Europe PMC Funders Group
Author Manuscript
Nature. Author manuscript; available in PMC 2013 April 11.
Published in final edited form as:
Nature. 2012 October 11; 490(7419): 278–282. doi:10.1038/nature11415.
Europe PMC Funders Author Manuscripts
Restoration of auditory evoked responses by human ES cellderived otic progenitors
Wei Chen1,2,*, Nopporn Jongkamonwiwat1,2,4,*, Leila Abbas1,2, Sarah Jacob Eshtan1,2,
Stuart L. Johnson2, Stephanie Kuhn2, Marta Milo2, Johanna K. Thurlow1,2, Peter W.
Andrews1,2, Walter Marcotti2, Harry D. Moore1,2, and Marcelo N. Rivolta1,2,3
1Centre
for Stem Cell Biology, University of Sheffield, Sheffield S10 2TN, United Kingdom
of Biomedical Sciences, University of Sheffield, Sheffield S10 2TN, United Kingdom
4Faculty of Health Sciences, Srinakharinwirot University, Ongkharak, Nakhonnayok 26120,
Thailand
2Department
Abstract
Europe PMC Funders Author Manuscripts
Deafness is a condition with a high prevalence worldwide, produced primarily by the loss of the
sensory hair cells and their associated spiral ganglion neurons (SGNs). Of all the forms of
deafness, auditory neuropathy is of a particular concern. This condition, defined primarily by
damage to the SGNs with relative preservation of the hair cells 1, is responsible for a substantial
proportion of patients with hearing impairment 2. While the loss of hair cells can be circumvented
partially by a cochlear implant, no routine treatment is available for sensory neuron loss since poor
innervation limits the prospective performance of an implant 3. Using stem cells to recover the
damaged sensory circuitry is a potential therapeutic strategy. Here, we present a protocol to induce
differentiation from human embryonic stem cells (hESCs) using signals involved in the initial
specification of the otic placode. We obtained two types of otic progenitors able to differentiate in
vitro into hair cell-like cells and auditory neurons that display expected electrophysiological
properties. Moreover, when transplanted into an auditory neuropathy model, otic neuroprogenitors
engraft, differentiate and significantly improve auditory evoked response (ABR) thresholds. These
results should stimulate further research into the development of a cell-based therapy for deafness.
Hair cell-like phenotypes and sensory neurons, with different degrees of functional
maturation, have been obtained from mouse stem populations 4-10. After transplantation,
some cell types have showed engraftment but none have demonstrated evidence of
functional recovery 10-15. Although useful for research purposes, these products are
unsuitable for a therapeutic application and to date appropriate cell types of human origin
have remained elusive. Neuroprogenitors isolated from mature human cochleae display
limited proliferative and differentiating potential 16 while hESCs-derived neural crest cells
Correspondence should be addressed to M.N.R (m.n.rivolta@sheffield.ac.uk).. 3Corresponding author: Centre for Stem Cell Biology
and Department of Biomedical Sciences, University of Sheffield, Alfred Denny Building, Western Bank, Sheffield S10 2TN, UK
Phone: 44 (0) 114 2222385 Fax: 44 (0) 114 222 2787 m.n.rivolta@sheffield.ac.uk.
*These authors contributed equally to this work.
Supplementary Information, Methods and Spreadsheets are linked to the online version of the paper.
Author Contributions W.C., N.J., L.A., S.J.E and J.K.T: Collection and/or assembly of data, data analysis and interpretation; S.L.J.,
S.K, and W.M.: Collection and/or assembly of electrophysiology data, its analysis and interpretation; M.M.: Biocomputational
analysis of gene array data; P.W.A. and H.D.M.: provision of study material, administrative support; M.N.R: Conception and design,
financial support, collection and/or assembly of data, its analysis and interpretation, manuscript writing, final approval of manuscript.
Author information Microarray datasets have been deposited at the NCBI Gene Expression Omnibus and they can be retrieved with
accession number GSE36754. The authors declare no competing financial interest.
Chen et al.
