市野 学

Purpose: Renal scarring is a serious complication that often occurs with chronic pyelonephritis in the presence of vesicoureteral reflux. In a previous study we established a rat model of renal scarring in which we found the up-regulation of neutrophil-gelatinase associated lipocalin at the mRNA and protein levels. In this study we evaluated urinary neutrophil-gelatinase associated lipocalin as a potential biomarker for progression of renal scarring in patients with vesicoureteral reflux. Materials and Methods: A total of 34 patients diagnosed with vesicoureteral reflux without evidence of current urinary tract infection and 28 normal healthy children were enrolled in this study. Renal scars were evaluated by (99m)technetium dimercapto-succinic acid renal scan in 24 of the reflux cases. Urinary neutrophil-gelatinase associated lipocalin levels were monitored by ELISA. Results: In normal subjects urinary neutrophil-gelatinase associated lipocalin was high during infancy, decreased rapidly within the following year and reached a low stable level from age 3 years onward. Urinary neutrophil-gelatinase associated lipocalin levels, normalized to age matched standards, were significantly increased in patients with vesicoureteral reflux compared to controls. These levels did not correlate with reflux grade, but were significantly higher in patients with radiological evidence of renal scarring irrespective of reflux grade. Conclusions: Estimation of urinary neutrophil-gelatinase associated lipocalin may be useful as a noninvasive diagnostic or prognostic biomarker for renal scarring.

Purpose: Recurrent upper urinary tract infection is a common complication of vesicoureteral. reflux that often leads to irreversible renal scarring. In our previous study of a rat model of renal bacterial infection we performed global gene expression profiling of the kidney during the onset of renal scarring. We have further investigated the product of an up-regulated gene product, NGAL, in this animal model to evaluate its potential usefulness as a biomarker of renal scarring. Materials and Methods: Renal NGAL mRNA and protein levels were examined by real-time polymerase chain reaction, Western blot and immunohistochemistry. Urinary NGAL levels were monitored by direct enzyme-linked immunosorbent assay. Results: Rat renal NGAL mRNA and protein levels were found to be increased soon after bacterial injection. They then decreased rapidly but subsequently persisted at high levels until the 6-week time point after injection. On histological analysis we found that NGAL protein was overproduced in macrophages and renal tubular cells 2 weeks after injection. However, renal tubular cells continued to produce NGAL 6 weeks after injection, whereas this expression was lost in infiltrating cells. Rat urinary NGAL levels were also markedly increased at the early stages of infection and they persisted at high levels throughout the latter stages of the experiment. Conclusions: Urinary NGAL may be a potential noninvasive diagnostic biomarker of renal scarring.

Renal scarring is a serious complication of chronic pyelonephritis that occurs due to vesicoureteral reflux. In our study, we performed global expression profiling of the kidney during renal scarring formation in a rat pyelonephritis model. An inoculum of Escherichia coli was injected directly into the renal cortex. Histologically, renal scarring developed during the 3-to-4 week period after injection. The time-course expression profile of 18,442 genes was then analyzed using microarrays, followed by validation with real-time reverse transcriptase-polymerase chain reaction (RT-PCR). Most of the genes found to be up-regulated during renal scarring are associated with immune and defense responses, including cytokines, chemokines and their receptors, complement factors, adhesion molecules and extracellular matrix proteins. These genes were up-regulated as early as 1 week after injection, when no fibrotic changes were yet evident, peaked at 2 weeks, and gradually decreased thereafter. However, a subset of cytokine genes was found to be persistently activated even at 6 weeks after injection, including interleukin (IL)-1 beta, transforming growth factor (TGF)-beta, and IL-3. Further statistical analysis indicated that the pathways mediated by these cytokines are activated concomitantly with renal scarring formation. The products of these genes may thus potentially be novel non-invasive diagnostic or prognostic biomarkers of renal scarring.