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Arteriolar C4d in IgA Nephropathy: A Cohort Study
Bernardo Faria1, Pedro Canão2, Qingqing Cai3
1Nephrology and Infectious Disease R&D Group, INEB, Institute of Investigation and Innovation in Health (i3S), University of Porto, Porto, Portugal; Division of Nephrology, Department of Internal Medicine, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands.
Insights
Arteriolar C4d (C4dA) deposition in kidney biopsies indicates a higher risk of progressive kidney disease in immunoglobulin A nephropathy (IgAN). This finding suggests C4dA may serve as a valuable biomarker for predicting IgAN progression.
Area of Science:
- Nephrology
- Immunopathology
- Complement System
Background:
- Glomerular C4d (C4dG) indicates lectin pathway activation in IgAN and correlates with kidney damage.
- Vascular lesions in IgAN biopsies with complement deposition are linked to disease progression.
Purpose of the Study:
- To investigate the clinical significance of arteriolar C4d (C4dA) in IgAN kidney biopsy tissue.
- To determine if C4dA is associated with disease progression in IgAN.
Main Methods:
- Retrospective cohort study of 126 adult IgAN patients.
- Immunohistochemistry used to classify C4dG and C4dA deposition.
- Analysis of vascular lesions and association with progressive kidney disease using multivariable Cox regression.
Main Results:
- C4dA was present in 17% of patients and associated with hypertension, arterial intima fibrosis, and chronic microangiopathy.
- Both C4dA and C4dG were significantly associated with progressive kidney disease.
- C4dA remained an independent predictor of progressive kidney disease after adjusting for other factors.
Conclusions:
- Arteriolar C4d (C4dA) is a potential biomarker for predicting disease progression in IgAN.
- Further investigation in larger cohorts is warranted to confirm the predictive value of C4dA.
Rationale & Objective:
Glomerular C4d (C4dG) as an indicator of the lectin pathway of complement activation in immunoglobulin A nephropathy (IgAN) has been associated with more severe kidney damage. Recent studies have suggested that vascular lesions in IgAN biopsy specimens with complement deposition are also associated with disease progression. We aimed to study the clinical significance of arteriolar C4d (C4dA) in IgAN kidney biopsy tissue.
Study Design:
Retrospective cohort study.
Setting & Participants:
Kidney biopsy specimens from 126 adults with IgAN diagnosed by Oxford classification criteria were stained using immunohistochemistry and classified according to C4dG and C4dA deposition. Additionally, vascular lesions including acute and chronic microangiopathy, arteriolar hyalinosis, and arterial intima fibrosis were characterized.
Predictor:
C4dA.
Outcome:
Progressive kidney disease, defined as a decline in estimated glomerular filtration rate by≥50% or occurrence of kidney failure.
Analytical Approach:
The association of C4dA and C4dG with baseline clinical and histologic characteristics, as well as progressive kidney disease, were assessed with survival analysis using multivariable Cox regression analysis.
Results:
C4dA was identified in 21 (17%) patients and was associated with mean arterial pressure, arterial intima fibrosis, and chronic microangiopathy. C4dA was also significantly associated with C4dG and both were associated with progressive kidney disease. In regression analysis, C4dA remained significantly associated with progressive kidney disease after adjusting for other significant predictors, including baseline estimated glomerular filtration rate, mean arterial pressure, and the presence of crescents.
Limitations:
Findings based on the retrospective evaluation of a single center's experience, limited number of events, a small number of patients with a broad range of kidney disease stages, and use of immunohistochemistry rather than immunofluorescence to detect C4d.
Conclusions:
C4dA is a potential biomarker for disease progression in IgAN. It should be further investigated in larger cohorts to determine the value of C4dA in improving prediction of IgAN disease progression.
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