Galanin-Mediated Inflammatory Responses in Zebrafish Spinal Cord Regeneration

Spinal cord injury (SCI) causes significant sensory and motor deficits and paralysis due to the limited regenerative capacity of the mammalian central nervous system (CNS). The inflammatory response triggered by the injury is critical for successful spinal cord regeneration. Galanin is a neuropeptide acting primarily as an inhibitory neuromodulator or neurotransmitter in the central and peripheral nervous systems. Galanin is also expressed in various non-neuronal cell types, including immune cells. Galanin has been implicated in neuroprotection and inflammation; however, its contribution to spinal cord regeneration is not well defined. Here, we investigated the function of galanin in SCI repair in zebrafish (Danio rerio), which possess the remarkable ability to regenerate the CNS. We performed spinal cord transection on 3 days post fertilization (dpf) zebrafish larvae and found that the galanin knockout mutant zebrafish showed delayed axonal regeneration and functional recovery, reduced inflammation-related gene expression during the early inflammatory phase, and impaired migration of neutrophils to the lesion site. These results suggest that galanin plays an important role in the regenerative process of the spinal cord by regulating the inflammatory response caused by SCI.