Development of Excised Larynx

Quasi-static ultrasound elastography of ex-vivo porcine vocal folds during passive elongation and adduction

OBJECTIVES

The elastic properties of the vocal folds have great influence on the primary sound and thus on the entire subsequent phonation process. Muscle contractions in the larynx can alter the elastic properties of the vocal fold tissue. Quasi-static ultrasound elastography is a non-destructive examination method that can be applied to ex-vivo vocal folds. In this work, porcine vocal folds were passively elongated and adducted and the changes of the elastic properties due to that manipulations were measured.

METHODS

Manipulations were performed by applying force to sewn-in sutures. Elongation was achieved by a suture attached to the thyroid cartilage, which was pulled forward by defined weights. Adduction was effected by two sutures exerting torque on the arytenoid cartilage. A series of ten specimens was examined and evaluated using a quasi-static elastography algorithm. In addition, the surface stretch was measured optically using tattooed reference points.

RESULTS

This study showed that the expected stiffening of the tissue during the manipulations can be measured using quasi-static ultrasound elastography. The measured effect of elongation and adduction, both of which result in stretching of the tissue, is stiffening. However, the relative change of specific manipulations is not the same for the same load on different larynges, but is rather related to stretch caused and other uninvestigated factors.

CONCLUSION

The passive elongation and adduction of vocal folds stiffen the tissue of the vocal folds and can be measured using ultrasound elastography.

Impact of Rehydration Following Systemic Dehydration on Vocal Fold Gene Expression

OBJECTIVE

Biological data on the beneficial effects of vocal fold rehydration are lacking. This study aimed to examine the effects of acute systemic dehydration on vocal fold gene expression and determine whether rehydration would reverse these changes.

METHODS

Male New Zealand White rabbits (N = 24, n = 8/group) provided the animal model. Systemic dehydration was induced by 5 days of water volume restriction. Rehydration was provided by ad-lib water for 3 days following dehydration. Euhydrated rabbits were used as the control group. Vocal fold tissue was dissected. Seventeen genes were selected based on physiological function and role in supporting vocal fold structure, oxidative stress, hemodynamics, and extracellular matrix turnover. Relative gene expression was assessed by RT-qPCR.

RESULTS

Rehydration following systemic dehydration can modulate gene expression, with expression patterns suggesting that rehydration reverses dehydration-induced changes in over half of the tested genes. CLIC5 (chloride intracellular channel 5) and EFEMP1 (EGF containing fibulin extracellular matrix protein 1) genes were significantly upregulated in the dehydration group compared with the euhydrated control. A1BG (alpha-1B-glycoprotein) and IL1RAP (interleukin 1 receptor accessory protein) were downregulated by rehydration compared with the dehydration group.

CONCLUSION

This study provides molecular evidence for a transcriptional response to rehydration following acute systemic dehydration in the vocal folds. These data are the first to study gene expression following realistic dehydration and rehydration paradigms and provide biological data to support clinical recommendations to increase water intake after acute dehydration.

LEVEL OF EVIDENCE

NA Laryngoscope, 133:3499-3505, 2023.