Effective treatment options are not available for improving vocal function and quality of life for patients with vocal fold scarring. Cell-based therapies are suggested to have the innate capacity for promoting vocal fold scar repair, but lack of knowledge regarding the optimal cell source has stymied the development of such therapeutics. Candidate cell sources include mesenchymal stromal cells derived from either bone marrow (BM-MSC) or adipose tissue (AT-MSC). Both cell types demonstrate sensitivity to their biomechanical environment which can alter highly relevant aspects of cell function including secretion of trophic factors, extracellular matrix (ECM) remodeling, and propensity for cell differentiation. To date, trials of MSC-mediated repair of vocal fold scar have been performed in animal models which are not biomechanically translatable to the human larynx. The objective of this application is to determine if MSC (BM and/or AT) are biomechanically valid cell sources for vocal fold tissue engineering. Based on our preliminary data, our central hypothesis is that MSC (AT and BM) can be activated to a vocal fold fibroblast (VFF) genotype by vibratory strain which mimics human phonation. A bioreactor capable of reproducing the vocal fold mechanoenvironment ex vivo will be used to test this hypothesis for Aims 1 and 2.
Specific Aim 1 contrasts genomic expression of MSC and VFF following vibration and tensile strain (stretch) at human physiological levels using DNA microarray. Global gene expression profiles will provide biomechanical genotypes which will be utilized as criteria for determining suitability of MSC (BM and AT) compared to VFF as cell sources for vocal fold lamina propria regeneration. We expect to uncover biomechanical linkage for genes involving ECM remodeling, cell proliferation, cell-matrix and cell-cell adhesion, and immunomodulation. Prior to proceeding to a clinical trial, it is also essential to verify that MSC exposed to biomechanical forces of the vocal folds long-term will not trigger transformation to harmful mesenchymal stromal cell derivatives, such as osteoblasts, chondroctyes or myoblasts.
In Specific Aim 2, we will examine mechanically mediated MSC differentiation as a function of time. This work is highly significant and innovative because it exploits biomechanical linkage to answer the fundamental question concerning the ideal cell type(s) to source for vocal fold regeneration. Additionally, our experimental design will identify genes implicated in vibration-induced modulation of VFF, which is important because virtually nothing is known about how vibratory strain alters the cells in the larynx. These gene markers will inform innumerable areas of inquiry in vocal fold biology (such as phonotraumatic disease development and treatment) and will also launch the applicant's independent line of research.
The goal of this research is to identify optimal cell source(s) for vocal fold scarring therapeutics. To this end, we will evaluate mesenchymal stromal cells (MSC) in a context which simulates the biomechanical forces of the human larynx. Study findings will advance knowledge of cell response to phonation-like vibration and inform the design of biomechanically relevant treatment for vocal fold regeneration prior to a clinical trial.