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| Transmission electron microscopy of the submicroscopic structure of the stria vascularis in Cx30 -/-mice. Visible cavity-like damage in the SV of Cx30 -/-mice compared with WT mice. Scale bar: 5 µm, 1 µm.
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GJB2 and GJB6 are adjacent genes encoding connexin 26 (Cx26) and connexin 30 (Cx30), respectively, with overlapping expressions in the inner ear. Both genes are associated with the commonest monogenic hearing disorder, recessive isolated deafness DFNB1. Cx26 plays an important role in auditory development, while the role of Cx30 in hearing remains...
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Context 1
... Structure in Cx30 -/-Mice Figure 5 shows the transmission electron microscopy images of the submicroscopic structure of the SV in Cx30 -/-mice. There was some visible vacuolar injury in the SV of Cx30 -/-mice compared with WT mice, which suggested that Cx30 deletion might cause mild damage to the SV. ...
Similar publications
Non-sensory cells in the sensory epithelium of the cochlea are connected extensively by gap junctions. Functionally null mutations in GJB6 (encoding Cx30) cause hearing loss in humans. In this study, we injected AAV1-CB7- Gjb2 into the scala media between P0-2 in the cochlea of Gjb6 −/− mice. The injection increased Cx26 expression and significantl...
The connexin gene family is the most prevalent gene that contributes to hearing loss. Connexins 26 and 30, encoded by GJB2 and GJB6 respectively, are the most abundant expressed connexins in the inner ear. Connexin 43 which is encoded by GJA1 appears to be widely expressed in various organs, including the heart, skin, brain, and inner ear. The muta...
The connexin gene family is the most prevalent gene that contributes to hearing loss. Connexins 26 and 30, encoded by GJB2 and GJB6, respectively, are the most abundantly expressed connexins in the inner ear. Connexin 43, which is encoded by GJA1, appears to be widely expressed in various organs, including the heart, skin, the brain, and the inner...
The genetic causes of autosomal recessive nonsyndromic hearing loss (ARNSHL) are heterogeneous and highly ethnic-specific. We describe GJB2 (connexin 26) variants and carrier frequencies as part of our study and summarize previously reported ones for the Romanian population. In total, 284 unrelated children with bilateral congenital NSHL were enrol...
In the cochlea, connexin 26 (Cx26) and connexin 30 (Cx30) co‐assemble into two types of homomeric and heteromeric gap junctions between adjacent non‐sensory epithelial cells. These channels provide a mechanical coupling between connected cells, and their activity is critical to maintain cochlear homeostasis. Many of the mutations in GJB2 or GJB6, w...
Citations
... In none of these conditions, however, has it been necessary to invoke impaired strial barrier function as a primary driver of disease. The most prominently cited paper in this regard involved a mouse KO for connexin 30 (Cx30) (Cohen-Salmon et al., 2007; see also Chen et al., 2014Chen et al., , 2022, in which strial capillary leak was implicated in EP reduction and hearing loss. But subsequent studies revealed that mice were actually connexin 26/30 double KOs with broader degeneration, and that delimited Cx30 KOs did not show hearing loss or EP reduction (Boulay et al., 2013). ...
The blood-labyrinth-barrier (BLB) is a semipermeable boundary between the vasculature and three separate fluid spaces of the inner ear, the perilymph, the endolymph and the intrastrial space. An important component of the BLB is the blood-stria-barrier, which shepherds the passage of ions and metabolites from strial capillaries into the intrastrial space. Some investigators have reported increased “leakage” from these capillaries following certain experimental interventions, or in the presence of inflammation or genetic variants. This leakage is generally thought to be harmful to cochlear function, principally by lowering the endocochlear potential (EP). Here, we examine evidence for this dogma. We find that strial capillaries are not exclusive, and that the asserted detrimental influence of strial capillary leakage is often confounded by hair cell damage or intrinsic dysfunction of the stria. The vast majority of previous reports speculate about the influence of strial vascular barrier function on the EP without directly measuring the EP. We argue that strial capillary leakage is common across conditions and species, and does not significantly impact the EP or hearing thresholds, either on evidentiary or theoretical grounds. Instead, strial capillary endothelial cells and pericytes are dynamic and allow permeability of varying degrees in response to specific conditions. We present observations from mice and demonstrate that the mechanisms of strial capillary transport are heterogeneous and inconsistent among inbred strains.
