Increased MMP‐7 expression in biliary epithelium and serum underpins native liver fibrosis after successful portoenterostomy in biliary atresia

Abstract

The molecular mechanisms underlying progressive liver fibrosis following surgical treatment of biliary atresia (BA) remain unclear. Our aim was to address hepatic gene and protein expression and serum levels of matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) after successful portoenterostomy (PE), and relate them to histological signs of liver injury, clinical follow‐up data and biochemical markers of hepatic function. LIver biopsies and serum samples were obtained from 25 children after successful PE at median age of 3.3 years. Serum MMP concentrations were determined by enzyme‐linked immune sorbent assay. Hepatic gene expression of MMPs and TIMPs was analyzed using real‐time reverse‐transcription PCR. Liver expression of MMP‐7 and cytokeratin‐7 was studied using immunohistochemistry. Despite effective clearance of biochemical and histological cholestasis following PE, BA patients showed increased hepatic gene expression of MMP‐7 (29‐fold, p < 0.001), MMP‐2 (3.1‐fold, p < 0.001), MMP‐14 (1.7‐fold, p = 0.007), and TIMP‐1 (1.8‐fold, p < 0.001), when compared to controls. Similar to a biliary epithelial marker cytokeratin‐7, expression of MMP‐7 localized in biliary epithelium of bile ducts and ductal proliferations and periportal hepatocytes and was increased (p < 0.001) in relation to controls. BA patients had 6‐fold higher serum levels of MMP‐7 (p < 0.001), which correlated positively with hepatic MMP‐7 gene (r = 0.548, p = 0.007) and protein (r = 0.532, p = 0.007) expression. Patients showed a positive correlation between biliary MMP‐7 expression and Metavir fibrosis stage (r = 0.605, p = 0.001) and portal fibrosis grade (r = 0.606, p = 0.001). Neither similarly increased MMP‐7 expression nor correlation with liver fibrosis was observed in patients with intestinal failure‐associated liver disease and comparable Metavir stage. In conclusion, our findings support an unique role of altered hepatic expression of MMP‐7 in the progression of liver fibrosis after successful PE and introduce a potential therapeutic target to pharmacologically extend native liver survival by inhibiting MMP‐7 hyperactivity. Serum MMP‐7 may be a valuable postoperative prognostic tool in BA.

Diagnostic Accuracy of Serum Matrix Metalloproteinase‐7 for Biliary Atresia

“…Based on our data, serum MMP-7 may be helpful in facilitating the diagnosis of BA; however, because these syndromes make up less than 30% of our non-BA cohort, further studies are needed to test the diagnostic performance of serum MMP-7 to differentiate BA from rare cholestatic liver diseases such as Alagille syndrome, alpha-1-antitrypsin deficiency, citrin deficiency, and ductal plate malformation. Serum MMP-7 was previously shown to have a modest correlation with hepatic fibrosis in older patients with BA, (10) but our preliminary analysis does not support such correlation in young infants at the time of diagnosis. We recognize that the single time point (at diagnosis) and the immunostaining of only 10 patients limit the strength of our correlative analyses.…”

“…Using immunostaining to determine the cellular source of MMP-7 expression in diseased livers at the time of diagnosis, (7)(8)(9)(10)16) we found the protein expressed primarily in intrahepatic cholangiocytes of BA (n = 10), with signal also present in few nonparenchymal cells (Supporting Fig. S2A).…”

Biliary Atresia: Clinical and Research Challenges for the Twenty‐First Century

“…Although these pathways have not been studied after HPE, the rapid progression to cirrhosis suggests the existence of unique pathogenic processes that are not suppressed after HPE. One example is the increase of serum and liver matrix metalloproteinase 7 during progression of disease and its correlation with the fibrosis stage …”

“…One example is the increase of serum and liver matrix metalloproteinase 7 during progression of disease and its correlation with the fibrosis stage. (36)…”

“Extracellular matrix remodelling in the liver of rats subjected to dietary choline deprivation and/or thioacetamide administration”

“…Since early diagnosis of liver fibrosis is important, the presented data herein suggest that members of the MMPs‐TIMPs family could prove to be important markers in identifying the stage and/or progression of liver fibrosis in chronic liver diseases …”