Urinary mRNA and lupus disease flare

Urine soluble urokinase plasminogen activator receptor as a potential biomarker of lupus nephritis activity

There is a lack of non-invasive biomarkers to identify lupus nephritis (LN). Soluble urokinase plasminogen activator receptor (suPAR) is a sensitive biomarker of ongoing inflammation and a potential marker of podocyte dysfunction. The aim of this study was to assess urine and plasma suPAR in LN. 14 systemic lupus erythematosus (SLE) patients with newly diagnosed LN, 8 active SLE patients (SLEDAI >8) without LN and 31 healthy individuals were enrolled. Urine and plasma samples were taken before the initiation of LN induction therapy, and monthly thereafter. Global and renal disease activity were defined using the SLEDAI-2K and the SLEDAI-2K renal domain score, respectively. suPAR concentrations were measured with the suPARnostic Flex ELISA assay. Urine and plasma suPAR levels were elevated in SLE patients with active LN compared with resolved LN and healthy controls. Urine suPAR levels were comparable to healthy controls in active SLE without LN. Urine and plasma suPAR levels were higher before than after the initiation of LN induction therapy. Prospective follow-up measurements also suggested that urine suPAR levels raised again in patients with a relapse of LN according to SLEDAI-2K renal domain score, whereas plasma suPAR levels did not correlate with renal disease activity. Urine suPAR is a promising LN activity biomarker, given its isolated elevation in urine in active LN and pronounced decrease with LN improvement.

Urinary biomarkers in lupus nephritis

Systemic lupus erythematosus (SLE) is the prototypical autoimmune disease that can affect any organ of the body. Multiple mechanisms may contribute to the pathophysiology of systemic lupus, including failure to remove apoptotic bodies, hyperactivity of self-reactive B and T lymphocytes, abnormal exposure to autoantigens, and increased levels of B-cell stimulatory cytokines. The involvement of the kidney, called lupus nephritis (LN), during the course of the disease affects between 30% and 60% of adult SLE patients, and up to 70% of children. LN is an immune-mediated glomerulonephritis that is a common and serious finding in patients with SLE. Nowadays, renal biopsy is considered the gold standard for classifying LN, besides its degree of activity or chronicity. Nevertheless, renal biopsy lacks the ability to predict which patients will respond to immunosuppressive therapy and is a costly and risky procedure that is not practical in the monitoring of LN because serial repetitions would be necessary. Consequently, many serum and urinary biomarkers have been studied in SLE patients for the complementary study of LN, existing conventional biomarkers like proteinuria, protein/creatinine ratio in spot urine, 24 ​h urine proteinuria, creatinine clearance, among others and non-conventional biomarkers, like Monocyte chemoattractant protein-1 (MCP-1), have been correlated with the histological findings of the different types of LN. In this article, we review the advances in lupus nephritis urinary biomarkers. Such markers ideally should be capable of predicting early sub-clinical flares and could be used to follow response to therapy. In addition, some of these markers have been found to be involved in the pathogenesis of lupus nephritis.

Urinary biomarkers for lupus nephritis: the role of the vascular cell adhesion molecule-1

Renal involvement is one of the main complications of systemic lupus erythematosus, causing a significant impact on patients' morbidity and mortality. Renal biopsy is still the gold standard of diagnosis, but it has many limitations. In this sense, several recent studies aim to identify biomarkers that not only predict disease activity and renal histology, but also lead to earlier treatment. In previous studies, the soluble vascular cell adhesion molecule-1 measured in urine showed a strong association with the presence of lupus nephritis, with clinical and histological activity indexes of the disease and with more severe renal lesions. This paper reviews the main urinary biomarkers of lupus nephritis that have been studied, with special emphasis on vascular cell adhesion molecule-1 results.