PTGDR2 and renal fibrosis: Ito and coworkers (399) blocked the activation of CRTH2, using an antagonist or genetic KO, and showed that UUO-induced TIF was ameliorated in CRTH2 KO mice or in mice treated with the CRTH2 antagonist, suggesting that the PGD2-CRTH2 pathway promotes renal fibrosis.