The development of the mammalian outer and middle ear

Biomaterials for non-invasive trans-tympanic drug delivery: requirements, recent advances and perspectives

Various non-invasive delivery systems have recently been developed as an alternative to conventional injections. Local transdermal administration represents the most attractive method due to the low systemic side effects, excellent ease of administration, and persistent drug release. The tympanic membrane (TM), a major barrier between the outer and middle ear, has a similar structure of the stratum corneum compared to the surface of the skin. After several attempts, non-invasive trans-tympanic drug delivery has been regarded as a promising option in the treatment of middle and inner ear diseases. The round window membrane (RWM) was a possible non-invasive delivery approach from the middle to inner ear. The improved permeability of nanocarriers crossing the RWM is a current hotspot in therapeutics for inner ear diseases. In this review, we include the latest studies exploring non-invasive trans-tympanic delivery to treat middle and inner ear diseases. Both passive and active delivery systems are described. A summary of the benefits and disadvantages of various delivery systems in clinical practice and production procedures is introduced. Finally, future possible approaches for its effective application as a non-invasive middle and inner ear drug delivery system are characterised.

FBLN2 is associated with Goldenhar syndrome and is essential for cranial neural crest cell development

Goldenhar syndrome, a rare craniofacial malformation, is characterized by developmental anomalies in the first and second pharyngeal arches. Its etiology is considered to be heterogenous, including both genetic and environmental factors that remain largely unknown. To further elucidate the genetic cause in a five-generation Goldenhar syndrome pedigree and exploit the whole-exome sequencing (WES) data of this pedigree, we generated collapsed haplotype pattern markers based on WES and employed rare variant nonparametric linkage analysis. FBLN2 was identified as a candidate gene via analysis of WES data across the significant linkage region. A fbln2 knockout zebrafish line was established by CRISPR/Cas9 to examine the gene's role in craniofacial cartilage development. fbln2 was expressed specifically in the mandible during the zebrafish early development, while fbln2 knockout zebrafish exhibited craniofacial malformations with abnormal chondrocyte morphologies. Functional studies revealed that fbln2 knockout caused abnormal chondrogenic differentiation, apoptosis, and proliferation of cranial neural crest cells (CNCCs), and downregulated the bone morphogenic protein (BMP) signaling pathway in the zebrafish model. This study demonstrates the role of FBLN2 in CNCC development and BMP pathway regulation, and highlights FBLN2 as a candidate gene for Goldenhar syndrome, which may have implications for the selection of potential screening targets and the development of treatments for conditions like microtia-atresia.

BMP signaling maintains auricular chondrocyte identity and prevents microtia development by inhibiting protein kinase A

Elastic cartilage constitutes a major component of the external ear, which functions to guide sound to the middle and inner ears. Defects in auricle development cause congenital microtia, which affects hearing and appearance in patients. Mutations in several genes have been implicated in microtia development, yet, the pathogenesis of this disorder remains incompletely understood. Here, we show that Prrx1 genetically marks auricular chondrocytes in adult mice. Interestingly, BMP-Smad1/5/9 signaling in chondrocytes is increasingly activated from the proximal to distal segments of the ear, which is associated with a decrease in chondrocyte regenerative activity. Ablation of Bmpr1a in auricular chondrocytes led to chondrocyte atrophy and microtia development at the distal part. Transcriptome analysis revealed that Bmpr1a deficiency caused a switch from the chondrogenic program to the osteogenic program, accompanied by enhanced protein kinase A activation, likely through increased expression of Adcy5/8. Inhibition of PKA blocked chondrocyte-to-osteoblast transformation and microtia development. Moreover, analysis of single-cell RNA-seq of human microtia samples uncovered enriched gene expression in the PKA pathway and chondrocyte-to-osteoblast transformation process. These findings suggest that auricle cartilage is actively maintained by BMP signaling, which maintains chondrocyte identity by suppressing osteogenic differentiation.

The multifaceted links between hearing loss and chronic kidney disease

Hearing loss affects nearly 1.6 billion people and is the third-leading cause of disability worldwide. Chronic kidney disease (CKD) is also a common condition that is associated with adverse clinical outcomes and high health-care costs. From a developmental perspective, the structures responsible for hearing have a common morphogenetic origin with the kidney, and genetic abnormalities that cause familial forms of hearing loss can also lead to kidney disease. On a cellular level, normal kidney and cochlea function both depend on cilial activities at the apical surface, and kidney tubular cells and sensory epithelial cells of the inner ear use similar transport mechanisms to modify luminal fluid. The two organs also share the same collagen IV basement membrane network. Thus, strong developmental and physiological links exist between hearing and kidney function. These theoretical considerations are supported by epidemiological data demonstrating that CKD is associated with a graded and independent excess risk of sensorineural hearing loss. In addition to developmental and physiological links between kidney and cochlear function, hearing loss in patients with CKD may be driven by specific medications or treatments, including haemodialysis. The associations between these two common conditions are not commonly appreciated, yet have important implications for research and clinical practice.

Spatially resolved single-cell atlas of ascidian endostyle provides insight into the origin of vertebrate pharyngeal organs

The pharyngeal endoderm, an innovation of deuterostome ancestors, contributes to pharyngeal development by influencing the patterning and differentiation of pharyngeal structures in vertebrates; however, the evolutionary origin of the pharyngeal organs in vertebrates is largely unknown. The endostyle, a distinct pharyngeal organ exclusively present in basal chordates, represents a good model for understanding pharyngeal organ origins. Using Stereo-seq and single-cell RNA sequencing, we constructed aspatially resolved single-cell atlas for the endostyle of the ascidian Styela clava. We determined the cell composition of the hemolymphoid region, which illuminates a mixed ancestral structure for the blood and lymphoid system. In addition, we discovered a cluster of hair cell-like cells in zone 3, which has transcriptomic similarity with the hair cells of the vertebrate acoustico-lateralis system. These findings reshape our understanding of the pharynx of the basal chordate and provide insights into the evolutionary origin of multiplexed pharyngeal organs.

Genetics and Epigenetics in the Genesis and Development of Microtia

Microtia is a congenital malformation of the external and middle ear associated with varying degrees of severity that range from mild structural abnormalities to the absence of the external ear and auditory canal. Globally, it is the second most common congenital craniofacial malformation and is typically caused by inherited defects, external factors, or the interaction between genes and external factors. Epigenetics notably represents a bridge between genetics and the environment. This review has devoted attention to the current proceedings of the genetics and epigenetics of microtia and related syndromes.

