Biomarkers for lupus nephritis: the quest continues

FGF23-related hypophosphatemic rickets preceding the onset of systemic lupus erythematosus: A juvenile case

Key Clinical Message

This case report describes the clinical course of a juvenile female with FGF23-related hypophosphatemic rickets preceding the onset of SLE. Our study demonstrates the possibility of hypophosphatemic rickets as an early symptom of SLE.

Abstract

Fibroblast growth factor 23 (FGF23)-related hypophosphatemic rickets is observed in both genetic and acquired disorders. Various reports describe FGF23-related hypophosphatemia with systemic lupus erythematosus (SLE), although FGF23-related hypophosphatemia preceding the onset of SLE has never been described. Here, we report the case of a 9-year-old female with FGF23-related hypophosphatemic rickets preceding the onset of SLE. The patient presented to us with arthralgia in the lower extremities and abnormality of gait lasting for 8 months. She was diagnosed with FGF23 hypophosphatemic rickets due to the presence of hypophosphatemic rickets symptoms and high serum levels of FGF23. Additional examination excluded hereditary diseases and tumor-induced osteomalacia. Three months after diagnosis of FGF23-related hypophosphatemic rickets, she developed nephritis and was diagnosed with SLE. She was treated with prednisolone, hemodialysis, and disease-modifying drugs, as well as oral sodium phosphate to improve hypophosphatemia. Serum anti-double-stranded DNA antibody (dsDNAab) and plasma tumor necrosis factor-α (TNF-α) were elevated at FGF23-related hypophosphatemic rickets diagnosis. During the clinical course, serum FGF23 correlated with dsDNAab and TNF-α serum levels, which are involved in SLE disease activity. In this case, FGF23-related hypophosphatemic rickets without hereditary diseases or tumor-induced osteomalacia occurred before the appearance of juvenile SLE symptoms, and serum FGF23 represented disease activity in SLE.

Endothelial cell activation and glycocalyx shedding - potential as biomarkers in patients with lupus nephritis

Lupus nephritis (LN) is a common and severe manifestation of systemic lupus erythematosus and an important cause of acute and chronic kidney injury. Early diagnosis of LN and preventing relapses are key to preserving renal reserve. However, due to the complexity and heterogeneity of the disease, clinical management remains challenging. Kidney biopsy remains the gold standard for confirming the diagnosis of LN and subsequent assessment of kidney histopathology, but it is invasive and cannot be repeated frequently. Current clinical indicators of kidney function such as proteinuria and serum creatinine level are non-specific and do not accurately reflect histopathological changes, while anti-dsDNA antibody and C3 levels reflect immunological status but not kidney injury. Identification of novel and specific biomarkers for LN is prerequisite to improve management. Renal function deterioration is associated with changes in the endothelial glycocalyx, a delicate gel-like layer located at the interface between the endothelium and bloodstream. Inflammation induces endothelial cell activation and shedding of glycocalyx constituents into the circulation. This review discusses the potential role of soluble glycocalyx components as biomarkers of active LN, especially in patients in whom conventional serological and biochemical markers do not appear helpful.

Urine SERPINC1/ORM1 as biomarkers for early detection of lupus nephritis in MRL-lpr mice

Background

To evaluate the usefulness of urine SERPINC1 and ORM1 as biomarkers for early detection of lupus nephritis (LN).

Methods

Using proteomics, we screened for potential urine biomarkers that differentiate LN from systemic lupus erythematosus (SLE) patients without nephritis. In addition, urine levels of target biomarkers were measured by ELISA in 13- and 23-week-old MRL-lpr (murine model for LN) and MRL/MpJ mice. Histological analysis was also performed on the kidneys of 23-week-old mice.

Results

Urine SERPINC1 and ORM1 were elevated in SLE patients with newly diagnosed LN compared with SLE patients without LN (SERPINC1, AUC=.892, P<.001; ORM1, AUC=.886, P<.001). Levels of urine SERPINC1 and ORM1 were also significantly higher in MRL-lpr mice than in MRL/MpJ mice at 13 and 23 weeks (SERPINC1: p<.01 and p<.001 at 13 and 23 weeks, respectively; ORM1: p<.01 at 13 and 23 weeks). In contrast, a significant difference in urine albumin between the two groups was only observed at 23 weeks (p<.001) not at 13 weeks (p=.83). Regarding the kidney pathology of MPL-lpr mice, urine ORM1 and urine albumin, but not urine SERPINC1, were positively correlated with the activity index (ORM1, rho =.879, p<.001; albumin, rho =.807, p=.003) and chronicity index (ORM1, rho =.947, p<.001; albumin, rho =.869, p<.001).

Conclusion

We propose that urine SERPINC1 and ORM1 are novel biomarkers for early LN.

Serum cystatin C and βeta-2 microglobulin as potential biomarkers in children with lupus nephritis

Objectives: In this study, we aimed to assess serum levels of Cystatin C (Cys C) and beta-2 microglobulin (β2M) in juvenile systemic lupus erythematosus (JSLE) patients and to investigate their role as potential biomarkers of lupus nephritis (LN) and overall disease activity.

Patients and methods: Between December 2018 and November 2019, a total of 40 patients with JSLE (11 males, 29 females; mean age: 12.6±2.5 years; range, 7.5 to 16 years) and 40 age- and sex-matched controls (10 males, 30 females; mean age: 12.3±2.4 years; range, 7 to 16 years) were included in this study. Serum (s) Cys C and β2M levels were compared between the groups. The SLE Disease Activity Index (SLEDAI-2K), the renal SLEDAI (rSLEDAI), and the Renal Damage Index were used.

Results: JSLE patients had significantly elevated mean sCyc C and sβ2M levels (1.4±0.8 mg/mL and 2.8±0.9 mg/mL, respectively) compared to the controls (0.6±0.1 mg/mL and 2.0±0.2 mg/mL, respectively; p<0.00). The mean sCys C and sβ2M levels were significantly higher in the LN group, compared to non-LN patients (1.8±0.7 mg/mL and 3.1±1.0 mg/mL, respectively vs. 0.8±0.3 mg/mL and 2.4±0.6 mg/mL, respectively; p=0.002 and p=0.02, respectively). The sCys C levels had significant positive correlations with erythrocyte sedimentation rate (r=0.3, p=0.05), serum creatinine (r=0.41, p= 0.007), 24-h urinary protein (r=0.58, p<0.001), anti-double stranded deoxyribonucleic acid antibodies titers (r=0.55, p=0.002), extra-renal SLEDAI scores (r=0.36, p=0.04), rSLEDAI (r=0.46, p=0.002), and renal class (r=0.7, p=0.0001). Serum β2M levels were significantly negatively correlated with complement 4 levels (r=-0.31, p=0.04) and significantly positively correlated with extra-renal SLEDAI scores (r=0.3, p=0.05).

Conclusion: These findings confirm that sCys C and sβ2M levels are increased in JSLE patients in association with the overall active disease. However, sCys C level may act as a promising non-invasive biomarker for predicting kidney disease activity and biopsy classes in children with JSLE.

Distinctive modulation of hepcidin in cancer and its therapeutic relevance

Hepcidin, a short peptide synthesized primarily by hepatocytes in response to increased body iron and inflammation, is a crucial iron-regulating factor. Hepcidin regulates intestinal iron absorption and releases iron from macrophages into plasma through a negative iron feedback mechanism. The discovery of hepcidin inspired a torrent of research into iron metabolism and related problems, which have radically altered our understanding of human diseases caused by an excess of iron, an iron deficiency, or an iron disparity. It is critical to decipher how tumor cells manage hepcidin expression for their metabolic requirements because iron is necessary for cell survival, particularly for highly active cells like tumor cells. Studies show that tumor and non-tumor cells express and control hepcidin differently. These variations should be explored to produce potential novel cancer treatments. The ability to regulate hepcidin expression to deprive cancer cells of iron may be a new weapon against cancer cells.

