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European Journal of Cell Biology 2022The inner ear is composed by tiny and complex structures that, together with peripheral and central auditory pathways, are responsible for hearing processing. However,... (Review)
Review
The inner ear is composed by tiny and complex structures that, together with peripheral and central auditory pathways, are responsible for hearing processing. However, not only the anatomy of the cochlea, its compartments and related structures are complex. The mechanisms involved in the regulation of homeostasis in the inner ear fluid, which determines the ionic gradient necessary for hearing and balancing sensory excitability, is an intricate phenomenon that involves several molecules. Among them, Aquaporins (AQP) play a significant role in this process. AQP are part of a family of small, integral membrane proteins that regulate different processes, including bidirectional water and ionic flow in the inner ear. Changes in the expression of these proteins are essential to auditory physiology and several pathophysiological processes in the inner ear. This review focuses on the role of AQP in health and disease of the auditory system.
Topics: Aquaporins; Cochlea; Ear, Inner; Hearing
PubMed: 35779359
DOI: 10.1016/j.ejcb.2022.151252 -
Scientific Reports Oct 2017Deer are an iconic group of large mammals that originated in the Early Miocene of Eurasia (ca. 19 Ma). While there is some consensus on key relationships among their...
Deer are an iconic group of large mammals that originated in the Early Miocene of Eurasia (ca. 19 Ma). While there is some consensus on key relationships among their members, on the basis of molecular- or morphology-based analyses, or combined approaches, many questions remain, and the bony labyrinth has shown considerable potential for the phylogenetics of this and other groups. Here we examine its shape in 29 species of living and fossil deer using 3D geometric morphometrics and cladistics. We clarify several issues of the origin and evolution of cervids. Our results give new age estimates at different nodes of the tree and provide for the first time a clear distinction of stem and crown Cervidae. We unambiguously attribute the fossil Euprox furcatus (13.8 Ma) to crown Cervidae, pushing back the origin of crown deer to (at least) 4 Ma. Furthermore, we show that Capreolinae are more variable in bony labyrinth shape than Cervinae and confirm for the first time the monophyly of the Old World Capreolinae (including the Chinese water deer Hydropotes) based on morphological characters only. Finally, we provide evidence to support the sister group relationship of Megaloceros giganteus with the fallow deer Dama.
Topics: Animals; Deer; Ear, Inner; Fossils
PubMed: 29030580
DOI: 10.1038/s41598-017-12848-9 -
Journal of Anatomy Feb 2016The inner ear of mammals consists of the cochlea, which is involved with the sense of hearing, and the vestibule and three semicircular canals, which are involved with... (Review)
Review
The inner ear of mammals consists of the cochlea, which is involved with the sense of hearing, and the vestibule and three semicircular canals, which are involved with the sense of balance. Although different regions of the inner ear contribute to different functions, the bony chambers and membranous ducts are morphologically continuous. The gross anatomy of the cochlea that has been related to auditory physiologies includes overall size of the structure, including volume and total spiral length, development of internal cochlear structures, including the primary and secondary bony laminae, morphology of the spiral nerve ganglion, and the nature of cochlear coiling, including total number of turns completed by the cochlear canal and the relative diameters of the basal and apical turns. The overall sizes, shapes, and orientations of the semicircular canals are related to sensitivity to head rotations and possibly locomotor behaviors. Intraspecific variation, primarily in the shape and orientation of the semicircular canals, may provide additional clues to help us better understand form and function of the inner ear.
Topics: Animals; Ear, Inner; Hearing; Mammals
PubMed: 25911945
DOI: 10.1111/joa.12308 -
Proceedings of the National Academy of... Apr 2018The dispersal of modern humans from Africa is now well documented with genetic data that track population history, as well as gene flow between populations. Phenetic... (Comparative Study)
Comparative Study
The dispersal of modern humans from Africa is now well documented with genetic data that track population history, as well as gene flow between populations. Phenetic skeletal data, such as cranial and pelvic morphologies, also exhibit a dispersal-from-Africa signal, which, however, tends to be blurred by the effects of local adaptation and in vivo phenotypic plasticity, and that is often deteriorated by postmortem damage to skeletal remains. These complexities raise the question of which skeletal structures most effectively track neutral population history. The cavity system of the inner ear (the so-called bony labyrinth) is a good candidate structure for such analyses. It is already fully formed by birth, which minimizes postnatal phenotypic plasticity, and it is generally well preserved in archaeological samples. Here we use morphometric data of the bony labyrinth to show that it is a surprisingly good marker of the global dispersal of modern humans from Africa. Labyrinthine morphology tracks genetic distances and geography in accordance with an isolation-by-distance model with dispersal from Africa. Our data further indicate that the neutral-like pattern of variation is compatible with stabilizing selection on labyrinth morphology. Given the increasingly important role of the petrous bone for ancient DNA recovery from archaeological specimens, we encourage researchers to acquire 3D morphological data of the inner ear structures before any invasive sampling. Such data will constitute an important archive of phenotypic variation in present and past populations, and will permit individual-based genotype-phenotype comparisons.
