The CCL2-CCR2 axis determines whether glomerular endocapillary hypercellularity or wire-loop lesions develop through glomerular macrophage and neutrophil infiltration in lupus nephritis.

The CCL2-CCR2 axis is involved in lupus nephritis, however the precise roles in the mechanisms by which different pathological lesions develop after glomerular immune complex deposition remain elusive. Previously, we demonstrated that genetic CCR2 inhibition induced a histological switch from glomerular endocapillary hypercellularity to wire-loop lesions in murine lupus nephritis. This study aimed to clarify the CCL2-CCR2 axis-mediated cellular mechanism in the formation of these different pathological lesions. We injected MRL/lpr mouse-derived monoclonal IgG3 antibody-producing hybridomas, 2B11.3 or B1, into wild-type (WT) mice to selectively induce glomerular endocapillary hypercellularity or wire-loop lesions. The expression of chemokine and chemokine receptors was analyzed using RT-quantitative PCR and/or immunofluorescence. We found 2B11.3 caused glomerular endocapillary hypercellularity in WT mice with glomerular infiltration of larger numbers of CCR2-expressing macrophages and neutrophils phagocyting immune complex, whereas B1 induced wire-loop lesions. In glomerular endocapillary hypercellularity, CCL2 was identified as the ligand involved in the CCR2-positive cell infiltration; it was expressed by glomerular endothelial cells and macrophages. Notably, 2B11.3-induced glomerular endocapillary hypercellularity converted to wire-loop lesions with reduced glomerular macrophage and neutrophil infiltration in CCL2-deficient (Ccl2-/-) mice similarly observed in Ccr2-/- mice. Moreover, this histological conversion was also observed when both glomerular macrophage and neutrophil infiltration were inhibited in anti-Ly6G antibody-treated Ccr5-/- mice but not when only glomerular macrophage infiltration was inhibited in Ccr5-/- mice or when only glomerular neutrophil infiltration was inhibited in anti-Ly6G antibody-treated WT mice. In contrast, B1 injection caused wire-loop lesions in Ccl2-/- and Ccr2-/- mice, as observed in WT mice. Moreover, 2B11.3 induced CCL2 from glomerular endothelial cells to a larger extent than B1 when injected into Ccr2-/- mice. In conclusion, the CCL2-CCR2 axis determines whether glomerular endocapillary hypercellularity or wire-loop lesions develop by regulating glomerular infiltration of phagocytic cells: macrophages and neutrophils. © 2024 The Pathological Society of Great Britain and Ireland.

Endocapillary hypercellularity levels are associated with early complete remission in children with class IV lupus nephritis as the initial presentation of SLE.

BACKGROUND: Endocapillary hypercellularity (ECHC) is commonly seen in class IV lupus nephritis (LN), the most common and severe LN in children. Factors influencing early complete remission (CR) in pediatric class IV LN have been poorly described. We investigated the relationship between ECHC levels and early CR in pediatric class IV LN. METHODS: Patients with newly, simultaneously diagnosed systemic lupus erythematosus (SLE) and class IV LN by renal biopsy from 2012 to 2021 were studied. In this retrospective study, two pathologists who were blind to clinical information reviewed all pathological data retrospectively and classified glomerular lesions according to the revised criteria of the International Society of Nephrology and the Renal Pathology Society (ISN/RPS). The demographics, baseline clinical characteristics, laboratory parameters, renal histopathological findings, treatment regimen and CR at 6 months after immunosuppressive therapy were analyzed. ECHC was categorized as: > 50% (group A), 25-50% (group B) and < 25% (group C). CR was defined as absence of clinical symptoms, 24-hour urinary protein < 0.15 g, and normal levels of serum creatinine and albumin. RESULTS: Sixty-four patients were identified: 23, 15 and 26 in groups A, B and C, respectively. Group A had significantly higher levels of D-dimer, urine protein, and SLE disease activity index (SLEDAI) than groups B and C. Group C had a markedly higher estimated glomerular filtration rate (eGFR) than groups A and B. A substantially greater proportion of patients in group A had glomerular microthrombi and basement membrane thickening than in groups B and C. At 6 months post treatment, CR was achieved in 19 (82.6%), 5 (33.3%) and 11 (42.3%) in groups A, B and C, respectively (p < 0.05, group A vs groups B and C). Multiple logistic regression analysis revealed that ECHC and urine protein levels were significantly associated with CR. CONCLUSION: ECHC and urine protein levels may be valuable biomarkers for predicting early CR in pediatric class IV LN.