Stability of novel urinary biomarkers used for lupus nephritis

Background

The Renal Activity Index for Lupus (RAIL) is a composite score of six urinary biomarkers (neutrophil gelatinase-associated lipocalin (NGAL), monocyte chemoattractant protein-1 (MCP-1), kidney injury molecule-1 (KIM-1), ceruloplasmin, adiponectin, and hemopexin) used to monitor lupus nephritis activity in children. We tested stability of RAIL biomarkers prior to meaningful clinical use.

Methods

Urine samples were tested by ELISA under shipping conditions, freeze/thaw, ambient and longer-term storage. Statistical analysis was performed via Deming Regression, Bland-Altman and Spearman Correlation Coefficient.

Results

Biomarker concentration were comparable to freshly collected urine following storage at -80 °C for up to 3 months, and at 4 or 25 °C up to 48 h followed by -80 °C. Neither shipping on dry or wet ice exposure nor addition of two freeze-thaw cycles led to loss of signal, with excellent Spearman Correlation coefficients under all conditions.

Conclusions

RAIL biomarkers are stable following short-term storage at clinically relevant conditions.

The Interleukin-1 (IL-1) Superfamily Cytokines and Their Single Nucleotide Polymorphisms (SNPs)

Interleukins (ILs)—which are important members of cytokines—consist of a vast group of molecules, including a wide range of immune mediators that contribute to the immunological responses of many cells and tissues. ILs are immune-glycoproteins, which directly contribute to the growth, activation, adhesion, differentiation, migration, proliferation, and maturation of immune cells; and subsequently, they are involved in the pro and anti-inflammatory responses of the body, by their interaction with a wide range of receptors. Due to the importance of immune system in different organisms, the genes belonging to immune elements, such as ILs, have been studied vigorously. The results of recent investigations showed that the genes pertaining to the immune system undergo progressive evolution with a constant rate. The occurrence of any mutation or polymorphism in IL genes may result in substantial changes in their biology and function and may be associated with a wide range of diseases and disorders. Among these abnormalities, single nucleotide polymorphisms (SNPs) can represent as important disruptive factors. The present review aims at concisely summarizing the current knowledge available on the occurrence, properties, role, and biological consequences of SNPs within the IL-1 family members.

Immune-Related Urine Biomarkers for the Diagnosis of Lupus Nephritis

The kidney is one of the main organs affected by the autoimmune disease systemic lupus erythematosus. Lupus nephritis (LN) concerns 30-60% of adult SLE patients and it is significantly associated with an increase in the morbidity and mortality. The definitive diagnosis of LN can only be achieved by histological analysis of renal biopsies, but the invasiveness of this technique is an obstacle for early diagnosis of renal involvement and a proper follow-up of LN patients under treatment. The use of urine for the discovery of non-invasive biomarkers for renal disease in SLE patients is an attractive alternative to repeated renal biopsies, as several studies have described surrogate urinary cells or analytes reflecting the inflammatory state of the kidney, and/or the severity of the disease. Herein, we review the main findings in the field of urine immune-related biomarkers for LN patients, and discuss their prognostic and diagnostic value. This manuscript is focused on the complement system, antibodies and autoantibodies, chemokines, cytokines, and leukocytes, as they are the main effectors of LN pathogenesis.

Successful Urine Multiplex Bead Assay to Measure Lupus Nephritis Activity

Introduction

Lupus nephritis (LN) confers a poor prognosis, mainly from lack of effective laboratory tests to diagnose and to evaluate therapies. We have previously shown that a set of 6 urinary biomarkers (NGAL, KIM-1, MCP-1, adiponectin, hemopexin, and ceruloplasmin) are highly sensitive and specific to identify adult and pediatric patients with active LN using renal biopsy as reference standard. Using these combinatorial urinary biomarkers, the Renal Activity Score for Lupus (RAIL) score was established, with biomarkers measured by enzyme-linked immunosorbent assay (ELISA). To enhance clinical utility of the biomarkers and RAIL, we tested the performance of RAIL with biomarkers measured by ELISA to that of biomarkers measured by the bead multiplex method, hypothesizing that the multiplex bead method would be comparable.

Methods

Spot urine samples (n = 341) of 46 patients aged 20 to 73 years with or without LN were used. Samples were assayed both by ELISA and multiplex using LUMINEX. RAIL scores and biomarker quantities were assessed for agreement with intraassay correlation coefficients and compared using Bland−Altman and regression.

Results

Biomarker measurement by LUMINEX was successful for NGAL, KIM-1, MCP-1, and adiponectin, but not for ceruloplasmin and hemopexin. There was good agreement of the RAIL obtained from these 4 biomarkers, irrespective of assay method (intraclass correlation coefficient [ICC] = 0.78, 95% confidence interval [CI] = 0.78−0.82). The RAIL scores from 4 biomarkers further correlated with those when considering all 6 biomarkers (ICC = 0.97, 95% CI = 0.96−0.98).

Conclusion

The LUMINEX platform allows for the convenient and simultaneous measurement of 4 RAIL biomarkers. RAIL scores considering only these 4 biomarkers may be sufficient to accurately capture LN activity.

Clinical and histological significance of urinary CD11c+ macrophages in lupus nephritis

Background

Infiltration of immune cells into the kidney is one of the key features of lupus nephritis (LN). The presence of immune cells in the urine may be used as a non-invasive biomarker of LN. Here, we aimed to analyze the clinicopathologic significance of urinary CD11c⁺ macrophages in patients with LN.

Methods

The numbers and proportions of CD11c⁺ macrophages in the urine samples of patients with LN at the time of kidney biopsy were examined using flow cytometry. We also examined the association between the levels of urinary CD11c⁺ macrophages and the clinical and pathologic features of patients with LN.

Results

Compared with patients without LN or those with non-proliferative LN, patients with proliferative LN had significantly higher numbers and proportions of urinary CD11c⁺ macrophages, which were strongly correlated with the serum anti-dsDNA antibody titer. The numbers and proportions of urinary CD11c⁺ macrophages were significantly associated with the values of chronicity indices such as tubular atrophy and interstitial fibrosis. No significant relationships were found between the levels of urinary CD11c⁺ macrophages and the activity scores, degree of proteinuria, or lupus disease activity. Urinary CD11c⁺ macrophages were more abundant in patients who did not achieve renal response to induction treatment with immunosuppressants than in those who achieved complete or partial response. The receiver operating characteristic (ROC) curve analysis showed that the number of urinary CD11c⁺ macrophages was the most powerful predictor of renal response at 6 months (ROC-AUC = 1.00, p = 0.0004).

Conclusion

The urinary levels of CD11c⁺ macrophages were closely associated with the chronic pathologic changes of LN and renal response and may thus be used as a novel biomarker in LN.

Oxidative stress, inflammation and disease activity biomarkers in lupus nephropathy

Lupus nephropathy is a severe and frequent complication of systemic lupus erythematosus. Here, we assessed the biomarkers of oxidative stress, inflammation and disease activity in patients with lupus nephritis. Thirty-four patients with active lupus nephritis, 31 patients with inactive lupus nephritis and 20 lupus patients without renal damage (non-lupus nephritis) were studied. Oxidative stress biomarkers malonyldialdehyde, oxidized-to-total glutathione, catalase, superoxide dismutase and total antioxidant status were assessed, as well as inflammation biomarkers CRP, interleukin 6 and monocyte chemoattractant protein 1. Renal tubular disease biomarkers neutrophil gelatinase-associated lipocalin and β2-microglobulin were assessed, together with the classic disease activity biomarkers urinary protein/creatinine ratio, anti-dsDNA, anti-C1q antibody and complement proteins C3 and C4. Significant differences were found between active lupus nephritis and inactive lupus nephritis patients and between active lupus nephritis and non-lupus nephritis patients for all the assessed biomarkers (P < 0.05), except for catalase, superoxide dismutase and interleukin 6. There is an imbalance in the redox status in active lupus nephritis patients that would be involved in lipid peroxidation of the glomerular basal membrane that would alter its integrity and could also affect renal tubular function in these patients.

