Urine podocyte mRNAs mark progression of renal disease.
Because loss of podocytes associates with glomerulosclerosis, monitoring podocyte loss by measuring podocyte products in urine may be clinically useful. To determine whether a single episode of podocyte injury would cause persistent podocyte loss, we induced limited podocyte depletion using a diphtheria toxin receptor (hDTR) transgenic rat. We monitored podocyte loss by detecting nephrin and podocin mRNA in urine particulates with quantitative reverse transcriptase-PCR. Aquaporin 2 mRNA served as a kidney reference gene to account for variable kidney contribution to RNA amount and quality. We found that a single injection of diphtheria toxin resulted in an initial peak of proteinuria and podocyte mRNAs (podocin and nephrin) followed 8 d later by a second peak of proteinuria and podocyte mRNAs that were podocin positive but nephrin negative. Proteinuria that persisted for months correlated with podocin-positive, nephrin-negative mRNAs in urine. Animals with persistent podocyte mRNA in urine progressed to ESRD with global podocyte depletion and interstitial scarring. Podocytes in ectatic tubules expressed podocalyxin and podocin proteins but not nephrin, compatible with detached podocytes' having an altered phenotype. Parallel human studies showed that biopsy-proven glomerular injury associated with increased urinary podocin:aquaporin 2 and nephrin:aquaporin 2 molar ratios. We conclude that a single episode of podocyte injury can trigger glomerular destabilization, resulting in persistent podocyte loss and an altered phenotype of podocytes recovered from urine. Podocyte mRNAs in urine may be a useful clinical tool for the diagnosis and monitoring of glomerular diseases.
Sato
Yuji
Y
University of Michigan Health System, Division of Nephrology, Ann Arbor, MI 48109-0676, USA.
Wharram
Bryan L
BL
Lee
Sang Koo
SK
Wickman
Larysa
L
Goyal
Meera
M
Venkatareddy
Madhusudan
M
Chang
Jai Won
JW
Wiggins
Jocelyn E
JE
Lienczewski
Chrysta
C
Kretzler
Matthias
M
Wiggins
Roger C
RC
D000818:Animals; D030801:Animals, Genetically Modified; D051399:Aquaporin 2 / Q000235:genetics; D015415:Biomarkers; D018450:Disease Progression; D005260:Female; D066257:Heparin-binding EGF-like Growth Factor; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics; D007673:Kidney Cortex Necrosis / Q000235:genetics / Q000473:pathology*; D007674:Kidney Diseases / Q000235:genetics* / Q000473:pathology*; D007676:Kidney Failure, Chronic / Q000235:genetics / Q000473:pathology; D007678:Kidney Glomerulus / Q000473:pathology*; D008297:Male; D050199:Podocytes / Q000473:pathology*; D011507:Proteinuria / Q000235:genetics / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics / Q000652:urine*; D051381:Rats; D012016:Reference Values
C496025:Aqp2 protein, rat; D051399:Aquaporin 2; D015415:Biomarkers; C587883:HBEGF protein, human; C587885:Hbegf protein, rat; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D012333:RNA, Messenger