Use of Glomerular CD68+ Cells as a Surrogate Marker for Endocapillary Hypercellularity in Lupus Nephritis.

Introduction: Lupus nephritis (LN) class III or IV is strongly related to patient mortality and morbidity. The interobserver agreement of endocapillary hypercellularity by routine light microscopy, one of the most important lesions determining whether class III or IV is present, is moderate. In IgA nephropathy (IgAN), the presence of glomerular CD68+ cells was found to be a good surrogate marker for endocapillary hypercellularity. We investigated whether the presence of glomerular CD68+ cells could serve as a surrogate marker for endocapillary hypercellularity as well in LN. Methods: A total of 92 LN biopsies were scored for the number of glomerular CD68+ cells using CD68 staining, including endocapillary hypercellularity and the activity index (AI). A new AI was calculated in which CD68+ cells replaced endocapillary hypercellularity. Clinical parameters were obtained from time of biopsy, 1 year after, and 2 years after. Results: The number of glomerular CD68+ cells significantly correlated with endocapillary hypercellularity. A cutoff value of 7 for the maximum number of CD68+ cells within 1 glomerulus in a biopsy yielded a sensitivity of 88% and a specificity of 67% for the presence of endocapillary hypercellularity. Both endocapillary hypercellularity and CD68+ cells correlated with renal function during follow-up. The current and the new AI correlated equally well with the clinical outcome. Conclusion: In LN, CD68+ cells can be used as a surrogate marker for endocapillary hypercellularity.

Cell-Mediated Glomerulonephritis Without Immune Complexes in Native Kidney Biopsies: A Report of 7 Cases.

We report 7 native kidney biopsies with diffuse endocapillary hypercellularity without immune deposits, affecting 5 women and 2 men aged 52-85 years. All patients had acute kidney injury, and 4 had nephrotic-range proteinuria. Comorbidities included breast cancer in 2, pancreatitis in 1, and para-aortic lymphadenopathy and bilateral carpal tunnel syndrome in 1. Kidney biopsies were characterized by predominant T-cell and CD68-positive macrophage infiltration in glomerular capillaries without deposits. Coexisting lesions included small cellular crescents in 5, mild peritubular capillaritis in 1, mononuclear cell intimal arteritis in 1, acute tubulointerstitial nephritis in 4, and mild arteriolosclerosis in 1. During the mean follow-up duration of 24.8 months, 4 patients showed partial or complete initial remission in response to immunosuppression. However, 2 deteriorated when prednisone was rapidly tapered (1 of them achieved subsequent remission with increased prednisone). Three patients developed kidney failure. We propose that this unusual pattern of injury is mediated by abnormal cell-mediated immune response. The underlying causes and pathogenesis of this cell-mediated glomerulonephritis will require further study.

CCR2- and CCR5-mediated macrophage infiltration contributes to glomerular endocapillary hypercellularity in antibody-induced lupus nephritis.

