Long-term dietary folate deficiency accelerates progressive hearing loss on CBA/Ca mice

This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY).Dietary folic acid deficiency induced early hearing loss in C57BL/6J mice after two-months, corroborating the epidemiological association previously described between vitamin deficiency and this sensory impairment. However, this strain is prone to early hearing loss, and hence we decided to analyze whether the effects exerted by folate deprivation follow the same pattern in a mouse strain such as CBA/Ca, which is resistant to hearing impairment. Here, we show results of a long-term study on hearing carried out on CBA/Ca mice subjected to dietary folate deprivation. Systemic changes included decreased serum folate levels, hyperhomocysteinemia and signs of anemia in the group fed the folate-deficient diet. Initial signs of hearing loss were detected in this strain after 8-months of vitamin deficiency, and correlated with histological damage in the cochleae. In conclusion, the data presented reinforce the importance of adequate folic acid levels for the auditory system and suggest that the impact of dietary deficiencies may depend on the genetic background.RM was a fellow of the JAE-CSIC predoctoral program. This work was supported by grants of the Ministerio de Economía y Competitividad (SAF2014-53979-R to IV; BFU2009-08977 to MP), the European Union (FP7-AFHELO and TARGEAR to IV).Peer reviewe

Bases genéticas, moleculares y bioquímicas del envejecimiento auditivo ¿Qué nos enseñan los modelos experimentales

Age-related hearing loss (ARHL) affects one in three people older than 65 years and is the most prevalent sensorineural deficit. This type of hearing loss precedes and accelerates the onset of cognitive impairment and is associated with an increased risk for neurodegenerative diseases such as dementia and Alzheimer disease. The onset and progression of ARHL is influenced by genetic factors, which are still poorly understood, and environmental factors, which in particular include exposure to excessive noise and ototoxic substances. At present, no effective drug treatments are available for ARHL prevention or treatment, and therefore research in this field is a priority. In the research field, animal models offer a crucial tool for i) identifying new genes associated with ARHL, ii) understanding the cellular and molecular basis of auditory ageing and iii) defining new therapeutic targets and evaluating candidate treatments.La presbiacusia afecta a una de cada tres personas mayores de 65 años y constituye el déficit neurosensorial más prevalente. Antecede a la aparición de la fragilidad cognitiva, la acelera y se asocia con un mayor riesgo de padecer enfermedades neurodegenerativas como la demencia o el Alzheimer. La aparición y evolución de la presbiacusia están influidas por factores genéticos, todavía poco conocidos, y ambientales, entre los que destacan la exposición a ruido excesivo o a sustancias ototóxicas. En la actualidad no disponemos de tratamientos farmacológicos eficaces para prevenir o tratar la presbiacusia, por lo que la investigación en este campo es prioritaria. En este contexto, los modelos animales son una herramienta esencial para: a) identificar nuevos genes de presbiacusia, b) comprender las bases celulares y moleculares del envejecimiento auditivo, y c) definir nuevas dianas terapéuticas y evaluar posibles tratamientos

A Comparative Study of Age-Related Hearing Loss in Wild Type and Insulin-Like Growth Factor I Deficient Mice

Insulin-like growth factor-I (IGF-I) belongs to the family of insulin-related peptides that fulfils a key role during the late development of the nervous system. Human IGF1 mutations cause profound deafness, poor growth and mental retardation. Accordingly, Igf1−/− null mice are dwarfs that have low survival rates, cochlear alterations and severe sensorineural deafness. Presbycusis (age-related hearing loss) is a common disorder associated with aging that causes social and cognitive problems. Aging is also associated with a decrease in circulating IGF-I levels and this reduction has been related to cognitive and brain alterations, although there is no information as yet regarding the relationship between presbycusis and IGF-I biodisponibility. Here we present a longitudinal study of wild type Igf1+/+ and null Igf1−/− mice from 2 to 12 months of age comparing the temporal progression of several parameters: hearing, brain morphology, cochlear cytoarchitecture, insulin-related factors and IGF gene expression and IGF-I serum levels. Complementary invasive and non-invasive techniques were used, including auditory brainstem-evoked response (ABR) recordings and in vivo MRI brain imaging. Igf1−/− null mice presented profound deafness at all the ages studied, without any obvious worsening of hearing parameters with aging. Igf1+/+ wild type mice suffered significant age-related hearing loss, their auditory thresholds and peak I latencies augmenting as they aged, in parallel with a decrease in the circulating levels of IGF-I. Accordingly, there was an age-related spiral ganglion degeneration in wild type mice that was not evident in the Igf1 null mice. However, the Igf1−/− null mice in turn developed a prematurely aged stria vascularis reminiscent of the diabetic strial phenotype. Our data indicate that IGF-I is required for the correct development and maintenance of hearing, supporting the idea that IGF-I-based therapies could contribute to prevent or ameliorate age-related hearing loss

