The study, published in the Archives of Dermatological Research by a team led by Ashley N. Houff and Monique Kumar of the University of Central Florida College of Medicine, together with colleagues at Mass Eye and Ear and Harvard Medical School, set out to answer a deceptively simple question: do individuals with port-wine stains or Sturge-Weber syndrome experience hearing loss more often than the rest of the population? The answer, based on both a systematic review of the medical literature and a survey of patient support communities, is a cautious but intriguing maybe, one that could reshape how dermatologists, neurologists, and audiologists think about these conditions.

The biological rationale for the investigation rests on a single gene. Most cases of both port-wine stains and Sturge-Weber syndrome are driven by somatic mutations in GNAQ, a gene encoding the alpha q subunit of a heterotrimeric G protein, a molecular switch that relays signals from cell-surface receptors into the interior of the cell. The landmark 2013 discovery in the New England Journal of Medicine showed that a specific activating mutation in GNAQ, arising after fertilization and therefore present in only a mosaic subset of the body’s cells, underlies both the isolated birthmarks and the full syndrome. Because the mutation occurs during embryonic development, its distribution across tissues is unpredictable, which helps explain why the same genetic lesion can produce anything from a small skin patch to a life-altering neurological disorder.

What makes the hearing question scientifically plausible is that G proteins are not strangers to the inner ear. Earlier work on the mammalian cochlea identified G protein isoforms localized presynaptically in the efferent nerve terminals, the fibers that modulate how hair cells transmit sound information to the brain. If GNAQ signaling participates in the maintenance or function of cochlear structures or their vascular supply, a mosaic mutation affecting those tissues could, in principle, compromise hearing. The literature also contains tantalizing case reports, including a description of port-wine stains associated with large vestibular aqueduct syndrome in a patient carrying mutations in both GNAQ and SLC26A4, a gene classically linked to hereditary hearing loss.

To gather the available evidence, the researchers first combed PubMed for published reports of hearing impairment in patients with either condition. The search identified hearing loss documented in three individuals with port-wine stains alone and in 77 individuals with Sturge-Weber syndrome. Prior reports have described several possible mechanisms, including vascular malformations of the external auditory canal, as in a documented case of multiple angiomas within the ear canal, and broader neuro-otological manifestations in patients with hemifacial port-wine stains. Yet the total number of cases remained small, and no systematic estimate of how common hearing problems might be had ever been attempted.

To fill that gap, the team turned to an unconventional but increasingly popular research tool: electronic surveys distributed through Facebook support groups for people with port-wine stains and Sturge-Weber syndrome. The survey asked members about their diagnosis, whether they had experienced hearing impairment or loss, and, for those who had, the characteristics of that loss, including its severity, duration, and treatment. Eighty-four responses were included in the analysis. Of these, 50 respondents, or 59.5 percent, had port-wine stains alone, 31, or 36.9 percent, had both port-wine stains and Sturge-Weber syndrome, and 3, or 3.6 percent, had Sturge-Weber syndrome alone.

The headline finding was striking: 53 of the 84 respondents, a sample proportion of 63.1 percent with a 95 percent confidence interval spanning 52.4 to 72.6 percent, reported hearing loss. The researchers are careful, and rightly so, to emphasize what that number does and does not mean. Because the sample was self-selected, drawn from people motivated enough to join support groups and respond to a survey, it cannot be taken as a measure of prevalence in the general population of people with these conditions. The confidence interval, calculated using standard methods for binomial proportions, reflects the precision of the sample estimate rather than a true population rate. Still, the sheer proportion of respondents reporting hearing difficulties is difficult to dismiss, particularly when compared with background rates of hearing loss in the United States, which rise steeply with age but remain comparatively low in children and young adults.

The characteristics of the reported hearing loss add further texture. Among the 53 respondents with hearing loss, the overwhelming majority, 36 people or 67.9 percent, did not know what type of hearing loss they had, a gap that itself underscores how rarely these patients undergo formal audiological evaluation. Those who did know reported sensorineural loss, arising from the inner ear or auditory nerve, in 7 cases, mixed loss in 6, and conductive loss, involving the outer or middle ear, in 4. Severity spanned the full clinical spectrum: 21 respondents described their loss as mild, 18 as moderate, and 13 as severe. Most strikingly, the largest group, 21 respondents or 39.6 percent, reported that their hearing symptoms had persisted for more than ten years, suggesting a chronic process rather than a transient one.

