Publication Date

12-1-2007

Degree Program

Department of Biology

Degree Type

Master of Science

Abstract

Fishes are capable of regenerating sensory hair cells in the inner ear after exposure to excessive noise. However, a time course of auditory hair cell regeneration has not been characterized for zebrafish, nor has gene expression following noise exposure. To establish a time course of hair cell regeneration, adult zebrafish were exposed to a 100 Hz pure tone at 179 dB re 1 |u.Pa RMS for 36 hours, and then allowed to recover for 0 to 14 days before morphological analysis. Hair cell loss and recovery were determined using phalloidin and DAPI labeling to visualize hair cell bundles and nuclei, respectively. Cell proliferation was quantified through BrdU labeling. Immediately following noise exposure, zebrafish saccules exhibited significant hair cell bundle loss and reduced DAPI staining in the caudal region. Hair cell bundle counts increased over the course of the experiment, reaching pre-treatment levels at 14 days post-noise exposure. Cell proliferation peaked two days post-noise exposure in the caudal region, and to a lesser extent in the rostral region. Low levels of proliferation were also observed in untreated controls, indicating that cells of the zebrafish saccule are mitotically active in the absence of a damaging event. To characterize gene expression in the zebrafish inner ear following noise exposure, fish were noise-exposed as above, and then allowed ta recover for 2 or 4 days. The inner ears were then removed, and their RNA extracted and subjected to microarray analysis. Genes putatively involved in cell proliferation, wound healing, and apoptosis were identified, as were genes previously noted as highly expressed in hair cells. Understanding the pathways in which these genes participate during the process of hair cell regeneration may provide direction in the development of treatments for deafness in the future.

Disciplines

Medical Sciences

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