Page 2
Europe PMC Funders Author Manuscripts
may differentiate into sensory neurons by exposure to BMP but lack true otic
characteristics 17,18. Recently, we isolated a population of bipotent stem cells from the
human fetal cochlea (hFASCs), with the ability to produce hair cell-like cells and
neurons 19. However, although hFASCs can be expanded in vitro for ~25 population
doublings, they eventually undergo replicative senescence. Hence, there is a need for a
reliable, renewable source of human otic progenitors, with the ability to produce both cell
types for sensory replacement.
Europe PMC Funders Author Manuscripts
FGF signaling is necessary and sufficient for the induction in vivo of the otic placode, the
primordium of the hearing organ 20,21. Since in the mouse the ligands involved in placode
signaling have been identified as FGF3 and FGF10 22,23, we hypothesized that exposure to
these factors would trigger otic differentiation of hESCs. Initial experiments with embryoid
bodies (EBs) confirmed FGF3 and 10 induction of otic features (Supplementary Fig. 1a)
therefore we focused on developing a method devoid of this initial cell-aggregation step,
which is prone to high variability. Undifferentiated colonies of hESCs were dissociated for
plating as a monolayer on laminin-coated flasks (see Supplementary Methods). Under these
conditions, FGF3+10 treatment induced the placodal markers PAX8 and PAX2, either in the
presence of KOSR or under defined conditions using DFNB medium (Supplementary
Methods, Supplementary Figs. 1b-2). Global analyses of gene expression was performed
using Affymetrix GeneChip arrays and, after normalization (see Supplementary Methods),
samples were mined in two different ways. In the first we used the Gene Set Enrichment
Analysis (GSEA) tool 24 to look for genes that were enriched in the entire list of probe sets,
without establishing a priori cut off of differential expression (Supplementary Table 1-2).
This analysis showed that a set of otic markers was significantly enriched in the FGF-treated
samples when compared with the undifferentiated hESCs (normalized enriched score, NES:
0.568, family-wise error rate p-value, FWERp 0.046) or cells grown in DFNB (NES: 0.707,
FWERp 0.019) (Supplementary Table 1). A second type of analysis assessed genes
differentially expressed using predefined criteria for fold change cut off and statistical
significance (see Supplementary Methods). A total of 1,424 genes (represented by 2,124
probe sets) was differentially upregulated in the FGF-samples when compared to
undifferentiated hESCs, while 423 genes (505 probe sets) were upregultaed in the FGFtreated vs. the DFNB controls (Supplementary spreadsheets 1-2). On the other hand, 2,368
genes (3,231 probe sets) were downregulated in the FGF-samples vs hESCs and 482 genes
(607 probe sets) were downregulated vs DFNB (Supplementary spreadsheets 3-4). In a gene
ontology (GO) analysis, the GO terms ‘sensory organ development’ (EASE p-value score in
FGF vs hESC: 3.92 ×10−15; FGF vs DFNB: 0.022); ‘ear development’ (FGF vs hESC: 4.47
×10−8; FGF vs DFNB: 0.014) and ‘ear morphogenesis’ (FGF vs hESC: 3.08 ×10−6; FGF vs
DFNB: 0.0497) were highly enriched in the FGF-treated cells in both comparisons, while
‘mechanoreceptor differentiation’ and ‘auditory receptor differentiation’ were up in FGF vs
hESC (See Supplementary Spreadsheets 5-8). Both bioinformatics analyses therefore
suggested that the FGF treatment was generating a global change of transcription compatible
with the induction of otic progenitors.
We also used immunostaining to examine the co-expression of PAX8 and SOX2, to define
the otic progenitors at a cellular level. Otic progenitors grew as colonies after the inductive
phase. Initial immunolabelling showed a relatively large proportion of double positive cells
in the FGF-treated condition (~78%), in contrast to the relatively moderate upregulation of
otic transcripts detected with the arrays. However, a subset of cells expressed very high
levels of PAX8 and SOX2, and these were assessed with an automated microscopy platform
(InCell Analyzer 1000) that enabled quantification of the number of positive cells and their
relative intensity (Fig. 1 and Supplementary Figure 3). When a stringent threshold was
selected (75th intensity percentile per cell line and antibody, see Supplementary Methods)
18.3%±0.8 of the cells expressed high levels of PAX8 and SOX2 (PAX8hiSOX2hi) after
Nature. Author manuscript; available in PMC 2013 April 11.
