Research Project

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Project Summary/Abstract: Urinary stone disease (USD) is the 3rd most common urological disease in men and women. Prevention of USD and its associated costs and morbidity requires an understanding of early and late USD pathogenesis. Emerging evidence suggests pathophysiological interactions between intrarenal crystal nucleation, growth, and phagocytic cellular responses may play a key but unrecognized role in USD. Studies in vitro demonstrate that calcium phosphate (CaP) and calcium oxalate (CaOx) crystals induce renal tubular and phagocytic cellular secretion of cytokines, chemokines, and extracellular vesicles (EVs; exosomes and microvesicles). These biomarkers can attract blood or residential monocytes and convert monocytes into pro (M1) or anti (M2)- inflammatory macrophages (Mφ ’s ). Observations in experimental animal models and human tissues suggest that renal tissue monocytes and Mφ ’s can phagocytose and metabolize intrarenal crystals, and urinary stone formers appear to have increased medullary M1 and decreased M2 Mφ populations. In a hyperoxaluric mouse model, suppression of monocyte to M2 Mφ conversion significantly increased intrarenal CaOx deposition. Our studies also demonstrated that urinary excretion of EVs bearing inflammatory markers derived from specific segments of renal tubules were significantly lower in idiopathic calcium stone formers (ICSFs) compared to controls. Thus, multiple lines of evidence suggest that tubular and monocyte derived Mφ populations can phagocytose and degrade crystals as a crystal clearance mechanism, and defects in these clearance mechanisms could promote interstitial Randall’s plaque (RP) and/or collecting duct plug (CDP) formation. The proposed research project is designed to evaluate the role of Mφ ’s in RP and CDP formation using a novel hypercalciuric claudin-2 global knockout mouse model (over 3-24 months age) that resembles the phenotype of patients with idiopathic hypercalciuria and USD (Aim 1), and to define the frequency and spatial distribution of monocyte/ Mφ populations in carefully phenotyped ICSFs (20-70 years) with hydroxyapatite, brushite, and calcium oxalate stones plus varying amounts of RP (Aim 2). The proposed innovative study will elucidate the role of renal medullary pro-and anti-inflammatory phagocytic cells in the development of RP, CDP, and USD and whether urinary cytokines, chemokines or EVs carrying biomarkers of pro-/anti-inflammatory phagocytic cells can be used to non-invasively monitor intrarenal crystal deposition. Completion of this study will also facilitate the formation of a skilled multidisciplinary team including a promising early-stage surgeon-scientist (Dr Kevin Koo) under the mentorship of an experienced and skilled USD clinical and researcher (Dr. Lieske). The resulting preliminary data will provide evidence of the effectiveness of our team. This work will also enable submission of future detailed grant or center proposals that will extend these mechanistic studies, and has great potential to elucidate underlying pathogenic steps in USD genesisto identify novel therapeutic targets.