Treatment patterns revealed both the burden of the problem and the gaps in care. Thirty-four respondents with hearing loss, or 64.2 percent, reported receiving at least one form of treatment. Hearing aids were by far the most common intervention, used by 23 respondents, while 10 reported other surgeries, 5 reported other treatments, 2 reported medication, and one reported a cochlear implant. Because some respondents selected multiple treatment types, the individual percentages sum to more than the overall treatment rate. The predominance of hearing aids is consistent with the profile of chronic, largely irreversible hearing loss, and the presence of surgical interventions hints at the structural ear abnormalities that case reports have long suggested in this population.

The authors are explicit about the limits of their work. Self-perceived symptoms were not confirmed by audiometry, the gold-standard objective measurement of hearing thresholds, and the support-group sample cannot establish prevalence or prove an association between GNAQ-driven vascular malformations and hearing impairment. What the study does accomplish is to elevate a scattered handful of case reports into a coherent, testable hypothesis: that somatic GNAQ mutations, already known to disrupt blood vessels in the skin, brain, and eye, may also affect the delicate vascular and neural architecture of the auditory system. The authors call for future studies with objective audiological assessments to determine whether hearing loss is genuinely associated with port-wine stains and Sturge-Weber syndrome, and if so, to characterize its prevalence and mechanism well enough to inform screening recommendations. If those studies confirm the signal, the implications could be significant, since early identification of hearing loss in children is critical for language development, and a simple audiological screening protocol could prevent years of undiagnosed impairment in a vulnerable population. For now, the message for clinicians and families is one of heightened awareness: a birthmark on the face may be more than skin deep, and the possibility that it reaches the inner ear deserves a careful listen.

Subject of Research: Hearing impairment in patients with port-wine stains and Sturge-Weber syndrome linked to GNAQ mutations

Article Title: Hearing impairment in individuals with Port-wine stains and Sturge-Weber syndrome

Article References: Houff, A. N., Velez, D. E., Guerin, P., Gupta, S., Gupta, I., & Kumar, M. (2026). Hearing impairment in individuals with Port-wine stains and Sturge-Weber syndrome. Archives of Dermatological Research, 318(1), Article 514. https://doi.org/10.1007/s00403-026-04914-y

Image Credits: AI Generated

DOI: 10.1007/s00403-026-04914-y

Keywords: port-wine stains, Sturge-Weber syndrome, GNAQ, hearing loss, vascular malformations, neurocutaneous syndromes, cochlea, sensorineural hearing loss, audiology, somatic mutation, dermatology, patient survey

The research, published in GeroScience by Ho Yun Lee, Seung-Ho Shin, and Sung Wan Byun of Ewha Womans University College of Medicine, analyzed 5,436 adults aged 40 or older from the 2022–2023 Korea National Health and Nutrition Examination Survey (KNHANES). Phase angle is calculated from resistance and reactance recorded when a weak alternating current at 50 kilohertz passes through the body. Resistance reflects how strongly the body’s fluids impede the current, while reactance reflects the capacitive behavior of cell membranes—essentially, how intact and functional those membranes are. A higher phase angle therefore signals healthier cell membranes, a better balance of intracellular to extracellular fluid, and greater nutritional and functional reserve. A lower value has previously been linked to frailty, sarcopenia, malnutrition, disability, and mortality.

The technical details of the hearing assessment matter here. Audiologists computed the speech-frequency pure-tone average from thresholds at 0.5, 1, 2, and 4 kilohertz in each ear, taking the better ear as the primary outcome. They also calculated a high-frequency threshold from 4 and 8 kilohertz, the range where age-related hearing loss typically first appears. Hearing loss was defined as a better-ear pure-tone average of 25 decibels hearing level or worse, the conventional clinical cutoff. All analyses applied complex survey weights to make the sample representative of the entire noninstitutionalized Korean population, and the models progressed through stages of adjustment, from age and sex alone to the full panel of metabolic and lifestyle covariates.

