GDF2 and Hepatic fibrosis: Again, the controversy is heightened, as some studies have suggested a protective effect for BMP9 in liver fibrosis, and, to render an even more complicated picture, mouse strain-dependent responses have been found in terms of liver fibrosis upon genetic deletion of BMP9, which appear to be related to alterations in liver sinusoidal endothelial cell (LSEC) fenestrations and subsequent capillarization [1,2].