient-centered endpoint is being measured. In this review, we will first discuss the clinical utility of endpoints chosen to represent lupus nephritis in global disease activity scales. Second, we will review completed and active trials focused on lupus nephritis and discuss the endpoints chosen. There are many important lessons to be learned from existing assessment tools and clinical trials. Reviewing these points will help ensure that future efforts will yield meaningful disease activity measures and well-designed clinical trials to advance our understanding of lupus management

Meta-analysis of Human Papillomavirus Infection Concordance

Estimates of human papillomavirus (HPV) concordance among sexual partners are important for various public health activities, from counseling individual patients to predicting the impact of HPV vaccination

Combination therapy with rituximab, low-dose cyclophosphamide, and prednisone for idiopathic membranous nephropathy: a case series

BACKGROUND: Membranous nephropathy is a common cause of the nephrotic syndrome. Treatment with standard regimens fails to induce complete remission in most patients. We evaluated the efficacy of combination therapy with rituximab, low-dose, oral cyclophosphamide, and an accelerated prednisone taper (RCP) for the treatment of idiopathic membranous nephropathy. METHODS: We analyzed 15 consecutive patients with idiopathic membranous nephropathy treated with RCP at Massachusetts General Hospital. Seven patients (47%) received RCP as initial therapy, and the other eight patients (53%) received RCP for relapsing or refractory disease. All patients had at least 1 year of follow-up. The co-primary outcomes were attainment of partial and complete remission. Partial remission was defined as a urinary protein to creatinine ratio (UPCR) < 3 g/g and a 50% reduction from baseline. Complete remission was defined as a UPCR < 0.3 g/g. Secondary outcomes were serious adverse events and the change in proteinuria, serum creatinine, serum albumin, cholesterol, triglycerides, and immunoglobulin G levels after 1 year of treatment. RESULTS: Over a median follow-up time of 37 (IQR, 34-44) months, 100% of patients achieved partial remission and 93% of patients achieved complete remission at a median time of 2 and 13 months, respectively. After 1 year of treatment, median (IQR) UPCR declined from 8.2 (6.6-11.1) to 0.3 (0.2-0.7) g/g (P < 0.001). Three serious adverse events occurred over 51 patient years. No patients died or progressed to ESKD. CONCLUSIONS: Treatment of idiopathic membranous nephropathy with RCP resulted in high rates of complete remission. Larger studies evaluating this regimen are warranted

Clinical Features and Outcomes of a Racially Diverse Population with Fibrillary Glomerulonephritis

Fibrillary glomerulonephritis is characterized by randomly arranged fibrils, approximately 20 nm in diameter by electron microscopy. Patients present with proteinuria, hematuria and kidney insufficiency, and about half of the reported patients progress to end-stage kidney disease within 4 years. The dependence of patient characteristics and outcomes on race has not been explored. In this study, we describe a cohort of patients with fibrillary glomerulonephritis and compare their clinical characteristics and outcomes with those of patients previously described

The scavenger receptor SCARF1 mediates apoptotic cell clearance and prevents autoimmunity

Clearance of apoptotic cells is critical for control of tissue homeostasis however the full range of receptor(s) on phagocytes responsible for recognition of apoptotic cells remains to be identified. Here we show that dendritic cells (DCs), macrophages and endothelial cells use scavenger receptor type F family member 1 (SCARF1) to recognize and engulf apoptotic cells via C1q. Loss of SCARF1 impairs uptake of apoptotic cells. Consequently, in SCARF1-deficient mice, dying cells accumulate in tissues leading to a lupus-like disease with the spontaneous generation of autoantibodies to DNA-containing antigens, immune cell activation, dermatitis and nephritis. The discovery of SCARF1 interactions with C1q and apoptotic cells provides insights into molecular mechanisms involved in maintenance of tolerance and prevention of autoimmune disease

Myeloperoxidase Interacts with Endothelial Cell-Surface Cytokeratin 1 and Modulates Bradykinin Production by the Plasma Kallikrein-Kinin System

