ARG1 and renal fibrosis: Interestingly, while deletion of Arg2 specifically in proximal tubules failed to reduce renal fibrosis, indicating that proximal tubular epithelial cell Arg2 is not important to mediate renal tissue injury, arginase inhibition also failed to reduce renal tissue fibrosis in Ggt1Cre/Arg2fl/fl mice after UUO, indicating that part of the effect of arginase inhibition could be mediated through Arg1 and/or nonproximal tubular epithelial cells.