Assessment of Motoneuronal Regeneration and Wallerian Degeneration Following Axotomy in Postnatal Mice

Nerve injuries during early postnatal stages results in markedly different outcomes compared to adult injury, with significant motoneuronal death masking potential regenerative capacity. This study systematically evaluated motoneuronal survival, axonal regeneration, and Wallerian degeneration following peripheral nerve injury at distinct postnatal stages (P4, P10, and P30) in mice. Using ChAT-Cre/Ai9(RCL-tdT) and ChAT-Cre/RiboTag transgenic models, we assessed both histological and transcriptomic responses after sciatic nerve lesions. Injury at P4 induced substantial motoneuron death (1150%), whilst P10 and P30 animals showed minimal neuronal loss. However, when correcting for neuronal survival, P4 mice demonstrated the highest regenerative capacity, with surviving neurons achieving 100% axonal regeneration. Motoneuron-specific translatome analysis revealed that P30 animals activated a robust regeneration-associated gene (RAG) programme, including classical markers such as Atf3, Gap43, and Ngfr. In contrast, P4 neurons showed minimal RAG upregulation, suggesting they retain an intrinsic growth state that facilitates regeneration without requiring transcriptional reprogramming. P10 animals exhibited a transitional phenotype with impaired RAG activation and reduced regenerative capacity. Wallerian degeneration proceeded efficiently across all developmental stages, with age-specific differences in myelin clearance kinetics and macrophage recruitment. Transcriptomic analysis confirmed consistent downregulation of myelination programmes and upregulation of pro-regenerative markers following injury, regardless of age. These findings indicate that regenerative capacity is primarily determined by the intrinsic growth state of motoneurons rather than extrinsic factors. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=80 SRC="FIGDIR/small/691768v2_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@9079b4org.highwire.dtl.DTLVardef@12640b7org.highwire.dtl.DTLVardef@62e763org.highwire.dtl.DTLVardef@1453180_HPS_FORMAT_FIGEXP M_FIG C_FIG