CIBERER: Spanish national network for research on rare diseases: A highly productive collaborative initiative

13 páginas,1 figura, 3 tablas, 1 apéndice. Se extraen los autores pertenecientes a The CIBERER network que trabajan en Centros del CSIC del Appendix ACIBER (Center for Biomedical Network Research; Centro de Investigación Biomédica En Red) is a public national consortium created in 2006 under the umbrella of the Spanish National Institute of Health Carlos III (ISCIII). This innovative research structure comprises 11 different specific areas dedicated to the main public health priorities in the National Health System. CIBERER, the thematic area of CIBER focused on rare diseases (RDs) currently consists of 75 research groups belonging to universities, research centers, and hospitals of the entire country. CIBERER's mission is to be a center prioritizing and favoring collaboration and cooperation between biomedical and clinical research groups, with special emphasis on the aspects of genetic, molecular, biochemical, and cellular research of RDs. This research is the basis for providing new tools for the diagnosis and therapy of low-prevalence diseases, in line with the International Rare Diseases Research Consortium (IRDiRC) objectives, thus favoring translational research between the scientific environment of the laboratory and the clinical setting of health centers. In this article, we intend to review CIBERER's 15-year journey and summarize the main results obtained in terms of internationalization, scientific production, contributions toward the discovery of new therapies and novel genes associated to diseases, cooperation with patients' associations and many other topics related to RD research.This study has been funded by Instituto de Salud Carlos III (ISCIII) and Spanish Ministry of Science and InnovationPeer reviewe

Procedimiento para diseñar una cámara acústica reverberante para ensayos auditivos con animales

Procedimiento para diseñar una cámara acústica reverberante para ensayos auditivos con animales. El objeto principal de la presente invención es procedimiento para diseñar una cámara acústica reverberante de dimensiones (L1, L2, L3) cuyo campo acústico sea homogéneo espacial y espectralmente; las operaciones del procedimiento son: elegir una de las dimensiones L3; obtener las funciones (valor medio del campo acústico) y (desviación cuadrática media del campo acústico); y seleccionar, con base en las funciones obtenidas en la operación anterior, las dimensiones L1 y L2 óptimas que proporcionan el campo acústico más uniforme.Peer reviewedConsejo Superior de Investigaciones Científicas (España), Universidad Complutense de MadridA1 Solicitud de patentes con informe sobre el estado de la técnic

Comparison of different aminoglycoside antibiotic treatments to refine ototoxicity studies in adult mice

Hearing and balance receptors in the inner ear are highly susceptible to damage caused by a wide variety of toxic substances, including aminoglycosides. This class of antibiotics is commonly used in medicine, even though they may produce irreversible bilateral neurosensorial deafness. To identify potential ototoxic agents and novel therapeutic targets, it is necessary to generate standardized animal models of aminoglycoside ototoxicity, which will also serve to explore otic cell repair and regeneration. Although the mouse is the species most often used in biomedical research, due to the genetic information and genetically-modified strains available, there are few standard models of aminoglycoside ototoxicity in adult mice. Most protocols to produce ototoxicity in adult mice employ high doses of aminoglycosides for long periods of time, which causes systemic toxicity, side-effects and high mortality rates. Here, we compare the effects of systemic treatment with four different, yet common, aminoglycoside antibiotics in two mouse strains, evaluating their effects on mortality, cochlear morphology and auditory brainstem responses. Our data indicate that gentamicin and neomycin caused high mortality in the adult mouse without significantly changing the auditory threshold. Amikacin produced a tolerable rate of mortality but at doses that did not exhibit ototoxicity. Finally, intramuscular injection of kanamycin in C57BL/6JOlaHsd mice induced significant dosedependent bilateral hearing loss with a moderate rate of mortality and less discomfort than following subcutaneous administration.This work was supported in part by grants from DIGNA Biotech SA, the Spanish Ministries of Health and Education (BFU-200500084 and SAF 2008-00470), the Community of Madrid (CAM-PRICIT0530) and Mutua Madrileña (MM 2007).Peer Reviewe

