Peripheral Nerve Single-Cell Analysis Identifies Mesenchymal Ligands that Promote Axonal Growth (sympathetic neuron microarray data)

Peripheral nerves provide a supportive growth environment for developing and regenerating axons and are essential for maintenance and repair of many non-neural tissues. This capacity has largely been ascribed to paracrine factors secreted by nerve-resident Schwann cells. Here, we used single-cell transcriptional profiling to identify ligands made by different injured rodent nerve cell types and have combined this with cell-surface mass spectrometry to computationally model potential paracrine interactions with peripheral neurons. These analyses show that peripheral nerves make many ligands predicted to act on peripheral and CNS neurons, including known and previously uncharacterized ligands. While Schwann cells are an important ligand source within injured nerves, more than half of the predicted ligands are made by nerve-resident mesenchymal cells, including the endoneurial cells most closely associated with peripheral axons. At least three of these mesenchymal ligands, ANGPT1, CCL11, and VEGFC, promote growth when locally applied on sympathetic axons. These data therefore identify an unexpected paracrine role for nerve mesenchymal cells and suggest that multiple cell types contribute to creating a highly pro-growth environment for peripheral axons.周围神经可为发育中与再生中的轴突提供支持性生长微环境，同时对多种非神经组织的稳态维持与损伤修复至关重要。这一功能在很大程度上被归因于神经驻留施万细胞（Schwann cells）分泌的旁分泌因子。本研究通过单细胞转录谱分析（single-cell transcriptional profiling）鉴定了受损啮齿类动物神经各类细胞所产生的配体，并结合细胞表面质谱分析，通过计算建模预测其与外周神经元之间潜在的旁分泌相互作用。这些分析表明，周围神经可产生多种可作用于外周及中枢神经系统（CNS）神经元的配体，其中既包含已知配体，也涵盖此前未被表征的新型配体。尽管施万细胞是受损神经内重要的配体来源，但超过半数的预测配体由神经驻留间充质细胞产生，其中包括与外周轴突紧密结合的内膜细胞（endoneurial cells）。上述间充质来源配体中，至少有三种（ANGPT1、CCL11与VEGFC）在局部施用于交感轴突时可促进其生长。因此，本研究揭示了神经间充质细胞此前未被认知的旁分泌功能，并提示多种细胞类型共同参与构建了外周轴突高度促生长的微环境。