Monitoring metabolism: improving the management of age related hearing loss using mass spectrometry and vibrational spectroscopy techniques

Worrall, Amy Jayne

Abstract

Age-related hearing loss (ARHL) is the third most prevalent degenerative condition in the elderly, with cochlear fibrocyte inflammation preceding sensory cell loss. A deeper understanding of inflammatory mechanisms is essential for developing regenerative therapies.

In a novel multi-modal investigation, this study utilised Raman spectroscopy, FTIR spectroscopy (ATR-FTIR and Synchrotron S-FTIR), and SIFT-MS to analyse primary cochlear fibrocytes, their supernatant (culture media from cells), and headspace (culture vessel gas). Fibrocytes were stimulated with TNF-α and IL-1β (1–50 ng/mL) to assess dose-dependent inflammatory responses. Human cerumen was preliminarily examined for diagnostic potential.

Raman spectroscopy revealed inflammation-associated biochemical changes, including CoA depletion (927 cm⁻¹, 950 cm⁻¹), lipid accumulation (1447 cm⁻¹), oxidative stress markers (962 cm⁻¹) and disrupted protein/lipid membrane assemblies (1658cm-1). S-FTIR further revealed alterations in proteins (1527cm-1, 2800-3100cm-1), lipids (2800-3100cm-1), nucleic acids (<110cm-1, 1115-1130cm1), phospholipids (<110cm-1), and carbohydrates (80% accuracy, reinforcing the diagnostic relevance of these findings.

ATR-FTIR analysis of supernatant identified cytokine-driven disruptions in protein secondary structure (amide I: ~1650 cm⁻¹) and lipid composition (~1740 cm⁻¹), indicative of metabolic dysregulation. Proposed histidine-related spectral variations in supernatant and headspace suggest cytokine-induced alterations in amino acid metabolism. SIFT-MS headspace data, through changes seen in acetaldehyde and pyruvate, support a hypothesis of citric acid cycle disruption in inflamed fibrocytes.

Overall, this research advances understanding of cochlear inflammation in ARHL. Raman and S-FTIR facilitated detailed cellular examination while ATR-FTIR provided critical insights into supernatant composition – potentially translatable to cochlear fluid analyses. Cerumen demonstrated preliminary promise as a diagnostic biofluid. With further refinement, these findings could contribute to future ARHL detection and monitoring strategies.

Citation

Worrall, A. J. (2025). Monitoring metabolism: improving the management of age related hearing loss using mass spectrometry and vibrational spectroscopy techniques. (Thesis). Keele University. https://keele-repository.worktribe.com/output/1280024

• Thesis Type: Thesis
• Online Publication Date: Jun 26, 2025
• Deposit Date: Jun 18, 2025
• Publicly Available Date: Jun 27, 2025
• Public URL: https://keele-repository.worktribe.com/output/1280024
• Award Date: 2025-06