iMSC-secreted factors preserve renal capillary networks and ameliorate fibrosis by interrupting the macrophage STING/CD8⁺ T cell axis in ischemic kidney disease

Renal fibrosis, the common endpoint of chronic kidney disease, is exacerbated by renal ischemia. While human iPSC-derived MSCs (iMSCs) hold therapeutic promise, their role in modulating the ischemic renal microenvironment, particularly through macrophage-immune crosstalk, remains unclear. This study assesses whether iMSCs alleviate renal fibrosis by targeting macrophage-STING to restore capillaries.

The protective effects of iMSC-conditioned medium (iMSC-CM) were assessed in H₂O₂‑induced HK‑2 and HUVEC models using CCK‑8, ROS staining, scratch assay, and tube formation assays. A mouse model of unilateral ischemia‑reperfusion (UIR) was established; mice received intravenous iMSCs or PBS. Kidneys were analyzed by histology, immunohistochemistry, qPCR, and Western blot. Transcriptomic sequencing revealed enrichment of immune-related pathways, including the STING pathway. To validate the role of STING, UIR mice were treated with the STING agonist DMXAA with or without iMSCs, and STING activation was assessed in LPS-stimulated macrophages in vitro. Macrophage polarization was evaluated by F4/80 co‑staining with CD86 (M1) or CD206 (M2).

iMSC-CM mitigated H₂O₂-induced damage in HK-2 cells by promoting proliferation, reducing ROS levels, and suppressing fibrosis markers, and it promoted repair and angiogenesis in HUVECs. In vivo, iMSCs homed to injured kidneys, attenuated inflammation and fibrosis, notably reduced capillary rarefaction. Mechanistically, iMSC treatment profoundly inhibited STING activation in renal macrophages. This suppression disrupted a critical inflammatory axis: it reduced macrophage-derived IFN-β, leading to decreased infiltration of cytotoxic CD8⁺ T cells, which are detrimental to vascular endothelial cells. Consequently, the renal capillary network was preserved. Finally, STING agonist treatment abolished the anti-fibrotic benefits of iMSCs.

Collectively, this work reveals that iMSCs ameliorate renal fibrosis via the macrophage STING/CD8⁺ T cell axis, thereby preserving renal capillaries and highlighting a novel mechanism for iMSC-based therapy.