Differential analysis of urinary albumin for membranous nephropathy patients by online capillary isoelectric focusing - Mass spectrometry.

Membranous nephropathy (MN) is one of the most common causes of primary glomerular diseases worldwide. The M-type phospholipase A2 receptor (PLA2R), an antigen expressed in more than 70% of cases of idiopathic membranous nephropathy (IMN), is a biomarker which is now used by physicians for clinical diagnosis. Despite the prevalence of PLA2R in the cases of MN, it is not always effective to use PLA2R for differentiating primary or secondary MNs. On the other hand, urinary albumin assay is one of the de facto tests for kidney function testing for several decades. In this work, urinary albumin species between primary and secondary MN patients are compared using a newly developed capillary isoelectric focusing - mass spectrometry (CIEF-MS) technology. The distinct patterns of cationic and acidic urinary albumin species, as revealed by this novel CIEF-MS technology, suggest potential applications of this differential analysis for subtyping of membranous nephropathy. Further investigation of these cationic human albumin species in urine may provide clues to the disease onset and development of MN, thus facilitating treatment. In addition, this novel workflow of using CIEF-MS for urinary protein analysis may be beneficial to the research, pathology, prognosis, and diagnosis of many other types of kidney diseases, such as chronic kidney disease, diabetic nephrology, etc.