title: Urinary crystallization inhibitors do not prevent crystal binding.
abstract: OBJECTIVE
  Renal stone formation requires the persistent retention of crystals in the kidney. Calcium oxalate monohydrate (COM) crystal binding to Madin Darby canine kidney strain I (MDCK-I), a cell line that resembles the epithelium in the renal distal tubule/collecting duct, is developmentally regulated, while LLC-PK1 cells (American Type Tissue Collection), which are widely used as a model of the renal proximal tubule, bind crystals irrespective of their stage of epithelial development. Whereas to our knowledge the binding molecules for COM at the surface of LLC-PK1 cells are still unknown, crystals adhere to the hyaluronan (HA) rich pericellular matrix transiently expressed by mobile MDCK-I cells. In the current study we investigated whether crystal binding to either cell type is influenced by urinary substances, including glycoprotein inhibitors of crystallization
  
  
  METHODS
  We studied crystal binding to MDCK-I cells during wound repair, to confluent LLC-PK1 cells and to HA immobilized on a solid surface using [14C] COM pretreated or not pretreated with urine from healthy male volunteers. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analysis were performed to assess whether the crystals became coated with urine derived proteins
  
  
  RESULTS
  Western blot analysis demonstrated that pretreated COM crystals were covered with protein inhibitors of crystallization. However, this protein coat had no significant effect on the level of crystal binding to either cell type. In contrast, the adherence of urine treated crystals to immobilized HA was significantly reduced
  
  
  CONCLUSIONS
  The adherence of crystals to pericellular matrixes may encompass more than their simple fixation to the polysaccharide HA. Calcium oxalate crystal retention is not prevented by coating crystals with urinary constituents such as glycoproteins and, therefore, may predominantly depend on the surface properties of the renal tubular epithelium.
authors.affiliation: Department of Urology, Erasmus University Rotterdam, Rotterdam, The Netherlands.
authors.forename: Marieke S J
authors.initials: MS
authors.lastname: Schepers
authors.forename: Burt G
authors.initials: BG
authors.lastname: van der Boom
authors.forename: Johannes C
authors.initials: JC
authors.lastname: Romijn
authors.forename: Fritz H
authors.initials: FH
authors.lastname: Schröder
authors.forename: Carl F
authors.initials: CF
authors.lastname: Verkoelen
mesh_terms: D000818:Animals; D002129:Calcium Oxalate / Q000494:pharmacology*; D002478:Cells, Cultured; D003460:Crystallization; D004285:Dogs; D006801:Humans; D006820:Hyaluronic Acid / Q000494:pharmacology*; D007668:Kidney / Q000166:cytology* / Q000187:drug effects*; D007669:Kidney Calculi / Q000209:etiology*; D018374:LLC-PK1 Cells / Q000187:drug effects*; D013552:Swine; D014556:Urine
chemical_list: D002129:Calcium Oxalate; D006820:Hyaluronic Acid