Chen et al.
Page 3
Europe PMC Funders Author Manuscripts
FGF treatment (against 0% obtained without the growth factors, p<0.001) while 18%±2
cells were PAX8hi/FOXG1hi (compared to 4%±4 obtained in the control, p<0.001).
PAX8hiSOX2hiFOXG1hi cells also expressed the otic markers PAX2, NESTIN, SIX1 and
GATA3 (Fig. 2h and Supplementary Figs. 4-5a). It is likely that this subset of
PAX8hiSOX2hiFOXG1hi expressing cells represents the otic progenitors. The
reproducibility of the protocol was tested across the hESC lines H7, H14 and Shef3, which
all gave comparable results (see Fig. 1 and Supplementary Figure 3). FGF3 and 10 induced
two morphologically distinct types of otic colonies (Fig. 2a-h). One cell population showed
a flat phenotype, with large cytoplasm and formed epithelioid islands (Fig. 2a-d), while the
second was small, with denser chromatin and presented cytoplasmic projections (Fig. 2e-f).
Given their morphological appearance we have operationally named them otic epithelial
progenitor (OEP) and otic neural progenitor (ONP), respectively. The relative proportion of
these progenitors was dependent on the cell line, plating density and the degree of cell
separation (single cells versus cell clusters) (Supplementary Figs. 5-6 and Supplementary
Methods). Progenitor colonies were purified using sequential dissociation (see
Supplementary Methods), yielding moderately homogenous cultures of the desired cell
colony type and were expanded in OSCFM (Otic stem cell full media, Suppl. Methods).
Europe PMC Funders Author Manuscripts
The differentiation potential of OEPs and ONPs was tested in ‘neuralizing’ and ‘hair cell’
culture conditions developed previously using hFASCs 19 (see Supplementary Methods).
OEPs produced hair cell-like cells as defined by the simultaneous expression of ATOH1 and
BRN3C, or BRN3C and MYO7A (~45%) (Supplementary Fig. 7). A small subset
differentiated a rudimentary apical bundle, expressing ESPIN (Supplemntary Fig 8). These
hair cell-like cells also expressed an outward K+ current, the inward rectifier K+ current IK1
and an inward Ca2+ current (ICa) (Supplementary Fig. 9). Under ‘neuralizing’ conditions,
they produced a small proportion (~9%) of sensory neurons (Supplementary Fig 7). On the
other hand, ONPs were committed to produce neurons. Under ‘neuralizing’ conditions,
almost all cells developed a bipolar morphology and were positive for BRN3A and tubulinIII, as well as for -tubulinIII and NF200. They also expressed NEUROD1, ISLET-1
and TrkB, a delayed-rectifier K+ current (IK), a Na+ current (INa), and elicited single action
potentials (Supplementary Fig. 9). No hair cell differentiation was obtained from ONPs
under ‘neuralizing’ or ‘hair cell’ culture conditions. Detailed results are given in
Supplementary Information.
The properties of ONPs in vivo were studied by transplanting them into ouabain-treated
gerbils, a model of neuropathic deafness 25. Application of ouabain directly to the round
window selectively damages the type I SGNs, preserving the hair cells and the organ of
Corti 26 (Supplementary Fig. 10). After ouabain application, only a small number of SGNs
survived (6.4%, see Supplementary Table 3). Most of the surviving cells (~87%) were
peripherin+, type II neurons therefore less than 1% of the original population of type I
neurons remained (Supplementary Table 3 and Supplementary Fig. 13). Staining for myosin
VIIa and the presence of distortion product otoacoustic emissions (DPOAEs) confirmed that
the organ of Corti had not been damaged (Supplementary Figs. 10 and 11). DPOAEs are
sounds produced as a consequence of electromechanical feedback from the outer hair cells
and can be used to check their physiological integrity.
