Left‐right determination factor is down‐regulated in fibrotic renal tissue of human hydronephrosis
Authors: Yao Yi , Zhang Jie , Ye Da‐fu , Tan Da‐qing , Peng Jian‐ping , Xie Mei , Fang Li 
Published: August 2010

What’s known on the subject? and What does the study add?

Forty‐nine genes of the TGF‐β/BMP signalling pathway were identified differentially expressed in hydronephrosis‐induced fibrotic renal tissues and normal renal tissues. LEFTY, one of the lowest expressed genes in fibrotic kidney, was confirmed downregulated at both mRNA and protein levels. The findings will provide useful clues concerning the mechanism of renal fibrosis.

The expression profiling of the TGF‐β/BMP signalling related genes found in this article could provide useful clues concerning the mechanism of renal fibrosis. And the confirming of the downregulation of LEFTY in fibrotic kidney will further draw a hypothesis that LEFTY might enhance the recovery of tissue fibrosis through inhibiting TGF‐β signaling, and could therefore represent an ideal candidate as a therapeutic target for renal fibrosis.

OBJECTIVE

To compare the expressions of common fibrosis‐relevant genes in hydronephrosis‐induced fibrotic renal tissues and normal human renal tissues, thereby providing insights into the cellular and molecular mechanisms of renal fibrosis resulting from hydronephrosis.

PATIENTS AND METHODS

A total of 12 extensively fibrotic renal tissue samples from patients with hydronephrosis (H‐group) and six normal renal tissue samples from patients who underwent nephrectomy for renal cell carcinoma (N‐group), along with their clinical data, were collected at Renmin Hospital of Wuhan University in China between October 2005 and August 2007.

These tissue samples were compared for their transforming growth factor‐β (TGF‐β)/bone morphogenetic protein (BMP) pathway‐related gene profiles using a real‐time polymerase chain reaction (PCR) microarray.

Subsequently, reverse transcriptase‐PCR assays were used to validate the expression changes of left‐right determination factor (LEFTY), a gene of interest, at the mRNA level.

The different expression of LEFTY at the protein level was confirmed by western blotting and immunohistochemistry assays.

RESULTS

The results showed that 49 genes were differently expressed in fibrotic renal tissues relative to normal control tissues. Among these genes, 25 were up‐regulated and 24 were down‐regulated.

LEFTY‐B, one of the most markedly altered genes, was down‐regulated 13.55‐fold compared with N‐group tissues.

RT‐PCR showed that the LEFTY‐A (6.05‐fold down‐regulated, P < 0.001) and LEFTY‐B (12.5‐fold down‐regulated, P < 0.001) genes, two members of the LEFTY family in human tissues, were both significantly down‐regulated in H‐group tissues.

Similarly, down‐regulations of LEFTY‐A (0.25‐fold vs N‐group, P < 0.001) and LEFTY‐B (0.20‐fold vs N‐group, P < 0.001) proteins were detected by western blotting (P < 0.001).

Immunohistochemical staining showed different distributions of LEFTY in the two tissue samples, and quantitative image analyses confirmed that LEFTY protein expression was lower in H‐group tissues than in N‐group tissues (P < 0.001).

CONCLUSIONS

The gene and protein expressions of LEFTY were found to be down‐regulated in extensively fibrotic renal tissues induced by hydronephrosis.

LEFTY may represent an ideal candidate for a therapeutic target for renal fibrosis.