Evaluation of matrix metalloproteinases and their endogenous tissue inhibitors in biliary atresia-associated liver fibrosis

Abstract

Background/purpose: Matrix metalloproteinases (MMPs) and their endogenous tissue inhibitors (TIMPs) are major proteases responsible for remodeling the liver tissue, but their roles in biliary atresia (BA)--associated liver fibrosis are not clear.

Methods: A DNA microarray containing complementary DNA clones of 10 MMPs and 4 TIMPs was used to compare the expression profiles of the liver cytokines among 3 patients with BA at the time of Kasai procedure (KP) with 3 at the time of liver transplantation (LT). Liver samples from 2 children without liver fibrosis were used as normal controls. Those genes that were differentially expressed by more than 2-fold between groups were further quantified with real time quantitative reverse transcription-polymerase chain reaction (QRT-PCR) and validated with gel electrophoresis.

Results: In normal human liver, messenger RNAs (mRNAs) of TIMP-1, -2, and -3, but not of TIMP-4 and none of the 10 MMPs studied, were expressed in DNA microarray. With progression of liver fibrosis, only mRNA of MMP-7, but not other MMPs, was induced to express at a significantly higher level in the array. Despite its low level of expression, MMP-9 mRNA was significantly upregulated in KP but downregulated in LT, whereas MMP-2, which was not showed in the array, was significantly upregulated in LT than in KP and control in real time QRT-PCR. There was a more than 2-fold increase in TIMP-1 and TIMP-2 mRNA expression in LT over control in the array, which was confirmed in subsequent real time QRT-PCR. The expression of TIMP-3 mRNA was significantly downregulated in KP than in control.

Conclusions: This study verified differential expression of MMPs and TIMPs in different stages of BA, with emphasis on the role of TIMP-1, -2, and -3 as well as MMP-2, -7, and -9 transcripts in remodeling of liver tissue during the progress of BA-associated liver fibrosis.