Leilei Gong1 • Yun Gu1 • Xiaoxiao Han1 • Chengcheng Luan1 • Chang Liu1 • Xinghui Wang1 •  Yufeng Sun1 •  Mengru Zheng1 •  Mengya Fang1 •  Shuhai Yang1 •  Lai Xu1 •  Hualin Sun1 •  Bin Yu1 •  Xiaosong Gu1 •  Songlin Zhou1

1 Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Jiangsu Clinical Medicine Center of Tissue Engineering and Nerve Injury Repair, Co-Innovation Center of Neuroregeneration, Nantong University, Nantong 226001, China

Abstract

Nerve regeneration in adult mammalian spinal cord is poor because of the lack of intrinsic regeneration of neurons and extrinsic factors – the glial scar is triggered by injury and inhibits or promotes regeneration. Recent technological advances in spatial transcriptomics (ST) provide a unique opportunity to decipher most genes systematically throughout scar formation, which remains poorly understood. Here, we frst constructed the tissue-wide gene expression patterns of mouse spinal cords over the course of scar formation using ST after spinal cord injury from 32 samples. Locally, we profled gene expression gradients from the leading edge to the core of the scar areas to further understand the scar microenvironment, such as neurotransmitter disorders, activation of the pro-infammatory response, neurotoxic saturated lipids, angiogenesis, obstructed axon extension, and extracellular structure re-organization. In addition, we described 21 cell transcriptional states during scar formation and delineated the origins, functional diversity, and possible trajectories of subpopulations of fbroblasts, glia, and immune cells. Specifcally, we found some regulators in special cell types, such as Thbs1 and Col1a2 in macrophages, CD36 and Postn in fbroblasts, Plxnb2 and Nxpe3 in microglia, Clu in astrocytes, and CD74 in oligodendrocytes. Furthermore, salvianolic acid B, a blood–brain barrier permeation and CD36 inhibitor, was administered after surgery and found to remedy fbrosis. Subsequently, we described the extent of the scar boundary and profled the bidirectional ligand-receptor interactions at the neighboring cluster boundary, contributing to maintain scar architecture during gliosis and fbrosis, and found that GPR37L1_PSAP, and GPR37_PSAP were the most signifcant gene-pairs among microglia, fbroblasts, and astrocytes. Last, we quantifed the fraction of scar-resident cells and proposed four possible phases of scar formation: macrophage infltration, proliferation and diferentiation of scar-resident cells, scar emergence, and scar stationary. Together, these profles delineated the spatial heterogeneity of the scar, confrmed the previous concepts about scar architecture, provided some new clues for scar formation, and served as a valuable resource for the treatment of central nervous system injury.

Keywords

Spinal cord injury; Glial scar; Spatial transcriptomics; Microenvironment; Therapeutic strategy; Salvianolic acid

[SpringerLink]