Nephrolithksis is a result of crystal formation and retention within the kidneys. Several studies have shown that conditions are favorable for the formation of calcium phosphate (CaP) in early segments of the nephron namely proximal tubules and the loops of Henle. It is proposed that CaP formed in early segments promote nucleation of calcium oxalate (CaOx) in the collecting ducts. Renal epithelial cells exposed to non-physiologically high levels of oxakte and/or CaOx crystals experience both structural and functional changes, which may eventually lead to cell injury and death. These changes also promote crystal attachment to cell surfaces and retention within the renal tubules. As a protective response, CaOx crystals are often endocytosed at the luminal side and exocytosed into die interstitium where they are processed by the inflammatory defense indicated by the presence of monocytes, macrophages and giant cells. Interestingly CaP crystals seen in the renal interstitium do not induce an inflammatory response. Even though CaP is considered the primary crystal and crystal induced changes in epithelial cells are essential for crystal retention, studies have yet to investigate crystal cell interactions between CaP and renal epithelial cells. CaP has also been shown to dissolve in the acidic environment of the collecting ducts. It is our hypothesis that crystals formed in the urine contain a surface coat, which inhibits crystal dissolution. We also hypothesize that similar to CaOx crystals, an exposure to crystals of CaP also challenges the cells and leads to alterations in renal epithelial cells, which promote crystal retention. We propose to test our hypotheses by exposing proximal tubular origin HK-2 and collecting duct origin MDCK cells to CaP crystals in culture. Two forms of CaP, inorganic apatite and brushite as well as apatite and brushite coated with urinary macromolecules will be used. In addition we propose to investigate the interaction between CaP crystals and renal interstitial fibroblasts to find out why renal interstitial CaP deposits do not cause inflammation. We have the following Specific Aims. 1. To confirm that CaP crystals coated with urinary macromolecules, are resistant to dissolution and good nucleators of CaOx in acidic environment of collecting ducts. 2. To probe that exposure to CaP crystals is associated with renal epithelial cellular injury and that exposure of renal epithelial cells to CaP crystals causes free radical production and lipid peroxidation. 3. To show that production by renal epithelial cells of crystallization modulators such as osteopontin (OPN) and bikunin and a-1 microglobulin is upregulated on exposure to CaP crystals. 4. To demonstrate that CaOx crystal adherence to renal epithelial cells is increased by their previous exposure to CaP crystals and nucleation of CaOx crystals is promoted by surface membranes of the cells pre-exposed to CaP crystals. 5. To determine the molecular mechanism for the inability of renal interstitial CaP crystals to provoke an inflammatory reaction.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK065658-02
Application #
7049392
Study Section
Urologic and Kidney Development and Genitourinary Diseases Study Section (UKGD)
Program Officer
Rasooly, Rebekah S
Project Start
2005-04-01
Project End
2009-03-31
Budget Start
2006-04-01
Budget End
2007-03-31
Support Year
2
Fiscal Year
2006
Total Cost
$230,827
Indirect Cost
Name
University of Florida
Department
Pathology
Type
Schools of Medicine
DUNS #
969663814
City
Gainesville
State
FL
Country
United States
Zip Code
32611
Vincent, Charles R; Thomas, Tami L; Reyes, Leticia et al. (2013) Symptoms and risk factors associated with first urinary tract infection in college age women: a prospective cohort study. J Urol 189:904-10
Khan, Saeed R; Rodriguez, Douglas E; Gower, Laurie B et al. (2012) Association of Randall plaque with collagen fibers and membrane vesicles. J Urol 187:1094-100
Khan, Saeed R; Canales, Benjamin K (2011) Ultrastructural investigation of crystal deposits in Npt2a knockout mice: are they similar to human Randall's plaques? J Urol 186:1107-13
Khan, Saeed R; Glenton, Patricia A (2010) Experimental induction of calcium oxalate nephrolithiasis in mice. J Urol 184:1189-96
Khan, Saeed R; Canales, Benjamin K (2009) Genetic basis of renal cellular dysfunction and the formation of kidney stones. Urol Res 37:169-80
Khaskhali, Muhammad H; Byer, Karen J; Khan, Saeed R (2009) The effect of calcium on calcium oxalate monohydrate crystal-induced renal epithelial injury. Urol Res 37:1-6
Canales, Benjamin K; Higgins, LeeAnn; Markowski, Todd et al. (2009) Presence of five conditioning film proteins are highly associated with early stent encrustation. J Endourol 23:1437-42
Escobar, Carla; Byer, Karen J; Khaskheli, Hassan et al. (2008) Apatite induced renal epithelial injury: insight into the pathogenesis of kidney stones. J Urol 180:379-87
Khan, Saeed R; Glenton, Patricia A (2008) Calcium oxalate crystal deposition in kidneys of hypercalciuric mice with disrupted type IIa sodium-phosphate cotransporter. Am J Physiol Renal Physiol 294:F1109-15
Khan, Saeed R; Glenton, Patricia A; Byer, Karen J (2007) Dietary oxalate and calcium oxalate nephrolithiasis. J Urol 178:2191-6

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