Abstract

It has recently been shown that the oxygenregulated
factors erythropoietin (Epo) and vascular endothelial
growth factor (VEGF) confer protection on different
cells, including neuronal-derived ones. The receptors for
Epo and VEGF are widely expressed in different organs.
Since mammalian auditory hair cells can irreversibly be
damaged by different agents, we aimed to identify otoprotective
compounds. We focused on the role of Epo and
VEGF in the inner ear and review the recent studies. Epo
and its receptor are expressed in the inner ear. In vitro
experiments on auditory hair cells showed a protective
effect of Epo in ischemia- and gentamicin-induced hair cell
damage. In contrast, an in vivo study using an animal
model of noise-induced hearing loss showed a negative
effect of Epo. Also VEGF and its receptors are expressed in
the inner ear. Changes in the expression of VEGF or its
receptors have been found in the cochlea after noise
exposure, transcranial vibration and diabetic or aged animals.
Until now, there are no studies about a direct effect of
VEGF on auditory hair cells in vitro or in vivo. We could
exclude a protective effect of VEGF on gentamicininduced
auditory hair cell damage in vitro. Thus, we conclude
that Epo but not VEGF has a protective effect on
auditory hair cell damage at least in vitro. (Part of a multiauthor
review.)