Indiana University-Purdue University Indianapolis (IUPUI)Loss of the finite cochlear hair cells of the inner ear results in
sensorineural deafness. Human cochlear hair cells do not regenerate, and there
is no cure for deafness. Our laboratory has established a three-dimensional
culture system for deriving functional sensory hair cells from human pluripotent
stem cells. A major limitation of this approach is that derived hair cells exhibit a
morphological and gene expression phenotype reflective of native vestibular hair
cells. Previous studies have shown that establishment of localized domains of
gene expression along the dorso-ventral axis of the developing otic vesicle is
necessary for proper morphogenesis of both auditory and vestibular inner ear
structures. Sonic hedgehog (SHH) signaling has been shown to play a key role in
specification of the ventral otic vesicle and subsequent cochlear development.
Here, SHH treatment was pursued as a potential strategy for inducing a
patterning phenotype permissive to cochlear induction in vitro. Single-cell RNAsequencing
analysis revealed that while treatment with the SHH pathway agonist
Purmorphamine reduced expression of markers for the vestibular-yielding dorsal
otic vesicle, upregulation of ventral otic marker genes was modest. More
strikingly, the number of otic progenitors exhibiting a neuroprogenitor phenotype
increased in response to Purmorphamine treatment. These results suggest that
SHH pathway modulation in early-stage inner ear organoids may bias their
differentiation toward a neural lineage at the expense of an epithelial lineage.
The present study is the first to evaluate the patterning phenotype of human stem cell derived otic progenitors, and sheds light on the transcriptomic profile at this
critical point of inner ear development. This study may also cultivate future efforts
to derive cochlear cell types as well as inner ear neural cell types from human
pluripotent stem cells, and contribute to the establishment of a more complete in
vitro model of inner ear development.2021-08-2