The results were strikingly graded. Participants in the lowest sex-specific phase angle quartile had an average better-ear pure-tone average of 25.9 decibels, while those in the highest quartile averaged just 14.5 decibels. High-frequency thresholds fell from 43.6 to 24.8 decibels across the same gradient. Most dramatically, the prevalence of audiometric hearing loss dropped from 48.3 percent in the lowest quartile to 11.8 percent in the highest. In the fully adjusted regression models, each one-degree increase in phase angle was associated with a 1.50-decibel lower better-ear pure-tone average and a 1.51-decibel lower better-ear high-frequency threshold, both highly statistically significant. Each additional degree also corresponded to a 21 percent reduction in the odds of audiometric hearing loss, with an odds ratio of 0.79.

Perhaps the most intriguing finding emerged from an exploratory comparison with younger participants. When the researchers extended their analysis to people aged 12 to 39, the association between phase angle and hearing vanished entirely—coefficients hovered near zero and were nowhere near statistical significance. Among adults 40 and older, however, the association remained robust. This age-dependent pattern suggests that phase angle is not a general marker of hearing status across the lifespan but rather becomes informative specifically in the context of systemic aging, when physiological reserve begins to erode and the cochlea becomes vulnerable to cumulative metabolic and vascular stress.

The frequency-specific results added another layer of complexity. Inverse associations between phase angle and hearing thresholds appeared across the tested frequencies, but the estimates were largest and most consistent at low-to-mid frequencies, particularly around 2 kilohertz, and weaker at 8 kilohertz. That pattern diverges from the classical high-frequency-dominant configuration of presbycusis, which is typically attributed to degeneration of the basal turn of the cochlea. The authors are careful to frame this as hypothesis-generating rather than evidence of a distinct mechanism, but it hints that systemic reserve may influence cochlear structures differently than chronological aging alone does.

What biological pathways could connect a whole-body electrical measurement to the delicate sensory machinery of the inner ear? The cochlea is an extraordinarily metabolically active organ, and its energy supply depends on the stria vascularis, a vascularized structure that maintains the ionic gradients hair cells require to transduce sound. Chronic low-grade inflammation, oxidative stress, and vascular compromise—all conditions associated with lower phase angle in prior research—could degrade these systems over decades. Alterations in cellular membrane integrity and fluid balance, which phase angle directly reflects, may parallel changes in inner-ear homeostasis. The supplementary analyses bolster this systemic interpretation: higher phase angle was also associated with better quality-of-life scores on the EQ-5D, greater maximum handgrip strength, and lower odds of low grip strength among older adults.

Causality, however, remains firmly open. This was a cross-sectional study, capturing a single moment in time, so it cannot establish whether low phase angle precedes hearing decline or merely accompanies it. Genetic epidemiology complicates the picture further: a bidirectional Mendelian randomization study found no robust forward causal effect of body constitution on hearing loss, and a UK Biobank analysis observed associations between body composition and sensorineural hearing loss without clear genetic support for causation, pointing instead to shared genetic architecture or reverse pathways. Consistent with this caution, the associations in the present study survived adjustment for fat-free mass and percent body fat, indicating that phase angle carries information beyond body composition—but the authors explicitly state that the findings do not imply raising phase angle would improve hearing.

The study also has measurement caveats worth noting. Year-specific sensitivity analyses showed stronger associations in 2022, when a dedicated bioelectrical impedance survey weight was available, and attenuated, non-significant estimates in 2023, with formal heterogeneity between survey years. Residual confounding from lifetime noise exposure, ototoxic medications, socioeconomic factors, and prior otologic disease cannot be excluded, and phase angle itself can be influenced by hydration status and device characteristics, though KNHANES uses standardized examination protocols. Subgroup analyses by sex and age showed numerically larger associations in men and in adults 65 and older, but formal heterogeneity testing did not reach significance, so these patterns should be treated as exploratory.

The clinical message, for now, is one of integration rather than replacement. Phase angle is not a substitute for audiometry, and the authors caution that longitudinal validation is required before any screening application could be considered. But the findings reframe hearing loss as something more than an isolated ear problem: it appears to travel with the broader erosion of cellular integrity and physiological reserve that defines functional aging, alongside frailty, falls, depression, and dementia. If future cohort studies confirm that phase angle predicts hearing decline ahead of symptoms, a measurement already embedded in routine body-composition assessments could become an early, inexpensive flag for one of aging’s most common and most undertreated sensory impairments.