Development of Biomarker Models to Predict Outcomes in Lupus Nephritis

OBJECTIVE

The American College of Rheumatology guidelines for the treatment of lupus nephritis recommend change in induction therapy when response to therapy has not occurred within 6 months. Response is not defined, and renal fibrosis can occur while waiting for this end point. Therefore, a decision support tool to better define response is needed to guide clinicians when starting patients on therapy. This study was undertaken to identify biomarker models with sufficient predictive power to develop such a tool.

METHODS

Urine samples from 140 patients with biopsy-proven lupus nephritis who had not yet started induction therapy were analyzed for a panel of urinary biomarkers. Univariate receiver operating characteristic (ROC) curves were generated for each individual biomarker and compared to the ROC area under the curve values from machine learning models developed using random forest algorithms. Biomarker models of outcome developed with novel markers in addition to clinical markers were compared to those developed with traditional clinical markers alone.

RESULTS

Models developed with the combined traditional and novel biomarker panels demonstrated clinically meaningful predictive power. Markers most predictive of response were chemokines, cytokines, and markers of cellular damage.

CONCLUSION

This is the first study to demonstrate the power of low-abundance biomarker panels and machine learning algorithms for predicting lupus nephritis outcomes. This is a critical first step in research to develop clinically meaningful decision support tools.

Modular transcriptional repertoire analyses identify a blood neutrophil signature as a candidate biomarker for lupus nephritis

Objective

LN is a severe complication of SLE. Non-invasive biomarkers are needed for identifying patients at risk of a renal flare, for differentiating proliferative from non-proliferative forms and for assessing prognoses for LN.

Methods

We assessed the link between blood transcriptional signatures and LN using blood samples from patients with biopsy-proven LN, extra-renal SLE flares or quiescent SLE. Healthy controls, and control patients with glomerular diseases or bacterial sepsis were included. Modular repertoire analyses from microarray data were confirmed by PCR.

Results

A modular neutrophil signature (upregulation of module M5.15) was present in 65% of SLE patients and was strongly associated with LN. M5.15 activity was stronger in LN than in extra-renal flares (88 vs 17%). M5.15 was neither correlated to IFN modules, nor to SLEDAI or anti-dsDNA antibodies, but moderately to CS dose. M5.15 activity was associated with severity of LN, was stronger when proliferative, and decreased in patients responding to treatment. M5.15 activation was not caused by higher CS dose because it correlated only moderately to neutrophil count and was also observed among quiescent patients. Among quiescent patients, those with a past history of LN had higher M5.15 activity (50 vs 8%). M5.15 activation was present in patients with bacterial sepsis or ANCA-associated vasculitis, but not in patients with other glomerular diseases. Overall, M5.15 activation was associated with past, present or future flares of LN.

Conclusion

Modular neutrophil signature could be a biomarker for stratifying LN risk and for monitoring its response to treatment.

Trial registration

ClinicalTrials.gov, http://clinicaltrials.gov , NCT00920114.

Prospective validation of a novel renal activity index of lupus nephritis

Objectives The renal activity index for lupus (RAIL) score was developed in children with lupus nephritis as a weighted sum of six urine biomarkers (UBMs) (neutrophil gelatinase-associated lipocalin, monocyte chemotactic protein 1, ceruloplasmin, adiponectin, hemopexin and kidney injury molecule 1) measured in a random urine sample. We aimed at prospectively validating the RAIL in adults with lupus nephritis. Methods Urine from 79 adults was collected at the time of kidney biopsy to assay the RAIL UBMs. Using receiver operating characteristic curve analysis, we evaluated the accuracy of the RAIL to discriminate high lupus nephritis activity status (National Institutes of Health activity index (NIH-AI) score >10), from low/moderate lupus nephritis activity status (NIH-AI score ≤10). Results In this mixed racial cohort, high lupus nephritis activity was present in 15 patients (19%), and 71% had proliferative lupus nephritis. Use of the identical RAIL algorithm developed in children resulted in only fair prediction of lupus nephritis activity status of adults (area under the receiver operating characteristic curve (AUC) 0.62). Alternative weightings of the six RAIL UBMs as suggested by logistic regression yielded excellent accuracy to predict lupus nephritis activity status (AUC 0.88). Accuracy of the model did not improve with adjustment of the UBMs for urine creatinine or albumin, and was little influenced by concurrent kidney damage. Conclusions The RAIL UBMs provide excellent prediction of lupus nephritis activity in adults. Age adaption of the RAIL is warranted to optimize its discriminative validity to predict high lupus nephritis activity status non-invasively.

Interferon (IFN)-λ is a potential mediator in lupus nephritis

OBJECTIVES

Interferon (IFN)-α is thought to be central in the pathogenesis for lupus nephritis (LN) and recent studies also indicate a role for IFNλ. Little is known about these cytokines in the context of treatment response. We studied levels of IFNα and IFNλ in patients with LN in association with clinical and histological response (HR) to treatment.

METHODS

Fifty-six patients with active LN were included. Renal biopsies were performed at baseline and after immunosuppressive therapy. Serum levels of IFNα and IFNλ were analysed at both biopsy occasions and in 163 controls. The biopsies were evaluated according to the International Society of Nephrology/Renal Pathology Society classification. Clinical response was defined according to recent definitions. HR was defined as class I, II or III/IV-C on repeat biopsies. The expression of IFNλ in renal tissue was assessed by immunohistochemistry.

RESULTS

At baseline, serum levels of both IFNα and IFNλ were higher in patients versus controls (p=0.01 and p=0.03, respectively). There was no correlation between IFNα and IFNλ. Overall, IFNα decreased after treatment (p=0.003) but IFNλ remained unchanged. However in patients with HR, IFNλ decreased (p=0.01). The highest levels of IFNλ were seen in patients with poor HR. Immunostaining of renal tissue revealed expression of IFNλ, particularly in crescent formations, inflammatory infiltrates and tubular cells.

CONCLUSIONS

The study supports a role for IFNλ in LN, both in circulation and at a tissue level. Levels of IFNα and IFNλ did not correlate and were affected differently by immunosuppression, indicating that they are differently involved in subgroups of LN. Persistent increased levels of IFNλ were associated to an unfavourable HR to treatment.

The Level of IgA Antibodies to Endothelial Cells Correlates with Histological Evidence of Disease Activity in Patients with Lupus Nephritis

Anti-endothelial cell antibodies (AECA) are frequently detected in patients with systemic lupus erythematosus (SLE), but their pathological role remains unclear. We recently developed a solubilized cell surface protein capture enzyme-linked immunosorbent assay (CSP-ELISA) to detect antibodies against membrane proteins involved in autoimmune reactions. In this study, sera from 51 patients with biopsy-proven lupus nephritis (LN), 25 with SLE without renal involvement (non-LN SLE), 42 disease control (DC) subjects, and 80 healthy control (HC) subjects were tested for IgG- and IgA-AECA for human umbilical vein endothelial cells (HUVEC) and human glomerular EC (HGEC) by using CSP-ELISA. IgG- and IgA-AECA titers were significantly higher in LN and non-LN SLE patients than in the DC or HC (P < 0.001) groups. IgG- and IgA-AECA titers for HUVEC corresponded well with those for HGEC. The IgA-AECA level correlated with the SLE disease activity index and with histological evidence of active lesions (cellular proliferations, hyaline thrombi and wire loops, leukocytic infiltration, and fibrinoid necrosis) in LN patients (P < 0.001). The sensitivity of IgA-AECA as a diagnostic test for histological evidence of active lesions in LN patients was 0.92, with a specificity of 0.70. The significant correlation of IgA-AECA with glomerular hypercellularity indicates that IgA-AECA are associated with endothelial damage in LN.