Profiling of Long Non-Coding RNAs in Auricular Cartilage of Patients with Isolated Microtia

Introduction: Microtia is the second most common maxillofacial birth defect worldwide. However, the involvement of long non-coding RNAs (lncRNAs) in isolated microtia is not well understood. This study aimed at identifying lncRNAs that regulate the expression of genes associated with isolated microtia. Methods: We used our microarray data to analyze the expression pattern of lncRNA in the auricular cartilage tissues from 10 patients diagnosed with isolated microtia, alongside 15 control subjects. Five lncRNAs were chosen for validation using real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Results: We identified 4651 differentially expressed lncRNAs in the auricular cartilage from patients with isolated microtia. By Gene Ontology/Kyoto Encyclopedia of Genes and Genomes pathway (GO/KEGG) analysis, we identified 27 differentially expressed genes enriched in pathways associated with microtia. In addition, we predicted 9 differentially expressed genes as potential cis-acting targets of 12 differentially expressed lncRNAs. Our findings by qRT-PCR demonstrate significantly elevated expression levels of ZFAS1 and DAB1-AS1, whereas ADIRF-AS1, HOTAIRM1, and EPB41L4A-AS1 exhibited significantly reduced expression levels in the auricular cartilage tissues of patients with isolated microtia. Conclusions: Our study sheds light on the potential involvement of lncRNAs in microtia and provides a basis for further investigation into their functional roles and underlying mechanisms.

Distinct distribution of subplate neuron subtypes between the sensory cortices during the early postnatal period

Subplate neurons (SpNs) are a heterogeneous neuronal population actively involved in early cortical circuit formation. In rodents, many SpNs survive and form layer 6b. The molecular heterogeneity of SpNs raises the question of whether different subpopulations of SpNs survive through the early postnatal period similarly and whether such diverse SpN populations in the auditory cortex (ACtx) share a common distribution pattern with other sensory systems. To address that, we investigated the expression pattern of multiple specific SpN markers in the ACtx, as well as in the visual (VCtx) and somatosensory (SCtx) cortices as controls, using complexin 3 (Cplx3) antibodies and different SpN-specific Cre-driver mice, such as connective tissue growth factor (CTGF), dopamine receptor D1 (Drd1a), and neurexophilin 4 (Nxph4). We focused on two early time windows in auditory development: (1) during the second postnatal week (PNW) before ear-canal opening and (2) during the third PNW after ear-canal opening. We compared the expression pattern of different SpN markers in ACtx with VCtx and SCtx. At both examined timepoints, Cplx3 and Nxph4 expressing SpNs form the largest and smallest population in the ACtx, respectively. Similar distribution patterns are observable in the VCtx and SCtx during the second PNW but not during the third PNW, for a higher proportion of Drd1a expressing SpNs is detected in the VCtx and CTGF expressing SpNs in the SCtx. This study suggests that different populations of SpNs might contribute differently to the development of individual sensory circuits.

Development of the human primary and secondary jaw joints

This study investigates the development of the primary and secondary jaw joints in humans, focusing on their concomitance and subsequent disconnection. Development begins with the primary temporomandibular joint as a connection between Meckel's cartilage and the incus, while the secondary temporomandibular joint develops anteriorly as an articulation between the mandibular condyle and the mandibular fossa. Previous research in mice has provided insights into the morphogenesis of these joints, but their specific development of the 3D morphogenesis in humans remains unclear. To address this gap, histological serial sections of embryos and fetuses ranging from 19 to 230 mm crown-rump length were analyzed. The 3D morphogenesis of the middle ear and the temporomandibular joint was examined, paying attention to the morphological characteristics, timing, and potential mechanisms of movement and disconnection. The primary jaw joint is initially formed at 25 mm (8th week), followed by the appearance of the secondary jaw joint arising at 87 mm (12th week). Both joints persist present simultaneously, until a separation occurs between 150 and 230 mm (18th-24th week). It is remarkable that both joints remain concomitant and function somehow for a period exceeding 6 weeks, with the mechanism of their separation still unclear. Understanding the precise timing and functional movements involved with these temporarily connected joints is crucial for comprehending the overall development of the temporomandibular joint. Further research is needed to explore the molecular and cellular processes underlying these developmental changes.

Diagnosis and management of bilateral lipoma of the middle ear

INTRODUCTION

Middle ear lipomas are rare, accounting for less than 1% of all middle ear tumours. To our knowledge there have been only 16 reported patients with middle ear lipoma. Only one of these had bilateral congenital middle ear lipomas. The aim of this review is to comprehensive overview the diagnosis and management of congenital lipomas of the middle ear.

METHODS

A literature review was performed searching multiple data bases, using the key words "middle ear", AND "lipoma", AND "congenital". A total of 116 articles were identified. One hundred were excluded on various criteria, leaving 16 articles for detailed review. Additionally, we report the second case of bilateral congenital middle ear lipoma.

RESULTS

Based on this case report and literature review, the incidence of middle ear lipomas is greater in paediatric patients than in adult patients. Middle ear lipomas are distributed evenly between males and females. Three patients had recognised genetic syndromes, while five had prior ventilation tube placement. Clinically patients present with conductive hearing loss and middle ear effusions. In some cases, presence of a white or yellow mass behind the anterior aspect of the tympanic membrane is recognised. The most common location of the masses is in the anterosuperior quadrant of the middle ear, the site of predilection for small congenital cholesteatomas. An MRI scan is most useful in distinguishing between lipoma and cholesteatoma. All cases reported surgical excision of the middle ear lipoma. There was no evidence of recurrence noted up to 4 years follow up.

CONCLUSION

Though rare, congenital lipomas of the middle ear should be a differential diagnosis of a middle ear masses. Early identification can allow surgical lipoma resection with minimal disruption to the ossicular chain. Though there is currently no consensus regarding management, surgical removal and appropriate reconstruction of the ossicular chain if needed, is appropriate.

Middle ear innovation in Early Cretaceous eutherian mammals

The middle ear ossicles in modern mammals are repurposed from postdentary bones in non-mammalian cynodonts. Recent discoveries by palaeontological and embryonic studies have developed different models for the middle ear evolution in mammaliaforms. However, little is known about the evolutionary scenario of the middle ear in early therians. Here we report a detached middle ear preserved in a new eutherian mammal from the Early Cretaceous Jehol Biota. The well-preserved articulation of the malleus and incus suggest that the saddle-shaped incudomallear joint is a major apomorphy of Early Cretaceous eutherians. By contrast to the distinct saddle-like incudomallear articulation in therians, differences between the overlapping versus the half-overlapping incudomallear joints in monotremes and stem mammals would be relatively minor. The middle ear belongs to the microtype by definition, indicating its adaptation to high-frequency hearing. Current evidence indicates that significant evolutionary innovations of the middle ear in modern therians evolved in Early Cretaceous.

Neural crest cells give rise to non-myogenic mesenchymal tissue in the adult murid ear pinna

Despite being a major target of reconstructive surgery, development of the external ear pinna remains poorly studied. As a craniofacial organ highly accessible to manipulation and highly conserved among mammals, the ear pinna represents a valuable model for the study of appendage development and wound healing in the craniofacial complex. Here we provide a cellular characterization of late gestational and postnatal ear pinna development in Mus musculus and Acomys cahirinus and demonstrate that ear pinna development is largely conserved between these species. Using Wnt1-cre;ROSAmT/mG mice we find that connective tissue fibroblasts, elastic cartilage, dermal papilla cells, dermal sheath cells, vasculature, and adipocytes in the adult pinna are derived from cranial crest. In contrast, we find that skeletal muscle and hair follicles are not derived from neural crest cells. Cellular analysis using the naturally occurring short ear mouse mutant shows that elastic cartilage does not develop properly in distal pinna due to impaired chondroprogenitor proliferation. Interestingly, while chondroprogenitors develop in a mostly continuous sheet, the boundaries of cartilage loss in the short ear mutant strongly correlate with locations of vasculature-conveying foramen. Concomitant with loss of elastic cartilage we report increased numbers of adipocytes, but this seems to be a state acquired in adulthood rather than a developmental abnormality. In addition, chondrogenesis remains impaired in the adult mid-distal ear pinna of these mutants. Together these data establish a developmental basis for the study of the ear pinna with intriguing insights into the development of elastic cartilage.

