Abstract 18967: Optimal Activation of Innate Immunity is Necessary for Tail Fin Regeneration of Zebrafish Embryo
Objective: Previous studies have shown that activation of innate immunity is necessary for repair and regeneration. However, some contradictory reports indicate that activation of innate immunity might impair regeneration. Based on our previous in vitro work, we hypothesized that these contradictory findings might be explained if there is an optimal zone of innate immune activation that facilitates efficient regeneration in vivo. In this report, we provide experimental evidence for the in vivo existence of such an optimal zone (Goldilocks’ zone) of innate immune activation during embryonic zebrafish tail fin regeneration and show that initial difference of nitric oxide (NO) generation under different conditions of innate immune activation is responsible for such Goldilocks’ zone.
Methods: Tail fin of zebrafish embryos at 48 hpf were transected simultaneously at the tip of the notochord and exposed to different concentrations of poly I:C (0, 10 30 and 100 μg/ml) each day for 48 hours and percentage of tail fin regeneration was measured. In separate studies, we measured NO generation at tail fin transection site using DAF-FM diacetate under different experimental conditions.
Results: Our preliminary data indicates that there is an optimal range (“Goldilocks’ zone”) of innate immune activation for embryonic zebrafish tail fin regeneration. The concentration of poly I:C (PIC) which generated maximal regeneration was 30 μg/ml. On either side of optimal activation (i.e. at lower or higher concentrations of PIC), the efficiency of tail fin regeneration was significantly reduced. Specifically, we observed 69± 0.05%; 86±0.04; and 71± 0.04% regeneration of the tail fin at 10, 30 and 100 μg/ml of PIC respectively. Interestingly, NO production at tail fin transection site was highest at PIC 30μg/ml within 3 hours of innate immune activation and exposure to NFkB inhibitor bay11 or NOS inhibitor L-NAME abolished NO production and impeded tail regeneration at PIC 30.
Conclusion: There is an optimal zone of innate immune signaling necessary for greatest efficiency of regeneration. Understanding the role of NO and other biological mechanisms defining this “Goldilocks zone” will provide insights and potential therapeutic targets to improve efficiency of regeneration.
Author Disclosures: P.K. Chanda: None. G. Matrone: None. J.P. Cooke: None.
- © 2016 by American Heart Association, Inc.