A bioreactor for the dynamic mechanical stimulation of vocal-fold fibroblasts based on vibro-acoustography

Abstract

During voice production, the vocal folds undergo airflow-induced self-sustained oscillation at a fundamental frequency of around 100–1000 Hz, with an amplitude of around 1–3 mm. The vocal-fold extracellular matrix (ECM), with appropriate tissue viscoelastic properties, is optimally tuned for such vibration. Vocal-fold fibroblasts regulate the gene expressions for key ECM proteins (e.g., collagen, fibronectin, fibromodulin, and hyaluronic acid), and these expressions are affected by the stress fields experi- enced by the fibroblasts. This study attempts to develop a bioreactor for cultivating cells under a micromechanical environment similar to that in vivo, based on the principle of vibro-acoustography. Vocal-fold fibroblasts from primary culture were grown in 3D, biodegradable scaffolds, and were excited dynamically by the radiation force generated by amplitude modulation of two confocal ultrasound beams of slightly different frequencies. Low-frequency acoustic radiation force was applied to the scaffold surface, and its vibratory response was imaged by videostroboscopy. A phantom tissue (standard viscoelastic material) with known elastic modulus was also excited and its vibratory frequency and amplitude were measured by videostroboscopy. Results showed that the bioreactor was capable of delivering mechanical stimuli to the tissue constructs in a physiological frequency range (100–1000 Hz), supporting its potential for vocal-fold tissue engineering applications. [Work supported by NIH Grant R01 DC006101.]