Combined genome-wide association study of 136 quantitative ear morphology traits in multiple populations reveal 8 novel loci

Human ear morphology, a complex anatomical structure represented by a multidimensional set of correlated and heritable phenotypes, has a poorly understood genetic architecture. In this study, we quantitatively assessed 136 ear morphology traits using deep learning analysis of digital face images in 14,921 individuals from five different cohorts in Europe, Asia, and Latin America. Through GWAS meta-analysis and C-GWASs, a recently introduced method to effectively combine GWASs of many traits, we identified 16 genetic loci involved in various ear phenotypes, eight of which have not been previously associated with human ear features. Our findings suggest that ear morphology shares genetic determinants with other surface ectoderm-derived traits such as facial variation, mono eyebrow, and male pattern baldness. Our results enhance the genetic understanding of human ear morphology and shed light on the shared genetic contributors of different surface ectoderm-derived phenotypes. Additionally, gene editing experiments in mice have demonstrated that knocking out the newly ear-associated gene (Intu) and a previously ear-associated gene (Tbx15) causes deviating mouse ear morphology.

The applications of Targeted Delivery for Gene Therapies in Hearing Loss

Gene therapies are becoming more abundantly researched for use in a multitude of potential treatments, including for hearing loss. Hearing loss is a condition which impacts an increasing number of the population each year, with significant burdens associated. As such, this review will present the concept that delivering a gene effectively to the inner ear may assist in expanding novel treatment options and improving patient outcomes. Historically, several drawbacks have been associated with the use of gene therapies, some of which may be overcome via targeted delivery. Targeted delivery has the potential to alleviate off-target effects and permit a safer delivery profile. Viral vectors have often been described as a delivery method, however, there is an emerging depiction of the potential for nanotechnology to be used. Resulting nanoparticles may also be tuned to allow for targeted delivery. Therefore, this review will focus on hearing loss, gene delivery techniques and inner ear targets, including highlighting promising research. Targeted delivery is a key concept to permitting gene delivery in a safe effective manner, however, further research is required, both in the determination of genes to use in functional hearing recovery and formulating nanoparticles for targeted delivery.

Anatomical, Histological, and Morphometrical Investigations of the Auditory Ossicles in Chlorocebus aethiops sabaeus from Saint Kitts Island

Otological studies rely on a lot of data drawn from animal studies. A lot of pathological or evolutionary questions may find answers in studies on primates, providing insights into the morphological, pathological, and physiological aspects of systematic biological studies. Our study on auditory ossicles moves from a pure morphological (macroscopic and microscopic) investigation of auditory ossicles to the morphometrical evaluation of several individuals as well as to some interpretative data regarding some functional aspects drawn from these investigations. Particularities from this perspective blend with metric data and point toward comparative elements that might also serve as an important reference in further morphologic and comparative studies.

vwa1 Knockout in Zebrafish Causes Abnormal Craniofacial Chondrogenesis by Regulating FGF Pathway

Hemifacial microsomia (HFM), a rare disorder of first- and second-pharyngeal arch development, has been linked to a point mutation in VWA1 (von Willebrand factor A domain containing 1), encoding the protein WARP in a five-generation pedigree. However, how the VWA1 mutation relates to the pathogenesis of HFM is largely unknown. Here, we sought to elucidate the effects of the VWA1 mutation at the molecular level by generating a vwa1-knockout zebrafish line using CRISPR/Cas9. Mutants and crispants showed cartilage dysmorphologies, including hypoplastic Meckel’s cartilage and palatoquadrate cartilage, malformed ceratohyal with widened angle, and deformed or absent ceratobranchial cartilages. Chondrocytes exhibited a smaller size and aspect ratio and were aligned irregularly. In situ hybridization and RT-qPCR showed a decrease in barx1 and col2a1a expression, indicating abnormal cranial neural crest cell (CNCC) condensation and differentiation. CNCC proliferation and survival were also impaired in the mutants. Expression of FGF pathway components, including fgf8a, fgfr1, fgfr2, fgfr3, fgfr4, and runx2a, was decreased, implying a role for VWA1 in regulating FGF signaling. Our results demonstrate that VWA1 is essential for zebrafish chondrogenesis through effects on condensation, differentiation, proliferation, and apoptosis of CNCCs, and likely impacts chondrogenesis through regulation of the FGF pathway.

Inhibition of TGF-β signaling enables long-term proliferation of mouse primary epithelial stem/progenitor cells of the tympanic membrane and the middle ear mucosa

The surface of the middle ear is composed of the tympanic membrane (TM) and the middle ear mucosa (MEM). A number of diseases and conditions such as otitis media, middle ear cholesteatoma, and perforation of the TM have been reported to cause dysfunction of the middle ear, ultimately leading to high-frequency hearing loss. Despite its importance in repairing the damaged tissues, the stem/progenitor cells of the TM and the MEM epithelia remains largely uncharacterized due, in part, to the lack of an optimal methodology to expand and maintain stem/progenitor cells long-term. Here, we show that suppression of TGF-β signaling in a low Ca²⁺ condition enables long-term proliferation of p63-positive epithelial stem/progenitor cells of the TM and the MEM while avoiding their malignant transformation. Indeed, our data show that the expanded TM and MEM stem/progenitor cells respond to Ca²⁺ stimulation and differentiate into the mature epithelial cell lineages marked by cytokeratin (CK) 1/8/18 or Bpifa1, respectively. These results will allow us to expand epithelial stem/progenitor cells of the TM and MEM in quantity for large-scale analyses and will enhance the use of mouse models in developing stem cell-mediated therapeutic strategies for the treatment of middle ear diseases and conditions.

Development of the Primary and Secondary Jaw Joints in the Mouse

This study assesses the morphogenesis of the primary and secondary jaw joints. A collection of 11 murine heads, ranging from prenatal stage E13.5 to postnatal stage P10, were prepared as histological serial sections (thickness 8-10µm) and stained conventionally in order to examine them with light microscopy. Next, the regions of the developing temporomandibular joint and the middle ear ossicles were three dimensionally reconstructed using AnalySIS® software. This study gained new insight into the spatio-temporal development of the temporomandibular joint and the auditory ossicles. Furthermore, we newly visualized in 3D that during the developmental period from stages E16 to P4 two morphologically well-functional joints (the primary and secondary jaw joints) exist on either side and are mechanically connected via Meckel's cartilage. Potential separation mechanisms of these two joints are discussed and options for mathematical analysis are suggested.

