Single-cell RNA sequencing reveals dysregulated fibroblast subclusters in prurigo nodularis

Prurigo nodularis (PN) is an intensely pruritic, chronic inflammatory skin disease that disproportionately affects black patients. However, the pathogenesis of PN is poorly understood. We performed single-cell transcriptomic profiling, ligand receptor analysis and cell trajectory analysis of 28,695 lesional and non-lesional PN skin cells to uncover disease-identifying cell compositions and genetic characteristics. We uncovered a dysregulated role for fibroblasts (FBs) and myofibroblasts as a key pathogenic element in PN, which were significantly increased in PN lesional skin. We defined seven unique subclusters of FBs in PN skin and observed a shift of PN lesional FBs towards a cancer-associated fibroblast (CAF)-like phenotype, with WNT5A+ CAFs increased in the skin of PN patients and similarly so in squamous cell carcinoma (SCC). A multi-center PN cohort study subsequently revealed an increased risk of SCC as well as additional CAF-associated malignancies in PN patients, including breast and colorectal cancers. Systemic fibroproliferative diseases were also upregulated in PN patients, including renal sclerosis and idiopathic pulmonary fibrosis. Ligand receptor analyses demonstrated increased FB1-derived WNT5A and periostin interactions with neuronal receptors MCAM and ITGAV, suggesting a fibroblast-neuronal axis in PN. Type I IFN responses in immune cells and increased angiogenesis/permeability in endothelial cells were also observed. As compared to atopic dermatitis (AD) and psoriasis (PSO) patients, increased mesenchymal dysregulation is unique to PN with an intermediate Th2/Th17 phenotype between atopic dermatitis and psoriasis. These findings identify a pathogenic role for CAFs in PN, including a novel targetable WNT5A+ fibroblast subpopulation and CAF-associated malignancies in PN patients.

结节性痒疹（Prurigo nodularis, PN）是一种以剧烈瘙痒为特征的慢性炎症性皮肤病，显著更易累及黑人患者，但目前对其发病机制的认知仍较为有限。本研究对28695个结节性痒疹皮损及非皮损皮肤细胞开展了单细胞转录组测序（single-cell transcriptomic profiling）、配体受体分析（ligand receptor analysis）及细胞轨迹分析（cell trajectory analysis），以揭示疾病特异性的细胞组成与遗传特征。
研究发现，成纤维细胞（fibroblasts, FBs）与肌成纤维细胞的调控异常是结节性痒疹的关键致病因素，二者在结节性痒疹皮损皮肤中的数量显著升高。本研究在结节性痒疹皮肤中鉴定出7个独特的成纤维细胞亚群，并观察到皮损处的成纤维细胞向癌症相关成纤维细胞（cancer-associated fibroblast, CAF）样表型偏移：结节性痒疹患者皮肤中WNT5A阳性的癌症相关成纤维细胞数量升高，这一表型在鳞状细胞癌（squamous cell carcinoma, SCC）中也同样存在。
后续开展的多中心结节性痒疹队列研究显示，结节性痒疹患者罹患鳞状细胞癌及其他与癌症相关成纤维细胞相关的恶性肿瘤的风险升高，包括乳腺癌与结直肠癌；同时患者的系统性纤维增生性疾病（如肾硬化症、特发性肺纤维化）的相关基因表达也出现上调。
配体受体分析结果表明，FB1来源的WNT5A与骨桥蛋白（periostin）可分别与神经元受体MCAM及ITGAV增强相互作用，提示结节性痒疹中存在成纤维细胞-神经元轴信号通路。此外，研究还观察到免疫细胞的I型干扰素应答上调，以及内皮细胞的血管生成与通透性增加。
与特应性皮炎（atopic dermatitis, AD）及银屑病（psoriasis, PSO）患者相比，结节性痒疹的间充质失调具有特异性，其Th2/Th17表型介于特应性皮炎与银屑病之间。
这些研究结果明确了癌症相关成纤维细胞在结节性痒疹中的致病作用，包括一种新型可靶向的WNT5A阳性成纤维细胞亚群，以及结节性痒疹患者中与癌症相关成纤维细胞相关的恶性肿瘤风险。