Development and standardization of a simple zebrafish larval model of global hypoxia-reoxygenation: Recapitulating...

The use of zebrafish has increased substantially in recent years in early preclinical research due to its several advantages over other existing experimental models. However, there is still a need for complementary and non-invasive models of cerebral ischemia-reperfusion injury.

Six days old zebrafish larvae were subjected to varied concentrations of sodium sulfite to induce a controlled hypoxia with minimal mortality, followed by reoxygenation under normoxic condition. Ten minutes of hypoxia mediated by 1 g/L sodium sulfite, followed by 4 h reoxygenation induced a marked cerebral injury, evidenced by altered locomotor functions, and variations in molecular and biochemical markers.

Elevated malondialdehyde levels and reactive oxygen species were observed, indicating increased oxidative stress following the reoxygenation. The expression of genes associated with oxidative stress, inflammation and apoptosis was significantly altered. The blood-brain barrier integrity was found to be compromised following reoxygenation. The expression of NeuN was downregulated, and mitochondrial membrane potential was found to be depolarized.

Unlike adult zebrafish models, which raise greater ethical concerns, larval-based approaches are in many cases considered as an alternative. Existing larva models such as photochemical thrombosis and cobalt chloride exposure involve tissue reactivity, and need costly instrumentation setup. In contrast, the present protocol is simple, low-cost, linked with reduced mortality, and yields robust molecular and behavioral outcomes that closely reflect clinical condition.

These findings showed that sodium sulfite-induced global hypoxia followed by reoxygenation in zebrafish larvae to be an effective tool to model pathological features associated with cerebral ischemia-reperfusion injury.