Serum A08 C1q antibodies are associated with disease activity and prognosis in Chinese patients with lupus nephritis

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by overproduction of numerous autoantibodies. Many studies have sought to identify such biomarkers to distinguish patients with active lupus nephritis from SLE patients without renal involvement. Because antibodies to complement C1q appear to be prevalent in patients with active lupus nephritis, we analyzed the frequency of antigenic epitopes of C1q and their clinical significance in a large multicenter study of Chinese patients. The lupus cohort consisted of 210 patients with active lupus nephritis as a discovery cohort, 130 active patients as a validation cohort along with 130 SLE patients without clinical renal involvement, and 100 healthy controls. Serum antibodies to intact C1q, the collagen-like region, the globular head region, and the new linear A08 epitope to C1q were screened by specific ELISA. The frequency of antibodies to intact C1q, the C1q-collagen-like region, and the A08 antibodies in the discovery cohort were significantly higher than that in patients without renal involvement or healthy controls. Antibodies to the globular head region were not prevalent enough for further study. The results were confirmed in the validation cohort. The area under the curve for anti-A08 antibodies was significantly greater than those for both the intact and collagen-like region antibodies to discriminate between active lupus nephritis and active SLE without clinical renal involvement. The A08 antibodies were all negative at remission. The serum A08 antibody level correlated better with disease relapse than that of antibodies to either the intact or the collagen-like region, significantly predicting renal prognosis. Thus, serum levels of A08 C1q antibodies are closely associated with disease activity and prognosis in lupus nephritis.

Urinary soluble CD163 level reflects glomerular inflammation in human lupus nephritis

BACKGROUND

In addition to classically activated macrophages that have effector roles in tissue injury, alternatively activated M2 macrophages are involved in the resolution of inflammation in animal models of kidney disease. To clarify the clinical relevance of macrophage phenotypes in human glomerular diseases, we evaluated the renal accumulation of macrophages and plasma and urine levels of CD163, an M2 marker, in lupus nephritis (LN) patients.

METHODS

Kidney biopsies and plasma and urine samples were obtained from LN patients who underwent renal biopsy between 2008 and 2012. CD163⁺, CD68⁺ and CD204⁺ cells were counted in paraffin-embedded and frozen sections. LN histological activity was evaluated semiquantitatively using the biopsy activity index. Plasma and urinary soluble CD163 (sCD163) concentrations were also measured and evaluated for their significance as potential LN biomarkers.

RESULTS

Immunohistological analysis of glomeruli from LN patients revealed that >60% of CD68⁺ macrophages had merged with CD163⁺ cells. The increased number of glomerular CD163⁺ macrophages was correlated with LN severity, as determined by the biopsy active index (r = 0.635). Urinary (u-) sCD163 level was strongly correlated with glomerular CD163⁺ cell counts and histological disease score as well as urinary monocyte chemoattractant protein 1 levels (r = 0.638 and 0.592, respectively). Furthermore, the u-sCD163 level was higher in patients with active LN than in those with other diseases.

CONCLUSIONS

Glomerular CD163⁺ macrophages are the predominant phenotype in the kidneys of lupus patients. These findings indicate that the u-sCD163 level can serve as a biomarker for macrophage-dependent glomerular inflammation in human LN.

Insulin-Like Growth Factor Binding Protein-4 as a Marker of Chronic Lupus Nephritis

Kidney biopsy remains the mainstay of Lupus Nephritis (LN) diagnosis and prognostication. The objective of this study is to identify non-invasive biomarkers that closely parallel renal pathology in LN. Previous reports have demonstrated that serum Insulin-like growth factor binding protein 4 (IGFBP-4) was increased in diabetic nephropathy in both animal models and patients. We proceeded to assess if IGFBP4 could be associated with LN. We performed ELISA using the serum of 86 patients with LN. Normal healthy adults (N = 23) and patients with other glomerular diseases (N = 20) served as controls. Compared to the healthy controls or other glomerular disease controls, serum IGFBP-4 levels were significantly higher in the patients with LN. Serum IGFBP-4 did not correlate well with systemic lupus erythematosus disease activity index (SLEDAI), renal SLEDAI or proteinuria, but it did correlate with estimated glomerular filtration rate (R = 0.609, P < 0.0001). Interestingly, in 18 patients with proliferative LN whose blood samples were obtained at the time of renal biopsy, serum IGFBP-4 levels correlated strongly with the chronicity index of renal pathology (R = 0.713, P < 0.001). IGFBP-4 emerges a potential marker of lupus nephritis, reflective of renal pathology chronicity changes.

Insulin-like growth factor binding protein-2 as a novel biomarker for disease activity and renal pathology changes in lupus nephritis

Lupus nephritis (LN) is one of the most serious manifestations of systemic lupus erythematosus. Invasive renal biopsy remains the gold standard for the diagnosis and management of LN. The objective of this study is to validate serum insulin-like growth factor binding protein-2 (IGFBP-2) as a novel biomarker for clinical disease and renal pathology in LN. Eighty-five biopsy-proven lupus nephritis patients, 18 chronic kidney disease (CKD) patients and 20 healthy controls were recruited for enzyme-linked immunosorbent assay (ELISA) testing of serum IGFBP-2 levels. Compared to CKD patients of origins other than lupus or healthy controls, serum IGFBP-2 levels were elevated significantly in LN patients. Serum IGFBP-2 was able to discriminate LN patients from the other two groups of patients [area under the curve (AUC) = 0·65, 95% confidence interval (CI) = 0·52-0·78; P = 0·043 for LN versus CKD; 0·97, 95% CI = 0·93-1·00; P < 0·0001 for LN versus healthy controls]. Serum IGFBP-2 was a potential indicator of both global disease activity and renal disease activity in LN patients, correlated with serum creatinine levels (r = 0·658, P < 0·001, n = 85) and urine protein-to-creatinine levels (r = 0·397, P < 0·001, n = 85). More importantly, in 19 concurrent patient samples, serum IGFBP-2 correlated with the chronicity index of renal pathology (r = 0·576, P = 0·01, n = 19) but not renal pathological classification. In conclusion, serum IGFBP-2 is a promising biomarker for lupus nephritis, reflective of disease activity and chronicity changes in renal pathology.

Urinary Neutrophil Gelatinase-Associated Lipocalin to Monitor Lupus Nephritis Disease Activity

BACKGROUND

This study was conducted to determine whether there is an association between urinary neutrophil gelatinase-associated lipocalin (uNGAL) and urinary transforming growth factor-β1 (uTGF-β1) with lupus nephritis (LN) disease activity.

METHODS

Urine samples from 18 LN patients were collected every month for six months then examined for uNGAL, uTGF-β1, and renal domain Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) score.

RESULTS

The uNGAL levels were significantly different between active and inactive LN (P < 0.05). uTGF-β1 levels were not different between active and inactive LN (P < 0.05). There was a significant correlation between uNGAL levels and renal domain SLEDAI score (r = 0.417, P < 0.05). There was no correlation between uTGF-β1 levels and renal domain SLEDAI score (r = 0.031, P < 0.05).

CONCLUSION

uNGAL is better than uTGF-β1 for differentiation of active and inactive LN. uNGAL can be considered as a biomarker to monitor LN disease activity.

