Evaluation of Polyphenol-Rich Lemon Peel Extract Use in a Zebrafish Model of Spinal Cord Injury: Morphology, Repair-Associated Markers, and Inflammatory Profile

Flavonoids are a diverse group of natural polyphenolic compounds, recognized for their ability to modulate cellular pathways and mitigate the pathological processes of many neurodegenerative diseases. This study investigates the neurotrophic potential of a polyphenolic-rich lemon peel extract (Lpe) in a Zebrafish larvae spinal cord injury (SCI) model. To evaluate its potential effects, embryos were divided into six experimental groups: a baseline control group in which larvae were neither subjected to spinal cord injury nor treated (Ctrl Group); a group with larvae subjected to spinal cord injury at 3 dpf without treatment (SCI Group); a group treated continuously with Lpe (25 µg/mL) from 0 to 5 dpf without injury (Continuous Group); a group treated continuously with Lpe and injured at 3 dpf (Continuous SCI Group); a group treated with Lpe starting at 3 dpf without injury (Curative Group); and finally, a group injured at 3 dpf and treated simultaneously with Lpe (Curative SCI Group). Lpe treatment significantly downregulated proinflammatory cytokines (<i>tnfa</i>, <i>il1b</i>, and <i>xcl8</i>), and modulated the neuroregenerative pathways Wnt/β catenin, and neurotrophic factor Bdnf. Immunohistochemical analysis further revealed Sox2-positive cells localized around the central canal, consistent with activation of ependymal progenitor populations involved in injury-induced repair processes. These findings support the exploration of Lpe for mitigating SCI-induced damage.