Sensory hair cell death and regeneration in fishes

Abstract

Sensory hair cells are specialized mechanotransductive receptors required for hearing and vestibular function. Loss of hair cells in humans and other mammals is permanent and causes reduced hearing and balance. In the early 1980’s, it was shown that hair cells continue to be added to the inner ear sensory epithelia in cartilaginous and bony fishes. Soon thereafter, hair cell regeneration was documented in the chick cochlea following acoustic trauma. Since then, research using chick and other avian models has led to great insights into hair cell death and regeneration. However, with the rise of the zebrafish as a model organism for studying disease and developmental processes, there has been an increased interest in studying sensory hair cell death and regeneration in its lateral line and inner ears. Advances derived from studies in zebrafish and other fish species include understanding the effect of ototoxins on hair cells and finding otoprotectants to mitigate ototoxin damage, the role of cellular proliferation vs. direct transdifferentiation during hair cell regeneration, and elucidating cellular pathways involved in the regeneration process. This review will summarize research on hair cell death and regeneration using fish models, indicate the potential strengths and weaknesses of these models, and discuss several emerging areas of future studies.

Using Zebrafish to Study Human Deafness and Hearing Regeneration

“…noise or ototoxic chemicals). In contrast, non-mammalian vertebrates have no such limitations; from fish [7,14] to birds [60,61] , the majority of vertebrates can perfectly repair injuries to the sensory epithelium of the ear. In all cases, the new hair cells arise from the surrounding epithelium consisting of the supporting cells.…”

“…In mammals, such as humans, the damage is permanent. Typically, in fish, the supporting cells re-enter mitosis and hair cells differentiate from these activated supporting cells, rapidly and completely restoring full hearing [7] . In recent years, zebrafish has been increasingly used as a model for human disease, including human deafness, because its genome has been fully sequenced [10] , and targeted gene inactivation has become commonplace [11] .…”

“…Like most fish, zebrafish have two related sensory organs that utilize the mechanosensory hair cell receptors: (1) the inner ear similar to mammalian ears used to detect sound, gravity, and motion, and (2) the lateral line [7] , a fish-and amphibian-specific organ used to detect water flow over the surface of the body ( fig. 1 ).…”

Distribution and restoration of serotonin-immunoreactive paraneuronal cells during caudal fin regeneration in zebrafish

“…To this day, hydrodynamic sensing by aquatic animals has mainly been studied in the context of oscillatory signals in the fluid, traveling from a source distant from the fish, such as a prey or a predator. This type of hydrodynamic sensation is achieved by the canal neuromasts of the lateral line and the free neuromasts scattered across the body Van Trump and McHenry, 2008;Monroe et al, 2015). In contrast to the perception of distant signals, we postulated that local hydrodynamic changes in the vicinity of the caudal fin, such as shear stress amplitude and fluctuations due to turbulence in the boundary layer, could be detected by the HCS paraneuronal cells.…”

A model for reticular dysgenesis shows impaired sensory organ development and hair cell regeneration linked to cellular stress

“…The hair cells are then surrounded by two different types of non-sensory cells: supporting and mantle cells (23). Because of its structural simplicity and experimental accessibility, the lateral line, and in particular the PLL, has become a very popular model to study hair cells development and regeneration and it contributed significantly to the understanding of the molecular pathways that control those phenomena (26).…”