Bone morphogenetic protein-9/activin-like kinase 1 axis a new target for hepatic regeneration and fibrosis treatment in liver injury

Bone morphogenetic protein-9 (BMP-9), a member of the transforming growth factor (TGF)-β family of cytokines, is preferentially expressed in the liver from where is secreted into the blood (1-3). BMP-9 and BMP-10 are high-affinity ligands for the type I receptor activin-like kinase 1 (ALK1), whose participation in liver fibrosis has been previously suggested, and activin type II receptor A (ActRIIA) a BMP type II receptor with undefined role in liver biology. Although BMP-9 promotes epithelial to mesenchymal transition in hepatocellular carcinoma (HCC) cells, correlating with HCC aggressiveness in patients, and the BMP-9/ALK1 signaling has been related to liver pathologies, little was known about BMP-9 specific functions in liver cells and, particularly, after hepatic injury.