ONPs derived from Shef1 hESCs constitutively expressing either eGFP or Tomato
fluorescent protein were expanded in OSCFM, dissociated with trypsin and delivered
directly into the modiolus, approaching the cochlea through the round window. One set of
animals was transplanted 3-5 days after ouabain application (n=13) while another was
transplanted two weeks after the ototoxic drug (n=5). Since no functional or histological
differences were encountered between the two groups (p>0.05; Supplementary Fig. 12), they
were analyzed together. Two to three weeks after transplantation, five out of six animals had
Nature. Author manuscript; available in PMC 2013 April 11.
Chen et al.
Page 4
Europe PMC Funders Author Manuscripts
surviving, transplanted cells grafted in the modiolus, forming an ectopic spiral ganglion
(Fig. 3a-b). Cells in the marginal sides of the ectopic ganglion had undergone differentiation
as judged by -tubulin III staining (Fig. 3b) and displayed neural projections, targeting the
organ of Corti (Fig. 3c-d). Animals were then followed up for 10 weeks posttranplantation
(PT). Histological analysis after 10 weeks PT showed that the ectopic ganglion was still
present and cells had also migrated into the Rosenthal’s canal (Fig. 3e). Transplanted cells
expressed the 3A10 neurofilament-associated antigen and NKA 3, a marker of type I
neurons and afferent fibers in the inner ear 27 (Supplementary Fig. 14). Significantly,
projections from the transplanted cells that reached the organ of Corti were targeting the hair
cells, and fibers positive for NKA 3 and GluA2 were observed next to the basal pole of the
inner hair cells suggesting the presence of synaptic connections (Fig. 3g). Moreover, fibers
form the transplanted cells were visualized leaving the modiolus towards the brainstem (Fig.
3f). In the cochlear nucleus of three gerbils we found RFP-positive fibers also stained for
synaptophysin, suggesting synaptic connections with the central auditory path (Fig. 3h-i).
Transplanted ONPs contributed significantly to restore neuronal density (Fig. 3j, p<0.01).
While 112.5±11.9 TuJ1+ mm−2 cells were present in the ouabain-treated, untransplanted
ears, 546.4±30.6 TuJ1+ mm−2 were found after transplantation. From these, 94.9 ± 0.3%
were also GFP (or Tomato) positive, confirming their exogenous nature (Supplementary
Table 4). The number of projections detected in the brainstem was considerably lower than
the number of transplanted cell bodies identified in the ganglion. While this could be
explained by the limited sorting of fluorescent protein into the long afferent fibers, the
pathfinding of the central innervations should require further future exploration. No tumors
were detected in any of the transplanted animals at any stage throughout the experiment.
Europe PMC Funders Author Manuscripts
Functional performance was determined by measuring ABRs thresholds. These were
established based on the wave ii-wave iii (P2-N3) amplitude 28. These waves are generated
by the cochlear nucleus and the superior olivary complex cells, and reflect neural
connections with the central auditory pathway 29. After ouabain application, auditory
function was severely impaired, with thresholds rising from 20dBSPL to almost 80dbSPL,
the maximum intensity tested. Frequency discrimination was also abolished. The amplitudes
of wave ii-iii complexes were almost negligible at any of the frequencies explored at the
maximum intensity of 80dBSPL (Fig. 4d). ABRs were recorded at 1-2 week intervals.
Control animals (n=8) showed no sign of functional recovery throughout the experiment,
with a mean auditory threshold after 10 weeks of 75.14±2.3 dB; similar to the 76.37±1.8 dB
obtained after ouabain treatment. However in the transplanted animals (n=18), there was a
detectable improvement in the ABR thresholds (Fig. 4a-b) starting approximately four
weeks PT, with the mean auditory threshold lowered (improved) to 50.4±4.5 dB by 10
weeks PT. Furthermore, the mean auditory threshold shift, calculated as the difference
between the threshold at 10 weeks PT versus the one before ouabain treatment, was of
53±1.7 dB in the control animals, compared to 28.6±3.6 dB in the transplanted cohort (p
0.0002, Fig. 4c). This represents an overall functional improvement of ~46%. The range of
recovery went from modest to almost complete (see Supplementary Fig. 15), which is
remarkable considering the technical challenges involved in the procedure. Tonotopical
processing was also partially restored (Fig. 4d). A trend in the increment of wave ii-iii
amplitudes was detected at each frequency explored, with amplitudes being significantly
different at 22, 26 and 30 kHz, when compared to the untransplanted animals (p<0.05).