Subject of Research: Association between bioelectrical phase angle and audiometric hearing loss in middle-aged and older adults

Article Title: Lower bioelectrical phase angle is associated with audiometric hearing loss in middle-aged and older adults

Article References: Lee, H. Y., Shin, S.-H., & Byun, S. W. (2026). Lower bioelectrical phase angle is associated with audiometric hearing loss in middle-aged and older adults. GeroScience. https://doi.org/10.1007/s11357-026-02528-w

Image Credits: AI Generated

DOI: 10.1007/s11357-026-02528-w

Keywords: bioelectrical phase angle, hearing loss, audiometry, aging, bioelectrical impedance analysis, KNHANES, physiological reserve, sensory aging, cochlea, frailty, body composition, GeroScience

The implications reach well beyond cephalopod biology. In humans, the ability to hear depends on the cochlea, a snail-shaped organ in the inner ear that is lined with thousands of hair cells. Each of these cells carries a bundle of minute, hair-like projections called stereocilia. When sound vibrations reach the cochlea, they set these protrusions in motion, and the hair cells, which are wired directly into the nervous system, transmit messages to the brain where they are ultimately converted into meaningful sound. Because these delicate bundles cannot regenerate in humans, damage to them is a leading cause of permanent hearing loss, whether it occurs at birth or develops later in life.

Brian McDermott, associate professor at the Case Western Reserve School of Medicine, who led the research team, framed the significance of the finding in terms of both basic biology and human medicine. Squid, he noted, are cephalopods with a diverse population of hair cells on the surface of their bodies, a feature that may yield insights not only into how these fascinating animals detect water movement to survive, but also into how hearing and deafness occur in humans. The parallel is more than superficial. Sea creatures, including fish and cephalopods such as squid and octopuses, carry similar bundles of cilia on their bodies because their survival appears to depend on sensing different frequencies of water movement, much as the human ear detects different pitches of sound. In that sense, the skin of a squid seems to function like an ear spread across its entire body.

What makes the squid version of this sensory system especially valuable as a research model is a subtle but crucial difference from fish. The team’s work indicates that, unlike fish lateral lines, which have hair bundles that do not vary in length, squid appear to regulate the length of their hair bundles to tune individual cells to different frequencies. This is strikingly reminiscent of the organization of the human cochlea, where the bundles of stereocilia are taller in regions that detect low pitches and shorter where high pitches are detected. That graded architecture is what allows each hair cell to respond preferentially to a particular frequency of sound, and its presence in squid suggests that the underlying principles of frequency tuning may be shared across very distant branches of the animal tree.

This tuning similarity is precisely why the researchers see squid as a promising model for studying how human hearing works. Often, when a child is born deaf or a hearing person loses their hearing, it is the hair bundle that has been damaged, McDermott explained. Studying the squid’s hair bundle, he argued, holds promise for understanding how hearing loss occurs. Because squid hair cells are distributed across an accessible external surface rather than sealed inside the temporal bone, they offer an unprecedented experimental window into structures that are extraordinarily difficult to observe in living humans.

The discovery itself was made possible by an advanced imaging technique known as light sheet microscopy. The method uses a laser to create a thin sheet of light, illuminating just one plane of a specimen at a time. By capturing image after image in this way, researchers can build detailed three-dimensional reconstructions of entire biological structures while minimizing the phototoxic damage that conventional imaging inflicts on delicate tissue. For a specimen as large and structurally complex as a squid, this gentle, plane-by-plane illumination proved decisive, allowing the team to visualize hair cell distributions across the whole animal rather than in isolated fragments.

The research was conducted in part at the Marine Biological Laboratory in Woods Hole, Massachusetts, where McDermott’s team, which included Case Western Reserve graduate and undergraduate students, worked through a three-year fellowship program dedicated to studying how squid hear. At Woods Hole, the group collaborated with Carsten Wolff, associate director of Imaging Service and Imaging Scholar at the Marine Biological Laboratory, whose imaging expertise supported the light sheet work that revealed the full extent of the squid’s hair cell array. An image of a squid captured at the laboratory using light sheet microscopy documents the finding, showing hair cells distributed over the entire body rather than confined to the head and arms as previously understood.

