Urinary Transglutaminase 2 as a Biomarker for Kidney Allograft Fibrosis

After an informed consent is obtained, urine specimens will be collected prospectively before kidney transplantation (if available) and 3rd and 7th day, 1st, 3rd, and 6th month post-transplant. About 35\~50ml of urine sample is collected from each patient. For each urine specimen, 0.5 ml of a protease inhibitor mixture (5mM 4-(2-animoethyl) benzensulfonyl fluoride hydrolchloride, 2 μM Leupeptin-hemisulfate, and 3.3 mM Sodium azide) is added. To remove urinary sediments including whole cells, large membrane particles, and other debris, urine specimens are centrifuged at a rate of 4000 rpm for 15 minutes at 4 ℃. An aliquot of supernatant is stored at -80 ℃ until use. Urinary biomarkers including transglutaminase 2 are quantified using ELISA or CBA. In addition, urinary exosomes are isolated and analyzed. When a for-cause biopsy is done for some patients, the correlation between biomarkers and pathologic diagnosis will be assessed.