Nuclear Translocation Triggered at the Onset of Hearing in Cochlear Inner Hair Cells of Rats and Mice

PURPOSE

Nuclear position is precisely orchestrated during cell division, migration, and maturation of cells and tissues. Here we report a previously unrecognized, programmed movement of the nucleus in rat and mouse cochlear inner hair cells (IHCs) coinciding with the functional maturation of inner hair cells around the onset of hearing.

METHODS

We measured hair cell length and nuclear position from confocal scans of immunofluorescence-labeled hair cells from whole-mount cochlear preparations throughout post-natal development.

RESULTS

In early post-natal days, the IHC experiences a period of sustained growth, during which the nucleus sits at the very basal pole of the cell, far from the apically located mechano-transducing stereocilia, but close to where synapses with primary afferent and efferent neurons are forming. After IHCs reach their final length, the nucleus moves to occupy a new position half-way along the length of the cell. Nuclear translocation begins in the middle turn, completes throughout the cochlea within 2-3 days, and coincides with the emergence of endolymphatic potential, the acquisition of big-conductance potassium channels (BK), and the onset of acoustic hearing. IHCs cultured in-vitro without endolymphatic potential (EP) do not grow, do not express BK, and do not experience nuclear movement. IHCs cultured in high K+ solutions (to simulate EP) grow but do not experience nuclear movement or acquire BK channels.

CONCLUSION

Nuclear migration at the onset of hearing is a key step in the morphological maturation of IHCs. Whether this plays a role in functional maturation remains to be explored.

Potentials and limitations of pharmaceutical and pharmacological applications of bile acids in hearing loss treatment

Hearing loss is a worldwide epidemic, with approximately 1.5 billion people currently struggling with hearing-related conditions. Currently, the most wildly used and effective treatments for hearing loss are primarily focus on the use of hearing aids and cochlear implants. However, these have many limitations, highlighting the importance of developing a pharmacological solution that may be used to overcome barriers associated with such devices. Due to the challenges of delivering therapeutic agents to the inner ear, bile acids are being explored as potential drug excipients and permeation enhancers. This review, therefore, aims to explore the pathophysiology of hearing loss, the challenges in treatment and the manners in which bile acids could potentially aid in overcoming these challenges.

Evolution and development of the mammalian jaw joint: Making a novel structure

A jaw joint between the squamosal and dentary is a defining feature of mammals and is referred to as the temporomandibular joint (TMJ) in humans. Driven by changes in dentition and jaw musculature, this new joint evolved early in the mammalian ancestral lineage and permitted the transference of the ancestral jaw joint into the middle ear. The fossil record demonstrates the steps in the cynodont lineage that led to the acquisition of the TMJ, including the expansion of the dentary bone, formation of the coronoid process, and initial contact between the dentary and squamosal. From a developmental perspective, the components of the TMJ form through tissue interactions of muscle and skeletal elements, as well as through interaction between the jaw and the cranial base, with the signals involved in these interactions being both biomechanical and biochemical. In this review, we discuss the development of the TMJ in an evolutionary context. We describe the evolution of the TMJ in the fossil record and the development of the TMJ in embryonic development. We address the formation of key elements of the TMJ and how knowledge from developmental biology can inform our understanding of TMJ evolution.

Temporomandibular Joint and Otitis Media: A Narrative Review of Implications in Etiopathogenesis and Treatment

Otitis media (OM) and its recurring (rAOM), effusive (OME), and chronic forms, represent a frequent clinical challenge. The middle ear, the mandible, and the temporomandibular joint (TMJ) share several embryological and anatomical connections. Despite that, the role of mandibular malposition and TMJ dysfunction is frequently overlooked in the management of otitis media. In this narrative review, we present current evidence supporting the etiopathogenetic role of a dysfunctional stomatognathic system in the onset of OM and the effectiveness of orthognathic treatment in preventing rAOM and OME. In particular, a focus on the influence of TMJ on Eustachian tube function is provided.

Neurovascular responses to neuronal activity during sensory development

Understanding the development of intercellular communication in sensory regions is relevant to elucidate mechanisms of physiological and pathological responses to oxygen shortage in the newborn brain. Decades of studies in laboratory rodents show that neuronal activity impacts sensory maturation during two periods of postnatal development distinguished by the maturation of accessory structures at the sensory periphery. During the first of these developmental periods, angiogenesis is modulated by neuronal activity, and physiological levels of neuronal activity cause local tissue hypoxic events. This correlation suggests that neuronal activity is upstream of the production of angiogenic factors, a process that is mediated by intermittent hypoxia caused by neuronal oxygen consumption. In this perspective article we address three theoretical implications based on this hypothesis: first, that spontaneous activity of sensory neurons has properties that favor the generation of intermittent tissue hypoxia in neonate rodents; second, that intermittent hypoxia promotes the expression of hypoxia inducible transcription factors (HIFs) in sensory neurons and astrocytes; and third, that activity-dependent production of angiogenic factors is involved in pathological oxygen contexts.

Mammalian middle ear mechanics: A review

The middle ear is part of the ear in all terrestrial vertebrates. It provides an interface between two media, air and fluid. How does it work? In mammals, the middle ear is traditionally described as increasing gain due to Helmholtz’s hydraulic analogy and the lever action of the malleus-incus complex: in effect, an impedance transformer. The conical shape of the eardrum and a frequency-dependent synovial joint function for the ossicles suggest a greater complexity of function than the traditional view. Here we review acoustico-mechanical measurements of middle ear function and the development of middle ear models based on these measurements. We observe that an impedance-matching mechanism (reducing reflection) rather than an impedance transformer (providing gain) best explains experimental findings. We conclude by considering some outstanding questions about middle ear function, recognizing that we are still learning how the middle ear works.

NSS-Bridge Device for Post-Cesarean Delivery Analgesia: A Randomized Controlled Trial

Introduction

Percutaneous auricular nerve stimulation has been used for the treatment of symptoms associated with opioid withdrawal, including abdominal pain, nausea, and general discomfort. However, its potential utility for pain management and opioid minimization after surgery has not been investigated. The purpose of this study was to test the feasibility and acceptability of a trial protocol designed to assess the effectiveness of the NSS2-Bridge device as a non-pharmacologic alternative to opioids after cesarean delivery.

Methods

In a randomized control design, healthy women receiving cesarean delivery were randomized to receive the active device, placebo device, or no device. Devices were placed on the ear following cesarean delivery and left in place for 5 days. Feasibility and acceptability of the device was assessed by patient reports of device tolerability (rated on a 100mm visual analog scale where 0 is not tolerable at all and 100 is the most tolerable) as well as qualitative reporting. Additional outcomes assessed included proportion of patients not using opioids in hospital, as well as pain at rest, pain with movement, and total opioid consumption in the hospital and for the first 5 days after surgery.

Results

There were 60 patients included in the final analysis. Device tolerability was rated highly, with an average daily score of >75 mm on the visual analog scale. The trial retention rate was 89.7% with most exclusions (42.9%) occurring due to unanticipated development of care complexity (e.g., hemorrhage and additional surgical procedures), with only 1 exclusion (14.3%) due to device discomfort. The active device group achieved the highest proportion of opioid-free hospitalizations (40%) compared to placebo (20%) and no device groups (30%). Pain at rest and with movement was similar between treatment groups.