... Specific type of mutations can cause abnormalities at any particular step in the life cycle of connexins [27], result in connexins possessing a faulty subcellular localization, failing to transport to the cell membrane and preventing gap junction formation, ultimately leading to connexin dysfunction and hearing loss. Several mechanisms may be involved in transport disorders leading to connexin dysfunction and hearing loss, that is, impaired cochlear potassium recirculation [27,131], endothelial barrier breakage [132], defective gap junction facilitation of metabolite transport [133], disrupted adenosine-triphosphatecalcium signaling propagation [134,135] and dysfunctional energy supply [136]. ...
The connexin gene family is the most prevalent gene that contributes to hearing loss. Connexins 26 and 30, encoded by GJB2 and GJB6, respectively, are the most abundantly expressed connexins in the inner ear. Connexin 43, which is encoded by GJA1, appears to be widely expressed in various organs, including the heart, skin, the brain, and the inner ear. The mutations that arise in GJB2, GJB6, and GJA1 can all result in comprehensive or non-comprehensive genetic deafness in newborns. As it is predicted that connexins include at least 20 isoforms in humans, the biosynthesis, structural composition, and degradation of connexins must be precisely regulated so that the gap junctions can properly operate. Certain mutations result in connexins possessing a faulty subcellular localization, failing to transport to the cell membrane and preventing gap junction formation, ultimately leading to connexin dysfunction and hearing loss. In this review, we provide a discussion of the transport models for connexin 43, connexins 30 and 26, mutations affecting trafficking pathways of these connexins, the existing controversies in the trafficking pathways of connexins, and the molecules involved in connexin trafficking and their functions. This review can contribute to a new way of understanding the etiological principles of connexin mutations and finding therapeutic strategies for hereditary deafness.
... These studies indicated that Cx30 appeared to be dispensable for cochlear functions and GJB6 might not be associated with HL. Recently, Chen et al. used CRISPR/Cas9 technology to establish a new Cx30 knockout mouse model (Cx30 −/− ), which retained approximately 70% of Cx26 [134]. They found that the Cx30 −/− mouse models showed mild fullfrequency HL in 1, 3, and 6 months. ...
Hearing loss (HL) can be caused by a number of different genetic factors. Non-syndromic HL refers that HL occurs as an isolated symptom in an individual, whereas syndromic HL refers that HL is associated with other symptoms or abnormalities. To date, more than 140 genes have been identified as being associated with non-syndromic HL, and approximately 400 genetic syndromes can include HL as one of the clinical symptoms. However, no gene therapeutic approaches are currently available to restore or improve hearing. Therefore, there is an urgent necessity to elucidate the possible pathogenesis of specific mutations in HL-associated genes and to investigate the promising therapeutic strategies for genetic HL. The development of the CRISPR/Cas system has revolutionized the field of genome engineering, which has become an efficacious and cost-effective tool to foster genetic HL research. Moreover, several in vivo studies have demonstrated the therapeutic efficacy of the CRISPR/Cas-mediated treatments for specific genetic HL. In this review, we briefly introduce the progress in CRISPR/Cas technique as well as the understanding of genetic HL, and then we detail the recent achievements of CRISPR/Cas technique in disease modeling and therapeutic strategies for genetic HL. Furthermore, we discuss the challenges for the application of CRISPR/Cas technique in future clinical treatments.
... Specific type of mutations can cause abnormalities at any particular step in the life cycle of connexins [27], result in connexins possessing a faulty subcellular localisation, failing to transport to the cell membrane and preventing gap junction formation, ultimately leading to connexin dysfunction and hearing loss. Several mechanisms may be involved in transport disorders leading to connexin dysfunction and hearing loss, that is, impaired cochlear potassium recirculation [27,109], endothelial barrier breakage [110], defective gap junction facilitation of metabolite transport [111], disrupted adenosine-triphosphate-calcium signaling propagation [112,113] and dysfunctional energy supply [114]. ...