OBJECTIVES: LN comprises various glomerular lesions, including endocapillary hypercellularity with macrophage infiltration. In this study, we aimed to clarify the involvement of macrophage-tropic chemokine receptors in the pathogenesis of these glomerular lesions. METHODS: MRL/lpr mouse-derived monoclonal IgG3 antibody-producing hybridomas, 2B11.3 and B1, were injected intraperitoneally into BALB/c mice [wild type (WT)] to induce endocapillary hypercellularity and wire-loop lesions, respectively. The expression of chemokine and chemokine receptors was analysed by quantitative real-time PCR and IF. The roles of chemokine receptors in these lesions were evaluated using chemokine receptor-deficient mice or a selective CCR5 antagonist, maraviroc. RESULTS: 2B11.3 caused glomerular endocapillary hypercellularity with a significant number of glomerular CD68-positive macrophages. Further, enhanced expression of CCL2, CCL3, CCR2, CCR5 and CX3CR1 was observed in the renal cortex, compared with B1 injection, which induced wire-loop lesions. In 2B11.3-induced glomerular lesions, CD68 -positive glomerular macrophages expressed CCL2, CCL3, CCR2, CCR5 and CX3CR1, while glomerular endothelial cells expressed CCL2, CCL3, CX3CL1 and CCR2. When 2B11.3 was injected, CCR2-/- and CCR5-/-, but not CX3CR1-/-, mice exhibited reduced endocapillary hypercellularity, attenuated glomerular macrophage infiltration and improved serum blood urea nitrogen levels. Only CCR2-/- mice developed wire-loop lesions. B1 injection caused wire-loop lesions in these chemokine receptor-deficient mice to a similar extent as WT. Maraviroc treatment reduced 2B11.3-induced endocapillary hypercellularity and improved serum blood urea nitrogen levels. CONCLUSION: CCR2 and CCR5 regulate glomerular macrophage infiltration and contribute to the development of glomerular endocapillary hypercellularity in LN. CCR5 inhibition can be a specific therapy for endocapillary hypercellularity without inducing wire-loop lesions.

The Utility of Assessing CD68+ Glomerular Macrophages in Assessing Endocapillary Hypercellularity in IgA Nephropathy.

INTRODUCTION: IgA nephropathy (IgAN) is the most common form of glomerulonephritis across the world. Oxford classification defines criteria and effects of endocapillary hypercellularity on E score but the reproducibility of the same is debatable. Hence, there is a need for an objective marker that could establish a gold standard in assessing endocapillary hypercellularity. METHODS: Forty biopsies of proven IgAN were taken and grouped into two groups based on the presence or absence of endocapillary hypercellularity (n = 20 each). These biopsies were then stained by CD68 immune stain and the glomerular macrophages were quantified. Mean serum creatinine, presence of hypertension, degree of proteinuria and haematuria at the time of biopsy were also recorded and the correlation between these parameters and endocapillary hypercellularity was also studied. RESULTS: Mean glomerular CD 68+ cell count was significantly higher in glomeruli showing endocapillary hypercellularity. Utilising the objective cutoff values of 0.6 CD68+ per glomerulus, more than 8 glomerular CD68+ cells in the entire biopsy and/or around 4 CD68+ cells in the most inflamed glomerulus, endocapillary hypercellularity can be predicted with a sensitivity of 70-80% and specificity of 70%. After regrouping the biopsies based on the cutoff values obtained from the receiver operating curve analysis the mean urine RBC count per high power field showed a significant correlation with endocapillary hypercellularity. CONCLUSION: Glomerular CD68+ macrophage count seems to be a promising approach in assessing endocapillary hypercellularity. Further studies with emphasis on correlation with the clinical outcome are needed to validate its utility as an objective tool.

[The effect of endocapillary hypercellularity lesions on the renal prognosis and response to immunosuppressive therapy in IgA nephropathy].