Serum level of proximal renal tubular epithelial cell-binding immunoglobulin G in patients with lupus nephritis

In vitro data showed that immunoglobulin G (IgG) from lupus nephritis (LN) patients could bind to proximal renal tubular epithelial cells (PTEC), but the clinical relevance of such binding remained unclear. Binding of IgG and subclasses to PTEC was measured by cellular ELISA (expressed as OD index) in 189 serial serum samples from 23 Class III/IV ± V LN patients who had repeated renal flares (48 during renal flares, 141 during low level disease activity (LLDA)), and compared with 64 patients with non-lupus glomerular diseases (NLGD) and 23 healthy individuals. Total IgG PTEC-binding index was 0.34 ± 0.16, 0.29 ± 0.16, 0.62 ± 0.27 and 0.83 ± 0.38 in healthy controls, NLGD, LN patients during LLDA, and LN patients during nephritic flare, respectively (p < 0.001, LLDA vs. renal flare; p < 0.001, healthy controls or NLGD vs. LN during LLDA or renal flare). PTEC-binding index for IgG1 was 0.09 ± 0.05, 0.16 ± 0.12, 0.44 ± 0.34 and 0.71 ± 0.46 for the corresponding groups (p < 0.001, LLDA vs. renal flare; p < 0.001, healthy controls or NLGD vs. LN during LLDA or renal flare). Sixteen of 48 episodes (33.3%) of nephritic flare showed persistent PTEC-binding IgG seropositivity for more than 9.4 ± 3.1 months, despite clinical response to immunosuppressive treatment. Total IgG and IgG1 PTEC-binding correlated with anti-dsDNA level (r = 0.34 and 0.52, respectively, p < 0.001 for both), and inversely with C3 level (r = -0.26 and -0.50, respectively, p = 0.002 and<0.001). Sensitivity/specificity of PTEC-binding index in detecting renal flares was 45.8%/80.1% for total IgG (ROC AUC 0.630, p = 0.007) and 87.5%/35.5% for IgG1 (ROC AUC 0.615, p = 0.018). IgG1 PTEC-binding index correlated with tubulo-interstitial inflammation score in renal biopsy from corresponding patients. Our data suggested that total IgG and IgG1 PTEC-binding index in serum of LN patients correlate with serological activity, and in combination could predict renal flares. The correlation between IgG1 PTEC-binding and tubulo-interstitial inflammation suggests potential pathogenetic significance.

Elevated expressions of myeloid-related proteins-8 and -14 are danger biomarkers for lupus nephritis

Myeloid-related proteins, MRP-8 and -14, which have been identified as molecules that mediate the danger signaling in innate immune response, are also known as the DAMPs (damage associated molecular pattern molecules). The proteins were found in infiltrating macrophages and neutrophils at inflammatory sites. Their expression was correlated with severe forms of glomerulonephritis. Therefore, this study examined whether or not MRP-8 and -14 can be used as biomarkers for identifying severely active lupus nephritis (LN). Total blood leukocyte samples and renal biopsy tissues from a prospective cohort of LN patients were used to determine mRNA and protein expression levels of MRP-8 and -14. The mRNA levels of MRP-8 and -14 in total blood leukocytes were significantly higher in active LN patients than quiescent LN patients and healthy controls. Moreover, the mRNA levels of MRP-8 and -14 in the total blood leukocytes and kidney tissues were significantly correlated with therapeutic response and the mRNA expression levels in the kidney were associated with an early loss of the kidney function. MRP-8 and -14 can be used as non-invasive prognostic biomarkers in patients with LN.

Urine Monocyte Chemoattractant Protein-1 and Lupus Nephritis Disease Activity: Preliminary Report of a Prospective Longitudinal Study

Objective. This longitudinal study aimed to determine the urine monocyte chemoattractant protein-1 (uMCP-1) levels in patients with biopsy-proven lupus nephritis (LN) at various stages of renal disease activity and to compare them to current standard markers. Methods. Patients with LN—active or inactive—had their uMCP-1 levels and standard disease activity markers measured at baseline and 2 and 4 months. Urinary parameters, renal function test, serological markers, and renal SLE disease activity index-2K (renal SLEDAI-2K) were analyzed to determine their associations with uMCP-1. Results. A hundred patients completed the study. At each visit, uMCP-1 levels (pg/mg creatinine) were significantly higher in the active group especially with relapses and were significantly associated with proteinuria and renal SLEDAI-2K. Receiver operating characteristic (ROC) curves showed that uMCP-1 was a potential biomarker for LN. Whereas multiple logistic regression analysis showed that only proteinuria and serum albumin and not uMCP-1 were independent predictors of LN activity. Conclusion. uMCP-1 was increased in active LN. Although uMCP-1 was not an independent predictor for LN activity, it could serve as an adjunctive marker when the clinical diagnosis of LN especially early relapse remains uncertain. Larger and longer studies are indicated.

Biomarkers for Refractory Lupus Nephritis: A Microarray Study of Kidney Tissue

The prognosis of severe lupus nephritis (LN) is very different among individual patients. None of the current biomarkers can be used to predict the development of refractory LN. Because kidney histology is the gold standard for diagnosing LN, the authors hypothesize that molecular signatures detected in kidney biopsy tissue may have predictive value in determining the therapeutic response. Sixty-seven patients with biopsy-proven severely active LN by International Society of Nephrology/Renal Pathology Society (ISN/RPS) classification III/IV were recruited. Twenty-three kidney tissue samples were used for RNA microarray analysis, while the remaining 44 samples were used for validation by real-time polymerase chain reaction (PCR) gene expression analysis. From hundreds of differential gene expressions in refractory LN, 12 candidates were selected for validation based on gene expression levels as well as relevant functions. The candidate biomarkers were members of the innate immune response molecules, adhesion molecules, calcium-binding receptors, and paracellular tight junction proteins. S100A8, ANXA13, CLDN19 and FAM46B were identified as the best kidney biomarkers for refractory LN, and COL8A1 was identified as the best marker for early loss of kidney function. These new molecular markers can be used to predict refractory LN and may eventually lead to novel molecular targets for therapy.

Pathogenesis of renal disease in systemic lupus erythematosus--the role of autoantibodies and lymphocytes subset abnormalities

Lupus nephritis (LN) is a common and severe organ manifestation of systemic lupus erythematosus (SLE), and is associated with significant patient morbidity and mortality. Autoantibodies and aberrations in lymphocyte subsets have putative roles in the pathogenesis of SLE and LN, and might reflect disease activity and are amenable to immunosuppressive treatments. Anti-DNA is one of the well-studied autoantibodies, which correlates with disease activity and has direct nephritogenic effects on resident renal cells and various glomerular components. Other important autoantibodies in the pathogenesis of LN include anti-C1q, anti-α-actinin and anti-nucleosome antibodies. Changes in naive and memory B cells and plasma cells have been observed in SLE and LN patients. These B cell subsets exert diverse effects during pathogenesis of LN such as production of autoantibodies, secretion of proinflammatory and anti-inflammatory cytokines and presentation of auto-antigens to effector cells. Aberration of T lymphocytes, especially the T-helper subsets, is also highly pertinent in the development of LN. In this context, important T helper subsets include Th1, Th2, Th9, Th17, T_Reg and follicular T-helper cells. The growing knowledge on these autoantibodies and lymphocyte subset abnormalities will enhance our understanding of SLE and LN, and hence help devise better strategies for disease monitoring and treatment.

The cellular signature of urinary immune cells in Lupus nephritis: new insights into potential biomarkers

INTRODUCTION

Urinary T cells represent a reliable noninvasive biomarker for proliferative Lupus nephritis (LN). Little is known about the presence of T cell subsets, B cells and macrophages in the urine although they may further improve the validity of urinary cellular biomarkers for LN.

METHODS

We analyzed contemporaneous blood and urine samples of patients with active LN (n = 19), other Systemic Lupus Erythematosus (SLE) patients (n = 79) and urine samples of patients with diabetic nephropathy (DN; n = 14) and anti-neutrophil cytoplasmatic antibody (ANCA) associated vasculitis (AAV; n = 11) by flow cytometry.

