HAP1 Promotes Spinal Cord Injury Recovery Through BDNF Signaling Modulation

Spinal cord injury (SCI) is a severe medical condition resulting from trauma, disease or degeneration, leading to partial or complete loss of sensory and motor functions. Huntingtin-associated protein 1 (HAP1) is a classical neuronal protein that plays a crucial role in the nervous systems. Although numerous proteins and molecules have been extensively studied, the mechanisms underlying SCI pathogenesis remain incompletely understood. This study aimed to elucidate how HAP1 modulates functional recovery and tissue repair post-SCI through a multifaceted experimental approach.

Immunofluorescence staining was used to evaluate the spatial distribution and expression levels of HAP1 in spinal cord. An SCI model was established to assess behavioral functions using the Basso Mouse Scale, forced swim, inclined plate and hot plate tests. Luxol fast blue staining was used to assess morphological repair. The protein and mRNA expression levels of brain-derived neurotrophic factor (BDNF) were quantified post-SCI using enzyme-linked immunosorbent assay and quantitative real-time polymerase chain reaction, respectively. To elucidate the functional role of HAP1 in the SCI process, BDNF injections and behavioral tests were performed. Finally, RNA sequencing followed by bioinformatics analyses (Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathways and Gene Ontology (GO) term enrichment) were performed to identify differentially expressed genes and signaling pathways associated with HAP1 in the SCI process.

HAP1 is abundantly expressed in spinal cord neurons and plays a crucial role in post-traumatic recovery. HAP1 deficiency significantly impairs both functional recovery and morphological repair following spinal cord injury. Comparative analysis revealed lower BDNF levels in HAP1 heterozygous (HET) mice than in wild-type (WT) controls post-injury. Exogenous BDNF administration partially rescued behavioral deficits in HET mice, indicating BDNF-dependent compensatory mechanisms. RNA-seq analysis identified 444 differentially expressed genes and potential pathways associated with HAP1 in the SCI process.

HAP1 significantly enhances functional recovery and morphological repair post-SCI through potentiation of BDNF signaling pathways. These findings position HAP1 as a novel therapeutic target for SCI treatment.