The connexin gene family is the most prevalent gene that contributes to hearing loss. Connexins 26 and 30, encoded by GJB2 and GJB6 respectively, are the most abundant expressed connexins in the inner ear. Connexin 43 which is encoded by GJA1 appears to be widely expressed in various organs, including the heart, skin, brain, and inner ear. The mutations that arise in GJB2, GJB6 and GJA1 can all result in comprehensive or non-comprehensive genetic deafness in newborns. As it is predicted that connexins include at least 20 isoforms in humans, the biosynthesis, structural composition, and degradation of connexins must be precisely regulated so that the gap junctions can operate properly. Certain mutations result in connexins possessing a faulty subcellular localization, failing to transport to the cell membrane and preventing gap junction formation, ultimately leading to connexin dysfunction and hearing loss. In this review, we provide a discussion of the transport models for connexin 43, connexins 30 and 26, mutations affecting trafficking pathways of connexin 26, the existing controversies in trafficking pathways of connexins, and the molecules involved in connexin trafficking and their functions. This review can contribute to a new way of understanding the etiological principles of connexin mutations and finding therapeutic strategies for hereditary deafness.
... The supernatant was collected. ATP concentrations were analyzed by the standard protocol as reported before (Song et al., 2018;Chen et al., 2021). HMGB1 were assayed by Western blot. ...
Small molecule drugs are the next-generation of immune checkpoint inhibitors (ICIs), but their in vivo therapeutic outcomes remain unsatisfactory for a long time. Herein, we proposed a combinatory regimen that delivered a small molecule ICI and an immunogenic cell death inducer in an in-situ formed hydrogel scaffold based on thermosensitive materials (Pluronic F127). This platform increased the tumor retention of administrated small molecules, creating more opportunities for the interaction between drugs and tumor cells. We found that atorvastatin (ATO) effectively downregulated the expression of programmed death ligand 1 (PD-L1) and reversed compensative PD-L1 upregulation after cyclophosphamide (CTX) chemotherapy on CT26 colon tumors. CTX not only killed tumor cells to reduce the tumor burden, but also release damage-associated molecular patterns (DAMPs) to stimulate T cell immunity, therefore amplifying statin-mediated immunotherapy. The platform reported in this study might be promising to overcome the limitation of small molecule ICIs with short retention time and potentiate tumor chemo-immunotherapy.
... Connexins play a vital role in the intracellular communication of cells [12]. They consist of a variety of proteins that form functional channels at the non-junctional sites of the cell membrane and serve as a communication link between the cell cytoplasm and the space surrounding the internal environment of the cell [13]. Connexin 26 is encoded by GJB2, which has an important impact on inner ear development by facilitating ionic and metabolic homeostasis [14]. ...
Background
The GJB2 gene is reported to be the main hereditary factor responsible for non-syndromic hearing impairment in infants. Several kinds of hearing loss have been linked to elevated inflammatory markers. This study aimed to evaluate serum levels of IL-2, IL-4, IL-6, IL-10, IL-17, α-TNF, and γ-IFN and the severity of hearing loss.
Material/Methods
Ninety newborns were divided into 3 groups: severe hearing impairment (31 infants), moderate hearing impairment (30 infants), and normal hearing (29 infants). Hearing screening was performed using otoacoustic emissions test. Mutations of the GJB2 gene were detected with Sanger sequencing. The patients had DNFB1 mutation. Seven blood inflammatory markers were tested using Cytometric Bead Array. We performed the t test to examine differences in expression of 7 inflammatory markers between sexes in the groups. The correlation between indicators within groups was studied using the Pearson correlation test. Correlation of different indicators among groups was studied using the Spearman correlation test.
Results
When compared among the 3 groups (severe, moderate hearing impairment, and normal hearing group), we found that IL-10 had a positive correlation with the severity of GJB2-associated hearing loss, which was statistically significant (P<0.05).
Conclusions
This research aimed to assess the relationship of 7 serum inflammatory markers with GJB2-associated hearing loss in infants. Inflammatory marker IL-10 had a positive correlation with the severity of GJB2-associated infant hearing loss, and it might have the potential to become a future therapeutic target.
