Injection of human mesenchymal stem cells improves healing of vocal folds after scar excision—A xenograft analysis

Abstract

Using a xenograft model the aim was to analyze if injection of human mesenchymal stem cells (hMSC) into the rabbit vocal fold (VF), after excision of an established scar, can improve the functional healing of the VF. Prospective design with an experimental xenograft model. The VFs of 12 New Zealand rabbits were injured by a bilateral localized resection. After 9 weeks the scar after the resection was excised and hMSC were injected into the VFs. After another 10 weeks 10 VFs were dissected and stained for histology. Lamina propria thickness and relative content of collagen type I were measured. Viscoelasticity of 14 VFs at phonatory frequencies was quantified by a simple-shear rheometer. The hMSC survival was determined using a human DNA specific reference probe, that is, FISH analysis. The viscoelastic measurements, that is, dynamic viscosity and elastic shear modulus for the hMSC-treated VFs, were found to be similar to those of normal controls and were significantly lower than those of untreated controls (P < .05). A significant reduction in lamina propria thickness was also shown for the hMSC treated VFs compared with the untreated VFs (P < .05). This histologic finding corresponded with the viscoelastic results. No hMSC survived 10 weeks after the injection. Human mesenchymal stem cells injected into the rabbit VF following the excision of a chronic scar, were found to enhance the functional healing of the VF with reduced lamina propria thickness and restored viscoelastic shear properties.