CAR-M2 immunotherapy resolves renal fibrosis via revascularization and apoptosis of profibrotic Cxcr2+ endothelial cells

Renal fibrosis is a common outcome of chronic kidney disease (CKD), forming a fibrotic niche characterized by fibroblast activation and vascular rarefaction. Currently, there are no effective treatment strategies targeting fibrotic niche. Here, we show that chimeric antigen receptor-modified M2 macrophages (CAR-M2) targeting FAP and secreting interleukin (IL)-4 are delivered via an injectable HAMA-CS hydrogel beneath the renal subcapsule and attenuate renal fibrosis while promoting renal revascularization. The single-cell RNA sequencing reveals the heterogeneity and interaction of stroma and endothelial cells (ECs). A fibrosis-related Cxcr2⁺ EC subset is identified, and its specific depletion effectively mitigates renal fibrosis. Further results reveal that CAR-M2 can release matrix metalloproteinase 2 (MMP2) in close proximity to activate retinoid X receptor alpha (Rxra) in the Cxcr2⁺ ECs and further triggers its mitochondrial autophagy, leading to apoptosis. Our research provides innovative strategies and proof of principle for the immunotherapy of organ fibrosis.