In this retrospective cohort study, we aim to evaluate the effect of endocapillary hypercellularity (E) lesions on the renal prognosis and response to immunosuppressive therapy, especially diffuse endocapillary hypercellularity lesion in IgA nephropathy (IgAN). A total of 365 patients with IgAN and E lesions and 31 patients with diffuse E lesions and over 12-month follow-up period were included in this study. We performed an 1∶1 propensity score to identify controls with matched clinical and pathological features from 769 IgAN patients without E lesions. The end-point was defined as a 30% decrease in estimated glomerular filtration rate (eGFR) or end-stage kidney disease. The kidney survival of the two groups was compared by Kaplan-Meier analysis. During median follow-up period of 41 months, kidney survival rates in patients with E lesions were 96.0% at 1 year, 83.6% at 3 years, 67.7% at 5 years; while they were 96.9% at 1 year, 83.6% at 3 years, and 68.7% at 5 years in patients without E lesions (P=0.265).The HR of immunosuppressive therapy was 1.038 (95%CI 0.749-1.440) and 1.113 (95%CI 0.770-1.609) in patients not receiving immunosuppressive therapy (P=0.781). (2) During median follow-up period of 52.5 months, the kidney survival rates in patients with diffuse E-lesion were 100.0% at 1 year, 96.2% at 3 years, 74.5% at 5 years; while they were 96.2% at 1 year, 82.3% at 3 years, and 63.7% at 5 years in patients without E-lesion (P=0.158). The HR of immunosuppressive therapy was 0.625 (95%CI 0.213-1.839) and 0.447 (95%CI 0.028-7.191) in patients not receiving immunosuppressive therapy (P=0.825). E lesion or diffuse E lesion may not be associated with prognosis or response to immunosuppressive therapy.

The implications of focal segmental glomerulosclerosis in children with IgA nephropathy.

Focal segmental glomerular sclerotic lesions in IgA nephropathy (IgAN), considered for years a chronic histologic feature related to proteinuria in remnant nephrons without any active role in the pathogenesis and progression of glomerular damage of IgAN, have been recently reconsidered. The Oxford classification of IgAN reported it as the "S" score and found it to be an independent risk factor for progression of IgAN. Its prognostic value was confirmed also in children. The identification of some histologic subvariants of the S lesion has produced interesting insights into different pathogenetic mechanisms of glomerular damage in IgAN. Tip lesion and podocyte hypertrophy are considered secondary to active podocytopathy and are correlated with higher levels of proteinuria and a faster decline in glomerular filtration rate. Moreover, endocapillary and mesangial hypercellularity might contribute in children with IgAN to formation and progression of S lesions. Considering the pathophysiology of these processes, children with some S features may benefit not only from nephroprotective measures but also from immunosuppression.

Mycophenolate Mofetil Combined With Prednisone Versus Full-Dose Prednisone in IgA Nephropathy With Active Proliferative Lesions: A Randomized Controlled Trial.

BACKGROUND: Observational studies suggest that patients with immunoglobulin A nephropathy (IgAN) with active proliferative lesions show a good response to immunosuppressive treatment. STUDY DESIGN: Multicenter, prospective, randomized, controlled trial. SETTING & PARTICIPANTS: 176 patients with IgAN with active proliferative lesions (cellular and fibrocellular crescents, endocapillary hypercellularity, or necrosis), proteinuria with protein excretion ≥ 1.0g/24h, and estimated glomerular filtration rate > 30mL/min/1.73m2. INTERVENTION: Mycophenolate mofetil (MMF) group: MMF, 1.5g/d, for 6 months and prednisone, 0.4 to 0.6mg/kg/d, for 2 months and then tapered by 20% per month for the next 4 months; prednisone group: prednisone, 0.8 to 1.0mg/kg/d, for 2 months and then tapered by 20% per month for the next 4 months. All patients were followed up for another 6 months. OUTCOMES: The primary end point was complete remission rate at 6 and 12 months. RESULTS: At baseline, median estimated glomerular filtration rates were 90.2 and 94.3mL/min/1.73m2 and mean proteinuria was protein excretion of 2.37 and 2.47g/24h in the MMF and prednisone groups, respectively. At 6 months, complete remission rates were 37% (32 of 86 patients) and 38% (33 of 88 patients); the between-group difference was not statistically significant (P=0.9). At 12 months, complete remission rates were 48% (35 of 73 patients) and 53% (38 of 72 patients) in the MMF and prednisone groups, respectively; the between-group difference was not statistically significant (P=0.6). Incidences of Cushing syndrome and newly diagnosed diabetes mellitus were lower in the MMF group than in the prednisone group. LIMITATIONS: Not all participants were treated with renin-angiotensin system blockers, relatively short follow-up. CONCLUSIONS: MMF plus prednisone versus full-dose prednisone did not differ in reducing proteinuria, but patients treated with the former had fewer adverse events in patients with IgAN with active proliferative lesions.

