Fucoidan promotes mechanosensory hair cell regeneration following aminoglycoside induced cell damage

Abstract

Lateral line system of the zebrafish is a useful model for study of hair cell toxicity and regeneration. We found that low molecular weight fucoidan (LMWF) stimulated the regeneration of mechanosensory hair cells after neomycin induced cell death in zebrafish lateral line. In the past decade, anticoagulant, antiviral, antitumor, anti- complement, immunomodulatory, anti-inflammatory, and antioxidant activities of fucoidan have been reported. Fucoidan is also known to promote tissue regeneration. In this study, we found that LMWF enhanced hair cell regeneration after neomycin-induced ototoxicity in both wild-type and transgenic zebrafish larva. The aims of this study were to quantify the regenerative effects of LMWF and determine their relationship to the Notch and FGF signaling pathways. Wild-type zebrafish and three different transgenic zebrafish lines (Pou4f3::GFP, scm1::GFP, and ET20::GFP) were used. At 4.5 to 6 days post-fertilization, lateral-line hair cells of larvae were eliminated using neomycin (500 μM). Larvae were then treated with LMWF. Neuromasts were observed using confocal microscopy. Stereocilia morphology was observed using scanning electron microscopy, and the location and status of regeneration was assessed using 5-bromo-2-deoxyuridine (BrdU) incorporation. Hair cells damaged by neomycin treatment regenerated faster in wild-type and Pou4f3::GFP larvae treated with LMWF (50 μg/ml) than in untreated controls. LMWF also enhanced the regeneration of supporting cells in scm1::GFP and ET20::GFP larvae. Increased numbers of BrdU- labeled cells were found after LMWF treatment in neuromast regions corresponding to internal and peripheral supporting cells. The effect of LMWF was mimicked by the Notch-signaling inhibitor N-[N- (3,5-difluorophenacetyl)-1-alanyl]-S-phenylglycine t-butyl ester (DAPT), but the effects of LMWF and DAPT were not additive. LMWF enhances the regeneration of hair cells damaged by neomycin. The mechanism may involve the Notch signaling pathway. LMWF shows promise as a therapeutic agent for hearing and balance disorders.