... GJB2 mutations are mainly characterized by degeneration of outer hair cells and hypoplasia of the vascular stripe and are the main cause of deafness in 50% of pre-speech deafness (Hochman et al., 2010). In addition, GJB6 mutation in rodents was found to reduce Ca 2+ in Kölliker's organ-supporting cells, leading to an increased hearing threshold (Rodriguez et al., 2012;Chen et al., 2021a); while Cx26 cKD mice also showed reduced ATP release, downregulation of ATP-dependent calcium signaling, the disappearance of calcium waves and increased hearing threshold in Kölliker's organ-supporting cells . ...
The Kölliker’s organ is a transient cellular cluster structure in the development of the mammalian cochlea. It gradually degenerates from embryonic columnar cells to cuboidal cells in the internal sulcus at postnatal day 12 (P12)–P14, with the cochlea maturing when the degeneration of supporting cells in the Kölliker’s organ is complete, which is distinct from humans because it disappears at birth already. The supporting cells in the Kölliker’s organ play a key role during this critical period of auditory development. Spontaneous release of ATP induces an increase in intracellular Ca ²⁺ levels in inner hair cells in a paracrine form via intercellular gap junction protein hemichannels. The Ca ²⁺ further induces the release of the neurotransmitter glutamate from the synaptic vesicles of the inner hair cells, which subsequently excite afferent nerve fibers. In this way, the supporting cells in the Kölliker’s organ transmit temporal and spatial information relevant to cochlear development to the hair cells, promoting fine-tuned connections at the synapses in the auditory pathway, thus facilitating cochlear maturation and auditory acquisition. The Kölliker’s organ plays a crucial role in such a scenario. In this article, we review the morphological changes, biological functions, degeneration, possible trans-differentiation of cochlear hair cells, and potential molecular mechanisms of supporting cells in the Kölliker’s organ during the auditory development in mammals, as well as future research perspectives.
... It is like the phenotype of DFNA3 or DFNB1. The common pathophysiological alterations of these model mice are the active cochlear amplification impairment which showed that distortion product otoacoustic emission (DPOAE) failed to evoke at an early stage (Chen et al., 2021). With aging, hair cells at the basal turn first start to damage and then gradually expand to the middle and apic turns (Fetoni et al., 2018). ...
... Potassium recycling is such a process that potassium flows through ion channels in the cochlear GJ system from the perilymph into the endolymph, participating in the formation of hair cell receptor potentials and stable endocochlear potential (EP), finally returning to the perilymph (Lv et al., 2021; Figure 1). Potassium recycling is thought to be critical for maintaining high endolymphatic potassium concentrations and EP (Chen et al., 2021). ...
... Once acoustic stimulation, the positively charged EP becomes the driving force to promote potassium ions of endolymph in the scala media to pass through the mechanotransduction channel in the top of hair cells and generates auditory receptor current and potential. Thus, the positive EP is necessary for hearing maintenance Chen et al., 2021). Gap junction coupling is required to produce positive EP. ...
Hereditary deafness is one of the most common human birth defects. GJB2 gene mutation is the most genetic etiology. Gap junction protein 26 (connexin26, Cx26) encoded by the GJB2 gene, which is responsible for intercellular substance transfer and signal communication, plays a critical role in hearing acquisition and maintenance. The auditory character of different Connexin26 transgenic mice models can be classified into two types: profound congenital deafness and late-onset progressive hearing loss. Recent studies demonstrated that there are pathological changes including endocochlear potential reduction, active cochlear amplification impairment, cochlear developmental disorders, and so on, in connexin26 deficiency mice. Here, this review summarizes three main hypotheses to explain pathological mechanisms of connexin26-related hearing loss: potassium recycling disruption, adenosine-triphosphate-calcium signaling propagation disruption, and energy supply dysfunction. Elucidating pathological mechanisms underlying connexin26-related hearing loss can help develop new protective and therapeutic strategies for this common deafness. It is worthy of further study on the detailed cellular and molecular upstream mechanisms to modify connexin (channel) function.
