Transforming cochlear supporting cells into auditory hair cells for inner ear sensory organ regeneration Public
Pan, Alexander Yan (2012)
Published
Abstract
The cochlear sensory domain, known as the organ of Corti, within
the mammalian
inner ear is composed of sensory hair cells and interdigitating
non-sensory supporting
cells. The hair cells are the primary receptor cells responsible
for detecting and
transmitting sound signal. Loss of these cells in humans leads to
permanent hearing loss,
since mammalian hair cells cannot be regenerated. In contrast,
lower vertebrate classes
exhibit spontaneous regeneration of hair cells fol owing damage by
proliferation and
conversion of the supporting cells. Atoh1 is a hair cell
differentiation factor, and previous
studies have shown that overexpressing Atoh1 can induce the
expression of hair cell
markers in cochlear non-sensory cells. However, these cells are
usually located outside the
sensory region domain. Furthermore, our previous study suggests
that Atoh1 has a very
limited ability to induce hair cell differentiation in non-sensory
supporting cells within the
sensory domain in the postnatal mammalian inner ear. In many
regenerative species, hair
cell regeneration in the mature cochlea occurs only after the loss
of existing hair cells.
Therefore, I hypothesized that the presence of existing hair cells
inhibits Atoh1-mediated
conversion of supporting cells in mammals. To test this hypothesis,
I first developed an
efficient hair cell ablation protocol involving two different
ototoxic aminoglycosidic drugs. I
then induced Atoh1 expression first throughout the cochlear
epithelium, then specifically
within the supporting cells. I show that ablating the endogenous
hair cells modestly
increases the number of hair cells converted from non-sensory
supporting cells. Together,
this data indicates that the in vitro cochlear explant model
can be used to efficiently test
various conditions for hair cell regeneration and that the
competency of supporting cells
conversion into hair cells may be modulated to achieve hair cell
regeneration.
Table of Contents
INTRODUCTION......................................................................................................................................
1
EXPERIMENTS/METHODS
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5
Organotypic culture of postnatal mouse cochleae
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5
Transgenic mouse models
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5
Characterization of ototoxic drug conditions
.........................................................................................
5
Induction of transgenic Atoh1 in transgenic cochlear explant
cultures ....................................... 6
Immunohistochemistry and imaging
........................................................................................................
6
Cell counts and statistical analyses
............................................................................................................
7
RESULTS
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8
Neomycin and gentamicin efficiently ablate hair cells in
cochlear explants .............................. 8
Inducing overexpression of Atoh1 throughout the cochlear
epithelium induces
regeneration of new hair cells
..................................................................................................................
10
Inducing overexpression of Atoh1 specifically in supporting
cells leads to new ectopic hair
cells within the sensory region
.................................................................................................................
11
DISCUSSION
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13
REFERENCES
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18
ACKNOWLEDGEMENTS
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20
FIGURES
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21
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