Conclusions

This trial protocol designed to test the efficacy of NSS2-Bridge device for post-cesarean pain management is feasible and acceptable. Larger proportions of patients not using opioids in the active device group justifies additional investigation on device effectiveness in pregnant and postpartum people at highest risk for pain.

Transcriptome Analyses Provide Insights into the Auditory Function in Trachemys scripta elegans

An auditory ability is essential for communication in vertebrates, and considerable attention has been paid to auditory sensitivity in mammals, birds, and frogs. Turtles were thought to be deaf for a long time; however, recent studies have confirmed the presence of an auditory ability in Trachemys scripta elegans as well as sex-related differences in hearing sensitivity. Earlier studies mainly focused on the morphological and physiological functions of the hearing organ in turtles; thus, the gene expression patterns remain unclear. In this study, 36 transcriptomes from six tissues (inner ear, tympanic membrane, brain, eye, lung, and muscle) were sequenced to explore the gene expression patterns of the hearing system in T. scripta elegans. A weighted gene co-expression network analysis revealed that hub genes related to the inner ear and tympanic membrane are involved in development and signal transduction. Moreover, we identified six differently expressed genes (GABRA1, GABRG2, GABBR2, GNAO1, SLC38A1, and SLC12A5) related to the GABAergic synapse pathway as candidate genes to explain the differences in sexually dimorphic hearing sensitivity. Collectively, this study provides a critical foundation for genetic research on auditory functions in turtles.

Evaluation and Nonsurgical Treatment of Neonatal Ear Anomalies: A Case Report

BACKGROUND

Inspection and evaluation of the neonate's ears are important parts of the neonatal examination. Neonates display a wide variety of ear size and configuration. In many cases, ear molding techniques obviate the need for future surgical correction. This article provides a review of the fetal ear development and describes common physical examination findings of the newborn's external ear. A case report reviews a successful nonsurgical treatment of a minor ear deformity.

CLINICAL FINDINGS

Newborn infant with near absent to very thin bilateral helical rims and otherwise normal bilateral ear shape and structures.

PRIMARY DIAGNOSIS

Bilateral Stahl's ear deformity.

INTERVENTIONS

The EarBuddies product was applied to bilateral ears in an outpatient pediatric plastic surgery clinic. This product remained in place for 8 weeks.

OUTCOMES

The family was pleased with the overall progress and shape of their child's ears. At 18 months of age, the family has no desire to pursue surgical correction of their child's ears.

PRACTICE RECOMMENDATIONS

Assessment of the newborn's external ear is part of a routine admission examination. Careful attention to abnormal or unusual findings allows for prompt evaluation and nonsurgical intervention.

Ultrasound evaluation of fetal bone development in the collared (Pecari tajacu) and white-lipped peccary (Tayassu pecari)

The study of fetal development allows for evaluating the different strategies adopted by mammal species to maximize neonatal survival. Autonomous locomotion is fundamental for newborns to perform foraging activities and increases newborn survival from predation. In this study, we assess the gestational bone development of 53 collared (CP, Pecari tajacu) and 61 white-lipped (WLP, Tayassu pecari) peccaries, collected through the collaboration of subsistence hunters in the Amazon. The bone mineralization and biometry of the axial and appendicular skeleton were assessed by ultrasound examinations, and the timing of the main bone developmental events was calculated in relation to the total dorsal length (TDL) and the percentage of the total gestational period (GP). The first US signs of mineralization of the axial skeleton in CP and WLP were observed in fetuses with 3.4 cm (42 gestation days, 30% GP_CP ) and 5.1 cm (51 gestation days, 32% GP_WLP ). The early development of the appendicular skeleton was observed by the synchronic appearance of the mineralized scapula, humerus, radius, ulna, ilium, ischium, femur, tibia, and fibula at 36% GP_CP (50 gestation days), and 35% GP_WLP (56 gestation days)_. The pubis was mineralized in fetuses at 55% GP_CP (75 gestation days) and 59% GP_WLP (94 gestation days). The mineralization was observed in all autopod bones at 79% GP_CP (109 gestation days) and 67% GP_WLP (106 gestation days). All primary ossification centers in long bones of thoracic and pelvic limbs were mineralized in advanced fetuses (GP_{CP and} GP_WLP ≥75%). The mineralized patella was not observed in advanced fetuses in either species. Secondary ossification centers first appeared at the distal epiphysis of the femur in the CP (99 gestation days, 72% GP_CP ) and the distal epiphysis of the radius, femur, and tibia in the WLP (106 gestation days, 67% GP_WLP ). Advanced fetuses of CP and WLP presented 60% (15/25) and 68% (17/25) of the total secondary ossification centers observed present in the adult domestic pig, while newborns from the domestic pig presented 52% (13/25). The early intrauterine development of the skeletal system in both peccary species suggests a precocial development strategy, which likely correlates with neonatal ability to escape predators and reduces the dependence on parental care.

Advances and future perspectives in epithelial drug delivery

Epithelial surfaces protect exposed tissues in the body against intrusion of foreign materials, including xenobiotics, pollen and microbiota. The relative permeability of the various epithelia reflects their extent of exposure to the external environment and is in the ranking: intestinal≈ nasal ≥ bronchial ≥ tracheal > vaginal ≥ rectal > blood-perilymph barrier (otic), corneal > buccal > skin. Each epithelium also varies in their morphology, biochemistry, physiology, immunology and external fluid in line with their function. Each epithelium is also used as drug delivery sites to treat local conditions and, in some cases, for systemic delivery. The associated delivery systems have had to evolve to enable the delivery of larger drugs and biologicals, such as peptides, proteins, antibodies and biologicals and now include a range of physical, chemical, electrical, light, sound and other enhancement technologies. In addition, the quality-by-design approach to product regulation and the growth of generic products have also fostered advancement in epithelial drug delivery systems.

The evo-devo origins of the nasopharynx

The process by which upper respiratory tract structures have changed over deep evolutionary time is, in part, reflected in the process of embryologic development. The nasopharynx in particular is a centrally located space bounded by components of the respiratory portion of the nasal cavity, cranial base, soft palate, and Eustachian tube. The development of these components can be understood both in terms of embryologic structures such as the branchial arches and paraxial mesoderm and through fossil evidence dating as far back as the earliest agnathan fish of the Cambrian Period. Understanding both the evolution and development of these structures has been an immeasurable benefit to the otolaryngologist seeking to model disease etiology of both common and rare conditions. This discussion is a primer for those who may be unfamiliar with the central importance of the nasopharynx both in terms of our evolutionary history and early embryological development of vital cranial and upper respiratory tract structures.

Morphometric study of the human malleus during prenatal development

OBJECTIVES

Establish normal reference values for the human malleus during the second and third trimesters of pregnancy, and describe its growth dynamics and ossification process.

METHODS

Thirty spontaneously aborted human fetuses, 12-36 weeks of age, were examined. Temporal bones were obtained en bloc and processed using the skeletal clearing and staining technique. Each malleus was obtained by microdissection. Measurements of anatomical points of the malleus were performed. Ossification was recorded. Statistics were applied.