The anatomical map that emerged from this effort carries the title of the published paper, An anatomical map of squid lateral lines, and it establishes for the first time the full layout of these sensory arrays in a cephalopod. Lateral lines are familiar to biologists from fish, where they run along the flanks and head and detect water displacement, currents, and the movement of prey and predators. The squid version, now shown to be far more extensive than earlier work suggested, appears to serve a comparable survival function, giving the animal a body-wide sense of the shifting water around it. The diversity of hair cell populations across that surface hints at a level of sensory sophistication that researchers are only beginning to appreciate.

For hearing science, the value of the squid model lies in the combination of accessibility and relevance. Human cochlear hair cells are hidden within one of the hardest bones in the body, are present in limited numbers, and do not regenerate once damaged, which makes direct study of living human hair bundles nearly impossible. Animal models have therefore long been essential to hearing research, but the most common laboratory organisms do not reproduce the graded frequency tuning of the mammalian cochlea in their peripheral hair cells. Squid, with hair bundles whose lengths vary in a way that mirrors cochlear organization, may allow scientists to examine how bundles are built, maintained, and damaged under conditions that are directly relevant to human deafness.

The research also underscores how much remains to be learned from animals that are often studied for other reasons. Cephalopods have long fascinated biologists for their camouflage, their behavior, and their unusually large nervous systems, yet their peripheral sensory world has remained poorly charted. The finding that the entire body surface of a squid functions as a frequency-tuned sensory sheet adds a new dimension to that picture and suggests that the evolutionary solutions to detecting water movement may converge on the same structural principles that evolution arrived at independently in the vertebrate ear. If the squid’s hair bundles can illuminate the mechanisms by which human hair bundles fail, the humble squid swimming off the coast of Massachusetts may end up contributing to one of medicine’s most persistent challenges: understanding, and ultimately preventing, the loss of hearing.

Subject of Research: Full-body mapping of frequency-tuned hair cells in squid lateral lines and their relevance to human hearing research

Article Title: Newly discovered hair cells on squid may offer clues to understand hearing loss in humans

Article References: Newly discovered hair cells on squid may offer clues to understand hearing loss in humans. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: squid, hair cells, hearing loss, cochlea, stereocilia, lateral lines, light sheet microscopy, Marine Biological Laboratory, Current Biology, cephalopods, frequency tuning, Case Western Reserve University

The team, working with young and aged C57BL/6J mice, began by confirming what epidemiological studies had long hinted at. Auditory brainstem response testing showed that 85 percent of the aged animals failed to respond to sounds below 70 decibels, with click-evoked and frequency-specific thresholds markedly elevated across the 4 to 32 kilohertz range. Distortion product otoacoustic emissions were also impaired at high frequencies, indicating that the cochlea’s mechanical amplifier had faltered alongside its neural signaling. In short, these mice were a faithful model of human presbycusis.

To find out what was happening at the cellular level, the investigators isolated pericytes from the stria vascularis, the metabolically ravenous, ribbon-like structure that powers the cochlea and houses the blood-labyrinth barrier. Using fluorescence-activated cell sorting to purify pericytes marked by PDGFR-beta, they performed transcriptome sequencing on cells from young and aged mice. The results were striking: both Igf1 and Slc25a33, a gene encoding a mitochondrial nucleotide carrier, were significantly downregulated in the aged pericytes. Pathway enrichment analyses flagged the TGF-beta signaling pathway as one of the most differentially activated routes in the aging cells, alongside terms linked to cell junctions and the cytoskeleton.

Immunofluorescence staining of cochlear sections confirmed the story in tissue. IGF-1 and SLC25A33 proteins, which normally co-localize within the stria vascularis, showed a pronounced age-dependent decline, and the change was most dramatic in pericytes themselves. Critically, the levels of the IGF-1 receptor did not differ between young and aged pericytes, suggesting that the defect lies in the supply of the hormone rather than in the cell’s ability to sense it. When the researchers blocked IGF-1 signaling in cultured human brain vascular pericytes with the inhibitor NVP-AEW541, SLC25A33 messenger RNA and protein both fell; adding recombinant IGF-1 pushed them back up. Endothelial cells, by contrast, did not respond in the same way, marking pericytes as the specific cellular target of this regulatory axis.

