Researchers from the INCLIVA Biomedical Research Institute in Valencia, Spain, together with collaborators, have shown that microRNAs (miRNAs) in the urine of patients with systemic lupus erythematosus (SLE) are found mainly in exosomes, and the most significant SLE-associate increase in a specific miRNA associated with SLE was found in miR-146a (100-fold increase) and this increase was specifically in patients with active lupus nephritis. Among the exosomal miRNAs tested, only the miR-146a discriminated the presence of active lupus nephritis. The research was published online on September 21, 2015 in PLOS ONE. The article was titled “Increased Urinary Exosomal MicroRNAs in Patients with Systemic Lupus Erythematosus.” In their work, the research team quantified specific miRNAs in the urine of patients with SLE (n = 38) and healthy controls (n = 12) by quantitative reverse-transcription PCR in cell-free urine, exosome-depleted supernatant, and exosome pellet obtained by ultracentrifugation. In the ontrol group, miR-335* and miR-302d were consistently higher in exosomes than in exosome-depleted supernatant, and miR-200c and miR-146a were higher in the cell-free fraction. In SLE patients, all urinary miRNAs tested were mainly in exosomes, with lower levels outside them (p<0.05 and p<0.01, respectively). The researchers noted that this pattern was especially relevant in patients with active lupus nephritis compared to the control group or to SLE patients in absence of lupus nephritis, with miR-146a being the most augmented (100-fold change, p<0.001). Among the exosomal miRNAs tested, only the miR-146a discriminated the presence of active lupus nephritis. The researchers concluded that urinary miRNAs are contained primarily in exosomes in SLE, and the main increment was found in the presence of active lupus nephritis.
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