RESULTS

Sixty mallei were obtained. At the end of development, the following measurements were obtained in millimeters: head length, 2.87 (2.30-3.44); neck length, 1.15 (0.92-1.38); manubrium length, 4.45 (3.75-5.16); total length, 8.51 (8.02-8.99); neck width, 1.33 (0.70-1.97); manubrium width, 0.84 (0.82-0.86); and Meckel cartilage width, 0.43 (0.06-0.95). The angle of the longitudinal axis of the malleus was 160° (156-164°). The ossification process of the malleus followed a stereotyped pattern that began at week 16, at the level of the neck, with a single center that expanded to the head and then to the manubrium. Toward the end of development, only the umbo remained cartilaginous. There were no sex-based differences in human malleus size during prenatal development. From the beginning of the second trimester of pregnancy, the longitudinal axis of the malleus acquires dimensions comparable to adults.

CONCLUSION

The study of the malleus development provides clues that would explain some anomalies in its development, and can influence decision-making during the placement and design of prostheses in the malleus.

The Role of Inhibitory Interneurons in Circuit Assembly and Refinement Across Sensory Cortices

Sensory information is transduced into electrical signals in the periphery by specialized sensory organs, which relay this information to the thalamus and subsequently to cortical primary sensory areas. In the cortex, microcircuits constituted by interconnected pyramidal cells and inhibitory interneurons, distributed throughout the cortical column, form the basic processing units of sensory information underlying sensation. In the mouse, these circuits mature shortly after birth. In the first postnatal week cortical activity is characterized by highly synchronized spontaneous activity. While by the second postnatal week, spontaneous activity desynchronizes and sensory influx increases drastically upon eye opening, as well as with the onset of hearing and active whisking. This influx of sensory stimuli is fundamental for the maturation of functional properties and connectivity in neurons allocated to sensory cortices. In the subsequent developmental period, spanning the first five postnatal weeks, sensory circuits are malleable in response to sensory stimulation in the so-called critical periods. During these critical periods, which vary in timing and duration across sensory areas, perturbations in sensory experience can alter cortical connectivity, leading to long-lasting modifications in sensory processing. The recent advent of intersectional genetics, in vivo calcium imaging and single cell transcriptomics has aided the identification of circuit components in emergent networks. Multiple studies in recent years have sought a better understanding of how genetically-defined neuronal subtypes regulate circuit plasticity and maturation during development. In this review, we discuss the current literature focused on postnatal development and critical periods in the primary auditory (A1), visual (V1), and somatosensory (S1) cortices. We compare the developmental trajectory among the three sensory areas with a particular emphasis on interneuron function and the role of inhibitory circuits in cortical development and function.

The impact of Drew Noden's work on our understanding of craniofacial musculoskeletal integration

The classical anatomist Drew Noden spearheaded craniofacial research, laying the foundation for our modern molecular understanding of development, evolution and disorders of the craniofacial skeleton. His work revealed the origin of cephalic musculature and the role of cranial neural crest in early formation and patterning of the head musculoskeletal structures. Much of modern cranial tendon research advances a foundation of knowledge that Noden built using classical quail-chick transplantation experiments. This elegant avian chimeric system involves grafting of donor quail cells into host chick embryos to identify the cell types they can form and their interactions with the surrounding tissues. In this review, we will give a brief background of vertebrate head formation and the impact of cranial neural crest on the patterning, development and evolution of the head musculoskeletal attachments. Using the zebrafish as a model system, we will discuss examples of modifications of craniofacial structures in evolution with a special focus on the role of tendon and ligaments. Lastly, we will discuss pathologies in craniofacial tendons and the importance of understanding the molecular and cellular dynamics during craniofacial tendon development in human disease. This article is protected by copyright. All rights reserved.

Ear Abnormalities Among Children with Fetal Alcohol Spectrum Disorder: A Systematic Review and Meta-Analysis

OBJECTIVE

To systematically review and conduct meta-analysis on studies that report the type and prevalence of functional and structural ear abnormalities among children with prenatal alcohol exposure and/or fetal alcohol spectrum disorder (FASD).

STUDY DESIGN

MEDLINE, PubMed, Embase, Web of Science, PsycINFO, ERIC, CINAHL, and Maternity and Infant Care were searched from 1806 through March 2021. Reference lists of relevant articles were manually searched. Studies reporting on functional and/or structural ear abnormalities among children (<18 years) with prenatal alcohol exposure and/or FASD were eligible. Data extraction and quality assessment were performed by one reviewer and independently checked by another. A random effects meta-analysis was conducted.

RESULTS

A total of 31 studies met the inclusion criteria and 25 were included in the meta-analyses, representing a total of 843 children with prenatal alcohol exposure and 1653 children with FASD. Functional ear abnormalities with the highest pooled prevalence were chronic serous otitis media (88.5%; 95% CI, 70.4%-99.3%), abnormal auditory filtering (80.1%; 95% CI, 76.5%-84.3%), and unspecified conductive hearing loss (68.0%; 95% CI, 51.9%-82.2%). Structural ear abnormalities with the highest pooled prevalence were microtia (42.9%; 95% CI, 26.8%-59.7%), railroad track ear (16.8%; 95% CI, 8.1%-27.7%), and misplaced ear (12.3%; 95% CI, 7.6%-17.9%).

CONCLUSIONS

Our findings highlight the importance of examining the ears during assessment for FASD, and the need for public health messaging regarding the harms of prenatal alcohol exposure.

The EDA deficient mouse has Zymbal's gland hypoplasia and acute otitis externa

In mice, rats, dogs and humans, the growth and function of sebaceous glands and eyelid Meibomian glands depend on the ectodysplasin signalling pathway. Mutation of genes encoding the ligand EDA, its transmembrane receptor EDAR and the intracellular signal transducer EDARADD leads to hypohidrotic ectodermal dysplasia, characterised by impaired development of teeth and hair, as well as cutaneous glands. The rodent ear canal has a large auditory sebaceous gland, the Zymbal’s gland, the function of which in the health of the ear canal has not been determined. We report that EDA-deficient mice, EDAR-deficient mice and EDARADD-deficient rats have Zymbal’s gland hypoplasia. Eda^Ta mice have 25% prevalence of otitis externa at postnatal day 21 and treatment with agonist anti-EDAR antibodies rescues Zymbal’s glands. The aetiopathogenesis of otitis externa involves infection with Gram-positive cocci, and dosing pregnant and lactating Eda^Ta females and pups with enrofloxacin reduces the prevalence of otitis externa. We infer that the deficit of sebum is the principal factor in predisposition to bacterial infection, and the Eda^Ta mouse is a potentially useful microbial challenge model for human acute otitis externa.

Summary: Ectodysplasin-deficient mice have growth retardation of the auditory sebaceous Zymbal's gland and are predisposed to spontaneous bacterial infection of the outer ear canal by opportunistic pathogens.