... In this study, we focused on the effect of Cx30 total deletion on hearing function during aging. Cx30 inactivation causes profound deafness (Teubner, 2003;Cohen-Salmon et al., 2007;Sun et al., 2009;Chen et al., 2022), but in some cases, it strongly reduces the expression of Cx26 (Ortolano et al., 2008;Lynn et al., 2011). Overexpression of Cx26 in Cx30 KO mice rescued hearing (Ahmad et al., 2007), but not vice versa (Qu et al., 2012). ...
... Looking for a molecular mechanism, we focused on the crossroad among oxidative stress, inflammation, and vascular dysfunction, considering that these damaging factors are common pathological markers of aging processes both in physiological cochlear-aging and in the genetic model of ARHL (Someya et al., 2009;Fetoni et al., 2018;White et al., 2018;Wang and Puel, 2020;Fetoni et al., 2022). Moreover, at the same time, deletions of connexins have been related to oxidative-inflammatory processes (Fetoni et al., 2018;Hua et al., 2021), as well as to vascular dysfunction and reduced endocochlear potential (Cohen-Salmon et al., 2007;Gentile et al., 2021;Chen et al., 2022). Our data, demonstrating that the absence of Cx30 and the consequent downregulation of Cx26 are associated with increased ROS amount in Cx30 ΔΔ aged-cochleae, suggest that connexin hemichannels play a key role in protecting against oxidative stress during aging, probably allowing diffusion of antioxidant molecules to counteract redox imbalance. ...
... Our hypothesis is that the increase of oxidative stress and cochlear redox imbalance caused by connexin downregulation can, in turn, cause stria vascularis dysfunction and vascular dysregulation, worsening cochlear-aging processes. Moreover, our results are consistent with the literature findings showing alterations in cochlear blood flow and extravasation in Cx30 KO animal models (Cohen-Salmon et al., 2007) and a crucial role of Cx30 in maintaining the endocochlear potential (Chen et al., 2022). Considering that cochlear vascular changes, vasoconstriction, or alterations in cochlear blood flow are well known risk factors for ARHL (Lyu et al., 2020;Peixoto Pinheiro et al., 2021), it is plausible that total deletion of Cx30, in conjunction with Cx26 downregulation, can increase cochlear susceptibility to vascular damage, exacerbating aging processes. ...
Pathogenic mutations in the Gjb2 and Gjb6 genes, encoding connexin 26 (Cx26) and connexin 30 (Cx30), respectively, have been linked to the most frequent monogenic hearing impairment, nonsyndromic hearing loss, and deafness DFNB1. It is known that Cx26 plays an important role in auditory development, while the role of Cx30 in hearing remains controversial. Previous studies found that partial deletion of Cx26 can accelerate age-related hearing loss (ARHL), a multifactorial complex disorder, with both environmental and genetic factors contributing to the etiology of the disease. Here, we investigated the role of Cx30 in cochlear-aging processes using a transgenic mouse model with total deletion of Cx30 (Cx30 ΔΔ mice), in which Cx30 was removed without perturbing the surrounding sequences. We show that these mice are affected by exacerbated ARHL, with increased morphological cochlear damage, oxidative stress, inflammation, and vascular dysfunctions. Overall, our data demonstrate that Cx30 deletion can be considered a genetic risk factor for ARHL, making cochlear structures more susceptible to aging processes.
The stria vascularis (SV), part of the blood-labyrinth barrier, is an essential component of the inner ear that regulates the ionic environment required for hearing. SV degeneration disrupts cochlear homeostasis, leading to irreversible hearing loss, yet a comprehensive understanding of the SV, and consequently therapeutic availability for SV degeneration, is lacking. We developed a whole-tissue explant model from neonatal and adult mice to create a robust platform for SV research. We validated our model by demonstrating that the proliferative behaviour of the SV in vitro mimics SV in vivo, providing a representative model and advancing high-throughput SV research. We also provided evidence for pharmacological intervention in our system by investigating the role of Wnt/β-catenin signaling in SV proliferation. Finally, we performed single-cell RNA sequencing from in vivo neonatal and adult mouse SV and revealed key genes and pathways that may play a role in SV proliferation and maintenance. Together, our results contribute new insights into investigating biological solutions for SV-associated hearing loss.
