Indiana University-Purdue University Indianapolis (IUPUI) / Hearing loss and vestibular dysfunction are inner ear disease states that arise from
an array of diverse etiologies that interfere with mechanosensory hair cell function,
including: congenital syndromes, noise-induced trauma, ototoxic drugs, and aging. The
investigation of normal inner ear development and the pathological aberrations that cause
inner ear disease has been previously advanced through formation of an easily generated,
scalable, accurate in vitro model system that readily facilitates experimental applications.
This model utilizes a 3D floating cell culture protocol which guides differentiation of
stem cell aggregates into inner ear organoids, which are vesicles containing a sensory
epithelium with functioning mechanosensory hair cells. Inner ear organoid formation
enables studying the effects of modulating the signaling pathways that guide developing
inner ear structure and function. The Notch signaling pathway heavily influences the
formation of the inner ear through two major mechanisms: lateral induction of sensory
progenitor cells and lateral inhibition to determine which of those progenitors
differentiate into mechanosensory hair cells. The effects of inhibiting Notch signaling
within the inner ear organoid system were explored through application of the ɣ-secretase
inhibitor MDL28170 (MDL) at a concentration of 25μM on day 8 of organoid culture.
Aggregates were harvested on day 32, fixed, sectioned, and stained according to a
standard immunohistochemistry protocol. Sections were stained for the mechanosensory
hair cell markers Myosin7a (Myo7a) and Sox2. MDL-treated aggregates demonstrated statistically significant reductions in the total number of vesicles and the number of
vesicles containing hair cells compared to control aggregates. In contrast to control
aggregates which demonstrated two distinct organoid variants (protruding and
embedded), MDL-treated aggregates only formed the embedded variant. Differences in
the expression pattern of Sox2, which is also a marker of stemness and neural progenitor
cells were also noted between the two conditions. MDL-treated aggregates demonstrated
regions of ‘ectopic’ Sox2 expression whereas Sox2 expression in control aggregates was
consistently expressed within Myo7a+ regions.
| Identifer | oai:union.ndltd.org:IUPUI/oai:scholarworks.iupui.edu:1805/10907 |
| Date | 10 May 2016 |
| Creators | Elghouche, Alhasan Najib |
| Contributors | Hashino, Eri, Nelson, Rick F., Koehler, Karl Russell |
| Source Sets | Indiana University-Purdue University Indianapolis |
| Language | en_US |
| Detected Language | English |
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