During an inflammatory state, functional myeloperoxidase (MPO) is released into the vessel as a result of intravascular neutrophil degradation. One mechanism of resulting cellular injury involves endothelial internalization of MPO, which causes oxidative damage and impairs endothelial signaling. We report the discovery of a protein that facilitates MPO internalization, cytokeratin 1 (CK1), identified using affinity chromatography and mass spectrometry. CK1 interacts with MPO in vitro, even in the presence of 100% human plasma, thus substantiating biological relevance. Immunofluorescent microscopy confirmed that MPO added to endothelial cells can co-localize with endogenously expressed CK1. CK1 acts as a scaffolding protein for the assembly of the vasoregulatory plasma kallikrein-kinin system; thus we explored whether MPO and high molecular weight kininogen (HK) reside on CK1 together or whether they compete for binding. The data support cooperative binding of MPO and HK on cells such that MPO masked the plasma kallikrein cleavage site on HK, and MPO-generated oxidants caused inactivation of both HK and kallikrein. Collectively, interactions between MPO and the components of the plasma kallikrein-kinin system resulted in decreased bradykinin production. This study identifies CK1 as a facilitator of MPO-mediated vascular responses and thus provides a new paradigm by which MPO affects vasoregulatory systems

ANCA antigens, proteinase 3 and myeloperoxidase, are not expreΔed in endothelial cells

ANCA antigens, proteinase 3 and myeloperoxidase, are not expressed in endothelial cells. Background. One hypothesis for the pathogenesis of vasculitis associated with antineutrophil cytoplasmic autoantibodies (ANCAs) proposes that ANCAs bind to ANCA antigens, such as proteinase 3 (PR3) or myeloperoxidase (MPO), which are produced by endothelial cells and expressed on their surfaces. There are conflicting reports, however, on whether endothelial cells express the ANCA antigen PR3, and there are no reports on endothelial expression of MPO. The aim of this study was to determine the presence or absence of PR3 and MPO mRNA in both venous and arterial endothelial cells, employing standard reverse transcription-polymerase chain reaction (RT-PCR) techniques and also the quantitative and highly specific method, TaqMan PCR. Methods. RT-PCR (with 3 primer sets) and TaqMan PCR, a method for detecting low copy transcripts, were used to probe for PR3 and MPO transcripts in human endothelial cells from umbilical vein (HUVEC) and artery (HUAEC) and from lung microvascular (HLMVEC). Cells were treated with interferon-γ (200 units/mL) or tumor necrosis factor-α (3 or 10 ng/mL) or both. Results. Transcripts for PR3 and/or MPO were not detected in HUVEC, HUAEC, and HLMVEC by standard RT-PCR. Analyses for PR3 protein confirmed that PR3 is not expressed in HUVEC. HUVEC and HUAEC were negative for PR3 and MPO by TaqMan PCR. Conclusions. PR3 and MPO are not expressed in HUVEC, HUAEC, or HLMVEC. Endothelial cell presentation of endogenous PR3 and MPO antigens is not involved in the pathogenesis of ANCA-associated vasculitis. Alternative explanations need to be explored to determine the pathogenic effect of ANCAs

Clinical Features of Reported Ethylene Glycol Exposures in the United States

BackgroundEthylene glycol is highly toxic and represents an important cause of poisonings worldwide. Toxicity can result in central nervous system dysfunction, cardiovascular compromise, elevated anion gap metabolic acidosis and acute kidney injury. Many states have passed laws requiring addition of the bittering agent, denatonium benzoate, to ethylene glycol solutions to reduce severity of exposures. The objectives of this study were to identify differences between unintentional and intentional exposures and to evaluate the utility of denatonium benzoate as a deterrent.Methods and FindingsUsing the National Poison Data System, we performed a retrospective analysis of reported cases of ethylene glycol exposures from January 2006 to December 2013. Outcome classification was summed for intentionality and used as a basis for comparison of effect groups. There were 45,097 cases of ethylene glycol exposures resulting in 154 deaths. Individuals more likely to experience major effects or death were older, male, and presented with more severe symptoms requiring higher levels of care. Latitude and season did not correlate with increased exposures; however, there were more exposures in rural areas. Denatonium benzoate use appeared to have no effect on exposure severity or number.ConclusionDeaths due to ethylene glycol exposure were uncommon; however, there were major clinical effects and more exposures in rural areas. Addition of denatonium benzoate was not associated with a reduction in exposures. Alternative means to deter ingestion are needed. These findings suggest the need to consider replacing ethylene glycol with alternative and less toxic agents

The immune cell landscape in kidneys of patients with lupus nephritis.

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