Why would losing SLC25A33 matter so much? The protein is a mitochondrial carrier that helps sustain oxidative phosphorylation and redox balance. When the team silenced Slc25a33 with shRNA, flow cytometry using MitoSOX Red revealed a surge in mitochondrial reactive oxygen species leaking from the electron transport chain. The pericytes then began to change character. Alpha-smooth muscle actin, the signature of a contractile, myofibroblast-like state, rose sharply at both the messenger RNA and protein levels, while E-cadherin, a junctional protein associated with quiescent, barrier-stabilizing pericytes, dropped. The cells were undergoing a phenotypic switch from quiet vascular support cells into activated, fibrosis-prone contractile cells.

The mechanistic thread connecting these events proved to be TGF-beta signaling. In SLC25A33-deficient pericytes, TGF-beta messenger RNA and protein were elevated, and phosphorylated Smad2, the activated form of the transcriptional mediator, increased robustly. Total Smad2, Smad3, and Smad4 levels were unchanged, and phosphorylated Smad3 did not budge, indicating a selective engagement of the canonical Smad2 arm. When the researchers treated the deficient cells with MitoTEMPO, a mitochondrial antioxidant, the excess reactive oxygen species fell and TGF-beta, phospho-Smad2, and alpha-SMA all declined, placing mitochondrial oxidative stress upstream of the signaling cascade. Conversely, blocking the TGF-beta receptor with LY2109761 restored E-cadherin and suppressed the contractile markers, confirming that the pathway mediates the differentiation program.

The decisive test came in living animals. Delivering recombinant IGF-1 directly into the cochlea of aged mice through the round window membrane boosted SLC25A33 expression in the stria vascularis, while the IGF-1 inhibitor deepened its decline. Using adeno-associated virus vectors tailored for inner ear transduction, the team then overexpressed or knocked down Slc25a33 in the aged cochlea. Overexpression reduced alpha-SMA and TGF-beta signaling and raised E-cadherin; knockdown did the opposite. Transmission electron microscopy laid bare the structural consequences: in IGF-1-suppressed mice, pericytes showed abnormal morphology, loose associations with endothelial cells, and widened tight junctions, hallmarks of a leaky blood-labyrinth barrier. Exogenous IGF-1 preserved those intimate pericyte-endothelial contacts and restored tight junction integrity.

Most importantly for patients, the intervention worked functionally. IGF-1 supplementation significantly lowered click-evoked auditory brainstem response thresholds in aged mice, and at 12 kilohertz the treated animals heard markedly better than both untreated and IGF-1-suppressed controls. In mice whose Slc25a33 had been silenced by viral knockdown, treatment with the TGF-beta receptor inhibitor LY2109761 raised levels of the tight junction proteins Claudin-5 and Occludin in the stria vascularis, easing barrier disruption. The findings were further validated in an independent mouse strain, CBA/CaJ, where aged animals likewise showed reduced IGF-1 and SLC25A33 protein in the stria vascularis, indicating that the mechanism generalizes across genetic backgrounds.

The study thereby assembles a complete causal chain: aging lowers IGF-1, which suppresses the mitochondrial carrier SLC25A33 in strial pericytes; mitochondrial reactive oxygen species accumulate; the TGF-beta/Smad2 pathway activates; pericytes transform into contractile, pro-fibrotic cells; the blood-labyrinth barrier breaks down; and hearing deteriorates. This mirrors the pericyte-to-myofibroblast transitions documented at the blood-brain barrier, where elevated alpha-SMA similarly undermines vascular stability, and it echoes the ROS-driven epithelial-to-mesenchymal transitions long observed in other tissues. The cochlea, with its extraordinarily high metabolic demand and dense mitochondrial population, appears uniquely vulnerable to this failure mode.