Direct drug application to the round window: A comparative study of ototoxicity in rats

[Objective]: To assess the validity of inducing ototoxicity in rats by applying a sponge soaked in kanamycin and furosemide on the round window. [Study Design]: Basic, randomized, nonblind experimental study. [Setting]: Animal models of cochlear damage and reliable methods of local drug delivery are fundamental to study hearing loss and to design new therapies. [Subjects and Methods]: Four experimental groups of six Wistar rats with different methods of drug administration were used: (1) injection of subcutaneous kanamycin (400 mg/kg) and intravenous furosemide (100 mg/kg); (2) local application of a sponge soaked in saline close to the round window; (3) animals for which the sponge was soaked in a solution containing kanamycin (200 mg/mL) and furosemide (50 mg/mL); and (4) sham-operated rats. The tympanic bulla was exposed using a ventral approach, and a bullostomy was performed to visualize the round window membrane. Cochlear function was assessed by measuring the auditory brainstem response, and hearing thresholds in response to click and tone burst stimuli were determined as peak and interpeak latencies. At the end of the study, cochlear histology was analyzed. [Results]: Systemic administration of kanamycin and furosemide induced profound hearing loss and severe hair cell damage. Local delivery of these ototoxic drugs caused comparable damage but avoided the systemic side effects of the drug. Sham-operated and saline control animals did not experience functional alterations. [Conclusion]: Situating a sponge soaked in kanamycin and furosemide on the round window membrane through the ventral approach is a reliable method to provoke local ototoxicity in rats. © 2009 American Academy of Otolaryngology-Head and Neck Surgery Foundation.Peer Reviewe

Procedimiento para diseñar una cámara acústica reverberante para ensayos auditivos con animales

[EN] The principal objective of this 1 invention is a method for designing a reverberating acoustic chamber with dimensions (L1, L2, L3) and with a spatially and spectrally uniform acoustic field; the steps of the method are: select one of the dimensions L3; obtain the functions Lpm (L1,L2) (mean value of the acoustic field) and σ(L1,L2) (mean quadratic deviation of the acoustic field); and select, on the basis of the functions obtained in the previous step, the optimum L1 and L2 dimensions that provide the most uniform acoustic field.[ES] Resumen: El objeto principal de la presente invención es procedimiento para diseñar una cámara acústica reverberante de dimensiones (L1,L2, L3) cuyo campo acústico sea homogéneo espacial y espectralmente; las operaciones del procedimiento son: elegir una de las dimensiones L3; obtener las funciones Lpm (L1,L2) (valor medio del campo acústico) y σ(Ll,L2) (desviación cuadrática media del campo acústico); y seleccionar, con base en las funciones obtenidas en la operación anterior, las dimensiones L1 y L2 óptimas que proporcionan el campo acústico más uniforme.Peer reviewedConsejo Superior de Investigaciones Científicas (España), Universidad Complutense de Madrid (UCM)A1 Solicitud de patentes con informe sobre el estado de la técnic

Age-related functional and structural retinal modifications in the Igf1-/- null mouse

