Optimizing spinal cord injury in zebrafish larvae: effects of age on the injury response

Abstract

Zebrafish are an increasingly popular model to study spinal cord injury (SCI) regeneration. The transparency of larval zebrafish makes them ideal to study cellular processes in real time. Standardized approaches, including age of injury, are not readily available making comparisons of the results with other models challenging. In this study, we systematically examined the response to spinal cord transection of larval zebrafish at three different ages (3-7 days post fertilization or dpf) to determine whether the developmental complexity of the central nervous system affects the overall response to SCI. We then used imaging and behavioral analysis to evaluate whether differences existed based on the age of injury. All ages of larval zebrafish upregulated the required genes for glial bridge formation, ctgfa and gfap, at the site of injury, consistent with studies from adult zebrafish. Though all larval ages upregulated factors required to promote glial bridging, young larval zebrafish (3 dpf) were better able to regenerate axons independent of the glial bridge, unlike older zebrafish (7 dpf). Consistent with this data, locomotor experiments demonstrated that some swimming behavior occurs independent of glial bridge formation, further highlighting the need for standardization of this model and recovery assays. Overall, we found subtle cellular differences based on the age of transection in zebrafish, underlining the importance of considering age when designing experiments aimed at understanding regeneration.

Differential roles of diet on development and spinal cord regeneration in larval zebrafish

“…1C,D) with only a 16% increase in body length during recovery suggesting that resources are prioritized towards regeneration over growth after an injury in larval zebrafish. Consistent with previous studies, (26,31,32) larval zebrafish began the formation of a glial bridge 2-3 days post-injury (dpi) with 74% of larvae forming a glial bridge at 5 dpi (Table 1). As growth after transection was less than that seen during normal development, we next tracked survival (Fig.…”

“…By 5 dpf, the nutrition from the yolk sac of zebrafish larvae is mostly exhausted, and larvae begin to rely on exogenous feed sources. (32) We wondered whether larvae injured after yolk sac depletion would be similarly affected by diet. For these experiments, we fed larvae 5-6 dpf, transected fish at 7 dpf, and resumed feeding at 8 dpf.…”