Effects of DAPT and Atoh1 overexpression on hair cell production and hair bundle orientation in cultured Organ of Corti from neonatal rats.
BACKGROUND
In mammals, hair cells do not undergo spontaneous regeneration when they are damaged and result in permanent hearing loss. Previous studies in cultured Organ of Corti dissected from neonatal animals have shown that both DAPT (r-secretase inhibitor in the Notch signal pathway) treatment and Atoh1 overexpression can induce supernumerary hair cells. The effects of simultaneous DAPT treatment and Atoh1 over expression in the cells of cultured Organ of Corti from neonatal rats are still obscure.


RESULTS
In this study, we set out to investigate the interaction of DAPT treatment and Atoh1 overexpression as well as culture time and the location of basilar fragment isolated form neonatal rat inner ear. Our results showed that DAPT treatment induced more hair cells in the apical turn, while Atoh1 overexpression induced more extra hair cells in the middle turn of the cultured Organ of Corti. When used together, their effects are additive but not synergistic. In addition, the induction of supernumerary hair cells by both DAPT and Atoh1 overexpression is dependent on the treatment time and the location of the cochlear tissue. Moreover, DAPT treatment causes dramatic changes in the orientation of the stereociliary bundles of hair cells, whereas Atoh1 overexpression didn't induce drastic change of the polarity of stereociliary bundles.


CONCLUSIONS
Taken together, these results suggest that DAPT treatment are much more potent in inducing supernumerary hair cells than Atoh1 overexpression and that the new hair cells mainly come from the trans-differentiation of supporting cells around hair cells. The orientation change of stereociliary bundle of hair cells may be attributed to the insertion of the newly formed hair cells. The immature hair bundles on the newly formed hair cells may also contribute to the overall chaos of the stereociliary bundle of the sensory epithelia.
Department of Otolaryngology Head and Neck Surgery, Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, China.
Li-Dong
LD
Zhao
Wei-Wei
WW
Guo
Chang
C
Lin
Li-Xian
LX
Li
Jian-He
JH
Sun
Nan
N
Wu
Li-Li
LL
Ren
Xin-Xin
XX
Li
Hui-Zhan
HZ
Liu
Wie-Yen
WY
Young
Wei-Qiang
WQ
Gao
Shi-Ming
SM
Yang
D000818:Animals; D000831:Animals, Newborn; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics*; D002452:Cell Count; D016764:Cell Polarity / Q000187:drug effects / Q000235:genetics; D046508:Culture Techniques; D004151:Dipeptides / Q000494:pharmacology*; D005260:Female; D015870:Gene Expression; D006199:Hair Cells, Auditory, Inner / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D018072:Hair Cells, Auditory, Outer / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D008297:Male; D011480:Protease Inhibitors / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D059547:Stereocilia / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors
D051792:Basic Helix-Loop-Helix Proteins; D004151:Dipeptides; D011480:Protease Inhibitors; C000594380:Atoh1 protein, rat; C419410:N-(N-(3,5-difluorophenacetyl)alanyl)phenylglycine tert-butyl ester