Transcriptome Analysis in Idiopathic Nephrotic Syndrome: Steroid Responsiveness

Overview

Idiopathic nephrotic syndrome (INS) affects the glomerular barrier by damaging the podocytes with foot process effacement, leading to a pathological increase of permeability and protein loss. INS classification is based on the clinical response to glucocorticoid (GC) therapy. When GCs treatment fails to induce remission in a four-six weeks course, patients are defined as affected with steroid-resistant nephrotic syndrome (SRNS). The whole transcriptome sequencing could consent the INS classification at onset, prior to glucocorticoids (GCs) treatment, allowing to reduction of unuseful GCs treatment. RNA sequencing technologies allow an extensive characterization of the transcriptomic profile and permit global changes in gene expression levels between different conditions such as active and remission of the disease. Of great interest is the research of a molecular biomarker to predict steroid resistance, a predictor that is not yet available. Among the candidate biomarkers, pharmacogenomic determinants are promising, even if available studies are still limited. Among these, some epigenetic factors have been previously suggested. Data obtained in animal models suggests that nucleotide-binding oligomerization domain-like receptors (NOD-like receptor) pyrin domain containing 3 (NLRP3) inflammasome can be deregulated in a wide variety of glomerular diseases, including those causing INS. Another potential marker involved in steroid response is the long noncoding RNA GAS5. Data reported in the literature indicate that abnormal levels of GAS5 in peripheral blood mononuclear cells (PBMCs) may alter steroid effectiveness in autoimmune diseases, such as inflammatory bowel disease. Preliminary findings show that the study of NLRP3 promoter methylation could be reduced in the blood of SRNS compared with steroid-sensitive nephrotic syndrome (SSNS) patients. Moreover, unpublished encouraging results on the association between Growth Arrest Specific 5 (GAS5) expression and steroid response in INS in PBMCs were obtained in a preliminary study conducted on 8 patients with the first episode of INS. PBMCs were obtained and GAS5 gene expression was evaluated using TaqMan technology. Patients affected with SRNS presented significantly higher levels of GAS5 in comparison with the SSNS group. In PBMCs from SRNS patients, the GAS5 expression could reduce the availability for binding to GCs target genes of the activated GCs receptor and suppresses GC transcriptional activity.