Background/Purpose: Cutaneous lupus erythematosus (CLE) is a heterogenous, disfiguring, and difficult-to-treat manifestation of systemic lupus erythematosus (SLE) with scar formation in CLE subtypes such as discoid lupus erythematosus (DLE). Fibroblasts (FBs) are a diverse stromal cell type now recognized to participate in immunologic responses as well as initiation of dermal wound healing. Our recent study revealed that a subset of FBs from healthy-appearing, non-lesional SLE skin expresses a high type I IFN-induced gene signature and participates in significant myeloid crosstalk in the skin. Thus, we hypothesize that FB education by type I IFNs may modulate FB function and promote non-lesional to lesional CLE phenotypes in SLE patients. The goal of this study was to further characterize the impact of type I IFNs on skin FB function and confirm increased IFN responses in situ in FBs in DLE lesions and subacute lupus erythematosus (SCLE) lesions.

Methods: Fibroblast morphology was assessed by fluorescence staining of F-actin in healthy control FBs (n=5) and SLE FBs (n=3) from healthy-appearing skin in vitro, with and without IFN-α, and gene expression was explored by RNAseq. Similarly, FBs from non-lesional skin of SLE patients or controls were subjected to in vitro scratch wound assays and their ability to close the scratch in the presence or absence IFN-α was analyzed using an Incucyte system. Immunofluorescence staining of formalin-fixed paraffin embedded lesional skin sections from patients with DLE, SCLE, as well as healthy controls were stained with anti-vimentin and anti-MX1 primary antibodies, followed by fluorescently conjugated secondary antibodies and DAPI mounting medium. Statistical comparisons between groups were completed using an unpaired Student’s t-test (all data was normally distributed).

Results: We observed morphological differences between healthy control and SLE FBs from non-lesional skin by F-actin staining, with significantly less F-actin fluorescence and smaller cell size in SLE FBs compared to healthy control FBs (p < 0.05). In response to treatment with IFN-α, TNF, IL1B, and TRAF1 were increased in SLE skin FBs compared to healthy controls, supporting the presence of an IFN-driven inflammatory FB phenotype in SLE skin. Indeed, examination of MX1, a protein known to be upregulated in response to type I IFNs, was more robustly present in the dermis of DLE lesions compared to SCLE lesions, suggesting that fibroblast activation may be more robust in CLE lesions that may develop scar. Consistent with this notion, wound healing, as measured by scratch assays, was significantly impaired in SLE skin FBs versus healthy control FBs only in the presence of IFN-α, as not differences were observed in wound healing response in untreated cells.

Conclusion: These data support a mechanism by which education of fibroblasts by type I IFNs likely promotes amplification of inflammatory responses that contribute to cutaneous inflammation and dysfunctional skin FBs in SLE. Future work will focus on what cells these FBs are interacting with and how the abnormal morphology and function of FBs in SLE skin contribute to disease severity and heterogeneity in CLE subtypes.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/cutaneous-type-i-ifn-responses-in-systemic-lupus-erythematosus-are-associated-with-inflammatory-phenotype-and-altered-wound-healing-function-of-lupus-fibroblasts-from-non-lesional-skin/