Multimodal Atlas of the Murine Inner Ear: From Embryo to Adult

Ultra-tiny-scale technology for engineering human ear therapeutics

Ultra-tiny-scale technology representing engineered micro- and nano-scale materials has gained considerable attention for a wide range of applications, including hearing restoration. The advent of hearing loss and its recovery has been the topic of intense discussion since many decades. Although conventional treatments partially support hearing recovery, they present certain limitations such as subsequent immune response and donor site morbidity leading to even worsened sensory disturbances. Microscale- and nanoscale-based approaches such as tissue engineering, nanoparticle-assisted drug delivery systems, and micro/nanofabrication-aided auditory stimulations have been shown to play an efficient role in recovery from hearing disorders. In particular, the introduction of different biomaterials and biopolymers (natural and synthetic) with influential topographical cues and excellent biocompatibility has been found to conveniently bypass previous challenges posed by rigid human ear structures and provided a new path for improved and advanced hearing-recovery approaches. This review is focused on the development of micro/nanoengineering-based hearing recovery therapeutics and their significant impact on the future of hearing research. It discusses the physiological functions associated with the human ear and the mechanism underlying distinct hearing loss disorders as well as highlights various engineered ultra-tiny-scale-assisted strategies for developing advanced hearing therapeutics. Finally, we deliberate on commercialization aspect and future perspectives of implementing micro/nanotechnologies for hearing restoration platforms.

Wnt signalling facilitates neuronal differentiation of cochlear Frizzled10-positive cells in mouse cochlea via glypican 6 modulation

Degeneration of cochlear spiral ganglion neurons (SGNs) leads to irreversible sensorineural hearing loss (SNHL), as SGNs lack regenerative capacity. Although cochlear glial cells (GCs) have some neuronal differentiation potential, their specific identities remain unclear. This study identifies a distinct subpopulation, Frizzled10 positive (FZD10+) cells, as an important type of GC responsible for neuronal differentiation in mouse cochlea. FZD10 + cells can differentiate into various SGN subtypes in vivo, adhering to natural proportions. Wnt signaling enhances the ability of FZD10 + cells to function as neural progenitors and increases the neuronal excitability of the FZD10-derived neurons. Single-cell RNA sequencing analysis characterizes FZD10-derived differentiating cell populations, while crosstalk network analysis identifies multiple signaling pathways and target genes influenced by Wnt signaling that contribute to the function of FZD10 + cells as neural progenitors. Pseudotime analysis maps the differentiation trajectory from proliferated GCs to differentiating neurons. Further experiments indicate that glypican 6 (GPC6) may regulate this neuronal lineage, while GPC6 deficiency diminishes the effects of Wnt signaling on FZD10-derived neuronal differentiation and synapse formation. These findings suggest the critical role of Wnt signaling in the neuronal differentiation derived from cochlear FZD10 + cells and provide insights into the mechanisms potentially involved in this process.