title: Mass spectrometry as a novel method for detection of podocyturia in pre-eclampsia.
abstract: BACKGROUND
  Podocyturia, i.e. urinary loss of viable podocytes, may serve as a diagnostic tool for pre-eclampsia and as a marker of active renal disease. The current method to detect podocyturia is technically complex, lengthy and requires a high level of expertise for interpretation. The aim of this study was to develop a new technique for the identification of urinary podocytes, based on the detection of podocyte-specific tryptic peptides by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS), which will provide an operator-independent and highly reproducible method.
  
  
  RESULTS
  The diagnosis of pre-eclampsia was confirmed in the presence of hypertension (>140/90 mmHg) and proteinuria >0.3 g/24 h urine. The diagnosis of HELLP was confirmed based on the accepted clinical criteria of hemolysis, elevated liver enzymes and low platelet count. Random urine samples within 24 h prior to delivery were collected and centrifuged. One half of the sediment was cultured for 24 h to select for viable cells and then stained with a podocin antibody, followed by a secondary fluorescein isothiocyanate-labeled antibody to identify podocytes. The second half of the pellet was solubilized, digested and analyzed by LC-MS/MS using an internal standard. We have recruited 13 patients with pre-eclampsia and 6 patients with pre-eclampsia/HELLP syndrome. The presence of podocytes was confirmed in all patients by the podocyte culture method. In the respective samples, the presence of a podocin-specific tryptic peptide was confirmed with LC-MS/MS technology.
  
  
  CONCLUSIONS
  The LC-MS/MS method is a reliable technology for the identification of urinary podocytes, based on the presence of podocyte-specific proteins in the urine.
authors.affiliation: Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN, USA. Garovic.Vesna@Mayo.edu
authors.forename: Vesna D
authors.initials: VD
authors.lastname: Garovic
authors.forename: Iasmina M
authors.initials: IM
authors.lastname: Craici
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Wagner
authors.forename: Wendy M
authors.initials: WM
authors.lastname: White
authors.forename: Brian C
authors.initials: BC
authors.lastname: Brost
authors.forename: Carl H
authors.initials: CH
authors.lastname: Rose
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Grande
authors.forename: David R
authors.initials: DR
authors.lastname: Barnidge
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000652:urine*; D002853:Chromatography, Liquid; D005260:Female; D017359:HELLP Syndrome / Q000175:diagnosis* / Q000652:urine; D006801:Humans; D050199:Podocytes / Q000737:chemistry / Q000473:pathology*; D011225:Pre-Eclampsia / Q000175:diagnosis* / Q000652:urine; D011247:Pregnancy; D011379:Prognosis; D011507:Proteinuria / Q000175:diagnosis* / Q000652:urine; D053719:Tandem Mass Spectrometry
chemical_list: D015415:Biomarkers