Transcriptomic and proteomic profiling reveal insights of mesangial cell function in patients with IgA Nephropathy

IgA nephropathy (IgAN) is the most common glomerulonephritis in the world. The disease is characterized by galactose deficient IgA (gd-IgA) in the circulation forming immune complexes. The complexes are deposited in the glomerular mesangium leading to inflammation and loss of renal function, but the pathophysiology of the disease is still not fully understood. Using an integrated global transcriptomic and proteomic profiling approach we investigated the role of the mesangium in the onset and progression of IgAN. Global gene expression was investigated by microarray analysis of the glomerular compartment of renal biopsies from patients with IgAN. The influence of galactose deficient IgA (gd-IgA) on mesangial cells was investigated by proteomic profiling. By utilizing the previous published literature curated glomerular cell type-specific genes, we found that mesangial cells and their positive standard genes play a more dominant role in IgAN comparing to the podocyte standard genes. Additionally, the patient clinical parameters (serum creatinine values and estimated glomerular filtration rate - eGFR) significantly correlate with z-scores derived from expression profile of mesangial cell positive standard genes. 22 common pathways were identified both from in vivo microarray data and in vitro mesangial cell mass spectrometry data and the main part was inflammatory pathways. The correlation between clinical data and mesangial standard genes allows for a better understanding of the onset of IgAN. The genes, proteins and their corresponding pathways identified in this paper give us novel insights into the pathophysiological mechanisms leading to progression of IgAN.

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Liu P, Lassén E, Nair V, Berthier CC, Suguro M, Sihlbom C, Kretzler M, Betsholtz C, Haraldsson B, Ju W, Ebefors K, Nyström J