Questions remain before the discovery can be translated into therapy. Whether IGF-1 acts directly on pericytes through its receptor or partly through paracrine networks will require cell-specific knockout models, and IGF-1 almost certainly regulates additional mitochondrial and cytoprotective genes that contribute to barrier stability. Species differences between human and mouse pericytes also warrant caution. Still, the identification of SLC25A33 as a biomarker and potential drug target, and the demonstration that both hormone supplementation and TGF-beta blockade can partially rescue barrier structure and auditory function in aged animals, opens a genuinely new frontier. If future work confirms the axis in humans, protecting the inner ear’s microscopic vasculature could become a strategy for preserving hearing in a rapidly aging world population.

Subject of Research: The IGF-1/SLC25A33 regulation of blood-labyrinth barrier pericytes in age-related hearing loss

Article Title: IGF‐1/SLC25A33 Maintains Blood‐Labyrinth Barrier Integrity by Suppressing TGF‐β/Smad2‐Mediated Pericyte Activation in Age‐Related Hearing Loss

Article References: Xu, R., Tang, J., Lin, H., Li, Q., Feng, Y., Zhang, X., Hu, X., Yang, J., Li, Y., & Bai, Y. (2026). IGF ‐1/ SLC25A33 Maintains Blood‐Labyrinth Barrier Integrity by Suppressing TGF ‐β/Smad2‐Mediated Pericyte Activation in Age‐Related Hearing Loss. Aging Cell, 25(10), Article e70712. https://doi.org/10.1111/acel.70712

Image Credits: AI Generated

DOI: 10.1111/acel.70712

Keywords: age-related hearing loss, IGF-1, SLC25A33, pericytes, blood-labyrinth barrier, TGF-beta, Smad2, mitochondrial ROS, stria vascularis, presbycusis, cochlea, Aging Cell

The study focuses on a chemical tag known as N6-methyladenosine, or m6A, the most abundant internal modification found in messenger RNA. m6A marks are deposited by a family of writer enzymes, of which METTL3 is the principal methyltransferase, and they influence nearly every stage of an RNA molecule’s life, from processing and export to translation and decay. Because m6A modification has already been implicated in a wide range of aging-related diseases, the Chinese team reasoned that it might also play a role in the cochlea, where aging is accompanied by a slow-burning inflammatory state often described as inflammaging. What they found was a strikingly specific protective circuit linking RNA chemistry to the immune response.

To model the disease, the researchers used twelve-month-old C57BL/6 mice, a strain in which hearing loss develops predictably with age, and an in vitro system in which HEI-OC1 auditory cells were stressed with lipopolysaccharide, a bacterial inflammatory trigger, and D-galactose, a sugar that induces senescence-like damage in cells. Auditory function was quantified using auditory brainstem response testing, which measures how effectively the auditory nerve relays sound signals to the brain, while cochlear structure was examined with hematoxylin-eosin staining. Inflammatory signaling was tracked with enzyme-linked immunosorbent assays, quantitative PCR, Western blotting, and immunofluorescence, giving the team a multi-layered picture of gene expression, protein abundance, and cellular localization.

The first key observation was that two molecules were significantly depleted in the cochleae of the aging mice: METTL3 itself, and NFKBIA, the gene encoding nuclear factor-kappaB inhibitor alpha, the protein that keeps the master inflammatory transcription factor NF-κB locked in an inactive state. NF-κB is a central switch in the immune system; when it is released from its inhibitor, it enters the nucleus and switches on a battery of pro-inflammatory genes, including interleukin-6 and components of the NLRP3 inflammasome, a multiprotein complex that drives a highly destructive form of inflammatory cell death called pyroptosis. With NFKBIA levels falling in the aged cochlea, this braking system weakens, allowing the NF-κB/IL-6/STAT3 axis and the NLRP3 inflammasome to fire unchecked.

The team then tested what happens when each component is manipulated. In HEI-OC1 cells, overexpressing NFKBIA suppressed both the NLRP3 inflammasome and the pro-inflammatory NF-κB/IL-6/STAT3 cascade, confirming that this inhibitor acts as a genuine gatekeeper of cochlear inflammation. Conversely, when the researchers boosted METTL3, NF-κB-mediated inflammation subsided, but that protective effect was largely abolished when NFKBIA was knocked down with silencing techniques. This dependency revealed the order of operations: METTL3 does not calm inflammation directly; it does so by keeping NFKBIA abundant, and NFKBIA in turn restrains NF-κB and everything downstream of it.

