Supplementary Material for: Kidney Injury Molecule-1 and Periostin Urinary Excretion and Tissue Expression Levels and Association with Glomerular Disease Outcomes

<b><i>Introductions:</i></b> Kidney injury molecule-1 (KIM-1) and periostin (POSTN) are proximal and distal tubule injury biomarkers. We tested whether baseline urine KIM-1/Cr (uKIM-1/Cr) and/or uPOSTN/Cr correlated with disease severity or improved a remission prediction model. <b><i>Methods:</i></b> Baseline uKIM-1/Cr and uPOSTN/Cr were measured on spot urine samples from immunosuppression-free patients enrolled in Nephrotic Syndrome Study Network until December 15, 2014. Urine protein/Cr (UPCR) and albumin/Cr (UACR) were measured at baseline, 4 months, and until last follow-up. Glomerular and tubulointerstitial (TI) expression arrays were analyzed from a baseline research renal biopsy core collected during a clinically indicated biopsy. Renal diagnoses were centrally confirmed, sections scanned, and measured morphometrically. Correlations between baseline uKIM-1/Cr and uPOSTN/Cr and UPCR, UACR, histopathologic features, glomerular and TI KIM-1 and POSTN expression levels, and renal outcomes were assessed. <b><i>Results:</i></b> Baseline uKIM-1/cr correlated with UPCR and UACR and were associated with complete remission (CR) after adjustment for proteinuria, histopathologic diagnosis, and treatment. Baseline uKIM-1/Cr also correlated with degree of foot process effacement and acute tubular injury. Glomerular and TI KIM-1 expression levels correlated with UPCR and UACR. Higher TI KIM-1 expression levels correlated with interstitial fibrosis, tubular atrophy, and global glomerulosclerosis, while glomerular KIM-1 expression correlated with time to remission. Findings for POSTN were of lesser statistical strength. <b><i>Discussion/Conclusion:</i></b> Lower baseline uKIM-1/Cr values were associated with more rapid time to CR after adjusting for proteinuria, histopathologic diagnosis, and treatment. Increased TI KIM-1 expression levels in proteinuric states were associated with chronic morphological injury; lower glomerular expression levels were associated with a greater potential for proteinuria reversibility.