Hypothesis

Restoring elastin-rich extracellular matrix in the aged vocal fold lamina propria will reactivate satellite cell-mediated thyroarytenoid muscle regeneration by reducing elastin-derived inhibitory peptides that suppress myogenic differentiation.

Mechanistic Rationale

Aging increases collagen I/III and decreases elastin in the lamina propria [alterations-in-extracellular-matrix-composition-in-the-aging]. Elastin degradation generates bioactive peptides that can bind integrin αvβ3 on resident progenitor cells. In other tissues, such peptides activate TGF‑β/Smad3 signaling, promoting a fibrogenic phenotype and inhibiting satellite cell proliferation and differentiation [satellite-cell-regeneration-injury]. We propose that a similar mechanism operates in the larynx: loss of intact elastin shifts the local niche from supportive to inhibitory, directly contributing to the observed decline in thyroarytenoid satellite cell mitotic activity with age.

Sex hormone modulation of ECM gene expression [sex-hormones-ecm-gene-expression] may amplify or dampen this effect, explaining individual variability in presbyphonia progression.

Experimental Design

Model: Aged (24‑month) male and female Fischer rats; young (3‑month) controls. Intervention: Intralaminar propria injection of recombinant human tropoelastin or an elastin‑mimetic peptide hydrogel (silk‑HA base loaded with elastin‑derived sequences) versus vehicle control. Treatments administered weekly for 4 weeks. Outcomes:

• Satellite cell activity: Immunohistochemistry for Pax7, Ki67, and MyoD in thyroarytenoid muscle; quantification of proliferating progenitors per mm².
• Muscle morphology: Cross‑sectional area and fiber diameter via laminin staining; MRI‑based volumetric analysis to confirm atrophy changes [volumetric-analysis-vocal-fold-atrophy-mri].
• ECM composition: Second harmonic generation imaging for collagen; elastin autofluorescence; hydroxyproline assay for total collagen.
• Voice function: Acoustic analysis of fundamental frequency, jitter, and shimmer before and after intervention.
• Signaling readouts: Western blot for phospho‑Smad3 and integrin αvβ3 activation in isolated satellite cells.

Groups (n=8 per sex per group): young vehicle, aged vehicle, aged tropoelastin, aged elastin‑peptide hydrogel.

Expected Outcomes and Implications

If elastin restoration reverses the inhibitory niche, we anticipate:

• Significant increase in Pax7+/Ki67+ satellite cells in treated aged rats approaching young levels.
• Corresponding growth in thyroarytenoid cross‑sectional area and improved MRI volumetrics.
• Reduction in phospho‑Smad3 signaling and integrin αvβ3 activation in satellite cells.
• Improved acoustic parameters (lower jitter/shimmer, stabilized fundamental frequency).

A failure to observe these changes would falsify the hypothesis, indicating that elastin loss is not a primary driver of satellite cell dysfunction in presbyphonia.

Confirming this link would justify a dual‑target therapeutic strategy: ECM remodeling to reinstate a permissive niche for muscle regeneration, thereby addressing the current gap in treatments that focus solely on lamina propria repair [injectable-hydrogels-silk-ha]. This approach could be combined with voice therapy to translate tissue‑level gains into functional voice outcomes, moving beyond prevalence estimates toward clinically meaningful thresholds [prevalence-functional-impact].