Rance G, Carew P, Winata L, Sale P, Delatycki M, Sly D. Auditory neuropathy in mice and humans with Friedreich ataxia.
Ann Clin Transl Neurol 2023;
10:953-963. [PMID:
37060174 PMCID:
PMC10270266 DOI:
10.1002/acn3.51777]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Revised: 02/20/2023] [Accepted: 03/08/2023] [Indexed: 04/16/2023] Open
Abstract
OBJECTIVE
Recent studies have found that human Friedreich ataxia patients have dysfunction of transmission in the auditory neural pathways. Here, we characterize hearing deficits in a mouse model of Friedreich ataxia and compare these to a clinical population.
METHODS
Sixteen mice with a C57BL/6 background were evaluated. Eight were YG8Pook/J animals (Friedreich ataxia phenotype) and eight wild-type mice served as controls. Auditory function was assessed between ages 6 and 12 months using otoacoustic emissions and auditory steady-state responses. At study end, motor deficit was assessed using Rotorod testing and inner ear tissue was examined. Thirty-seven individuals with Friedreich ataxia underwent auditory steady-state evoked potential assessment and response amplitudes were compared with functional hearing ability (speech perception-in-noise) and disease status was measured by the Friedreich Ataxia Rating Scale.
RESULTS
The YG8Pook/J mice showed anatomic and functional abnormality. While otoacoustic emission responses from the cochlear hair cells were mildly affected, auditory steady-state responses showed exaggerated amplitude reductions as the animals aged with Friedreich ataxia mice showing a 50-60% decrease compared to controls who showed only a 20-25% reduction (F(2,94) = 17.90, p < 0.00). Furthermore, the YG8Pook/J mice had fewer surviving spiral ganglion neurons, indicating greater degeneration of the auditory nerve. Neuronal density was 20-25% lower depending on cochlear region (F(1, 30) = 45.02, p < 0.001). In human participants, auditory steady-state response amplitudes were correlated with both Consonant-Nucleus-Consonant word scores and Friedreich Ataxia Rating Scale score.
INTERPRETATION
This study found degenerative changes in auditory structure and function in YG8Pook/J mice, indicating that auditory measures in these animals may provide a model for testing Friedreich ataxia treatments. In addition, auditory steady-state response findings in a clinical population suggested that these scalp-recorded potentials may serve as an objective biomarker for disease progress in affected individuals.
Collapse