Microarray analysis of changes in renal phenotype in the ethylene glycol rat model of urolithiasis: potential and pitfalls.
OBJECTIVE
To investigate, in an initial study, the use of microarray analysis (MA) to develop an information base for urolithiasis. MA enables the screening of thousands of genes simultaneously making it the technique of choice for situations where the results are known, but the underlying mechanisms are not. Little is known about the pathological changes occurring in the kidney during urolithiasis and this has severely hampered efforts to develop effective therapeutics.


METHODS
Male rats were treated with 0.75% ethylene glycol for 2, 4 or 8 weeks; after death the kidneys were processed for RNA isolation and MA, conducted using a rat-based chip (one kidney/chip) and the results confirmed by reverse transcription-polymerase chain reaction (RT-PCR, 21 probe sets; control, four rats; treated, five rats). Targets were defined as different by the software if the fold change (FC) was >or= 2, and sorted into functional categories using a data-mining tool. The repeatability of MA was investigated by subjecting the 4-week samples to MA in two independent runs.


RESULTS
The results for targets with a FC of >or= 2 were plotted (y = 1.01x - 0.75; r(2) 0.84). Comparing the results obtained by RT-PCR and MA showed a good qualitative correlation for those targets having a FC of >or= 5 as determined by MA. Changes in the expression of genes associated with tubule function and regulation, oxidative damage, and inflammation were the most common in the functional categories. Changes in the expression of tubule-specific markers indicated that there was damage to the proximal (gamma-adducin, organic anion and cation transporters, sodium-hydrogen exchange protein-isoform 3) and distal tubules (gamma-adducin, kallikrein) at 2 and 4 weeks. Increased expression of mitochondrial uncoupling protein indicated that there were changes to the mitochondria and oxidative stress at 2 and 4 weeks.


CONCLUSIONS
This study shows the power of MA as an exploratory technique, and changes in the expression of several physiologically important genes whose expression has not previously been reported to be affected by hyperoxaluria or calcium oxalate crystalluria.
The James and Eilleen Dicke Research Laboratory, Department of Urology, School of Medicine, Case Western Reserve University/University Hospitals of Cleveland, Cleveland, Ohio 44106-4931, USA.
Daniel H-C
DH
Chen
Hue-Lee C
HL
Kaung
Casey M
CM
Miller
Martin I
MI
Resnick
Susan R
SR
Marengo
D000818:Animals; D019855:Ethylene Glycol / Q000633:toxicity*; D007669:Kidney Calculi / Q000139:chemically induced / Q000235:genetics*; D008297:Male; D010641:Phenotype; D040081:Protein Array Analysis / Q000379:methods; D012313:RNA / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods
D012313:RNA; D019855:Ethylene Glycol