Abstract
Systemic lupus erythematosus (SLE) is a multisystem autoimmune disorder; lupus nephritis (LN) is the main cause of disability and death in SLE patients. Although long noncoding RNAs (lncRNAs) lack a protein-coding ability, they have a significant role in the regulation of gene expression. We aimed to evaluate cell-free lncRNAs (NEAT2, CTC-471 J1.2 and Inc-DC) as biomarkers for SLE and LN. Quantification of the expression level of cell-free lncRNAs (NEAT2, CTC-471J1.2 and lnc-DC) was performed by real-time PCR in 90 controls and 139 patients with SLE, who were further subdivided into 70 patients with LN and 69 patients without LN. The expression levels of the NEAT2 and Inc-DC genes were significantly up-regulated and that of the CTC-471J1.2 gene was down-regulated in patients with SLE versus controls. Additionally, NEAT2 showed the best performance to differentiate SLE patients from controls, with a sensitivity of 92% and a specificity of 89%. To predict the future development of LN, CTC-471J1.2 showed the highest sensitivity (87%) and specificity (90%). A significantly positive correlation was found between Inc-DC expression and the activity of SLE (as assessed by the SLEDAI score) in LN patients, and a negative correlation was found between CTC471J1.1 expression and the SLEDAI score in both SLE subgroups. We concluded that cell-free NEAT2 is the most sensitive biomarker for SLE diagnosis and that circulating CTC-471J1.2 is the most specific and sensitive diagnostic biomarker for LN. Both lnc-DC and CTC-471J1.2 could be considered predictive biomarkers for SLE activity and LN development.