Circulating microRNA-122, -21 and -223 as potential markers of liver injury following warm ischaemia and reperfusion in rats

The liver enzymes aspartate aminotransferase (AST), alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) are commonly used but not specific markers to quantify hepatic injury. In this in vivo study it was determined whether hepatic expression and serum levels of the microRNAs (miRNA) miR-122, -21 and -223 are altered and correlated with the release of liver enzymes after warm hepatic ischaemia and reperfusion (IR). Male Wistar rats were subjected to either 45 min of partial (70%) hepatic ischaemia and 240 min of reperfusion (n=7) or sham operation (n=5). Expression levels of miR-122, -21 and -223 were analysed in serum and liver tissue by quantitative polymerase chain reaction and tested for correlation with serum activities of AST, ALT and LDH. The relative expression levels of circulating miR-122 increased after IR and correlated with the serum activity of AST, ALT and LDH. Neither increased serum level of miR-21 nor elevated relative hepatic expression of miR-223 correlated with the serum activity of liver enzymes. The hepatic expression of miR-122 was unaffected by IR. The correlation between circulating miR-122 expression levels and liver enzyme activity qualifies miR-122 as a potential biomarker of warm hepatic IR injury.