Topics: Africa; Anatomy, Comparative; Animals; Biological Evolution; Cephalometry; Ear, Inner; History, Ancient; Human Genome Project; Human Migration; Humans; Imaging, Three-Dimensional; Phenotype; Primates; Tomography, X-Ray Computed
PubMed: 29610337
DOI: 10.1073/pnas.1717873115 -
Purinergic Signalling Jun 2022The inner ear comprises the cochlea and vestibular system, which detect sound and acceleration stimulation, respectively. The function of the inner ear is regulated by... (Review)
Review
The inner ear comprises the cochlea and vestibular system, which detect sound and acceleration stimulation, respectively. The function of the inner ear is regulated by ion transport activity among sensory epithelial cells, neuronal cells, non-sensory epithelial cells, and luminal fluid with a unique ionic composition of high [K] and low [Na], which enables normal hearing and balance maintenance. One of the important mechanisms regulating ion transport in the inner ear is purinergic signaling. Various purinergic receptors are distributed throughout inner ear epithelial cells and neuronal cells. To date, most studies have focused on the role of purinergic receptors in the cochlea, and few studies have examined these receptors in the vestibular system. As purinergic receptors play an important role in the cochlea, they would likely do the same in the vestibular system, which is fairly similar to the cochlea in cellular structure and function. Based on available studies performed to date, purinergic signaling is postulated to be involved in the regulation of ion homeostasis, protection of hair cells, otoconia formation, and regulation of electrical signaling from the sensory epithelium to vestibular neurons. In this review, the distribution and roles of purinergic receptors in the peripheral vestibular system are summarized and discussed.
Topics: Cochlea; Ear, Inner; Receptors, Purinergic; Signal Transduction; Vestibular System
PubMed: 35344126
DOI: 10.1007/s11302-022-09855-5 -
Nature Communications Dec 2019The adult mammalian inner ear lacks the capacity to divide or regenerate. Damage to inner ear generally leads to permanent hearing loss in humans. Here, we present that...
The adult mammalian inner ear lacks the capacity to divide or regenerate. Damage to inner ear generally leads to permanent hearing loss in humans. Here, we present that reprogramming of the adult inner ear induces renewed proliferation and regeneration of inner ear cell types. Co-activation of cell cycle activator Myc and inner ear progenitor gene Notch1 induces robust proliferation of diverse adult cochlear sensory epithelial cell types. Transient MYC and NOTCH activities enable adult supporting cells to respond to transcription factor Atoh1 and efficiently transdifferentiate into hair cell-like cells. Furthermore, we uncover that mTOR pathway participates in MYC/NOTCH-mediated proliferation and regeneration. These regenerated hair cell-like cells take up the styryl dye FM1-43 and are likely to form connections with adult spiral ganglion neurons, supporting that Myc and Notch1 co-activation is sufficient to reprogram fully mature supporting cells to proliferate and regenerate hair cell-like cells in adult mammalian auditory organs.
Topics: Animals; Cell Proliferation; Cochlea; Ear, Inner; Epithelial Cells; Ganglia, Sensory; Gene Expression Regulation; Hair Cells, Auditory, Inner; Humans; Mice; Proto-Oncogene Proteins c-myc; Receptor, Notch1; Regeneration
PubMed: 31797926
DOI: 10.1038/s41467-019-13157-7 -
Expert Opinion on Biological Therapy Feb 2019Sound is integral to communication and connects us to the world through speech and music. Cochlear hair cells are essential for converting sounds into neural impulses.... (Review)
Review
INTRODUCTION
Sound is integral to communication and connects us to the world through speech and music. Cochlear hair cells are essential for converting sounds into neural impulses. However, these cells are highly susceptible to damage from an array of factors, resulting in degeneration and ultimately irreversible hearing loss in humans. Since the discovery of hair cell regeneration in birds, there have been tremendous efforts to identify therapies that could promote hair cell regeneration in mammals.
