Visualizing collagen network within human and rhesus monkey vocal folds using polarized light microscopy

Area of Science:

• Vocal fold biomechanics
• Connective tissue histology
• Comparative anatomy

Background:

• Collagen fiber content and orientation are crucial for vocal fold viscoelasticity and oscillation.
• Understanding the vocal fold collagen network at micron-scale resolution is essential but challenging.
• Polarized light microscopy offers a method to visualize collagen distribution and alignment.

Purpose of the Study:

• To investigate the distribution and alignment of collagen fibers in human and rhesus monkey vocal folds.
• To compare the collagen networks between the two species.
• To correlate collagen network structure with vocal fold viscoelastic properties.

Main Methods:

• Human and rhesus monkey vocal fold sections were analyzed using polarized light microscopy.
• Tissue sections were cut at three different angles to capture network complexity.
• Picrosirius red staining was employed to visualize collagen fibers.

Main Results:

• Significant differences in collagen fiber distribution were observed across different section angles.
• Human vocal folds showed continuous variation in collagen distribution and high birefringence near the thyroarytenoid muscle and epithelium.
• Rhesus monkey vocal folds exhibited high birefringence near the epithelium and lower birefringence near the thyroarytenoid muscle.

Conclusions:

• The study identified distinct differences in collagen networks between human and rhesus monkey vocal folds.
• These structural variations provide a morphological basis for observed differences in species-specific vocal fold viscoelastic properties.