A new approach to geometrical measurements in an animal model of vocal fold scar

Characterization of vocal fold scar formation, prophylaxis, and treatment using animal models

PURPOSE OF REVIEW

To review recent literature on animal models used to study the pathogenesis, detection, prevention, and treatment of vocal fold scarring. Animal work is critical to studying vocal fold scarring because it is the only way to conduct systematic research on the biomechanical properties of the layered structure of the vocal fold lamina propria, and therefore develop reliable prevention and treatment strategies for this complex clinical problem.

RECENT FINDINGS

During the period of review, critical anatomic, physiologic, and wound healing characteristics, which may serve as the bases for selection of a certain species to help answer a specific question, have been described in mouse, rat, rabbit, ferret, and canine models. A number of different strategies for prophylaxis and chronic scar treatment in animals show promise for clinical application. The pathways of scar formation and methods for quantifying treatment-induced change have become better defined.

SUMMARY

Recent animal vocal fold scarring studies have enriched and confirmed earlier work indicating that restoring pliability to the scarred vocal fold mucosa is challenging but achievable. Differences between animal models and differences in outcome measurements across studies necessitate considering each study individually to obtain guidance for future research. With increased standardization of measurement techniques it may be possible to make more inter-study comparisons.

Liver-derived extracellular matrix as a biologic scaffold for acute vocal fold repair in a canine model

OBJECTIVES/HYPOTHESIS

The objective of the study was to evaluate a naturally derived liver extracellular matrix (L-ECM) scaffold for repair of an acute injury to the vocal fold lamina propria in a canine model.

METHODS

The vocal fold lamina propria was removed bilaterally in four dogs. One vocal fold in each dog was repaired with a porcine L-ECM scaffold, which was chosen because it contains hepatocyte growth factor, an antifibrotic growth factor that aids the healing of vocal folds. The other vocal fold was left untreated. At 3 months after surgery, morphologic and histologic analysis was performed to assess the vocal fold shape, collagen density, collagen composition, elastic fiber content, and glycosaminoglycan content.

RESULTS

The L-ECM-treated vocal fold showed increased collagen density in the superficial aspect of the vocal fold (P < .05). The L-ECM-treated vocal fold also showed an increased collagen III/I ratio as compared to the nontreated group (P < .05). However, the elastic fiber content was found to be increased in both groups, and the glycosaminoglycan content was decreased in both groups as compared to the normal vocal fold (P < .05) with no differences detected between groups.

CONCLUSIONS

The L-ECM scaffold did not restore the biochemical composition or histologic appearance of the injured vocal fold as compared to normal. However, the increased ratio of collagen III/I and elastic fiber content suggests that L-ECM leads to formation of connective tissue that may be more pliable as compared to no treatment. Additional investigation, including functional assessment, is warranted.