NanoString mRNA Profiling Identifies Inflammatory, Fibrotic Markers of IgA Nephropathy

NanoString technology may be a viable tool for identifying inflammatory targets related to IgA nephropathy (IgAN) disease progression, with results from a recent study suggesting patients may have a distinctive gene expression profile that is further altered by the presence of fibrosis.¹

Louis-Philippe Laurin, MD, MSc

Credit: Maisonneuve-Rosemont Hospital Research Center

C3 and TNFRSF1B were identified as promising biomarkers for monitoring disease progression, both of which were significantly upregulated in patients with IgAN compared to controls – further analysis revealed certain mRNA transcripts may also have utility as fibrotic markers.¹

Little is currently known about the inflammatory markers involved in IgAN, hindering its diagnosis and prognosis. In the absence of these biomarkers, clinicians’ ability to effectively treat IgAN and predict disease progression is limited. Understanding the clinical utility of inflammatory biomarker panels for IgAN will be pivotal for its management and treatment.²

“Although a number of clinical indicators have been found to help predict disease progression, specific biomarkers involved in the underlying inflammatory processes are not integrated into any prediction tool,” wrote Louis-Philippe Laurin, MD, MSc, clinical associate professor of medicine at the University of Montreal, and colleagues.¹

To validate the use of NanoString technology for identifying potential inflammatory biomarkers involved in the progression of IgAN, investigators measured the gene expression of patients with biopsy-proven IgAN and antineutrophil cytoplasmic antibody (ANCA)-associated pauci-immune glomerulonephritis between 2005 and 2021 diagnosed at a single tertiary care hospital in Montreal.¹

Only patients with formalin-fixed paraffin-embedded (FFPE) biopsy samples available for gene expression analysis were included. Patients with known secondary causes of IgAN were excluded. The primary outcomes were ESKD (eGFR < 15 ml/min/1.73m2, dialysis or kidney transplantation) or death.¹

A total of 30 patients with biopsy-proven IgAN and 7 cases of ANCA-associated pauci-immune glomerulonephritis were included for gene expression measurement and compared to delineate an expression profile specific to IgAN. Patients with IgAN were mostly Caucasian (76.7%) and female (73.3%). The mean age at biopsy was 44.7 years and mean baseline eGFR and proteinuria were 60.9 (Standard deviation [SD], 35.8) ml/min/1.73m2 and 3.2 (SD, 2.9) g/d, respectively.¹

A total of 29 genes implicated in different biological pathways, including complement activation, apoptosis, cell activation, and/or leucocyte stimulation, were studied. Genes for which RNA expression was associated with disease progression were analyzed for protein expression by immunofluorescence and compared with controls.¹

Upon analysis, IgAN patients had a distinct gene expression profile with decreased expression in IL-6 (P = .0076), INFG (P = .0175), and C1QB (P = .0180) compared to ANCA patients. Further assessment of biopsies from patients with IgAN and a high degree of fibrosis revealed C3 and TNFRSF1B exhibited a significant upregulation of protein expression compared to control tissue.¹

From NanoString mRNA expression profiles, investigators observed significant increases in PTEN (P = .0084), CASPASE 3 (P = .0106), TGM2 (P = .0413), TGFB1 (P = .0087), IL2 (P = .0247), and TNFRSF1B (P = .0097) among IgAN patients with level 2 fibrosis compared to those with none.¹

Investigators called attention to the small number of cases reducing the power of the study and the chances of finding statistically significant differences in the distribution of biomarkers with the NanoString technology. They also pointed out another potential limitation regarding the number of candidate genes examined.¹

“Our study validates the use of the NanoString technology as a promising tool for gene expression analysis in IgAN. Utilizing this innovative platform, we could simultaneously study multiple inflammatory biomarkers involved in IgAN and identify their activation patterns. We also validated the activation of genes known to contribute to kidney fibrosis, shedding light on the underlying mechanisms of disease progression,” investigators concluded.¹

References:

1. ^{Gaumond L, Lamarche C, Beauchemin S, et al. Identification of inflammatory biomarkers in IgA nephropathy using the NanoString technology: a validation study in Caucasians. Inflamm. Res. https://doi.org/10.1007/s00011-023-01848-3}
2. ^{National Kidney Foundation. IgA Nephropathy (Berger Disease). Accessed February 9, 2024. https://www.kidney.org/atoz/content/iganeph}