EMT in Liver Fibrosis

Abstract

Chronic liver disease is a common and epidemiologically important condition, leading to liver fibrosis and cirrhosis with many consecutive problems. In response to liver injury, activated myofibroblasts are responsible for excessive accumulation of extracellular matrix. However, the origin of myofibroblastic cells remains unclear. Myofibroblasts originate from hepatic stellate cells, portal myofibroblasts, interseptal (myo)fibroblasts, and bone marrow-derived fibrocytes. However, in other organs, numerous studies showed that myofibroblasts are derived by endothelial-to-mesenchymal transition (EMT) in response to chronic injury. In this process, mature epithelial cells lose their epithelial phenotype and gene expression characteristics and change into mesenchmyal cells. This process is well described in embryonal development, cancer progression, and metastasis; however, its existence and importance in liver fibrosis has been a topic of ongoing debates. This review summarizes the current knowledge on EMT in liver fibrosis and tries to discuss caveats and controversial results of recent studies.