Transcriptional response in the unaffected kidney after contralateral hydronephrosis or nephrectomy.

BACKGROUND: Unilateral loss of kidney function is followed by compensatory contralateral growth. The early, genome-wide transcriptional response of the untouched kidney to unilateral ureteral obstruction (UUO) or unilateral nephrectomy is unknown. METHODS: Twelve adult male Sprague-Dawley rats were subjected to UUO and twelve rats to unilateral nephrectomy. At time points 12, 24, and 72 hours after insult four rats each were sacrificed and the contralateral kidney harvested for genome-wide gene expression analysis, transcription factor analysis, and histomorphology. RESULTS: Microarray studies revealed that the majority of differentially expressed transcripts were suppressed in UUO and unilateral nephrectomy compared to control kidneys. The function of these suppressed genes is predominantly growth inhibition and apoptosis suggesting a net pro-hypertrophic response. Insulin-like growth factor-2 (IGF-2)-binding protein was one of the few activated genes. We observed a distinctly different molecular signature between UUO and unilateral nephrectomy at the three time points investigated. The early response in UUO rats suggests a counterbalance to the nonfiltering kidney by activation of transport pathways such as the aquaporins. Unilateral nephrectomy kidneys, on the other hand, respond immediately to contralateral nephrectomy by activation of cell cycle regulators such as the cyclin family. Several genes with weakly defined function were found to be associated with either UUO or unilateral nephrectomy. Transcription factor analysis of the identified transcripts suggests common regulation at least of some of these genes. All kidneys showed normal histology. CONCLUSION: Release of growth inhibition by nephrectomy leads to immediate cell cycle activation after unilateral nephrectomy, whereas UUO kidneys counterbalance filtration failure by activation of several transporters.

Alterations in gene expression in cadaveric vs. live donor kidneys suggest impaired tubular counterbalance of oxidative stress at implantation.

Recipients of live donor transplant kidneys (LIV) exhibit a significantly longer allograft half-life compared with cadaveric donor organs (CADs). The reasons are incompletely understood. Therefore this study sought to elucidate the genome-wide gene expression profiles in microdissected transplant kidney biopsies obtained from five cadaveric and five matched live donors before transplantation. cDNA microarrays were used to determine the transcripts in isolated glomeruli (G) and the tubulointerstitial (TI) compartment. Data were subjected to hierarchical clustering, maxT adjustment and a jackknife procedure to ensure robustness of reported findings; validation was performed by independent analysis of split biopsies and TaqMan-PCR. One hundred and thirteen sequences representing 62 unique genes (17 redundant features), and 34 ESTs separated G from TI. No difference in gene expression was found in G between LIV and CAD kidneys, but nine genes (two represented twice) and three ESTs were abundantly expressed in the CAD TI compared with LIV. The main biological function of these genes is counter regulation of oxidative stress. Promoter analysis of significant features suggested coregulated gene groups. These data suggest that CAD kidneys exhibit a distinctly different set of transcripts in the TI compartment but not in the G compartment when compared with LIV kidneys.

Genome-wide gene-expression patterns of donor kidney biopsies distinguish primary allograft function.

Roughly 25% of cadaveric, but rarely living donor renal transplant recipients, develop postischemic acute renal failure, which is a main risk factor for reduced long-term allograft survival. An accurate prediction of recipients at risk for ARF is not possible on the basis of donor kidney morphology or donor/recipient demographics. We determined the genome-wide gene-expression pattern using cDNA microarrays in three groups of 36 donor kidney wedge biopsies: living donor kidneys with primary function, cadaveric donor kidneys with primary function and cadaveric donor kidneys with biopsy proven acute renal failure. The descriptive genes were characterized in gene ontology terms to determine their functional role. The validation of microarray experiments was performed by real-time PCR. We retrieved 132 genes after maxT adjustment for multiple testing that significantly separated living from cadaveric kidneys, and 48 genes that classified the donor kidneys according to their post-transplant course. The main functional roles of these genes are cell communication, apoptosis and inflammation. In particular, members of the complement cascade were activated in cadaveric, but not in living donor kidneys. Thus, suppression of inflammation in the cadaveric donor might be a cheap and promising intervention for postischemic acute renal failure.

Impaired tubulointerstitial expression of endothelin-1 and nitric oxide isoforms in donor kidney biopsies with postischemic acute renal failure.

BACKGROUND: About 30% of cadaveric renal allografts, but almost never living-donor kidneys, develop postischemic acute renal-transplant failure (ARF). We therefore quantified the expression of essential reperfusion regulators in different compartments of cadaveric and living-donor kidney biopsies. METHODS: Specimens were obtained from donor kidneys at the end of the cold ischemia time before implantation and categorized into three groups according to donor source and early posttransplant function. Ten living-donor biopsies (LIV) were compared with nine cadaveric kidney biopsies (CAD) with primary posttransplant function (CAD-PF) and to nine with ARF (CAD-ARF). Laser capture microdissection was used to isolate glomeruli from tubulointerstitium. The gene expression of intercellular adhesion molecule (ICAM)-1, interleukin (IL)-1beta, endothelin (ET)-1, inducible nitric oxide synthase (iNOS), and endothelial nitric oxide synthase (eNOS) was quantified in glomeruli and tubulointerstitium by real-time polymerase chain reaction (TaqMan). RESULTS: Tubulointerstitial areas of all CAD kidneys revealed significantly lower mRNA levels of all investigated genes compared with LIV. Tubulointerstitial ET-1, iNOS, and eNOS in CAD-ARF averaged only half of the expression in CAD-PF kidneys. ICAM-1 and IL-1beta mRNA concentrations were equal in CAD-PF and CAD-ARF. Glomerular expression of the investigated genes was equal in CAD and LIV kidneys with the exception of ICAM-1 and ET-1, which were two times higher in CAD-PF compared with LIV and CAD-ARF. CONCLUSION: These data suggest that CAD compared with LIV kidneys have an impaired expression of immune and vasoregulatory genes in the tubulointerstitium, which may represent reduced cellular vitality and capacity to adaptation. The observed further reduction of ET-1, iNOS, and eNOS expression in CAD-ARF might contribute to reperfusion injury and delayed allograft function.