Pearls of Temporal Bone Imaging in Children with Hearing Loss

Hearing loss is one of the most common indications for temporal bone imaging in children. Hearing loss may be congenital or acquired, and it may be conductive, sensorineural, or mixed audiologically. Temporal bone imaging plays an important role in the assessment and management of this condition. An understanding of the embryology of ear structures better enables the radiologist to interpret abnormalities on imaging of the temporal bone. Here, we provide a general review of ear development and a description of known genetic defects that contribute to congenital ear anomalies associated with hearing loss. We provide appropriate imaging techniques for the temporal bone depending on the clinical presentation and a systematic approach to imaging for children with hearing loss. Diagnostic imaging for developmental anomalies of the ear and cholesteatoma will be discussed.

The genes for sensory perception of sound should be considered in gene diagnosis of congenital sensorineural hearing loss and microtia

Congenital sensorineural hearing loss (CSHL) and microtia are development-related diseases, sharing some factors and affecting children's hearing. However, genetic tests only focus on CSHL. We try to identify the common molecular mechanism of CSHL and microtia as candidates combining gene diagnosis biomarkers. Whole-exon sequencing (WES), Sanger sequencing, qPCR, and bioinformatics analyses were performed in microtia family (F1), family two, whose proband suffered from microtia and CSHL (F2), five microtia, and four CSHL individuals, respectively. We found that 40% microtia and 40% CSHL relevant genes were detected in F1 and a sharing pathway: the sensory perception of sound was identified. Moreover, the copy number variation in proband F2 was identified in one gene of the sharing pathway: EYA1. Meanwhile, two variants of BUB3 were identified in F1 data. BUB3 is related to development, dog ear type, direct and indirect interaction with microtia, and CSHL relevant genes. Notably, although the allele frequency of two variants of BUB3 showed significant differences between microtia and CSHL, the special microtia-relevant genotype also could be detected in one CSHL sample. These results suggest that the sensory perception of sound and the development of relevant pathways may be the common pathways of microtia and CSHL. Genes of these pathways can be used as candidates combining gene diagnosis biomarkers.

Evolution of Middle Ear Modelling Techniques: A Review

This review article attempts to analyze the various research studies conducted in developing the models to evaluate the anatomy of the middle ear, its biomechanics, and the applications of these models in normal and diseased states.

Various studies conducted over the past 50-60 years have been critically analyzed. We also discuss the various advantages and disadvantages of different methods of measurement of middle ear parameters. Beginning from anatomical modelling to histopathological sections and the latest three-dimensional (3D) reconstruction with finite element modelling, various methods of middle ear measurements have been critically analyzed.

At the end of this review, we have concluded that the best and most effective method of middle ear modelling is the 3D reconstruction using high-resolution computed tomography and finite element modelling.

Auricular field nerve stimulation using the NSS-2 BRIDGE® device as an alternative to opioids following kidney donor surgery

OBJECTIVES

The purpose of this study was to investigate the role that the NSS-2 BRIDGE^® device, an auricular field nerve stimulator, may play in reducing opioid requirement and pain in kidney donor surgery. It was not a randomized study. Electrophysiologic studies have demonstrated that the stimulation of the cranial nerves produced by the NSS-2 BRIDGE^® device modulates the ascending/descending spinal pain pathways, especially at the level of the limbic system.

METHODS

The design compared the effects of the NSS-2 BRIDGE^® device (NSS 2-BRIDGE^® device group; n=10) to a control group (n=10). In both groups, the surgery was performed using the same standard enhanced recovery after surgery protocol based on the use of a multimodal analgesic approach. For the active treatment group, the NSS-2 BRIDGE^® device was placed in the post anesthesia care unit. The primary endpoint was opioid requirement (oral morphine equivalent, OME in mg) at 24 h post-surgery. Secondary endpoints included pain (0-10), at 24 and 48 h, time to discharge from the recovery room, incidence of post-operative nausea and vomiting at 24 h, time to oral intake, time to ambulation, and time to discharge from the hospital. Data was analyzed using unpaired t-test and presented as mean ± standard deviation.

RESULTS

Compared to control, the use of the NSS-2 BRIDGE^® was associated with a 75.4% reduction in OME (33.6 vs. 8.3 mg; p=0.03) and 41.5% reduction in pain (5 vs. 3.28; p=0.06) at 24 h and a 73.3% difference in pain at 48 h (1.6 ± 1.6 vs. 6.0 ± 2.8; p=0.0004). There was no difference in non-opioid analgesics administration between groups.

CONCLUSIONS

The tolerability of NSS-2 BRIDGE^® device was reported by most to be excellent. This study suggests that the NSS-2 BRIDGE^® device may represent a complementary approach for controlling postoperative opioid consumption and pain in patients undergoing kidney donation.

Drug Delivery across Barriers to the Middle and Inner Ear

The prevalence of ear disorders has spurred efforts to develop drug delivery systems to treat these conditions. Here, recent advances in drug delivery systems that access the ear through the tympanic membrane (TM) are reviewed. Such methods are either non-invasive (placed on the surface of the TM), or invasive (placed in the middle ear, ideally on the round window [RW]). The major hurdles to otic drug delivery are identified and highlighted the representative examples of drug delivery systems used for drug delivery across the TM to the middle and (crossing the RW also) inner ear.

Functional anatomy of the vagus system - Emphasis on the somato-visceral interface

Due to its pivotal role in autonomic networks, the vagus attracts continuous interest from both basic scientists and clinicians. In particular, recent advances in vagus nerve stimulation strategies and their application to pathological conditions beyond epilepsy provide a good opportunity to recall basic features of vagal peripheral and central anatomy. In addition to the "classical" vagal brainstem nuclei, i.e., dorsal motor nucleus, nucleus ambiguus and nucleus tractus solitarii, the spinal trigeminal and paratrigeminal nuclei come into play as targets of vagal afferents. On the other hand, the nucleus of the solitary tract receives and integrates not only visceral but also somatic afferents. Thus, the vagus system participates significantly in what may be defined as "somato-visceral interface".

Auricular nerve stimulation using the NSS-2 BRIDGE device to reduce opioid requirement following laparoscopic Roux-en-Y gastric bypass

BACKGROUND

Evidence supports the use of complementary techniques to reduce pain and opioid use after surgery. The NSS-2 BRIDGE device (NBD; Innovative Health Solutions, Inc., Versailles, Indiana) modulates pain via stimulation of the nucleus of the auricular branch of the cranial nerves at the level of the brainstem and the limbic system.

OBJECTIVE

To investigate the role of auricular nerve field stimulation for pain control following gastric bypass surgery.

SETTINGS

U.S. academic medical center.

METHODS

A total of 18 subjects were included. Subjects were divided in 2 groups: NBD group (n = 8) and a control group (n = 10). The NBD was placed following laparoscopic Roux-en-Y gastric bypass (LRYGB) surgery in the recovery room. The effectiveness of NBD was assessed comparing the relative use of opioid consumption (oral morphine equivalents) and pain (0 = no pain to 10= worst possible pain) at 24 and 48 hours after surgery. In addition, the device tolerability (1-10) was assessed, with 8-10 considered excellent. Data were analyzed using unpaired t tests and presented as mean ± standard deviation. Alpha was set up at .1.