RESULTS

Numbers of urinary T cells, B cells and macrophages correlated with disease activity and were significantly higher in the active LN group. Urinary T cells showed excellent distinction of patients with active LN, CD8+ T cells (AUC of ROC = 1.000) and CD4+ T cells (AUC = 0.9969) alike. CD19+ B cells (AUC = 0.7823) and CD14+ macrophages (AUC = 0.9066), as well as the clinical standard proteinuria (AUC = 0.9201), failed to reach these high standards. Patients with DN or AAV also showed increased urinary cell counts, although the CD4/CD8-ratio was significantly lower in SLE compared to in DN (p = 0.0006). Urinary CD4+ T cells of active LN patients proved to be mainly of effector memory phenotype and expressed significantly more CD40L and ki67 than corresponding blood cells. Urinary Treg counts correlated with disease activity.

CONCLUSIONS

Despite of detectable urinary cell counts for B cells and macrophages, T cells remain the best urinary cellular biomarker for LN. A low CD4/CD8-ratio seems to be characteristic for LN.

Serum thiols as a biomarker of disease activity in lupus nephritis

Lupus Nephritis (LN) develops in more than half of the Systemic Lupus Erythematous (SLE) patients. However, lack of reliable, specific biomarkers for LN hampers clinical management of patients and impedes development of new therapeutics. The goal of this study was to investigate whether oxidative stress biomarkers in patients with SLE is predictive of renal pathology. Serum biochemical and oxidative stress markers were measured in patients with inactive lupus, active lupus with and without nephritis and compared to healthy control group. To assess the predictive performance of biomarkers, Receiver Operating Characteristic (ROC) curves were constructed and cut-offs were used to identify SLE patients with nephritis. We observed an increased oxidative stress response in all SLE patients compared to healthy controls. Among the several biomarkers tested, serum thiols had a significant inverse association with SLE Disease Activity Index (SLEDAI). Interestingly, thiols were able too aptly differentiate between SLE patients with and without renal pathology, and serum thiol levels were not affected by immunosuppressive drug therapy. The decreased thiols in SLE correlated significantly with serum creatinine and serum C3 levels. Further retrospective evaluation using serum creatinine or C3 levels in combination with thiol's cutoff values from ROC analysis, we could positively predict chronicity of renal pathology in SLE patients. In summary, serum thiols emerge as an inexpensive and reliable indicator of LN, which may not only help in early identification of renal pathology but also aid in the therapeutic management of the disease, in developing countries with resource poor settings.

IL-17 and IL-23 in lupus nephritis - association to histopathology and response to treatment

Background

Recent studies indicate a central role for the IL-23/IL-17 axis in the pathogenesis of lupus nephritis (LN) but the importance in the context of treatment outcome is unknown. We studied various cytokines, including the IL-23/IL-17 axis, in association to histopathology and response to therapy.

Methods

Fifty-two patients with active LN were included. Renal biopsies were performed at baseline and after immunosuppressive treatment. Serum levels of TNF-α, IFN-γ, IL-6, IL-10, IL-17, IL-23 and TGF-β were analysed at both biopsy occasions and in 13 healthy controls. IL-17 expression in renal tissue was assessed by immunohistochemistry. Biopsies were evaluated regarding WHO-classification and renal disease activity was estimated using the BILAG-index. Improvement of 2 grades in renal BILAG was regarded complete response, and 1 grade partial response.

Results

At baseline, all patients had high disease activity (BILAG A/B). Baseline levels of IL-6, IL-10, IL-17, IL-23 (p < 0.001) and IFN-γ (p = 0.03) were increased in patients vs. controls. In contrast, TGF-β was lower in patients compared to controls (p < 0.001).

Baseline levels of IL-17 were higher in patients with persisting active nephritis (WHO III, IV, V) after treatment, i.e. a poor histological response, vs. WHO I-II (p < 0.03). At follow-up, IL-23 were higher in BILAG-non-responders vs. responders (p < 0.05). Immunostaining of renal tissue revealed IL-17 expression in inflammatory infiltrates.

Conclusions

High baseline IL-17 predicted an unfavourable histopathological response, and BILAG-non-responders had high IL-23, indicating that that a subset of LN-patients has a Th-17 phenotype that may influence response to treatment and could be evaluated as a biomarker for poor therapeutic response.

Elevated Serum Levels of Syndecan-1 Are Associated with Renal Involvement in Patients with Systemic Lupus Erythematosus

Objective.

Syndecan-1 (SDC-1) is a major constituent of the endothelial glycocalyx, which plays a role in maintaining vascular homeostasis and functions as a glomerular filtration barrier. SDC-1 is readily shed into the blood under various conditions, but the clinical implication of circulating SDC-1 in patients with systemic lupus erythematosus (SLE) remains unclear. We aimed to investigate the association of serum SDC-1 level with certain clinical manifestations of SLE.

Methods.

We measured serum SDC-1 levels by ELISA in 111 patients with SLE, 18 with rheumatoid arthritis (RA), and 20 healthy subjects, and investigated its association with clinical manifestations and laboratory variables.

Results.

Serum SDC-1 levels were higher in patients with SLE than in those with RA and healthy controls (both p < 0.001) and were positively correlated with SLE Disease Activity Index (SLEDAI; r = 0.367, p < 0.001) and anti-dsDNA antibody level (r = 0.259, p = 0.007), but inversely correlated with serum C3 and CH50 levels (r = −0.305, p = 0.001 and r = −0.244, p = 0.012). Patients with active nephritis had higher serum SDC-1 levels than patients with inactive nephritis and those without nephritis (both p < 0.001). In addition, serum SDC-1 levels were correlated with renal SLEDAI score (r = 0.540, p < 0.001) and excretion of proteinuria as measured by spot urine protein/creatinine ratio (r = 0.538, p < 0.001). In 14 patients with lupus nephritis (LN) whose serum samples were obtained at the time of renal biopsy, there was a positive correlation between serum SDC-1 levels and activity index (r = 0.632, p = 0.015).

Conclusion.

Serum SDC-1 levels are increased in SLE patients with nephritis, indicating that SDC-1 might be a useful serum biomarker for active LN.

Measuring eosinophiluria, urinary eosinophil cationic protein and urinary interleukin-5 in patients with Lupus Nephritis

BACKGROUND

Urine is increasingly becoming an attractive biological fluid in clinical practice due to being an easily obtained, non-invasive sampling method, containing proteins and peptides. The aim of this study was to investigate eosinophiluria, urinary eosinophil cationic protein (uECP) and urinary IL-5 (uIL-5) in patients with Lupus Nephritis.

METHODS

Seventy-four patients with SLE-20 with clinical and laboratory evidence of lupus nephritis (LN group) and 54 without evidence of renal involvement (non-LN group)-were analyzed regarding eosinophiluria, uECP and uIL-5. Eosinophiluria was observed by Hansel's stain, ECP by fluoroenzymeimmunoassay and uIL-5 by quantitative sandwich enzyme immunoassay. Both uECP and urinary IL-5 (uIL-5) were corrected by urinary creatinine. Eosinophiluria and uECP were compared with glomerular erythrocyturia, protein/creatinine ratio (Pr/Cr ratio), serum creatinine, estimated glomerular filtration rate (eGFR), anti-double-stranded DNA (anti-dsDNA), serum levels of complement (C3 and C4), uIL-5/Cr ratio, and SLE disease activity index.

RESULTS

Patients of the LN group had higher eosinophiluria, uECP, uECP/Cr ratio levels, and uIL-5 than patients of the non-LN group (p<0.001 for all). These variables showed a statistically significant correlation with glomerular erythrocyturia, casts, Pr/Cr ratio, serum creatinine, eGFR, anti-dsDNA, uIL-5/Cr, and SLE disease activity index (all p<0.05).