Prognostic value of endocapillary hypercellularity in IgA nephropathy patients with no immunosuppression.

AIM: Interpretation of retrospective clinicopathological studies of IgA nephropathy (IgAN) has been confounded by immunosuppression bias. In published validation studies of the Oxford Classification of IgAN, an average of 33 % of patients received non-randomised steroid and/or cytotoxic therapy. In order to determine the true impact of proliferative lesions on the natural history of IgAN, analysis of patient cohorts that have received no immunosuppression is required. METHODS: We performed a retrospective single centre study of patients with IgAN managed without immunosuppressive therapy. Biopsies were scored according to the Oxford Classification. The primary outcomes were renal survival or a rapid loss of renal function defined as a decline in eGFR of >5 ml/min/year. RESULTS: 237 patients with IgAN were identified with a mean follow-up of 82 months. 200 had biopsies available for review, of which 156 were adequate for scoring using the Oxford Classification. 9/156 patients (5.8 %) received some immunosuppressive therapy, mostly for unrelated conditions: these were excluded. In multivariate COX regression, including histological and clinical data, the only independent predictors of time to ESRD were baseline eGFR (HR 0.96 per ml/min increase, p = 0.018), baseline proteinuria (HR 1.36 per doubling, p = 0.004) and endocapillary hypercellularity (HR 4.75 for E1 compared to E0, p < 0.001). Independent predictors of a rapid decline in eGFR were proteinuria (OR 1.45 per doubling, p = 0.006), endocapillary hypercellularity (OR 3.41 for E1 compared to E0, p = 0.025) and tubular atrophy/interstitial fibrosis (OR 8.77 for T2 compared to T0, p = 0.006). CONCLUSIONS: In a cohort of IgAN patients receiving no immunosuppression, endocapillary proliferation and tubular atrophy/interstitial fibrosis are independent predictors of rate of loss of renal function. The lack of predictive value of E score in other clinicopathological studies is most likely a result of immunosuppression-associated bias. Our findings provide evidence to support immunosuppressive treatment of endocapillary-pattern IgAN.

A case of endocapillary proliferative glomerulonephritis with macrophages phagocytosing monoclonal immunoglobulin lambda light chain.

Multiple myeloma (MM) is a plasma-cell neoplasm that can cause renal disorders. Renal lesions in MM can present with a very rare pathological manifestation involving a specific monoclonal immunoglobulin (Ig). We report the case of a 33-year-old woman who had edema, fatigue, elevated serum creatinine levels, hypoalbuminemia, and hypercholesterolemia. She had persistent hematuria and proteinuria lasting 3 years. Serum protein electrophoresis showed an M-spike, and serum immunofixation demonstrated the presence of monoclonal IgG λ. She had proteinuria in the nephrotic range, and a monoclonal λ fragment was present on urine immunofixation. Renal biopsy showed proliferative glomerulonephritis with λ light chain and C3c deposition and inflammatory cell infiltration with CD68. Macrophage lysosomes contained λ light chains, suggesting their partial phagocytosis. She was diagnosed with symptomatic MM and was treated with bortezomib and dexamethasone and an autologous peripheral stem cell transplant conditioned with intravenous melphalan. She achieved a partial response with decreased serum monoclonal protein and improved renal function. This case may be categorized as a monoclonal gammopathy-associated proliferative glomerulonephritis. The biopsy finding of partially phagocytosed Ig λ light chains by macrophages is very rare; this pathological condition is similar to crystal-storing histiocytosis.