Spatially controlled tenascin-C accumulation contributes to inflammatory disease persistence in giant cell aortitis.

Giant cell aortitis (GCA) is an inflammatory disease of the aortic wall with a characteristic giant cell pattern on pathology and can lead to life-threatening aortic aneurysm and dissection. Pathogenic GCA mechanisms underlying aortic inflammation and persistence remain elusive. Here, we demonstrate the complexity of medial layer destruction and immune cell infiltration in clinical granulomatous GCA and lymphoplasmacytic IgG4-related aortitis samples using imaging-based gene expression profiling. Single-cell spatial profiling revealed aortic wall remodeling in the GCA aortas, highlighting substantial phenotypic modulation in stromal cells, including vascular smooth muscle cells (SMCs) and fibroblasts. Specifically, we observed the expansion of stromal cells expressing Tenascin-C (TNC) mRNA and spatially refined TNC accumulation in lesion areas. We confirmed these findings histologically using diseased aortas resected from individuals with giant cell arteritis and clinically isolated aortitis. Mechanistically, our data suggest that TNC promotes a proinflammatory phenotype in primary human SMCs, elevating IL-6 levels partially through the TLR4/NF-κB pathway. IL-6 signaling propagates the proinflammatory loop by activating STAT3. Pharmacological blockade of the IL-6 receptor using tocilizumab alleviated the TNC-driven proinflammatory phenotype. We propose that TNC acts as a local catalyst of inflammatory disease persistence mainly via IL-6 signaling activation and offers a potential avenue for sustained disease remission.