CONCLUSION

These results provide evidence of increased urinary eosinophils, ECP and IL-5 in patients with SLE and LN; uECP/Cr ratio showed better correlation with markers of renal function and SLE disease activity.

Bone disease in newly diagnosed lupus nephritis patients

Introduction

Bone loss in Lupus Nephritis (LN) patients is common and multifactorial. The aim of this study was to evaluate the bone status of newly diagnosed LN patients and their correlation with inflammatory factors involved in LN physiopathology.

Methods

We studied 15 pre-menopausal patients with ≤2 months of diagnosed SLE and LN. Patients with prior kidney or bone disease were excluded. In addition to biochemical evaluation (including 25-hydroxyvitamin D₃ [25(OH)D] and Monocyte Chemotactic Protein (MCP1) dosage), we performed bone biopsies followed by osteoblast culture, histomorphometric and immunohistochemistry analysis.

Results

LN patients presented a mean age of 29.5±10 years, a proteinuria of 4.7±2.9 g/day and an estimated glomerular filtration rate (GFR) of 37(31–87) ml/min/1,73 m². They were on glucocorticoid therapy for 34±12 days. All patients presented vitamin D insufficiency (9.9±4.4 ng/ml, range 4–20). Urinary MCP1 correlated negatively with 25(OH)D (r = −0.53, p = 0.003) and positively with serum deoxypyridinoline (r = 0.53, p = 0.004). Osteoblasts isolated from LN bone biopsies presented a significantly higher expression of MCP-1 when compared to controls (32.0.±9.1 vs. 22.9±5.3 mean fluorescence intensities, p = 0.01). LN patients presented a significantly reduced osteoid volume, osteoid thickness, osteoid surface, mineralization surface and bone formation rate, associated with an increased eroded surface and osteoclast surface. Patient’s bone specimens demonstrated a reduced immunostaining for osteoprotegerin (0.61±0.82 vs. 1.08±0.50%, p = 0.003), and an increased expression of Receptor Activator of NF-κB ligand (RANKL) (1.76±0.92 vs. 0.41±0.28%, p<0.001) when compared to controls.

Discussion

Newly diagnosed LN patients presented a significant disturbance in bone metabolism, characterized by an impaired bone formation and mineralization, associated with an increase in resorption parameters. Glucocorticoid use, vitamin D insufficiency and inflammation might be involved in the physiopathology of bone metabolism disturbance.

Predictive role of urinary neutrophil gelatinase-associated lipocalin in lupus nephritis

OBJECTIVES

To evaluate the role of urinary neutrophil gelatinase-associated lipocalin (uNGAL), or lipocalin-2, in systemic lupus erythematosus (SLE) patients as a biomarker of renal activity and flares.

METHODS

Fifty subjects were divided into three groups: the first group comprised 14 SLE patients with no renal disease, the second group 16 SLE patients with active renal disease, the third group 20 apparently normal volunteers. At the beginning of the study clinical and laboratory data including uNGAL were collected. All patients were followed up serially in visits. At each visit, urine samples were collected for measurement of uNGAL as well as for standard urinalysis and a urine protein/creatinine ratio.

RESULTS

A highly significant difference was seen in uNGAL in all studied groups. Correlation was noticed between uNGAL and laboratory parameters of renal disease activity. There was significant positive correlation between renal SLEDAI and uNGAL levels. uNGAL is a significant predictor for renal disease activity and renal flare.

CONCLUSION

The more active the renal disease, the higher the measured levels of uNGAL, suggesting that it is a potential biomarker of active renal disease. uNGAL can be a predictive biomarker that could be followed serially to forecast renal disease activity and lupus nephritis flare.

Role of early repeated renal biopsies in lupus nephritis

Objectives

A renal biopsy is generally recommended for diagnosis and is necessary for classification of lupus nephritis (LN), but second biopsies after immunosuppressive therapy are seldom a routine procedure. We investigated how repeat biopsies contribute to the evaluation of treatment response and long-term outcome in LN.

Methods

Sixty-seven patients with active LN were included. Renal biopsies were performed at diagnosis and after standard induction immunosuppressive therapy in all patients (median 8 months), regardless of clinical outcome. Biopsies were evaluated according to the International Society of Nephrology/Renal Pathology Society classification. Clinical response was defined as complete (CR), partial (PR) or non-response (NR) according to recent definitions. Histological response (HR) was defined as Class I, II or III/IV-C on repeat biopsies. Long-term renal outcome was determined in 55 patients after a median of 10 years.

Results

CR was demonstrated in 25%, PR in 27% and NR in 48% of patients. HR was shown in 42% and histopathological non-response (HNR) in 58% of patients. Twenty-nine per cent of CR and 61% of patients with PR had active lesions on repeat biopsies, that is, were HNR. Poor long-term renal outcome was associated with high chronicity index at repeated biopsies, but not with clinical or histological response.

Conclusions

Despite apparent clinical response to immunosuppressive therapy, repeated biopsies revealed persisting active nephritis in almost half of the patients, thus providing additional information to clinical response criteria. Repeated renal biopsies may be a tool to improve the evaluation of treatment response in LN.

Mesangial cell-binding activity of serum immunoglobulin g in patients with lupus nephritis

In vitro data showed that immunoglobulin G (IgG) from patients with lupus nephritis (LN) could bind to cultured human mesangial cells (HMC). The clinical relevance of such binding was unknown. Binding of IgG and subclasses was measured in 189 serial serum samples from 23 patients with Class III/IV±V LN (48 during renal flares, 141 during low level disease activity (LLDA)). 64 patients with non-lupus glomerular diseases (NLGD) and 23 healthy individuals were used as controls. HMC-binding was measured with cellular ELISA and expressed as OD index. HMC-binding index of total IgG was 0.12±0.09, 0.36±0.25, 0.59±0.37 and 0.74±0.42 in healthy subjects, NLGD, LN patients during LLDA, and LN flares respectively (P = 0.046, LN flare vs. LLDA; P<0.001, for healthy controls or NLGD vs. LN during flare or LLDA). Binding of serum IgG₁ to HMC was 0.05±0.05, 0.15±0.11, 0.41±0.38 and 0.55±0.40 for the corresponding groups respectively (P = 0.007, LN flare vs. remission; P<0.001, for healthy controls or NLGD vs. LN during flare or remission). IgG₂, IgG₃ and IgG₄ from patients and controls did not show significant binding to HMC. Total IgG and IgG₁ HMC-binding index correlated with anti-dsDNA level (r = 0.26 and 0.39 respectively, P<0.001 for both), and inversely with C3 (r = −0.17 and −0.45, P<0.05 for both). Sensitivity/specificity of total IgG or IgG₁ binding to HMC in predicting renal flares were 81.3%/39.7% (ROC AUC 0.61, P = 0.03) and 83.8%/41.8% (AUC 0.63, P = 0.009) respectively. HMC-binding by IgG_1, but not total IgG, correlated with mesangial immune deposition in LN renal biopsies under electron microscopy. Our results showed that binding of serum total IgG and IgG₁ in LN patients correlates with disease activity. The correlation between IgG₁ HMC-binding and mesangial immune deposition suggests a potential pathogenic significance.

Multiplexing of miniaturized planar antibody arrays for serum protein profiling--a biomarker discovery in SLE nephritis

In the quest to decipher disease-associated biomarkers, miniaturized and multiplexed antibody arrays may play a central role in generating protein expression profiles, or protein maps, of crude serum samples. In this conceptual study, we explored a novel, 4-times larger pen design, enabling us to, in a unique manner, simultaneously print 48 different reagents (antibodies) as individual 78.5 μm(2) (10 μm in diameter) sized spots at a density of 38,000 spots cm(-2) using dip-pen nanolithography technology. The antibody array set-up was interfaced with a high-resolution fluorescent-based scanner for sensitive sensing. The performance and applicability of this novel 48-plex recombinant antibody array platform design was demonstrated in a first clinical application targeting SLE nephritis, a severe chronic autoimmune connective tissue disorder, as the model disease. To this end, crude, directly biotinylated serum samples were targeted. The results showed that the miniaturized and multiplexed array platform displayed adequate performance, and that SLE-associated serum biomarker panels reflecting the disease process could be deciphered, outlining the use of miniaturized antibody arrays for disease proteomics and biomarker discovery.

