Project description:We performed a microarray analysis of auditory midbrain (inferior colliculus, IC) mRNA from young adult CBA mice (controls) with good hearing, middle aged (MA) with good hearing, and old mild (MP) and severe (SP) presbycusic CBA mice. Fold Change data derived from RMA normalization revealed that the overall GABA receptor alpha 6 expression profiles for MA, MP and SP were down-regulated relative to young adult controls with good hearing. Relative real-time PCR for five GABA receptors confirmed this age-related down regulation quantitatively. Functional hearing data: Auditory Brainstem Responses (ABR) enriched the analysis to select the probe-sets that changed with age and hearing loss by the linear regression best-fit line model technique. GABA receptor genotype-phenotype correlations with auditory functional data indicated that GABA-receptor subtypes are under expressed in SP mice. Hierarchical clustering (HC) analyses yielded statistical significance of normalized GeneChip data Real-time PCR showed that Gabra6, GABA B receptor 1 (Gabbr1), and Gaba transporter protein Slc32a1 may be involved in physiological changes that occur in age-related hearing loss. Presbycusis – age-related hearing loss – is the number one communicative disorder of our aged population. In this study we analyzed gene expression for a set of GABA receptors in the inferior colliculus of aging CBA mice using the Affymetrix GeneChip MOE430A. Functional phenotypic hearing changes from RMA normalized microarray data (39 replicates) in four age-groups, Young Controls and Middle aged mice with good hearing, mild and sever e presbycusis from old mice. Fold change gene expression derived from RMA normalized data were first subjected to one-way ANOVA, and then linear regression was performed. The selected gene expression changes were confirmed by relative real-time relative to young adult controls with good hearing. Statistically significant and real time PCR confirmed GABA receptor genes; Gabra6, GABA B receptor 1 (Gabbr1), and Gaba transporter protein Slc32a1, may be involved in physiological changes that occur in age-related hearing loss. Lastly, gene expression measures of each age group were correlated with pathway/network relationships relevant to the inferior colliculus using Pathway Architect, to identify key pathways consistent with the gene expression changes observed In the study of Expression changes in IC GABA receptors in the Auditory Midbrain of young adult and aging presbycusis mice total of thirty nine chips were used. The normal aging mice were in Four groups Young adults Controls with good hearing (8 mice, 8 MOE430A GeneChips), Middle aged group with good hearing ( 17 mice, 17 MOE430A GeneChips), Mild Presbycusis with limited hearing loss (9 mice, 9 MOE430A GeneChips) and Severe Presbycusis (5 mice, 5 MOE430A GeneChips).

Project description:Spiral ganglion neurons (SGNs) and the associated components of the auditory nerve are primary carriers of auditory information from hair cells to the brain. Loss of SGNs occurs with many pathological conditions, resulting in permanent sensorineural hearing loss. Neural stem/progenitors (NSPs) have been well-characterized in several locations of adult brain and retina. However, it is unclear whether NSPs are present in the adult auditory nerve. Here we examined the self-renewal potential of the adult auditory nerve using ouabain application as a well-established mouse model of acute SGN injury. The observed increase in cell proliferation, alteration in enchromatin/heterochromatin ratio and down-regulation of histone deacetylase expression in glial cells suggest that the quiescent glial cells convert to an activated state after SGN degeneration. This was further confirmed by global gene expression analysis of injured auditory nerves, which showed up-regulation of numerous neurogenesis- and/or development-associated genes shortly after ouabain exposure. These genes include molecular markers commonly used for the identification of NSPs. Under a strict culture regimen, auditory nerve-derived cells of adult mouse ears gave rise to neurospheres, suggesting that multipotent NSPs are present in adult cochlear nerve. Neurosphere assays on Sox2 transgenic mice revealed that Sox2+ glial cells are the source for NSPs. Our data also showed that acute injury or hypoxia enhances neurosphere formation. Taken together, our study revealed that glial cells of adult cochlea exhibit several NSP characteristics, and hence these mature non-neuronal cells may be important targets for promoting self-repair of degenerative auditory nerves. Auditory nerves were removed from the temporal bones of adult CBA/CaJ mice, aged 8 to 12 weeks. Tissues were either collected and used directly as the tissue samples or dissociated and used for the cell culture samples. Dissociated auditory nerve cells were propagated and grown to full confluency (5-7 days), constituting the cultured cell samples. For neurosphere samples, growth medium was changed to neurosphere formation medium and the cells were cultured for an additional 12 days. All samples were prepared in triplicate (n=3).

Project description:Spiral ganglion neurons (SGNs) and the associated components of the auditory nerve are primary carriers of auditory information from hair cells to the brain. Loss of SGNs occurs with many pathological conditions, resulting in permanent sensorineural hearing loss. Neural stem/progenitors (NSPs) have been well-characterized in several locations of adult brain and retina. However, it is unclear whether NSPs are present in the adult auditory nerve. Here we examined the self-renewal potential of the adult auditory nerve using ouabain application as a well-established mouse model of acute SGN injury. The observed increase in cell proliferation, alteration in enchromatin/heterochromatin ratio and down-regulation of histone deacetylase expression in glial cells suggest that the quiescent glial cells convert to an activated state after SGN degeneration. This was further confirmed by global gene expression analysis of injured auditory nerves, which showed up-regulation of numerous neurogenesis- and/or development-associated genes shortly after ouabain exposure. These genes include molecular markers commonly used for the identification of NSPs. Under a strict culture regimen, auditory nerve-derived cells of adult mouse ears gave rise to neurospheres, suggesting that multipotent NSPs are present in adult cochlear nerve. Neurosphere assays on Sox2 transgenic mice revealed that Sox2+ glial cells are the source for NSPs. Our data also showed that acute injury or hypoxia enhances neurosphere formation. Taken together, our study revealed that glial cells of adult cochlea exhibit several NSP characteristics, and hence these mature non-neuronal cells may be important targets for promoting self-repair of degenerative auditory nerves. Analysis was conducted on auditory nerve samples from stages encompassing maturation and onset of hearing. Cochleas were collected from euthanized mice (CBA/CaJ) at perinatal (P) stages P0, P3, P7, P10, P14 and P21. Cochleas underwent microdissection to remove the outer bony cochlear shell and cochlear lateral wall, thus preserving the modiolus portion of cochlea which contains mainly the auditory nerve. Paired cochleas (i.e., from left and right ears) from each mouse were pooled to make individual samples. All sample types were done in experimental duplicate (n=2).

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External auditory canal microbiome

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