RESULTS

Compared with the control group, the use of NBD was associated with a 60.2% reduction in oral morphine equivalents (38.15 vs 15.2 mg; P < .1) and a 28% reduction in pain (5.0 vs 3.6; P = .1) at 24 hours after surgery. The tolerability of NBD was reported to be excellent.

CONCLUSIONS

This report suggests that NBD may represent an interesting alternative to control perioperative pain and limit opioid use following bariatric surgery. This needs to be confirmed by a placebo-controlled, randomized study.

Hypermineralization of Hearing-Related Bones by a Specific Osteoblast Subtype

Auditory ossicles in the middle ear and bony labyrinth of the inner ear are highly mineralized in adult mammals. Cellular mechanisms underlying formation of dense bone during development are unknown. Here, we found that osteoblast-like cells synthesizing highly mineralized hearing-related bones produce both type I and type II collagens as the bone matrix, while conventional osteoblasts and chondrocytes primarily produce type I and type II collagens, respectively. Furthermore, these osteoblast-like cells were not labeled in a "conventional osteoblast"-specific green fluorescent protein (GFP) mouse line. Type II collagen-producing osteoblast-like cells were not chondrocytes as they express osteocalcin, localize along alizarin-labeled osteoid, and form osteocyte lacunae and canaliculi, as do conventional osteoblasts. Auditory ossicles and the bony labyrinth exhibit not only higher bone matrix mineralization but also a higher degree of apatite orientation than do long bones. Therefore, we conclude that these type II collagen-producing hypermineralizing osteoblasts (termed here auditory osteoblasts) represent a new osteoblast subtype. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

External ears for non-invasive and stable monitoring of volatile organic compounds in human blood

Volatile organic compounds (VOCs) released through skin (transcutaneous gas) has been increasing in importance for the continuous and real-time assessment of diseases or metabolisms. For stable monitoring of transcutaneous gas, finding a body part with little interference on the measurement is essential. In this study, we have investigated the possibility of external ears for stable and real-time measurement of ethanol vapour by developing a monitoring system that consisted with an over-ear gas collection cell and a biochemical gas sensor (bio-sniffer). The high sensitivity with the broad dynamic range (26 ppb–554 ppm), the high selectivity to ethanol, and the capability of the continuous measurement of the monitoring system uncovered three important characteristics of external ear-derived ethanol with alcohol intake for the first time: there is little interference from sweat glands to a sensor signal at the external ear; similar temporal change in ethanol concentration to that of breath with delayed peak time (avg. 13 min); relatively high concentration of ethanol relative to other parts of a body (external ear-derived ethanol:breath ethanol = 1:590). These features indicated the suitability of external ears for non-invasive monitoring of blood VOCs.

Development of Auditory Cortex Circuits

The ability to process and perceive sensory stimuli is an essential function for animals. Among the sensory modalities, audition is crucial for communication, pleasure, care for the young, and perceiving threats. The auditory cortex (ACtx) is a key sound processing region that combines ascending signals from the auditory periphery and inputs from other sensory and non-sensory regions. The development of ACtx is a protracted process starting prenatally and requires the complex interplay of molecular programs, spontaneous activity, and sensory experience. Here, we review the development of thalamic and cortical auditory circuits during pre- and early post-natal periods.

Necessities, opportunities, and challenges for tympanic membrane perforation scaffolding-based bioengineering

Tympanic membrane (TM) perforation is a global clinical dilemma. It occurs as a consequence of object penetration, blast trauma, barotrauma, and middle ear diseases. TM perforation may lead to otitis media, retraction pockets, cholesteatoma, and conductive deafness. Molecular therapies may not be suitable to treat perforation because there is no underlying tissue matrix to support epithelium bridging. Chronic perforations are usually reconstructed with autologous grafts via surgical myringoplasty. Surgical treatment is uncomfortable for the patients. The grafting materials are not perfect because they produce an opaque membrane, fail in up to 20% of cases, and are suboptimal to restore acoustic function. Millions of patients from developing parts of the world have not got access to surgical grafting due to operational complexities, lack of surgical resources, and high cost. These shortcomings emphasize bioengineering to improve placement options, healing rate, hearing outcomes, and minimize surgical procedures. This review highlights cellular, structural, pathophysiological, and perforation specific determinants that affect healing, acoustic and surgical outcomes; and integrates necessities relevant to bioengineered scaffolds. This study further summarizes scaffolding components, progress in scaffolding strategies and design, and engenders limitations and challenges for optimal bioengineering of chronic perforation.

Neuroglial heterotopia of the middle ear: A case series and systematic literature review

Background

The differential diagnosis for mass forming lesions of the middle ear is broad. While uncommon, neuroglial heterotopias can occur in the middle ear and can be a source of diagnostic confusion for clinician, radiologist, and pathologist alike.

Methods

We identified three cases of neuroglial heterotopia of the middle ear in our institutional archives from 2000 to 2020 and performed extensive histological and immunohistochemical characterization of the three lesions. We conducted a systematic literature review to identify 27 cases published in the English literature between the years 1980 and 2020. Only cases with histological verification of neuroglial heterotopia specifically involving the middle ear were included. We compiled the clinical, radiological, and histopathological findings for all 30 cases.

Results

Patients most frequently presented with chronic otitis media (40%), hearing loss (40%), or prior history of ear surgery or trauma (13%). The median age at surgery was 49 years with a male predominance (M:F 2:1); however, a bimodal age distribution was noted with an earlier onset (11 years or younger) in a subset of patients. Immunohistochemical characterization showed mature neuronal and reactive glial populations with low Ki67 proliferation index and chronic inflammatory infiltrates. There was no neuronal dysplasia or glial atypia, consistent with benign, nonneoplastic, mature glioneuronal tissue.

Conclusion

Immunohistochemical characterization of these lesions and clinical follow-up confirms their benign natural history. Potential etiologies include developmental misplacement, trauma, and chronic inflammation/ reactive changes resulting in sequestered encephalocele.

An Essential Requirement for Fgf10 in Pinna Extension Sheds Light on Auricle Defects in LADD Syndrome

The pinna (or auricle) is part of the external ear, acting to capture and funnel sound toward the middle ear. The pinna is defective in a number of craniofacial syndromes, including Lacrimo-auriculo-dento-digital (LADD) syndrome, which is caused by mutations in FGF10 or its receptor FGFR2b. Here we study pinna defects in the Fgf10 knockout mouse. We show that Fgf10 is expressed in both the muscles and forming cartilage of the developing external ear, with loss of signaling leading to a failure in the normal extension of the pinna over the ear canal. Conditional knockout of Fgf10 in the neural crest fails to recapitulate this phenotype, suggesting that the defect is due to loss of Fgf10 from the muscles, or that this source of Fgf10 can compensate for loss in the forming cartilage. The defect in the Fgf10 null mouse is driven by a reduction in proliferation, rather than an increase in cell death, which can be partially phenocopied by inhibiting cell proliferation in explant culture. Overall, we highlight the mechanisms that could lead to the phenotype observed in LADD syndrome patients and potentially explain the formation of similar low-set and cup shaped ears observed in other syndromes.