Abstract

Background Spinal cord injury is a severe central nervous system disorder with high morbidity and mortality, whose pathological process is divided into primary and secondary injury. The regulation of neuroinflammation is a critical link in secondary injury, forming a positive feedback loop involving microglia and peripheral immune cells. Low-intensity pulsed ultrasound, a noninvasive physical therapy, exhibits significant potential in regulating inflammation and promoting microangiogenesis in orthopedics and nerve repair, providing new insights for intervening in the secondary pathological cascade of SCI. However, its therapeutic effects and underlying molecular mechanisms in SCI treatment have not been systematically and in-depth explored. Methods A total of 88 Sprague–Dawley rats were randomly divided into the sham operation group, SCI group, and SCI + LIPUS treatment group (nine subgroups with different parameter combinations) to establish a T10 segment SCI model. The SCI + LIPUS group received LIPUS intervention (20 min/day, 5 days/week) starting 1 day after modeling. Basso, Beattie, and Bresnahan locomotor scores were used to evaluate hindlimb motor function at multiple time points postoperatively. On Day 28, spinal cord samples were collected for hematoxylin–eosin staining and immunofluorescence staining to assess cavity area, microglial infiltration, and inflammatory microenvironment changes. In in vitro experiments, a lipopolysaccharide-induced BV2 microglial polarization model was established, followed by LIPUS intervention. Cell Counting Kit-8 assay, quantitative polymerase chain reaction, immunofluorescence staining, and Transwell co-culture with HT22 neurons combined with Western blot were used to detect cell viability, inflammatory factor expression, and neuronal apoptosis. RNA sequencing and bioinformatics analysis (GO/KEGG enrichment, protein–protein interaction network construction) were conducted on spinal cord tissues from the SCI and SCI + LIPUS