Biomaterial-based 3D human lung models replicate pathological characteristics of early pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive and incurable lung disease characterized by tissue scarring that disrupts gas exchange. Epithelial cell dysfunction, fibroblast activation, and excessive extracellular matrix deposition drive this pathology that ultimately leads to respiratory failure. Mechanistic studies have shown that repeated injury to alveolar epithelial cells initiates an aberrant wound-healing response in surrounding fibroblasts through secretion of mediators like transforming growth factor-β, yet the precise biological pathways contributing to disease progression are not fully understood. To better study these interactions there is a critical need for lung models that replicate the cellular heterogeneity, geometry, and biomechanics of the distal lung microenvironment. In this study, induced pluripotent stem cell-derived alveolar epithelial type II (iATII) cells and human pulmonary fibroblasts were arranged to replicate human lung micro-architecture and embedded in soft or stiff poly(ethylene glycol) norbornene (PEG-NB) hydrogels that recapitulated the mechanical properties of healthy and fibrotic lung tissue, respectively. The co-cultured cells were then exposed to pro-fibrotic biochemical cues, including inflammatory cytokines and growth factors. iATIIs and fibroblasts exhibited differentiation pathways and gene expression patterns consistent with trends observed during IPF progression in vivo. A design of experiments statistical analysis identified stiff hydrogels combined with pro-fibrotic biochemical cue exposure as the most effective condition for modeling fibrosis in vitro. Finally, treatment with Nintedanib, one of only two Food and Drug Administration (FDA)-approved drugs for IPF, was assessed. Treatment reduced fibroblast activation, as indicated by downregulation of key activation genes, and upregulated several epithelial genes. These findings demonstrate that human 3D co-culture models hold tremendous potential for advancing our understanding of IPF and identifying novel therapeutic targets.特发性肺纤维化（Idiopathic pulmonary fibrosis, IPF）是一种进行性且不可治愈的肺部疾病，以干扰气体交换的组织瘢痕形成为主要特征。上皮细胞功能障碍、成纤维细胞活化以及过量细胞外基质沉积共同驱动该病理进程，最终可导致呼吸衰竭。机制研究表明，肺泡上皮细胞的反复损伤会通过分泌转化生长因子-β等介质，触发周围成纤维细胞产生异常的伤口愈合反应，但促成IPF进展的确切生物学通路尚未完全阐明。为更好地研究这些相互作用，亟需能够复刻远端肺微环境的细胞异质性、组织结构与生物力学特性的肺脏模型。本研究中，研究人员将诱导多能干细胞衍生的II型肺泡上皮细胞（iATII）与人肺成纤维细胞进行共培养以构建人类肺微结构，并分别将其包埋于柔软或坚硬的聚乙二醇降冰片烯（PEG-NB）水凝胶中，该水凝胶分别模拟健康肺组织与纤维化肺组织的力学特性。随后，共培养细胞被施加促纤维化的生物化学信号刺激，包括炎性细胞因子与生长因子。iATII细胞与成纤维细胞所呈现的分化通路与基因表达模式，与体内IPF进展过程中的观测趋势相一致。实验设计统计分析表明，坚硬水凝胶联合促纤维化生物化学信号刺激的培养条件，是体外构建纤维化模型的最优方案。最后，本研究评估了尼达尼布（Nintedanib）的治疗效果——该药是仅有的两种获美国食品药品监督管理局（Food and Drug Administration, FDA）批准用于IPF治疗的药物之一。结果显示，该治疗可降低成纤维细胞活化程度，具体表现为关键活化基因的表达下调，并上调了多种上皮细胞相关基因的表达。上述研究结果表明，人类三维共培养模型对于加深我们对IPF的认知以及发掘全新治疗靶点具有巨大潜力。