The loss of normal alveolar capillary and deregulated angiogenesis occurs simultaneously in idiopathic pulmonary fibrosis (IPF); however the contributions of specific endothelial subpopulations in the development of pulmonary fibrosis are poorly understood. Herein, we perform single-cell RNA sequencing to characterize the heterogeneity of endothelial cells (ECs) in bleomycin (BLM)-induced lung fibrosis in rats. One subpopulation, characterized by the expression of Nos3 and Cav1, is mostly distributed in non-fibrotic lungs and also highly expresses genes related to the “response to mechanical stimulus” and “lung/heart morphogenesis” processes. Another subpopulation of ECs expanded in BLM-treated lungs, characterized by Cxcl12, is observed to be closely related to the pro-fibrotic process in the transcriptome data, such as “regulation of angiogenesis,” “collagen binding,” and “chemokine activity,” and spatially localized to BLM-induced neovascularization. Using CellPhoneDB software, we generated a complex cell–cell interaction network, which predicts the potential roles of EC subpopulations in recruiting monocytes, inducing the proliferation of fibroblasts and promoting the production and remolding of the extracellular matrix (ECM). Taken together, our data demonstrate the high degree of heterogeneity of ECs in fibrotic lung and it is proposed that the interaction between ECs, macrophages, and stromal cells contributes to pathologic IPF.

在特发性肺纤维化 (IPF) 中，正常肺泡毛细血管的丧失和失调的血管生成同时发生；然而，人们对特定内皮亚群在肺纤维化发展中的作用知之甚少。在此，我们进行单细胞 RNA 测序以表征博莱霉素 (BLM) 诱导的大鼠肺纤维化中内皮细胞 (ECs) 的异质性。一个以 Nos3 和 Cav1 表达为特征的亚群主要分布在非纤维化肺中，并且还高度表达与“对机械刺激的反应”和“肺/心脏形态发生”过程相关的基因。在 BLM 处理的肺中扩展的另一个 EC 亚群，以 Cxcl12 为特征，观察到与转录组数据中的促纤维化过程密切相关，例如“血管生成的调节”、“胶原结合”和“趋化因子活性”，并在空间上定位于 BLM 诱导的新血管形成。使用 CellPhoneDB 软件，我们生成了一个复杂的细胞-细胞相互作用网络，该网络预测了 EC 亚群在募集单核细胞、诱导成纤维细胞增殖和促进细胞外基质 (ECM) 的产生和重塑方面的潜在作用。总之，我们的数据证明了纤维化肺中 ECs 的高度异质性，并提出 ECs、巨噬细胞和基质细胞之间的相互作用有助于病理性 IPF。它预测了 EC 亚群在募集单核细胞、诱导成纤维细胞增殖和促进细胞外基质 (ECM) 的产生和重塑方面的潜在作用。总之，我们的数据证明了纤维化肺中 ECs 的高度异质性，并提出 ECs、巨噬细胞和基质细胞之间的相互作用有助于病理性 IPF。它预测了 EC 亚群在募集单核细胞、诱导成纤维细胞增殖和促进细胞外基质 (ECM) 的产生和重塑方面的潜在作用。总之，我们的数据证明了纤维化肺中 ECs 的高度异质性，并提出 ECs、巨噬细胞和基质细胞之间的相互作用有助于病理性 IPF。