When compared to the amplitudes before the ouabain application, the improvement was
~43%. Latencies were mostly similar to the ones before ouabain (Fig. 4e). The only
significant difference was detected at 30 kHz (BO: 4.58±0.2 ms, n=6; PT: 5.9±0.4 ms, n=5;
p<0.05) suggesting that some maturation was still taking place at this stage. Finally, there
was a significant correlation between the increment of neural density by transplanted cells
and the lowering of the ABR threshold (R2=0.3867, p<0.05, Fig. 4f).
Nature. Author manuscript; available in PMC 2013 April 11.
Chen et al.
Page 5
Europe PMC Funders Author Manuscripts
Our developmentally-informed protocol produced hESC-derived auditory hair cells and
neurons that closely resembled phenotypes obtained from hFASCs, providing validation of
their cochlear characteristics. This was further supported by the restoration of ABR
thresholds on transplantation of otic progenitors into a deaf adult mammal. The ability to
reinstate auditory neuron functionality paves the way for a future cell-based treatment for
auditory neuropathies. It may also, in combination with a cochlear implant, offer a
therapeutic solution to a wider range of patients that currently remain without viable
treatment.
Methods Summary
Europe PMC Funders Author Manuscripts
hESCs lines used (H7, H14, Shef1, Shef3, Shef1-EGFP and Shef1-Tomato), with a normal
karyotype, were maintained on mouse embryonic fibroblast feeders (MEFs) under standard
conditions. While EBs and initial monolayer experiments were performed in the presence of
Knock Out Serum Replacement (KOSR), we later adopted a chemically-defined medium.
This serum-free, chemically defined basal culture media included a 1:1 mixture of
Dulbeco’s Modified Eagle’s Medium (DMEM):Ham’s F12 and N2/B27 supplements
(DFNB). In most experiments, FGF3 and FGF10 were used at 50ng ml−1. Laminin (R&D
Systems) was used at 5 μg cm−2. Antibodies, PCR primers and microarray analysis are
detailed in the supplementary methods. To induce hair cell differentiation, progenitors were
transferred to gelatin-coated dishes and cultured with DFNB supplemented with all-trans
retinoic acid (10−6 M, Sigma) and EGF (20ng/ml) for 2-4 weeks. To induce neuronal
differentiation, cells dissociated with trypsin were plated on gelatin-coated dishes and
incubated in DFNB with bFGF (20ng/ml) and Sonic Hedgehog (Shh-C24II, 500ng/ml, R&D
Systems). On the third day, culture was supplemented with neurotrophin3 (NT-3, 10 ng/ml,
Petropech) and brain-derived neurotrophic factor (BDNF, 10 ng/ml, Petropech). Shh-C24II
was removed at the fourth-fifth day while the neurotrophins remained for the length of the
incubation, normally between 7-14 days. Conditions for electrophysiological recordings are
detailed in the supplementary methods. The auditory neuropathy model was generated by
applying 1 mM ouabain directly into the RW niche of adult gerbils. Either three days or 2
weeks later, hONPs, expressing eGFP or Tomato fluorescent protein were injected into the
modiolus. Functional recovery was monitored weekly by measuring ABRs and DPOAEs,
for up to 10 weeks. Cochleae were taken, fixed and processed for analysis. Details for the
hearing test and histological preparation are provided in the supplementary methods section.
Supplementary Material
Refer to Web version on PubMed Central for supplementary material.
Acknowledgments
This work was supported primarily by grants from Action on Hearing Loss (RNID) to M.N.R. Other support
included Deafness Research UK (M.N.R, W.M.), Wellcome Trust (088719, W.M.), MRC (P.W.A, HDM, M.N.R)
and ESTOOLS (P.W.A). S.L.J. was supported by a Wellcome Trust VIP award and the RNID. W.M. and S.L.J. are
Royal Society University Research Fellows. Confocal images were taken at the Light Microscopy Facility of the
Department of Biomedical Sciences. We are grateful for the advice by Dr. Mike Mulheran and Prof. Ian Russell on
the tests of auditory function, provided at the earlier stages of this project and to the assistance of Dr. Paul Gokhale
on the use of the InCell Analyzer. M.N.R. dedicates this work to the memory of his parents, Noemí Luján-Ceballos
and Juan Carlos Rivolta.