The mechanistic core of the paper lies in how METTL3 sustains NFKBIA. Using RNA immunoprecipitation combined with quantitative PCR, the researchers showed that METTL3 physically binds to NFKBIA messenger RNA. Using an m6A RNA methylation quantification kit and RNA stability assays, they demonstrated that this binding deposits m6A marks on the transcript and thereby enhances its stability, meaning the message survives longer in the cell and yields more of the inhibitory protein. In other words, METTL3 protects hearing not by changing the genome, but by chemically tuning how long a single anti-inflammatory message persists, a subtle epitranscriptomic intervention with outsized consequences for the inflammatory state of the inner ear.

The decisive experiment came in living animals. When the researchers overexpressed METTL3 in the ARHL mice, NFKBIA levels in the cochlea were restored, auditory brainstem response thresholds improved, and cochlear pathology visible under the microscope was ameliorated. At the molecular level, activation of the NLRP3 inflammasome and the NF-κB/IL-6/STAT3 pathway was suppressed, along with the downstream pyroptotic machinery marked by the gasdermin D-N domain. Taken together, the results trace a complete causal chain from an RNA methyltransferase, through m6A modification of a specific transcript, through a stabilized inhibitor of NF-κB, to reduced inflammatory signaling, preserved cochlear architecture, and better hearing in aged animals.

The significance of this work extends beyond otolaryngology. Chronic low-grade inflammation is now recognized as a shared driver of many age-related conditions, from cardiovascular disease to diabetes and neurodegeneration, and the NF-κB/IL-6/STAT3/NLRP3 axis identified here is a recurring motif across those disorders. Prior studies have shown that m6A modification maintains epithelial homeostasis in the colon through NF-κB signaling, and that other m6A regulators such as ALKBH5 can relieve neuroinflammation by increasing NFKBIA. The new findings place the aging cochlea squarely within this emerging framework, and they suggest that epitranscriptomic therapies, designed to adjust RNA methylation patterns rather than DNA sequences, could offer a way to dampen inflammaging in vulnerable tissues with considerable precision.

Important caveats remain before such a therapy could reach patients. The mouse model, while standard for presbycusis research, does not capture the full complexity of human hearing loss, which is shaped by genetics, noise exposure, vascular health, and lifestyle. Delivering METTL3 or its mRNA to the delicate structures of the inner ear poses formidable technical challenges, and globally enhancing m6A modification carries risks, since the same marks regulate thousands of transcripts, including some involved in cancer and immune function. The authors note that the datasets used in the study are available from the corresponding author on reasonable request, and the work was supported by the National Natural Science Foundation of China and a clinical research program of the Third Affiliated Hospital of Sun Yat-sen University.

Even so, the study offers something the field has lacked: a concrete, mechanistically validated molecular target for a condition long considered an inevitable consequence of growing old. If future work confirms that boosting METTL3 activity, or mimicking its effect on NFKBIA, is safe and feasible in humans, the era of treating age-related hearing loss with drugs rather than devices may come one step closer. For now, the message from Guangzhou is a compelling one: the difference between an aging ear that fails and one that endures may lie, in part, in a single methyl group attached to a single strand of messenger RNA.

Subject of Research: The role of METTL3-mediated m6A modification of NFKBIA in suppressing NF-κB-mediated inflammation in age-related hearing loss

Article Title: METTL3 mitigates age-related hearing loss by inhibiting NF-κB-mediated inflammatory responses through the m6A modification of NFKBIA

Article References: Tan, J., Luo, J., Li, L., Chen, D., Wang, J., Ge, C., & Li, P. (2026). METTL3 mitigates age-related hearing loss by inhibiting NF-κB-mediated inflammatory responses through the m6A modification of NFKBIA. Journal of Molecular Medicine, 104(1), Article 107. https://doi.org/10.1007/s00109-026-02714-5

Image Credits: AI Generated

DOI: 10.1007/s00109-026-02714-5

Keywords: age-related hearing loss, METTL3, NFKBIA, m6A modification, NF-κB, NLRP3 inflammasome, inflammaging, cochlea, RNA methylation, IL-6, STAT3, presbycusis