The Peripheral Atf3+ Neuronal Population is Responsible for Nerve Regeneration at Early Stage of Nerve Injury Revealed by Single-Cell RNA Sequencing
Peripheral nerve injury (PNI) could transform primary somatosensory neurons into regenerative state. However, details of transcriptomic changes associated to nerve regeneration of somatosensory neurons maintain unclear. 10x single-cell RNA sequencing (scRNA-seq) was conducted on mice dorsal root ganglia (DRG) cells after early stage of nerve injury on day 3 post-constriction chronic injury (CCI). We observed that a novel CCI-induced neuronal population (CIP) emerged and expressed high levels of activating transcription factor (Atf3), a neuronal injury marker. CIP neurons highly expressed regenerative associated genes (RAGs) and were enriched in regeneration-related gene ontology (GO) terms, suggesting these neurons could be a pro-regenerative population. Moreover, intercellular communication networks showed that CIP neurons have a close communication to satellite glia cells (SGCs) and specifically transmitted strong Fgf3-Fgfr1 signaling to SGCs, which could initiate regeneration-associated transcriptional changes of SGCs. This study also confirmed that the regenerative progress occurred at the early stage of nerve injury because immunohistochemistry showed the expression of ATF3 significantly increased since day 3 post-CCI and decreased at 1 month. Our bioinformatics analysis at single-cell resolution advances the knowledge of regenerative dynamic transcriptional changes of DRG cells after injuries and their underlying molecular mechanisms. Overall design: High-throughput analyses the lumbar4-5 dorsal root ganglia(DRG) from chronic construction injury(CCI) mice and naïve mice to explore genes and targets associated with nerve regeneration in the context of CCI. There are  4 samples, two from the naïve group and two from CCI group.