Murine Model of Chronic Spontaneous Urticaria‐Like Skin

Chronic spontaneous urticaria (CSU) is a common and distressing skin disorder affecting approximately 1% of the global population [1]. Although substantial progress has been made in defining the clinical and immunological features of CSU, its underlying mechanisms remain incompletely understood. A major barrier to mechanistic investigation is the lack of widely accepted animal models that faithfully recapitulate key aspects of the disease. While several murine models have been reported to induce urticaria-like skin reactions, their fidelity to human CSU lesions has not been systematically validated. Repetitive mast cell activation is central to CSU pathophysiology, as activated mast cells release preformed granule mediators together with a broad array of cytokines and chemokines that orchestrate immune cell recruitment and mediate interactions with skin-resident cells. These processes collectively sustain the chronic inflammatory microenvironment of CSU [2]. MC can be activated via multiple pathways. Although IgE-dependent MC activation through FcεRI was considered predominant in CSU pathology, many patients have normal total IgE levels, indicating that non-IgE mechanisms also contribute [3]. Among these pathways, MRGPRX2 is particularly relevant. To model these distinct modes of activation, we established a mouse model using repeated intradermal injections of FcεRI and MRGPRX2 agonists (Figure 1A) and compared the histological and transcriptional features with those observed in CSU patient skin (patient characteristics summarized in Table S1). This study was approved by the Ethics Committee of the Second Affiliated Hospital of Xi'an Jiaotong University (protocol 2022125); written informed consent was obtained from all participants. OVA- and SP-treated skin exhibited histological features resembling CSU lesions, including perivascular inflammatory infiltrates (Figure 1B), increased CD3+ lymphocytes (Figure 1C,D), and mast cells (Figure 1E,F) [4, 5]. Although mast cell degranulation and accumulation were comparable in OVA- and SP-treated mouse skin, CD3+ T cell infiltration was higher in OVA-treated skin, likely due to the greater production of cytokines and chemokines elicited by the FcεRI-mediated pathway [6]. To evaluate whether the mouse models recapitulate CSU-associated transcriptional changes, we performed RNA sequencing of OVA- and SP-stimulated mouse skin and compared the results with two publicly available CSU datasets (GSE57178 and GSE72540). Differentially expressed genes (DEGs) (Figure S1A–D) and shared DEGs between human datasets and the OVA or SP models (Figure S1E,F) were compared. Functional enrichment analysis using GSEA, GO, and KEGG demonstrated concordant activation of inflammatory pathways (Figure S2A–J). GSEA showed consistent induction of immune-inflammatory programs, KEGG enrichment highlighted cytokine receptor interactions, and GO analysis indicated marked immune cell recruitment and regulatory activation. To further delineate molecular interactions across datasets, protein–protein interaction (PPI) analysis was performed. In CSU patient skin, IL6 emerged as the most central hub gene in both transcriptomic datasets, indicating a pivotal role in disease-associated networks. Consistently, IL6 also occupied a central hub position in both the OVA- and SP-induced mouse models, together with additional immune-related hub genes, supporting a shared core inflammatory architecture between human CSU and the murine models (Figure 2A–D). The fidelity of transcriptional replication was assessed by comparing CSU-associated DEGs in OVA- and SP-stimulated mouse skin (Figure 2E,F), followed by custom gene set enrichment analysis, which revealed strong enrichment of CSU-upregulated gene signatures in both models, with higher enrichment scores in the FcεRI-mediated pathway compared to MRGPRX2 stimulation (Figure 2G,H). In conclusion, repetitive activation of FcεRI or MRGPRX2 recapitulates the core immunoinflammatory networks of human CSU, with higher fidelity in the FcεRI pathway. While transcriptomic analyses confirm these parallels, the model does not fully reproduce the chronicity, spontaneous recurrence, or systemic immune features of human CSU. Nevertheless, it provides a platform for dissecting CSU pathogenesis and evaluating mast cell driven mechanisms. Zhao Wang: conceptualization. Yanan He, Dan Ye, Jiahua Guo and Zhao Wang: investigation. Yanan He, Dan Ye: data curation. Zhao Wang, Yanan He: writing – original draft preparation. Zhao Wang, Yanan He, Weihui Zeng: writing – review and editing. Yanan He, Dan Ye: visualization. Zhao Wang: supervision. Zhao Wang: project administration; Zhao Wang: funding acquisition. All authors have read and agreed to the published version of the manuscript. This work was funded by the National Natural Science Foundation of China (NSFC) (82201966) and Natural Science Basic Research Program of Shaanxi (2023-JC-QN-0924) to Zhao Wang. The authors declare no conflicts of interest. The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions. Figure S1: Differentially expressed gene (DEG) analysis. Figure S2: Functional enrichment analysis of DEGs by GSEA, KEGG, and GO. Table S1: Patient characteristics. 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