[Background]: Mutations in the gene encoding human insulin-like growth factor-I (IGF-I) cause syndromic neurosensorial deafness. To understand the precise role of IGF-I in retinal physiology, we have studied the morphology and electrophysiology of the retina of the Igf1(-/-) mice in comparison with that of the Igf1(+/-) and Igf1(+/+) animals during aging. [Methods]: Serological concentrations of IGF-I, glycemia and body weight were determined in Igf1(+/+), Igf1(+/-) and Igf1(-/-) mice at different times up to 360days of age. We have analyzed hearing by recording the auditory brainstem responses (ABR), the retinal function by electroretinographic (ERG) responses and the retinal morphology by immunohistochemical labeling on retinal preparations at different ages. [Results]: IGF-I levels are gradually reduced with aging in the mouse. Deaf Igf1(-/-) mice had an almost flat scotopic ERG response and a photopic ERG response of very small amplitude at postnatal age 360days (P360). At the same age, Igf1(+/-) mice still showed both scotopic and photopic ERG responses, but a significant decrease in the ERG wave amplitudes was observed when compared with those of Igf1(+/+) mice. Immunohistochemical analysis showed that P360 Igf1(-/-) mice suffered important structural modifications in the first synapse of the retinal pathway, that affected mainly the postsynaptic processes from horizontal and bipolar cells. A decrease in bassoon and synaptophysin staining in both rod and cone synaptic terminals suggested a reduced photoreceptor output to the inner retina. Retinal morphology of the P360 Igf1(+/-) mice showed only small alterations in the horizontal and bipolar cell processes, when compared with Igf1(+/+) mice of matched age. [Conclusions]: In the mouse, IGF-I deficit causes an age-related visual loss, besides a congenital deafness. The present results support the use of the Igf1(-/-) mouse as a new model for the study of human syndromic deaf-blindness.This research was funded by grants from the Spanish Ministry of Science and InnovationSAF2010-21879 and RETICSRD07/0062/0008 to PdlV; BFU2009-07793/BFI, Fundaluce, ONCE and RETICSRD07/0062/0012 to NC; and SAF2008-0064, SAF2011-24391 and Intra-CIBERER programs to IV-N.Peer Reviewe

Swept-sine noise-induced damage as a hearing loss model for preclinical assays

This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY).Mouse models are key tools for studying cochlear alterations in noise-induced hearing loss and for evaluating new therapies. Stimuli used to induce deafness in mice are usually white and octave band noises that include very low frequencies, considering the large mouse auditory range. We designed different sound stimuli, enriched in frequencies up to 20 kHz (>violet> noises) to examine their impact on hearing thresholds and cochlear cytoarchitecture after short exposure. In addition, we developed a cytocochleogram to quantitatively assess the ensuing structural degeneration and its functional correlation. Finally, we used this mouse model and cochleogram procedure to evaluate the potential therapeutic effect of transforming growth factor β1 inhibitors P17 and P144 on noise induced hearing loss. CBA mice were exposed to violet swept-sine noise with different frequency ranges (2-20 or 9-13 kHz) and levels (105 or 120 dB SPL) for 30 minutes. Mice were evaluated by auditory brainstem response and otoacoustic emission tests prior to and 2, 14 and 28 days after noise exposure. Cochlear pathology was assessed with gross histology; hair cell number was estimated by a stereological counting method. Our results indicate that functional and morphological changes induced by violet swept-sine noise depend on the sound level and frequency composition. Partial hearing recovery followed the exposure to 105 dB SPL, whereas permanent cochlear damage resulted from the exposure to 120 dB SPL. Exposure to 9-13 kHz noise caused an auditory threshold shift in those frequencies that correlated with hair cell loss in the corresponding areas of the cochlea that were spotted on the cytocochleogram. In summary, we present mouse models of noise-induced hearing loss, which depending on the sound properties of the noise, cause different degrees of cochlear damage, and could therefore be used to study molecules which are potential players in hearing loss protection and repair.This work was supported by grants from MINECO (SAF2011-24391), Fundación de Investigación Médica Mutua Madrileña (FMM2012), European FP7-INNOVA2-AFHELO and FP7-PEOPLE-IAPP-TARGEAR to IVN and FIS PI 10/00394 for TR. S.M.-C. holds a CIBERER (ISCIII) postdoctoral contract.Peer Reviewe