Fibroblasts orchestrate the pathogenesis of fibrotic and glial scar in spinal cord injury

Spinal cord injury (SCI) is a severe neurological dysfunction, and its pathogenesis remains inadequately understood. Here, to spatiotemporally decode the cellular and molecular pathogenesis of SCI, we performed spatial transcriptomics analysis of 12,930 single cells from 21 samples of SCI contusion model mice. We identified the specific cellular subtypes, differentially expressed genes (DEGs), cell signaling networks, site-specific genes (SSGs), and transcription factors involved in SCI. Our analysis indicated that fibroblasts served as the hub of intracellular communication in the SCI site, sent continuous immune signals to neurocytes, and induced the other cell types to express high levels of the fibroblast marker gene Col1a2. Pseudotime analysis visualized trajectories that emerged from fibroblasts, passed through microglia and ended at neurons after SCI. When the proportion of fibroblasts and their cellular communications were attenuated by solu-medrol treatment, the BMS and MEP performance of SCI mice increased significantly; moreover, the ratio of Col1a2+ cells decreased markedly, and a new subtype of fibroblasts expressing Arg1 appeared. Our results highlight the vital pathological position of fibroblasts and indicate it as a significant therapeutic target for SCI. Eight-week-old C57 mice were subjected to contusion SCI (10 mice) or sham operation (2 mice) and then used for specimen extraction. The sections collected included 14 cross sections (Cro) (6 sections taken at 7 days post SCI (dpi), 6 sections taken at 14 dpi, and 2 sections taken from the sham control) and 7 coronal sections (Cor) (2 sections taken at 7 dpi, 2 sections taken at 14 dpi, one section taken at 7 dpi after solu-medrol therapy at 6 dpi, one section taken at 14 dpi after solu-medrol therapy at 6 dpi, and one section taken from the sham control).