Hua Feng, Wang Hao-Ran, Bai Yun-Feng, Sun Jin-Peng, Wang Wei-Shun, Xu Ying, Zhang Ming-Shun, Liu Jun
Department of Orthopedics, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China.
Department of Orthopedics, Sir Run Run Hospital, Nanjing Medical University, Nanjing, Jiangsu Province, China.
Neural Regen Res. 2023 Oct;18(10):2252-2259. doi: 10.4103/1673-5374.369120.
In response to spinal surgery, neurons secrete a large amount of substance P into the epidural area. Substance P is involved in macrophage differentiation and fibrotic disease. However, the specific roles and mechanisms of substance P in epidural fibrosis remain unclear. In this study, we established a mouse model of L1-L3 laminectomy and found that dorsal root ganglion neurons and the macrophages infiltrating into the wound area released sphingolipids. In vitro experiments revealed that type 1 macrophages secreted substance P, which promoted differentiation of type 1 macrophages towards a type 2 phenotype. High-throughput mRNA-seq analysis revealed that the sphingolipid metabolic pathway may be involved in the regulation of type 2 macrophages by substance P. Specifically, sphingomyelin synthase 2, a component of the sphingolipid metabolic pathway, promoted M2 differentiation in substance P-treated macrophages, while treating the macrophages with LY93, a sphingomyelin synthase 2 inhibitor, suppressed M2 differentiation. In addition, substance P promoted the formation of neutrophil extracellular traps, which further boosted M2 differentiation. Blocking substance P with the neurokinin receptor 1 inhibitor RP67580 decreased the number of M2 macrophages in the wound area after spinal surgery and alleviated epidural fibrosis, as evidenced by decreased fibronectin, α-smooth muscle actin, and collagen I in the scar tissue. These results demonstrated that substance P promotes M2 macrophage differentiation in epidural fibrosis via sphingomyelin synthase 2 and neutrophil extracellular traps. These findings provide a novel strategy for the treatment of epidural fibrosis.
作为对脊柱手术的反应，神经元会向硬膜外区域分泌大量的P物质。P物质参与巨噬细胞分化和纤维化疾病。然而，P物质在硬膜外纤维化中的具体作用和机制仍不清楚。在本研究中，我们建立了L1-L3椎板切除术的小鼠模型，发现背根神经节神经元和浸润到伤口区域的巨噬细胞释放鞘脂。体外实验表明，1型巨噬细胞分泌P物质，促进1型巨噬细胞向2型表型分化。高通量mRNA测序分析表明，鞘脂代谢途径可能参与P物质对2型巨噬细胞的调节。具体而言，鞘脂代谢途径的一个组成部分鞘磷脂合酶2促进了P物质处理的巨噬细胞中的M2分化，而用鞘磷脂合酶2抑制剂LY93处理巨噬细胞则抑制了M2分化。此外，P物质促进中性粒细胞胞外陷阱的形成，这进一步促进了M2分化。用神经激肽受体1抑制剂RP67580阻断P物质，可减少脊柱手术后伤口区域M2巨噬细胞的数量，并减轻硬膜外纤维化，瘢痕组织中的纤连蛋白、α-平滑肌肌动蛋白和I型胶原减少证明了这一点。这些结果表明，P物质通过鞘磷脂合酶2和中性粒细胞胞外陷阱促进硬膜外纤维化中M2巨噬细胞的分化。这些发现为硬膜外纤维化的治疗提供了一种新策略。
