DataSheet5_Single-cell transcriptome dynamics of the autotaxin-lysophosphatidic acid axis during muscle regeneration reveal proliferative effects in mesenchymal fibro-adipogenic progenitors.PDF

Lysophosphatidic acid is a growth factor-like bioactive phospholipid recognising LPA receptors and mediating signalling pathways that regulate embryonic development, wound healing, carcinogenesis, and fibrosis, via effects on cell migration, proliferation and differentiation. Extracellular LPA is generated from lysophospholipids by the secreted hydrolase—ectonucleotide pyrophosphatase/phosphodiesterase 2 (ENPP2; also, AUTOTAXIN/ATX) and metabolised by different membrane-bound phospholipid phosphatases (PLPPs). Here, we use public bulk and single-cell RNA sequencing datasets to explore the expression of Lpar1–6, Enpp2, and Plpp genes under skeletal muscle homeostasis and regeneration conditions. We show that the skeletal muscle system dynamically expresses the Enpp2-Lpar-Plpp gene axis, with Lpar1 being the highest expressed member among LPARs. Lpar1 was expressed by mesenchymal fibro-adipogenic progenitors and tenocytes, whereas FAPs mainly expressed Enpp2. Clustering of FAPs identified populations representing distinct cell states with robust Lpar1 and Enpp2 transcriptome signatures in homeostatic cells expressing higher levels of markers Dpp4 and Hsd11b1. However, tissue injury induced transient repression of Lpar genes and Enpp2. The role of LPA in modulating the fate and differentiation of tissue-resident FAPs has not yet been explored. Ex vivo, LPAR1/3 and ENPP2 inhibition significantly decreased the cell-cycle activity of FAPs and impaired fibro-adipogenic differentiation, implicating LPA signalling in the modulation of the proliferative and differentiative fate of FAPs. Together, our results demonstrate the importance of the ENPP2-LPAR-PLPP axis in different muscle cell types and FAP lineage populations in homeostasis and injury, paving the way for further research on the role of this signalling pathway in skeletal muscle homeostasis and regeneration, and that of other organs and tissues, in vivo.

溶血磷脂酸（Lysophosphatidic acid, LPA）是一类类生长因子生物活性磷脂，可识别LPA受体并通过调控细胞迁移、增殖与分化，介导参与胚胎发育、伤口愈合、癌变及纤维化等生理病理过程的信号通路。细胞外LPA由溶血磷脂经分泌型水解酶——胞外核苷酸焦磷酸酶/磷酸二酯酶2（ectonucleotide pyrophosphatase/phosphodiesterase 2, ENPP2，又名自分泌运动因子AUTOTAXIN/ATX）生成，并可被多种膜结合磷脂磷酸酶（PLPPs）代谢。本研究利用公开的批量及单细胞RNA测序数据集，探究了Lpar1–6、Enpp2及Plpp基因在骨骼肌稳态与再生条件下的表达模式。研究发现，骨骼肌系统可动态表达ENPP2-LPAR-PLPP基因轴，其中Lpar1是LPA受体家族中表达量最高的成员。Lpar1由间质成脂祖细胞（fibro-adipogenic progenitors, FAPs）及腱细胞表达，而FAPs主要表达Enpp2。对FAPs的聚类分析鉴定出了代表不同细胞状态的群体，其中表达高水平标志物Dpp4与Hsd11b1的稳态细胞，呈现出显著的Lpar1与Enpp2转录组特征。然而，组织损伤会瞬时抑制Lpar家族基因及Enpp2的表达。目前关于LPA调控组织驻留FAPs命运与分化的作用尚未被阐明。体外实验中，LPAR1/3及ENPP2的抑制剂可显著降低FAPs的细胞周期活性，并损害其成脂分化能力，表明LPA信号通路参与调控FAPs的增殖与分化命运。综上，本研究结果证实了ENPP2-LPAR-PLPP基因轴在不同骨骼肌细胞类型及FAP谱系群体稳态与损伤过程中的重要作用，为进一步研究该信号通路在体内骨骼肌稳态与再生，以及其他器官组织中的功能奠定了基础。