Laryngeal cancer is often diagnosed at an advanced stage when treatment options are limited and most often restricted to laryngectomy. As this procedure requires a permanent tracheostoma, it is associated with additional complications such as a high risk of infection, fistulae formation and loss of the natural voice. In addition, restoration of the most important laryngeal function, protection of the airways, usually leads to deterioration of other functions like speaking or swallowing. To date, no method exists to simultaneously restore all laryngeal functions, resulting in a poor quality of life in the long term.
In future, a tissue engineered autologous laryngeal replacement could provide a way to ensure airway protection and voice production in parallel. A tissue engineered vocal fold would represent a milestone in developing a complete laryngeal replacement. As the native vocal folds undergo a broad variety of mechanical stresses in vivo such as tension, shear and impact, they exhibit specific biomechanical characteristics that also have to be met by tissue engineered constructs. In this study, we therefore developed a bioreactor that combines vibrational stimulation and stretching for the in vitro culture of vocal fold replacement tissues.
To fulfil the tissue’s in vivo properties, we targeted a bioreactor with a frequency range between 100 and 300 Hz in combination with 20 % tensile strain, allowing alternating stimulation patterns with resting periods. Compatible scaffolds for cell seeding include elastic membranes and hydrogels. In addition, we aimed for a reusable, sterilizable and straight-forward design that is easy to implement. Electrical components were designed to avoid contact with the humidified incubator atmosphere, thus enabling long-term cultivation over several days to weeks.
We developed a vocal fold bioreactor consisting of a transparent polymethyl methacrylate (PMMA) cylinder, polyoxymethylene (POM) scaffold holders and POM based housing parts. A linear module connected to a stepper motor implements the stretching of the scaffold while piezoelectric patches transmit vibration. Appropriate oxygenation of the medium is achieved via a silicon tubing loop. Cell compatibility of the bioreactor was evaluated for culture periods of up to 7 days.
Our bioreactor offers new perspectives for in vitro studies on mechanobiological processes in regenerating tissues. In addition, it represents a first step towards developing a vocal fold replacement tissue that may in the future provide new treatment options for laryngeal cancer patients after total laryngectomy."