Evidence for resident memory T cells and necroptosis as drivers of fibrosis in eosinophilic fasciitis and morphea

Summary: Abstract Body: The pathogenesis of eosinophilic fasciitis (EF) and morphea is poorly understood. There are currently no FDA-approved treatments for either condition, and no cure exists to reverse established fibrosis. We analyzed skin biopsies from EF and morphea patients with established fibrosis compared to adult healthy skin (HS) using gene expression profiling, Ingenuity Pathway Analysis (IPA), and immunostaining. We used digital spatial profiling (DSP) to evaluate early inflammatory lesions from both conditions and HS. In established fibrosis, morphea and EF shared 51/61 differentially expressed genes, 80/99 canonical pathways, and 40/51 upstream regulators. There was significant upregulation of cytotoxic injury signatures, antigen-specific T cell activation genes (ZAP70, LAT, ITK) and activation of T cell receptor signaling, despite their pauci-inflammatory histological appearance. The number of T cells in morphea and EF did not differ from HS, suggesting a potential role for skin resident memory T cells (TRM) in chronic fibrosis. IPA predicted activation of necroptosis, an immunogenic form of cell death, in morphea (z = 3.9) and EF (z = 2.668). Compared to HS, morphea and EF showed significantly increased expression of necroptosis effector RIPK3. Immunostaining revealed increased numbers of T cell-associated apoptotic and necroptotic endothelial cells in EF and morphea compared to HS, implicating T cell-driven vascular injury in both conditions. Immunostaining showed TRM-associated necroptotic endothelial cells. DSP of early inflammatory EF and morphea skin demonstrated that the fibrotic niche includes macrophages expressing TREM2, a lipid sensor that recognizes DAMPs released from necroptotic cells. CXCR3-secreting macrophages and fibroblasts in early disease co-localized with CD8+ T cells, which we hypothesize become TRM and maintain chronic fibrotic injury through immunogenic cell death. Our findings suggest that targeting TRM or necroptosis may be a novel therapeutic approach in treating cutaneous fibrosis. William J. Crisler¹, Rachael Rowley¹, Maria Machado¹, Qian Zhan¹, Ruth Ann Vleugels¹, Rachael A. Clark¹, Avery LaChance¹ 1. Dermatology, Brigham and Women's Hospital, Boston, MA, United States. Translational Studies: Cell and Molecular Biology