AREAS COVERED
Here, we will review recent studies describing spontaneous hair cell regeneration and direct cellular reprograming as well as other factors that mediate mammalian hair cell regeneration.
EXPERT OPINION
Numerous combinatorial approaches have successfully reprogrammed non-sensory supporting cells to form hair cells, albeit with limited efficacy and maturation. Studies on epigenetic regulation and transcriptional network of hair cell progenitors may accelerate discovery of more promising reprogramming regimens.
Topics: Animals; Cellular Reprogramming; Ear, Inner; Epigenesis, Genetic; Hair Cells, Auditory; Humans; Regeneration
PubMed: 30584811
DOI: 10.1080/14712598.2019.1564035 -
Hearing Research Oct 2018The isolated anatomical position and blood-labyrinth barrier hampers systemic drug delivery to the mammalian inner ear. Intratympanic placement of drugs and permeation... (Review)
Review
The isolated anatomical position and blood-labyrinth barrier hampers systemic drug delivery to the mammalian inner ear. Intratympanic placement of drugs and permeation via the round- and oval window are established methods for local pharmaceutical treatment. Mechanisms of drug uptake and pathways for distribution within the inner ear are hard to predict. The complex microanatomy with fluid-filled spaces separated by tight- and leaky barriers compose various compartments that connect via active and passive transport mechanisms. Here we provide a review on the inner ear architecture at light- and electron microscopy level, relevant for drug delivery. Focus is laid on the human inner ear architecture. Some new data add information on the human inner ear fluid spaces generated with high resolution microcomputed tomography at 15 μm resolution. Perilymphatic spaces are connected with the central modiolus by active transport mechanisms of mesothelial cells that provide access to spiral ganglion neurons. Reports on leaky barriers between scala tympani and the so-called cortilymph compartment likely open the best path for hair cell targeting. The complex barrier system of tight junction proteins such as occludins, claudins and tricellulin isolates the endolymphatic space for most drugs. Comparison of relevant differences of barriers, target cells and cell types involved in drug spread between main animal models and humans shall provide some translational aspects for inner ear drug applications.
Topics: Animals; Drug Delivery Systems; Ear, Inner; Hearing; Hearing Loss; Humans; Labyrinth Diseases; Pharmaceutical Preparations
PubMed: 30442227
DOI: 10.1016/j.heares.2018.06.017 -
Current Opinion in Neurobiology Aug 2008The mammalian inner ear largely lacks the capacity to regenerate hair cells, the sensory cells required for hearing and balance. Recent studies in both lower vertebrates... (Review)
Review
The mammalian inner ear largely lacks the capacity to regenerate hair cells, the sensory cells required for hearing and balance. Recent studies in both lower vertebrates and mammals have uncovered genes and pathways important in hair cell development and have suggested ways that the sensory epithelia could be manipulated to achieve hair cell regeneration. These approaches include the use of inner ear stem cells, transdifferentiation of nonsensory cells, and induction of a proliferative response in the cells that can become hair cells.
Topics: Animals; Cell Differentiation; Cell Transdifferentiation; Ear, Inner; Hair Cells, Auditory; Humans; Regeneration; Stem Cell Transplantation; Stem Cells
PubMed: 18929656
DOI: 10.1016/j.conb.2008.10.001 -
Biophysical Journal Oct 2021The inner ear is one of the most complex structures in the mammalian body. Embedded within it are the hearing and balance sensory organs that contain arrays of hair... (Review)
Review
The inner ear is one of the most complex structures in the mammalian body. Embedded within it are the hearing and balance sensory organs that contain arrays of hair cells that serve as sensors of sound and acceleration. Within the sensory organs, these hair cells are prototypically arranged in regular mosaic patterns. The development of such complex, yet precise, patterns require the coordination of differentiation, growth, and morphogenesis, both at the tissue and cellular scales. In recent years, there is accumulating evidence that mechanical forces at the tissue, the cellular, and the subcellular scales coordinate the development and organization of this remarkable organ. Here, we review recent works that reveal how such mechanical forces shape the inner ear, control its size, and establish regular cellular patterns. The insights learned from studying how mechanical forces drive the inner ear development are relevant for many other developmental systems in which precise cellular patterns are essential for their function.
Topics: Animals; Cell Differentiation; Ear, Inner; Hair Cells, Auditory; Hearing; Morphogenesis
PubMed: 34242589
DOI: 10.1016/j.bpj.2021.06.036