Pyong-Gon Moon^1,2, Jeong-Eun Lee^1,2, Sungyong You³, Taek-Kyun Kim³, Ji-Hoon Cho³, In-San Kim^2,4, Tae-Hwan Kwon^2,4, Chan-Duck Kim⁵, Sun-Hee Park⁵, Daehee Hwang³, Yong-Lim Kim⁵ and Moon-Chang Baek^1,2,*

¹ Department of Molecular Medicine, School of Medicine, Kyungpook National University, Daegu, Republic of Korea
² Cell and Matrix Biology Research Institute, School of Medicine, Kyungpook National University, Daegu, Republic of Korea
³ School of Interdisciplinary Bioscience and Bioengineering and Department of Chemical Eng., POSTECH, Pohang, Republic of Korea
⁴ Department of Biochemistry and Cell Biology, School of Medicine, Kyungpook National University, Daegu, Republic of Korea
⁵ Department of Internal Medicine, Kyungpook National University Hospital, Daegu, Republic of Korea

^*Correspondence: Professor Moon-Chang Baek, Department of Molecular Medicine, School of Medicine, Kyungpook National University, 101 Dongin-dong 2 Ga, Jung-gu, Daegu, 700-422, Republic of Korea

To identify biomarker candidates associated with early IgA nephropathy (IgAN) and thin basement membrane nephropathy (TBMN), the most common causes presenting isolated hematuria in childhood, a proteomic approach of urinary exosomes from early IgAN and TBMN patients was introduced. The proteomic results from the patients were compared with a normal group to understand the pathophysiological processes associated with these diseases at the protein level. The urinary exosomes, which reflect pathophysiological processes, collected from three groups of young adults (early IgAN, TBMN, and normal) were trypsin‐digested using a gel‐assisted protocol, and quantified by label‐free LC‐MS/MS, using an MSE mode. A total of 1877 urinary exosome proteins, including cytoplasmic, membrane, and vesicle trafficking proteins, were identified. Among the differentially expressed proteins, four proteins (aminopeptidase N, vasorin precursor, α‐1‐antitrypsin, and ceruloplasmin) were selected as biomarker candidates to differentiate early IgAN from TBMN. We confirmed the protein levels of the four biomarker candidates by semi‐quantitative immunoblot analysis in urinary exosomes independently prepared from other patients, including older adult groups. Further clinical studies are needed to investigate the diagnostic and prognostic value of these urinary markers for early IgAN and TBMN. Taken together, this study showed the possibility of identifying biomarker candidates for human urinary diseases using urinary exosomes and might help to understand the pathophysiology of early IgAN and TBMN at the protein level.

Keywords : Biomarker, Biomedicine, Exosomes, IgA nephropathy, Thin basement membrane nephropathy