Quantitative differentiation of normal and scarred tissues using second-harmonic generation microscopy.

Area of Science:

• Biomedical Optics
• Materials Science
• Histology

Background:

• Vocal fold scarring, a common issue, leads to voice impairment.
• Accurate characterization of scar tissue is crucial for effective treatment.
• Current methods for assessing scar tissue can be invasive or lack quantitative precision.

Purpose of the Study:

• To develop and apply a quantitative image analysis technique to differentiate normal and scarred hamster cheek pouch tissue.
• To assess collagen fiber direction and density using second-harmonic generation (SHG) microscopy.
• To establish objective endpoints for characterizing vocal fold scarring in vivo.

Main Methods:

• Utilized a home-built upright microscope with an ultrafast fiber laser for SHG imaging.
• Acquired depth-resolved epi-collected SHG images of collagen fibers in control and electrocautery-scarred hamster cheek pouches.
• Applied 2D Fourier analysis and intensity thresholding to quantify average fiber direction and density.

Main Results:

• Scarred tissues exhibited significantly lower average fiber direction variance (0.61 ± 0.03) compared to controls (0.73 ± 0.04), indicating increased alignment.
• Scarred tissues showed significantly greater fiber density (0.72 ± 0.09) than control tissues (0.18 ± 0.03).
• The image analysis successfully quantified increased collagen deposition and alignment characteristic of fibrosis.

Conclusions:

• Quantitative analysis of SHG images provides an objective method to differentiate scarred from normal tissue.
• This technique enables precise characterization of collagen fiber deposition and alignment in fibrosis.
• The non-invasive approach is valuable for monitoring scar treatments and understanding fibrosis in preclinical and clinical research.