Voice is produced when the vocal folds are driven into a wave-like motion by the airstream from the trachea, converting aerodynamic energy and airflow into acoustic energy in the form of sound. The key to this great mechanical versatility lie in the unique structure and composition of the tissue. Each vocal fold consists of a pliable vibratory layer of connective tissue, known as the lamina propria (LP), sandwiched between a muscle and an epithelial layer. The structure and mechanics of the LP change gradually from the muscle to the epithelium. Numerous environmental, mechanical and pathological factors can damage this delicate tissue, resulting in a wide spectrum of voice disorders that affect millions o Americans. Current treatment options for vocal fold disorders are limited, and the development of new procedures has been slow owing to the inaccessibility of the tissue, its susceptibility to damage, and the anatomical differences of animal models from the human tissue. This project aims to engineer a reliable, physiologically relevant in vitro tissue model that can be used to investigate vocal fold development, health, and disease, and more importantly, to facilitate the development and testing of new treatment options. The central hypothesis of the proposed work is that vocal fold-mimetic synthetic extracellular matrices (sECMs) displaying a layered and gradient structure with tissue- like anisotropy will provide the resident cells with guidance cues for the establishment of appropriate tissue structures. The initial template effects from the sECMs will be further reinforced by the application of physiologically relevant vibratory stimulations, ultimately producing a viable and functional vocal fold tissue model.
In Aim 1, we will create sECMs using modular building blocks and employing a rapid bioorthogonal reaction at well-defined interfaces. The resultant sECM will consist of a bottom fibrous layer, a basement membrane-like top layer and a middle gel layer with a gradient of crosslinking density and biochemical signals.
In Aim 2, we will produce and characterize stem cell-derived vocal fold epithelial cells. The differentiated epithelial cells will be grown on sECMs populated by primary human vocal fold fibroblasts (VFFs). Culture conditions will be identified to foster the epithelialization of the engineered LP.
In Aim 3, we will fabricate a self- oscillating tissue construct, consisting of the VFF-laden sECM supported on a cell-free synthetic hydrogel with geometry and mechanics reflecting that of the vocal fold muscle. The construct, maintained under standard cell culture conditions, will be regularly transferred to an oscillatory bioreactor or mechanical stimulations. Under the engineered, vocal fold-mimetic microenvironment, VFFs will actively remodel the synthetic environment, secrete native matrix components, and communicate with the tethered epithelial cells to establish a cohesive and functional tissue. Overall, the combination of tissue-mimetic synthetic matrix, pluripotent stem cells and a vibratory culture device offers an exciting opportunity for the engineering of reliable and viable vocal fold tissue models.
This project seeks to develop a hydrogel-based cellular model of the human vocal fold lamina propria. A multilayered synthetic matrix with well-defined spatial gradients and tissue-like anisotropy, combined with a dynamic culture device that recaptures the mechanical environments of the native tissue, will provide regulatory signals to guide cell growth, matrix remodeling and tissue maturation. The engineered tissue model can be used as a reliable platform for studying vocal fold physiology and pathology, as well as for the screening and testing of new treatment options.
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