EZH2-mediated macrophage-to-myofibroblast transition contributes to calcium oxalate crystal-induced kidney fibrosis

Long-term nephrocalcinosis leads to kidney injury, fibrosis, and even chronic kidney disease (CKD). Reports have proved macrophages can transition into myofibroblasts(MMT), leading to collagen deposition and fibrosis in CKD. However, the effect of MMT in calcium oxalate (CaOx) crystal-induced kidney fibrosis remains unclear. This study demonstrated that histone methyltransferase EZH2-mediated MMT contributes to CaOx crystal-induced fibrosis. We identified abundant MMT cells by immunofluorescence and flow cytometry in kidney tissues of patients with CaOx-related CKD, CaOx nephrocalcinosis mouse model, and CaOx-treated RAW264.7 macrophage cells. A high level of MMT cell infiltration was associated with a decline in the glomerular filtration rate in CaOx nephrocalcinosis patients. Clodronate Liposomes-mediated macrophage depletion attenuates calcium oxalate crystal-induced fibrosis in mice. Subsequently, transcriptomic and single-cell sequencing revealed that EZH2 was highly expressed in kidneys with CaOx deposition, especially in macrophages. Further study demonstrated that EZH2 inducible knock-out or pharmacological inhibition by GSK-126 attenuated MMT and renal fibrosis in vivo and in vitro. Mechanistically, ChIP and transcriptomic sequencing showed that EZH2 inhibition reduced the enrichment of H3K27me3 on the DUSP23 gene promoter and elevated DUSP23 expression. The Co-IP and molecular docking analysis showed that DUSP23 mediated the dephosphorylation of pSMAD3 (S423/425), the key regulator of MMT. In addition, DUSP23 over-expression could alleviate SMAD3-mediated MMT. Thus, our study found that EZH2 promotes kidney fibrosis by meditating MMT via the DUSP23/SMAD3 pathway in nephrocalcinosis. To explore the differentially expressed genes between kidney stone mice and the control mice, RNA-Seq was performed. Male C57BL/6 mice were treated with 120 mg/kg of glyoxylic acid intraperitoneal injection once a day for 12 days to construct the CaOx kidney stone model. The control mice were treated with equal volume of saline. The kidney tissues were harvested. Differential expression genes were identified between the two groups.