References
1. Vlastarakos PV, Nikolopoulos TP, Tavoulari E, Papacharalambous G, Korres S. Auditory
neuropathy: endocochlear lesion or temporal processing impairment? Implications for diagnosis and
Nature. Author manuscript; available in PMC 2013 April 11.
Chen et al.
Page 6
Europe PMC Funders Author Manuscripts
Europe PMC Funders Author Manuscripts
management. International journal of pediatric otorhinolaryngology. 2008; 72:1135–1150.
[PubMed: 18502518]
2. Uus K, Bamford J. Effectiveness of population-based newborn hearing screening in England: ages
of interventions and profile of cases. Pediatrics. 2006; 117:e887–893. [PubMed: 16651292]
3. Bradley J, Beale T, Graham J, Bell M. Variable long-term outcomes from cochlear implantation in
children with hypoplastic auditory nerves. Cochlear implants international. 2008; 9:34–60.
[PubMed: 18246534]
4. Li H, Liu H, Heller S. Pluripotent stem cells from the adult mouse inner ear. Nat Med. 2003;
9:1293–1299. [PubMed: 12949502]
5. Li H, Roblin G, Liu H, Heller S. Generation of hair cells by stepwise differentiation of embryonic
stem cells. Proc Natl Acad Sci U S A. 2003; 100:13495–13500. [PubMed: 14593207]
6. Oshima K, et al. Mechanosensitive hair cell-like cells from embryonic and induced pluripotent stem
cells. Cell. 2010; 141:704–716. [PubMed: 20478259]
7. Jeon SJ, Oshima K, Heller S, Edge AS. Bone marrow mesenchymal stem cells are progenitors in
vitro for inner ear hair cells. Molecular and cellular neurosciences. 2007; 34:59–68. [PubMed:
17113786]
8. Kondo T, Johnson SA, Yoder MC, Romand R, Hashino E. Sonic hedgehog and retinoic acid
synergistically promote sensory fate specification from bone marrow-derived pluripotent stem cells.
Proc Natl Acad Sci U S A. 2005; 102:4789–4794. [PubMed: 15778294]
9. Coleman B, Fallon JB, Pettingill LN, de Silva MG, Shepherd RK. Auditory hair cell explant cocultures promote the differentiation of stem cells into bipolar neurons. Exp Cell Res. 2007;
313:232–243. [PubMed: 17112512]
10. Reyes JH, et al. Glutamatergic neuronal differentiation of mouse embryonic stem cells after
transient expression of neurogenin 1 and treatment with BDNF and GDNF: in vitro and in vivo
studies. J Neurosci. 2008; 28:12622–12631. [PubMed: 19036956]
11. Corrales CE, et al. Engraftment and differentiation of embryonic stem cell-derived neural
progenitor cells in the cochlear nerve trunk: growth of processes into the organ of Corti. J
Neurobiol. 2006; 66:1489–1500. [PubMed: 17013931]
12. Hildebrand MS, et al. Survival of partially differentiated mouse embryonic stem cells in the scala
media of the guinea pig cochlea. J Assoc Res Otolaryngol. 2005; 6:341–354. [PubMed: 16208453]
13. Sekiya T, et al. Transplantation of conditionally immortal auditory neuroblasts to the auditory
nerve. Eur J Neurosci. 2007; 25:2307–2318. [PubMed: 17445229]
14. Lang H, et al. Transplantation of mouse embryonic stem cells into the cochlea of an auditoryneuropathy animal model: effects of timing after injury. J Assoc Res Otolaryngol. 2008; 9:225–
240. [PubMed: 18449604]
15. Hu Z, Ulfendahl M, Olivius NP. Central migration of neuronal tissue and embryonic stem cells
following transplantation along the adult auditory nerve. Brain Res. 2004; 1026:68–73. [PubMed:
15476698]
16. Rask-Andersen H, et al. Regeneration of human auditory nerve. In vitro/in video demonstration of
neural progenitor cells in adult human and guinea pig spiral ganglion. Hear Res. 2005; 203:180–
191. [PubMed: 15855043]
17. Shi F, Corrales CE, Liberman MC, Edge AS. BMP4 induction of sensory neurons from human
embryonic stem cells and reinnervation of sensory epithelium. Eur J Neurosci. 2007; 26:3016–
3023. [PubMed: 18005071]
18. Lee G, et al. Isolation and directed differentiation of neural crest stem cells derived from human
embryonic stem cells. Nature biotechnology. 2007; 25:1468–1475.
