Purpose: Normal tissue radioprotectants alleviate radiation-induced damages and preserve critical organ functions. Investigating their efficacy in vivo remains challenging, especially in enclosed organs like the brain. An animal model that enables direct visualization of radiation-induced apoptosis while possessing the structural complexity of a vertebrate brain facilitates these studies in a precise and effective manner.
Materials and methods: We employed a secA5 transgenic zebrafish expressing secreted Annexin V fused with a yellow fluorescent protein to visualize radiation-induced apoptosis in vivo. We developed a semi-automated imaging method for standardized acquisition of apoptosis signals in batches of zebrafish larvae. Using these approaches, we studied the protective effect of amifostine (WR-2721) in the irradiated zebrafish larval brain.
Results: Upon 2 Gy total-body 137Cs irradiation, increased apoptosis could be visualized at high resolution in the secA5 brain at 2, 24, and 48 hour post irradiation (hpi). Amifostine treatment (4 mM) during irradiation reduced apoptosis significantly at 24 hpi and preserved Wnt active cells in the larval brain. When the 2 Gy irradiation was delivered in combination with cisplatin treatment (0.1 mM), the radioprotective effect of amifostine was also observed.
Conclusions: Our study reveals the radioprotective effect of amifostine in the developing zebrafish larval brain, and highlights the utility of secA5 transgenic zebrafish as a novel system for investigating normal tissue radioprotectants in vivo.
Keywords: Radiation; Wnt signaling; amifostine; apoptosis; cell death; cisplatin; progenitors.