PTGER4 and acute kidney injury: The snRNA-Seq data showed that EP4 was selectively and gradually upregulated in renal macrophages in IRI-induced AKI-to-CKD mouse model, whereas the expressions of EP1, EP2 and EP3 had no consistent change (Figure 1B), hinting that EP4 in macrophages might play a significant role in the progression of AKI to CKD.