#5492 TRANSCRIPTOME ANALYSIS IN LUPUS NEPHRITIS: DIFFERENCES IN GENE EXPRESSION BETWEEN DIAGNOSIS AND RENAL REMISSION IN KIDNEY TISSUE

Abstract

Abstract Background and Aims Transcriptome analysis in kidney tissue from lupus nephritis patients (LN) provide useful information about gene expression. We designed a pilot study in paraffin-embedded kidney tissue (FFPE) from LN patients to evaluate differences between gene expression at diagnosis (kidney biopsy diagnosis) and 2 years after achieve a complete renal response (protocol kidney biopsy). We evaluated if transcriptome analysis results could be verified through immunofluorescence staining (IF) in kidney biopsies (diagnosis biopsy vs protocol biopsy). Method We included diagnosis and protocol biopsies from 16 LN patients with class III and/or IV. All patients received prednisone (0.5 mg/kg) plus mycophenolic acid. Complete renal remission was defined as normal renal function, uPCOR < 300 mg/gr and inactive urine sediment. RNA Sequencing (RNA-Seq) was performed in FFPE, Human MSigDB Collections were used for gene enrichment analysis and Gene sets derived from the Biological Process Gene Ontology (GO) V7.2 is the library used in the study. Results 16 LN patients were included, Class III (43.8%), Class IV (43.8%) and Mixed Class (12.5%). 100% patients were women and Caucasian with mean age 40.9±7.1 years. RNA-Seq showed 2 overexpressed groups of genes (GO) in diagnosis biopsies, expression of this GO was not detected in protocol biopsies: GO-Complement_activation (NES 2.26, p = 4.2E -0.5): Properdin, Ficolin, C3, Factor B, C3AR1, C4 y CDC59. GO- Humoral_Inmune_Response_Mediated_Circulating_Inmunoglobulin (NES 2.10, p = 7,6E -0.6): IgG1, IgG2, IgA, chemokine receptors 2 y 7 and receptor 13 TNF. Results were verified using IF staining in kidney biopsies, in protocol biopsies were observed a significant reduction in C1q and C3 complement proteins staining: C1q (78% vs 22.2%, p = 0,006), C3 (73.3% vs 27.8%, p = 0.005); results in immunoglobulins staining also agree with transcriptome analysis results, so that we observed significant reduction in IgA and IgG: IgG (69% vs 36.4%, p = 0.009) and IgA (83.3% vs 16.7%, p = 0.02) while IgM staining not showed differences between diagnosis biopsy and protocol biopsy (43.8% vs 45.5%). Conclusion Transcriptome analysis in kidney tissue from LN patients, identified complement proteins and humoral mediators overexpressed at LN diagnosis and infraexpressed at complete renal remission; the results could help nephrologist to investigate the role of these protein as LN biomarkers.