Serum miR-192 Is Related to Tubulointerstitial Lesion and Short-Term Disease Progression in IgA Nephropathy

Clinical manifestation and renal histology serve as the current "gold standard" for evaluation of renal lesions in IgA nephropathy. MiR-192 is regarded as a potential noninvasive biomarker for kidney disease. We sought to elucidate a relationship between intrarenal, serum, and urinary exosomal miR-192 with renal lesions and disease progression in IgA nephropathy.

Serum and urinary exosomal miR-192 were detected and correlated with clinical and pathological parameters from consecutive IgA nephropathy patients (n = 50) and healthy control patients (n = 25). Patients then received a follow-up of 24 months after biopsy. Disease progression was defined as a 40% reduction in estimated glomerular filtration rate. Expression of miR-192 was quantified by Taqman RT-PCR. Intrarenal -miR-192 was detected in 8 IgA nephropathy patients and 4 matched patients receiving kidney nephrectomy as controls via in situ hybridization. TGF-β1 and E-cadherin expression in renal tissue was evaluated using immunohistochemistry.

Intrarenal miR-192 was correlated with serum miR-192 (r = 0.690, p = 0.013). Both intrarenal and serum miR-192 decreased in IgA nephropathy patients and were correlated with estimated glomerular filtration ratio. Patients with lower intrarenal and serum miR-192 levels had a higher interstitial fibrosis and tubular atrophy score, more severe lesions in tubular atrophy, and interstitial inflammation. Renal E-cadherin expression was correlated (r = 0.484, p = 0.004) and TGF-β1 was inversely correlated (r = -0.527, p < 0.001) with serum miR-192 in IgA. Patients with higher serum miR-192 had a lower disease progression rate over the course of 2 years (0 vs. 16%, p = 0.028). No correlation was found in urinary exosomal miR-192 with the clinical and pathological parameters mentioned earlier.

Lower serum miR-192 in IgA nephropathy patients indicates lower intrarenal miR-192 expression, more severe tubular atrophy, interstitial inflammation, and fibrotic tendency (with higher TGF-β and E-cadherin in renal miR-192). IgA nephropathy patients with higher serum miR-192 are less likely to have renal function decline over the course of 2 years.