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Laboratory-based results Nonmammalian vertebrate hair cell regeneration reveals existence of inner ear stem cells In , Corwin and Cotanche 5 and, independently, Ryals and Rubel 6 reported that cochlear hair cells regenerate after acoustic trauma in birds. Figure 2. Generating replacement hair cells by reexpressing Atonal homolog 1 Atoh1 The basic helix-loop-helix transcription factor Atoh1 also known as Math1 has emerged as a candidate for gene-based treatment of auditory and vestibular disorders 19 , Generating replacement hair cells by disrupting Notch signaling In the normally quiescent bird auditory epithelium, hair cell regeneration seems to reactivate developmental programs, and the Notch signaling pathway is probably the one we know most about.
Generating replacement hair cells by inhibiting cell cycle inhibitors In birds and many nonmammalian vertebrates, supporting cells are able to produce new hair cells through two mechanisms: transdifferentiation and mitotic regeneration. Therapeutic approaches State-of-the-art treatment for hearing loss consists of devices such as hearing aids for mild to profound hearing loss, and cochlear implants for profound hearing loss and deafness. Stem cells and cell delivery Several laboratories have begun to explore the implantation of stem cell—derived precursor cells into the damaged cochlea.
Small molecule modulators of gene expression and pharmacotherapeutics Many of the difficulties specifically associated with progenitor cell transplantation and gene delivery can be overcome with small molecule activators or inhibitors of gene expression. Conclusions and outlook Substantial progress has been made in recent years to accumulate tools that potentially can be used, alone or in combination, to develop strategies for hair cell regeneration.
References 1. Cochlear inner and outer hair cells: functional differences. Otol Neurotol. Histopathology and molecular genetics of hearing loss in the human. Int J Pediatr Otorhinolaryngol. Ann Otol Rhinol Laryngol. Regeneration of sensory hair cells after acoustic trauma. Hair cell regeneration after acoustic trauma in adult Coturnix quail. Hearing loss and cochlear pathology in monkeys after noise exposure. Acta Otolaryngol Stockh ; 81 — Raphael Y, Altschuler RA. Reorganization of cytoskeletal and junctional proteins during cochlear hair cell degeneration. Cell Motil Cytoskeleton.
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Distinct population of hair cell progenitors can be isolated from the postnatal mouse cochlea using side population analysis. Stem Cells. Zhai S, et al. Isolation and culture of hair cell progenitors from postnatal rat cochleae. J Neurobiol. Mammalian cochlear supporting cells can divide and trans-differentiate into hair cells. Math1 gene transfer generates new cochlear hair cells in mature guinea pigs in vivo. J Neurosci. Izumikawa M, et al. Auditory hair cell replacement and hearing improvement by Atoh1 gene therapy in deaf mammals.
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Noise-induced cochlear synaptopathy: Past findings and future studies - ScienceDirect
Overexpression of Math1 induces robust production of extra hair cells in postnatal rat inner ears. Functional auditory hair cells produced in the mammalian cochlea by in utero gene transfer. Loss of Fgfr3 leads to excess hair cell development in the mouse organ of Corti. Dev Dyn. Mansour SL, et al. Hearing loss in a mouse model of Muenke syndrome.
Hum Mol Genet. Notch ligands with contrasting functions: Jagged1 and Delta1 in the mouse inner ear. Daudet N, et al. Notch regulation of progenitor cell behavior in quiescent and regenerating auditory epithelium of mature birds. Dev Biol. Notch signaling regulates the extent of hair cell regeneration in the zebrafish lateral line. Yamamoto N, et al. J Mol Med. Takebayashi S, et al. Multiple roles of Notch signaling in cochlear development. Notch signaling regulates the pattern of auditory hair cell differentiation in mammals. Hori R, et al. Pharmacological inhibition of Notch signaling in the mature guinea pig cochlea.
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