NCVS Occupational Grant Group

Occupational Grant

CURRENT STATUS

Twenty-five NCVS dosimeters have been built and are being distributed to about 100 grade school and high school teachers in the Denver area, to be used by each teacher for two weeks at a time. Data collection has been completed on about 45 teachers so far, both male and female.

The NCVS Dosimeter automatically records how much time is spent speaking, the intensity of the speech and the speaking pitch of the user. It also interactively prompts the user to rate his or her vocal effort and quality of soft phonation every 2 hours. By combining the accumulated voice data with the individual’s self-rating data, the dosimeter can be used by speech scientists and clinicians to help determine the complex relationships among voice use, recovery time and vocal fatigue.

Initial findings suggest that the vocal folds of these teachers often accomplish more than 1 million cycles of vibration per day, and that out of a 12-hour measurement period, there is a total time of 1.5 hours of pure voicing. If one thinks of the motion of the vocal folds in terms of total distance traveled, then anyone who has to talk for a living can easily exceed a distance of 1 km per hour of pure voicing.

Other potential uses include monitoring voice use among singers and actors, and studies are being proposed for this purpose at the Denver Center for the Performing Arts.

Work done in 2005-2006

Study 1. Maximum flow declination rate (MFDR) in the glottis is known to correlate strongly with vocal intensity in voicing. This declination, or negative slope on the glottal airflow waveform, is in part attributable to the maximum area declination rate (MADR) and in part to the overall inertia of the air column of the vocal tract (lungs to lips). The purpose of this theoretical study was to show the possible contributions of air inertance and MADR to MFDR. A simplified computational model of the kinematics of vocal fold movement was utilized to compute a glottal area function. The glottal flow was computed interactively with lumped vocal tract parameters in the form of resistance and inertive reactance. It was shown that MADR depends almost entirely on the ratio of vibrational amplitudes of the lower to upper margins of the vocal fold tissue. Adduction, vertical phase difference, and prephonatory convergence of the glottis have a lesser effect on MADR. A relatively simple rule was developed that relates MFDR to a vibrational amplitude ratio and vocal tract inertance. It was concluded that speakers and singers have multiple options for control of intensity, some of which involve more source-filter interaction than others. A paper by I.R. Titze entitled “Theoretical analysis of maximum flow declination rate versus maximum area declination rate in phonation” was just published in Journal of Speech and Hearing Disorders.

Study 2. The maculae flavae of the human vocal folds include dense extracellular matrices and compacted cells with a stellate morphology. These vocal-fold stellate cells are thought to participate in the metabolism of extracellular matrices essential in maintaining vocal-fold viscoelasticity required for phonation. We have isolated and cultured these new cells and have tested the hypothesis that they maintain a distinct cellular and biochemical phenotype. We have compared proliferation rates, changes on immunophenotype, and intracellular lipid and vitamin A storage. Vocal-fold stellate cells undergo culture-induced transdifferentiation to a myofibroblast-like phenotype with an altered phenotype resembling, but not identical to, activated hepatic and pancreatic stellate cells. Our results reveal that these cells are capable of responding to exogenous all-trans retinol in culture. Exposure to this synthetic co-factor causes deactivation characterized by decreased proliferation, loss of the activated stellate cell marker, alpha-smooth muscle actin, and restoration of intracellular lipid and vitamin A metabolite storage. These data establish a new and distinct cellular target for future investigations of the viscoelastic properties of the vocal-fold mucosa during normal phonation, aging, vocal-fold scarring, laryngeal fibrosis, and myofibroblastoma. A paper by T. J. Fuja, M. N. Probst-Fuja, and I. R. Titze entitled “Transdifferentiation of vocal-fold stellate cells and all-trans retinol-induced deactivation” has been published in Cell Tissue Research.

Study 3. The regulation of extracellular matrix (ECM) constituency is critical in maintaining vocal cord biomechanical viscoelasticity required for phonation. Recently our laboratory successfully isolated and cultured a novel cell called a vocal fold stellate cell (VFSC), thought to play a central role in laryngeal ECM metabolism, aging, scarring and cancer. Our laboratory has shown that these cells undergo transdifferentiation that is partially reversed by exposure to all-trans retinol (ATROH). Here we make the first report on the expression of various ECM components, MMPs, TIMPs, pro-fibrogenic cytokines, and other ECM modulators in transdifferentiated and deactivated VFSCs. We show that VFSCs maintain an ECM expression pattern similar to laryngeal cancer and scars but distinct from tracheal fibroblasts. Exposure to ATROH differentially affects the VFSC expression of ECM components, matrix-regulating enzymes, and fibrogenic factors suggesting that the inhibitory effects of this synthetic cofactor should be studied further in laryngeal fibrosis and scarring. We also show that increased exposure to retinol induces sequential reorganization of the actin cytoskeleton in activated VFSCs. Our findings demonstrate that VFSCs are capable of regulating vocal fold ECM constituency important throughout normal laryngeal development. Furthermore, our results implicate VFSC activation in ECM misregulation which is a hallmark of several laryngeal pathologies. A paper by T.J. Fuja, M.N. Probst-Fuja, and I.R. Titze entitled “Changes in expression of extracellular matrix genes, fibrogenic factors, and actin cytoskeletal organization in retinol treated and untreated vocal fold stellate cells” has been published in Matrix Biology.

Study 4. The human vocal folds are a complex layering of cells and extracellular matrix. Vocal fold extracellular matrix uniquely contributes to the biomechanical viscoelasticity required for human phonation. We investigated the adhesion of vocal fold stellate cells, a novel cell type first cultured by our laboratory, and fibroblasts to eight vocal fold extracellular matrix components: elastin, decorin, fibronectin, hyaluronic acid, laminin and collagen types I, III and IV. Our data demonstrate that these cells adhere differentially to said substrates at 5 to 120 min. Cells were treated with hyaluronidase and Y-27632, a p160ROCK-specific inhibitor, to test the role of pericellular hyaluronan and Rho-ROCK activation in early and mature adhesion. Reduced adhesion resulted; greater inhibition of fibroblast adhesion was observed. We modulated the fibronectin affinity exhibited by both cell types using Nimesulide, an inhibitor of fibronectin integrin receptors alpha5beta1 and alphavbeta3. Our results are important in understanding vocal fold pathologies, wound healing, scarring, and in developing an accurate organotypic model of the vocal folds. A paper by T. J. Fuja, E. M. Ostrem, M. N. Probst-Fuja, and I. R. Titze entitled “Differential cell adhesion to vocal fold extracellular matrix constituents” is in press in Matrix Biology.