Introduction: The pathophysiology of congenital obstructive uropathy has been studied intensively in several animal models. A reliable parameter for early detection of relevant obstruction is not yet identified. For further investigation of the complex regulatory events of obstructive uropathy, we used a cDNA microarray technology for a parallel differential expression analysis of about 15000 different genes of obstructed, contralateral and healthy kidneys of rats with spontaneous congenital obstructive uropathy.
Methods: Total cellular RNA of obstructed, contralateral and healthy control kidneys of 32-35 days old rats was extracted and pooled. RNA quality and quantity was assessed using a Bioanalyzer 2100. mRNA expression for selected marker genes was assessed by real time PCR. High throughput gene expression profiling was performed with cDNA microarrays with differentially labeled cDNA targets.
Results: Beside expected typical alterations of several growth factors such as TGF-beta, EGF, IGF-1, PDGF, we observed overexpression of extracellular matrix proteins and a decreased activity of antioxidant enzymes. Additionally, NFkappaB, a nuclear transcription factor involved in the development of interstitial fibrosis, was slightly up-regulated in the obstructed kidneys. Down-regulation of genes involved in tubular sodium transport indicated impaired concentration ability of the obstructed kidneys. Furthermore, we found up-regulation of pro-apoptotic genes including transcripts for the proapoptotic protein Siva. Interestingly, TNFalpha, another factor involved in the pathophysiology of congenital obstructive uropathy, was not differentially regulated.
Conclusions: The alterations of the genes for growth factors, extracellular matrix proteins, antioxidant enzymes, sodium transport and genes involved in apoptosis support the representative character of this animal model for congenital obstructive uropathy. In the rather advanced stage of congenital renal obstruction a possible explanation of the lacking differential regulation of TNFalpha highlights it as a possible marker of earlier stages of obstruction. Furthermore, the possible involvement of the Siva/CD27 pathway in the apoptotic cascade also offers a new possibility to find a sensitive marker to detect renal obstruction already in an earlier stage.