Single-Cell and Spatial Transcriptome Profiling Identifies a Tenascin C-Enriched Niche Promoting Kidney Inflammation

Background: Kidney fibrosis is often accompanied by inflammatory cell infiltration and interstitial inflammation. Among all inflammatory cells, macrophage infiltration plays an important role in the occurrence and development of renal fibrosis. However, the mechanism by which macrophages promote renal fibrosis remain to be elucidated. In this study, we demonstrate that tenascin-C-enriched microenvironment promotes the development of renal inflammation and fibrosis by activating macrophages. Methods: Unilateral ischemic-reperfusion injury (UIRI) and unilateral ureteral obstruction (UUO) were used as models of kidney fibrosis. Single-cell RNA sequencing (scRNA-Seq) and spatial transcriptome (ST) sequencing techniques were used to characterize various cell subpopulations after kidney injury. Decellularized kidney tissue scaffold (dKTS) was prepared. The role of tenascin-C (TNC) in macrophage activation and proliferation was investigated in vitro. TLR4-KO mice and TLR4 inhibitor were used in vivo. A bone marrow chimera model was established by transplanting the bone marrow from TLR4 KO to WT mice. Results: Single-cell and spatial transcriptome profiles of normal and UIRI kidney showed a significant increase of macrophages in the injured site, which was closely associated with TNC expression. Compared with the TNC-low region, the TNC-high region was associated with an increased infiltration of macrophages and activation of proinflammatory and profibrotic signaling. TNC-enriched dKTS from fibrotic kidney induced macrophage activation and proliferation, characterized by an increased expression of TNF-α, c-Fos, PCNA, c-Myc, TLR4, p-P65 and P65. Furthermore, TNC induced the activation, proliferation, migration and phagocytosis of macrophages via activating TLR4/NF-κB signaling in vitro. Inhibition or knockout of TLR4 and knockdown of TNC alleviated renal inflammation and fibrosis by inhibiting the activation, proliferation and migration of macrophages. Conclusion: This study showed that TNC-enriched microenvironment promotes the development of renal inflammation and fibrosis by activating macrophages via TLR4/NF-κB signaling. Targeted inhibition of TNC and TLR4 could be novel therapeutic strategies for protecting kidney against inflammation in CKD.