Project Summary/Abstract:
Urinary stone disease (USD) is third most common and painful 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 interactions between intrarenal crystal nucleation, growth, and
phagocytic cellular responses plays 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 cell
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 (Mf’s). Observations in experimental animal models and human tissues suggests
that renal tissue monocytes and Mf’s can phagocytose and metabolize crystals, and urinary stone formers
appear to have increased medullary M1 and decreased M2 Mf populations. In a hyperoxaluric mouse model,
suppression of monocyte to M2 Mf 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 Mf populations can phagocytose
and degrade crystals as a crystal clearance mechanism, and defects in these clearance mechanisms could
result in interstitial Randall’s plaque (RP) and collecting duct plugs (CDP) or even grow directly into USD. The
proposed research project is designed to evaluate the role of Mf’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/ Mf populations in carefully phenotyped ICSFs (20-70 years) with hydroxyapatite, brushite, and
calcium oxalate stones and 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 genesis and identify novel therapeutic targets.