19. Chen W, et al. Human fetal auditory stem cells can be expanded in vitro and differentiate into
functional auditory neurons and hair cell-like cells. Stem Cells. 2009; 27:1196–1204. [PubMed:
19418454]
20. Martin K, Groves AK. Competence of cranial ectoderm to respond to Fgf signaling suggests a twostep model of otic placode induction. Development. 2006; 133:877–887. [PubMed: 16452090]
21. Freter S, Muta Y, Mak SS, Rinkwitz S, Ladher RK. Progressive restriction of otic fate: the role of
FGF and Wnt in resolving inner ear potential. Development. 2008; 135:3415–3424. [PubMed:
18799542]
Nature. Author manuscript; available in PMC 2013 April 11.
Chen et al.
Page 7
Europe PMC Funders Author Manuscripts
22. Alvarez Y, et al. Requirements for FGF3 and FGF10 during inner ear formation. Development.
2003; 130:6329–6338. [PubMed: 14623822]
23. Wright TJ, Mansour SL. Fgf3 and Fgf10 are required for mouse otic placode induction.
Development. 2003; 130:3379–3390. [PubMed: 12810586]
24. Subramanian A, et al. Gene set enrichment analysis: a knowledge-based approach for interpreting
genome-wide expression profiles. Proc Natl Acad Sci U S A. 2005; 102:15545–15550. [PubMed:
16199517]
25. Schmiedt RA, Okamura HO, Lang H, Schulte BA. Ouabain application to the round window of the
gerbil cochlea: a model of auditory neuropathy and apoptosis. J Assoc Res Otolaryngol. 2002;
3:223–233. [PubMed: 12382099]
26. Lang H, Schulte BA, Schmiedt RA. Ouabain induces apoptotic cell death in type I spiral ganglion
neurons, but not type II neurons. J Assoc Res Otolaryngol. 2005; 6:63–74. [PubMed: 15735933]
27. McLean WJ, Smith KA, Glowatzki E, Pyott SJ. Distribution of the Na,K-ATPase alpha subunit in
the rat spiral ganglion and organ of corti. J Assoc Res Otolaryngol. 2009; 10:37–49. [PubMed:
19082858]
28. Burkard R, Boettcher F, Voigt H, Mills J. Comments on “Stimulus dependencies of the gerbil
brain-stem auditory-evoked response (BAER). I: Effects of click level, rate and polarity” [J.
Acoust. Soc. Am. 85, 2514-2525 (1989)]. The Journal of the Acoustical Society of America. 1993;
94:2441–2442. [PubMed: 8227757]
29. Boettcher FA, Mills JH, Norton BL. Age-related changes in auditory evoked potentials of gerbils.
I. Response amplitudes. Hear Res. 1993; 71:137–145. [PubMed: 8113132]
Europe PMC Funders Author Manuscripts
Nature. Author manuscript; available in PMC 2013 April 11.
Chen et al.
Page 8
Europe PMC Funders Author Manuscripts
Europe PMC Funders Author Manuscripts
Figure 1. FGF3 and 10 generates otic progenitors
Bar chart showing the percentage of highly double positive cells at the FGF 75th percentile
threshold (n=3; mean + s.e.m).
Nature. Author manuscript; available in PMC 2013 April 11.
Chen et al.
