Emergence of inflammatory fibroblasts with aging in Hermansky-Pudlak syndrome associated pulmonary fibrosis

The longitudinal cellular interactions that drive pulmonary fibrosis are not well understood. To investigate the disease underpinnings associated with fibrosis onset and progression, we generated a scRNAseq atlas of lungs from young and aged mouse models of multiple subtypes of Hermansky-Pudlak syndrome (HPS), a collection of rare autosomal recessive diseases associated with albinism, platelet dysfunction, and pulmonary fibrosis. We identified an age-dependent increase in SAA3+ inflammatory lung fibroblasts in HPS mice, including in double-mutant HPS1-2 mice which develop spontaneous fibrosis. HPS1 fibroblasts showed increased expression of IL-1R1, whereas alveolar type II epithelial cells from HPS2 mice induced the inflammatory gene signature in co-cultured fibroblasts. scRNAseq of lung tissue from three HPS1 patients similarly showed the presence of inflammatory fibroblasts and increased IL1R1 expression on fibroblasts. These data posit complex interactions between dysfunctional epithelial cells, inflammatory fibroblasts, and recruited immune cells, suggesting potential opportunities for mitigation of the fibrotic cascade. Overall design: To investigate age and genotype-dependent mRNA expression differences in multiple lung cell types using scRNA-seq.驱动肺纤维化发生的动态细胞互作机制目前尚未完全阐明。为探究纤维化起始与进展相关的疾病分子基础，我们构建了年轻与老年小鼠的多种亚型赫曼斯基-普德拉克综合征（Hermansky-Pudlak syndrome, HPS）模型的肺脏单细胞RNA测序（single-cell RNA sequencing, scRNA-seq）图谱。赫曼斯基-普德拉克综合征是一组罕见的常染色体隐性遗传病，临床表现为白化病、血小板功能异常及肺纤维化。 我们在HPS模型小鼠中发现，SAA3阳性炎症性肺成纤维细胞的比例随年龄增长而显著升高，其中包括可自发形成肺纤维化的HPS1-2双突变小鼠。HPS1型成纤维细胞的白细胞介素-1受体1（IL-1R1）表达水平上调，而HPS2模型小鼠的肺泡II型上皮细胞可在共培养体系中诱导成纤维细胞产生炎症基因表达特征。对3名HPS1患者的肺组织进行scRNA-seq分析，同样检测到炎症性成纤维细胞的存在，且成纤维细胞的IL1R1表达水平显著升高。 上述研究结果表明，功能异常的上皮细胞、炎症性成纤维细胞与招募的免疫细胞之间存在复杂的互作调控网络，为干预纤维化级联反应提供了潜在的治疗机遇。 实验整体设计：本研究利用单细胞RNA测序技术，探究不同年龄与基因型背景下多种肺脏细胞类型的mRNA表达差异。