Single-Cell Sequencing-Based Exploration of the Role of Tip Cells on Astrocytes and Macrophages After Spinal Cord Injury.

Excessive inflammation is a capital cause of scar formation and inflammation microenvironment that result in challenge of axonal regeneration after spinal cord injury (SCI). Macrophages and astrocytes play important roles in the inflammatory response. Tip cells, a critical endothelial sub-population, play pivotal roles in post-injury vascular regeneration. Nevertheless, their characteristics in SCI remain poorly documented. This study based on single cell RNA sequencing (scRNA-seq) and in vitro experiment, investigates the effects of tip cells on astrocytes and macrophages. For astrocytes, tip cells can recruit astrocytes to migrant, contribute to the formation of fence-like structure of astrocytes, finally inhibit the diffusion of inflammation via the Angptl4-Sdc4 ligand-receptor pathway. For macrophages, similarly through the Angptl4-Sdc4 ligand-receptor pathway, tip cells can promote macrophages to polarize more toward the M2 phenotype and inhibit their polarization toward M1 phenotype, thus alleviate the inflammatory response. Tip cells after SCI exhibit conserved ribosomal protein expression, implicating ribosome-dependent signaling in their function. These finding highlight the critical role of tip cells in microenvironment after SCI, offering a potential treatment target for SCI.