Page 9
Europe PMC Funders Author Manuscripts
Figure 2. Otic epithelial (OEPs) and Otic Neuro progenitors (ONPs)
Europe PMC Funders Author Manuscripts
a and b. Morphology of an OEP colony. Bar is 100 μm. In all remaining panels, bar is 50
μm. c and d. Show the partial lifting of OEPs when treated with a short, mild trypsin
incubation. e and f. Typical morphology of ONPs, showing cytoplasmic projections. g. Sideby-side ONP and OEP colonies, double-labeled for PAX8 and SOX2. h. ONP colony
labeled for PAX8 and NESTIN.
Nature. Author manuscript; available in PMC 2013 April 11.
Chen et al.
Page 10
Europe PMC Funders Author Manuscripts
Europe PMC Funders Author Manuscripts
Figure 3. Transplantation of otic progenitors restores a population of spiral ganglion neurons
a. Mid-modiolar section of a transplanted cochlea showing the location of the newly formed,
ectopic ganglion. b. Detail of the ganglion showing neuronal differentiation by TuJ1
staining (red). Neural fibers project from the ganglion towards the organ of Corti (c and d,
arrows), passing through the Rosenthal’s canal (c and d, asterisk). e. New neuronal bodies
(arrows) are also found in the Rosenthal’s canal (asterisk). f. Ectopic ganglion at the base of
the modiolus, projecting TuJ1+ fibers centrally, towards the internal auditory meatus. g.
RFP+ fibers (arrowheads) approaching the inner hair cells and expressing GluA2 (green),
primarily concentrated in postsynaptic densities (PSDs) around the basal pole of IHCs
Nature. Author manuscript; available in PMC 2013 April 11.
Chen et al.
Page 11
Europe PMC Funders Author Manuscripts
(arrow). Dotted lines show the positions of the IHCs. Fibers (including PSDs) were also
positive for NKA 3 (purple), a marker of afferent terminals. Nine out of ten animals
analyzed had fibers contacting the IHC, while the three animals labeled for GluA2, were
positive. h, i. RFP+ fibers in the cochlear nucleus, expressing synaptophysin (green, arrows).
In (h), the fiber branches and surrounds the cell, with morphology highly reminiscent of the
maturing endbulb of Held. j. SGN density 10 weeks after transplantation. Conditions
compared are cochleae treated with ouabain and sham operated versus those with ouabain
and transplanted with ONPs. Density was significantly increased (p<0.01) from 112.5±11.9
(n=3; mean + s.e.m) to 546.4±30.6 (n=8). As a reference, the density of the control,
untreated cochleae was 1,743±71.5 TuJ1+ cells mm−2. Scale bars for a-f are 100 μm and for
g-i are 50 μm.
Europe PMC Funders Author Manuscripts
Nature. Author manuscript; available in PMC 2013 April 11.
Chen et al.
Page 12
Europe PMC Funders Author Manuscripts
Figure 4. Transplanted cells provide a recovery of ABR thresholds
Europe PMC Funders Author Manuscripts
a. Evolution of the mean ABR thresholds (click) obtained in the transplanted animals (n=18;
mean ± s.e.m) compared to the controls (n=8). b. Trace ABR showing the abolition of
waves after ouabain treatment (AO) and the restoration of the complexes 10 weeks
posttransplanation (PT). c. Graph showing the mean auditory threshold shift reduction
obtained by the transplantation (transplanted 28.6±3.6 dB; n=18 vs 53±1.7 dB; n=8 in the
control, p 0.0002; mean + s.e.m). d. Comparison of the wave ii-iii amplitudes obtained by
tone ABRs. A general trend of enhanced amplitudes was obtained across all frequencies
tested, being significantly different from the untransplanted controls at 22, 26 and 30 kHz.
Amplitudes before ouabain (BO) were equivalent between the transplanted (n=6) and
untransplanted animals (n=5; mean ± s.e.m). e. Latencies of wave ii-iii complexes were, in
general, comparable before ouabain and after transplantation. Only at 30 kHz, a significant
delay was observed (BO: 4.58±0.2 ms, n=6; PT: 5.9±0.4 ms, n=5; p<0.05; mean ± s.e.m). f.
A significant correlation was observed between the mean density of TuJ1/GFP positive cells
and the ABR thresholds (n=8; p<0.05).
Nature. Author manuscript; available in PMC 2013 April 11.
View publication stats