The kidney biopsy in lupus nephritis: is it still relevant?

The kidney biopsy is the standard of care for diagnosis of lupus nephritis and remains necessary to ensure accurate diagnosis and guide treatment. Repeat biopsy should be considered when therapy modifications are necessary, as in cases with incomplete or no response, or when stopping therapy for those in remission. There are several promising biomarkers of kidney disorders; however, these markers need to be validated in a prospective clinical trial before being applied clinically. Molecular analysis may provide the information presently lacking from current evaluation of kidney disorders and may better inform on prognosis and treatment considerations.

Lupus mimickers

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by multisystem organ involvement, heterogeneity of clinical features, and variety in degree of severity. The differential diagnosis is a crucial aspect in SLE as many other autoimmune diseases portray clinical similarities and autoantibody positivity. Lupus mimickers refer to a group of conditions that exhibit both clinical features and laboratory characteristics, including autoantibody profiles that resemble those present in patients with SLE, and prompt a diagnostic challenge in everyday clinical practice. Thus, lupus mimickers may present as a lupus-like condition (i.e., 2 or 3 criteria) or as one meeting the classification criteria for SLE. Herein we review and classify the current literature on lupus mimickers based on diverse etiologies which include infections, malign and benign neoplasms, medications, and vaccine-related reactions.

Plasma CD147 reflects histological features in patients with lupus nephritis

OBJECTIVE

A glycosylated transmembrane protein, CD147, has been implicated in regulating lymphocyte responsiveness and leukocyte recruitment. As lupus nephritis (LN) often follows a relapsing-remitting disease course, accurate understanding of the disease activity would be extremely helpful in improving prognosis. Unfortunately, neither clinical nor serological data can accurately reflect the histological features of LN. The present study investigated whether CD147 can accurately predict pathological features of LN.

METHODS

Plasma and spot urine samples were collected from 64 patients who underwent renal biopsy between 2008 and 2011. Disease activity for LN tissues was evaluated using the biopsy activity index, and compared to levels of biomarkers including CD147.

RESULTS

In LN tissues, CD147 induction was striking in injured glomeruli and infiltrating inflammatory cells, but not in damaged tubules representing atrophy. Plasma CD147 levels accurately reflected the histological disease activity. However, prediction using a single molecule would be quite difficult because of the complex pathogenesis of LN. The diagnostic accuracy of multiplex parameters indicated that the combination including plasma CD147 might yield excellent diagnostic abilities for guiding ideal LN therapy.

CONCLUSION

Plasma CD147 levels might offer useful insights into disease activity as a crucial biomarker in patients with LN.

Recombinant antibody microarray for profiling the serum proteome of SLE

Systemic lupus erythematosus (SLE) is a severe autoimmune connective tissue disease. Our current knowledge about the serum proteome, or serum biomarker panels, reflecting disease and disease status is still very limited. Affinity proteomics, represented by recombinant antibody arrays, is a novel, multiplex technology for high-throughput protein expression profiling of crude serum proteomes in a highly specific, sensitive, and miniaturized manner. The antibodies are deposited one by one in an ordered pattern, an array, onto a solid support. Next, the sample is added, and any specifically bound proteins are detected and quantified. The binding pattern is then converted into a relative protein expression map, or protein map, deciphering the composition of the sample at the molecular level. The methodology provides unique opportunities for delineating serum biomarkers reflecting SLE, thus paving the way for improved diagnosis, classification, and prognosis.

Nanosized contrast agents to noninvasively detect kidney inflammation by magnetic resonance imaging

Several molecular imaging methods have been developed that use nanosized contrast agents to detect markers of inflammation within tissues. Kidney inflammation contributes to disease progression in a wide range of autoimmune and inflammatory diseases, and a biopsy is currently the only method of definitively diagnosing active kidney inflammation. However, the development of new molecular imaging methods that use contrast agents capable of detecting particular immune cells or protein biomarkers will allow clinicians to evaluate inflammation throughout the kidneys and to assess a patient's response to immunomodulatory drugs. These imaging tools will improve our ability to validate new therapies and to optimize the treatment of individual patients with existing therapies. This review describes the clinical need for new methods of monitoring kidney inflammation and recent advances in the development of nanosized contrast agents for the detection of inflammatory markers of kidney disease.

Biomarkers in systemic lupus erythematosus: challenges and prospects for the future

The search for lupus biomarkers to diagnose, monitor, stratify, and predict individual response to therapy is currently more intense than ever before. This effort is essential for several reasons. First, epidemic overdiagnosis and underdiagnosis of lupus, even by certified rheumatologists, leads to errors in therapy with concomitant side effects which may be more serious than the disease itself. Second, identification of lupus flares remains as much an art as it is a science. Third, the capacity to stratify patients so as to predict those who will develop specific patterns of organ involvement is not currently possible but would potentially lead to preventive therapeutic strategies. Fourth, only one new drug for the treatment of lupus has been approved by the US Food and Drug Administration in over 50 years. A major obstacle in this pipeline is the dearth of biomarkers available to prove a patient has responded to an experimental therapeutic intervention. This review will summarize the challenges faced in the discovery and validation of lupus biomarkers, the most promising lupus biomarkers identified to date, and the promise of future directions.

Urinary CXCL-10/IP-10 and MCP-1 as markers to assess activity of lupus nephritis

Objective

IP-10 and MCP-1 are pro-inflammatory chemokines which are involved in the immunopathogenesis of lupus nephritis and may thus be useful biomarkers.

Methods

SLE patients fulfilling ACR 1997 criteria were included. SLEDAI was calculated and blood and urine samples collected. Active lupus was defined as SLEDAI ≥4. Active patients were divided into active renal (proteinuria ≥ 500 mg/day or active sediment in urine) and active non-renal lupus. Patients with active renal lupus were followed until the nephritis became inactive, when a second sample was collected. Serum and urinary levels of MCP-1 and IP-10 (pg/ml) were measured by ELISA. Urinary values were normalized for urinary spot creatinine (in mg/dL. Thus the values were expressed as pg/mg creatinine × 100 creatinine).

Results

A total of 136 patients with SLE including 78 active (46 active renal and 32 active non-renal) were included. Median age was 25 (10–55) years and SLE duration was 23 (six to 48) months. Both serum (data not shown) and urinary levels of MCP-1 (35.2 (12.7–71.7), 9.4 (4.4–17), p < 0.001) and IP-10 (9.5 (4.4–17.9), 3.9 (1.9–9.3), p < 0.001) were higher in active compared to inactive SLE. However, in active renal compared to active non-renal SLE, there was no difference in serum levels; only urinary levels of MCP-1 (46.2 (19.9–125), 12.7 (5.8–43.9), p < 0.001) and IP-10 (12.5 (5.6–22.7), 5.2 (2.3–12.2), p < 0.05) were higher. On longitudinal follow-up of active renal patients ( n = 24), there was a decrease in urinary levels of MCP-1 and IP-10 ( p = 0.005). On ROC analysis, urinary MCP-1 outperformed C4 and urinary IP-10, but was similar to dsDNA and C3 in differentiating active renal from non-renal SLE.

Conclusions

Urinary and serum IP-10 and MCP-1 are potentially useful markers of lupus activity; however, only the urinary levels are indicative of renal activity. However, on ROC analysis, they are not better than conventional markers.