[Neurotrophic action of insulin-like growth factor-I in the inner ear].
BACKGROUND
Loss of hearing constitutes one of the most frequent disabling sensory impairments in the developed world. Different therapeutic approaches are currently being studied, including treatment with stem cells, genetic manipulation and pharmacological protection.


OBJECTIVE
To evaluate the role played by insulin-like growth factor-I (IGF-I) in the development, maintenance and repair of auditory functioning.


METHODS
Proper development of the inner ear is dependent on a suitable coordination of the cell processes of proliferation, differentiation, neurogenesis and programmed cell death, which are regulated by different factors, one of which is IGF-I. During the embryogenesis of the inner ear, this factor is expressed in abundance and is essential for cell survival and maintaining neuronal precursors. Studies conducted in Igf-1-/- null mice have highlighted its importance in the development and continued functioning of the inner ear. Mice with a deficit in this gene display morphological disorders that correspond to severe functional deficiencies, which are confirmed by analysing brainstem auditory evoked potentials. A deficit of IGF-I in humans is also accompanied by profound sensory hypoacusis.


CONCLUSIONS
In a scenario like this, IGF-I appears as a key factor in the development of auditory functioning and a candidate for regenerative therapy of the inner ear.
Rodríguez-de la Rosa
L
L
Instituto de Investigaciones Biomédicas Alberto Sols, CSIC-UAM, 28029 Madrid, España.
Contreras-Rodríguez
J
J
Cediel-Algovia
R
R
León
Y
Y
Sánchez-Calderón
H
H
Murillo-Cuesta
S
S
Riquelme-Galiana
R
R
de Diego-Sastre
J I
JI
Prim-Espada
M P
MP
Varela-Nieto
I
I
D000818:Animals; D007758:Ear, Inner / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D006309:Hearing / Q000502:physiology*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D009414:Nerve Growth Factors / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology
D009414:Nerve Growth Factors; D007334:Insulin-Like Growth Factor I