Nicole Y. K. Li

A Patient-Specific in silico Model of Inflammation and Healing Tested in Acute Vocal Fold Injury

The development of personalized medicine is a primary objective of the medical community and increasingly also of funding and registration agencies. Modeling is generally perceived as a key enabling tool to target this goal. Agent-Based Models (ABMs) have previously been used to simulate inflammation at various scales up to the whole-organism level. We extended this approach to the case of a novel, patient-specific ABM that we generated for vocal fold inflammation, with the ultimate goal of identifying individually optimized treatments. ABM simulations reproduced trajectories of inflammatory mediators in laryngeal secretions of individuals subjected to experimental phonotrauma up to 4 hrs post-injury, and predicted the levels of inflammatory mediators 24 hrs post-injury. Subject-specific simulations also predicted different outcomes from behavioral treatment regimens to which subjects had not been exposed. We propose that this translational application of computational modeling could be used to design patient-specific therapies for the larynx, and will serve as a paradigm for future extension to other clinical domains.

Biosimulation of inflammation and healing in surgically injured vocal folds.

Objectives The pathogenesis of vocal fold scarring is complex and remains to be deciphered. The current study is part of research endeavors aimed at applying systems biology approaches to address the complex biological processes involved in the pathogenesis of vocal fold scarring and other lesions affecting the larynx. Methods We developed a computational agent-based model (ABM) to quantitatively characterize multiple cellular and molecular interactions involved in inflammation and healing in vocal fold mucosa after surgical trauma. The ABM was calibrated with empirical data on inflammatory mediators (eg, tumor necrosis factor) and extracellular matrix components (eg, hyaluronan) from published studies on surgical vocal fold injury in the rat population. Results The simulation results reproduced and predicted trajectories seen in the empirical data from the animals. Moreover, the ABM studies suggested that hyaluronan fragments might be the clinical surrogate of tissue damage, a key variable that in these simulations both is enhanced by and further induces inflammation. Conclusions A relatively simple ABM such as the one reported in this study can provide new understanding of laryngeal wound healing and generate working hypotheses for further wet-lab studies.

Preliminary Data on Prevention and Treatment of Voice Problems in Student Teachers

OBJECTIVES/HYPOTHESES To assess the utility of a targeted voice hygiene (VH) program compared to VH plus voice training intervention (VH+VT) for the prevention and treatment of voice problems in student teachers. STUDY DESIGN Prospective, randomized. METHODS Thirty-one student teachers with low (good) and high (poor) voice handicap index (VHI) scores in Pittsburgh and Hong Kong were randomly assigned to (1) a targeted, individually tailored VH program, (2) the VH program plus resonant VT (VH+VT), or (c) a control group. Participants assigned to intervention groups were monitored for their adherence to their programs for their first 4 weeks of student teaching. VHI data were collected again 4 weeks postintervention (both sites) and 8 weeks postintervention, following a no-contact washout period (Pittsburgh). RESULTS Descriptive data analysis indicated that across both sites, for initially healthy participants, the VH program was sufficient to prevent worsening of VHI scores that occurred in all control participants over the first 4-8 weeks of student teaching. The addition of VT did not consistently enhance protective benefits over VH alone. In contrast, for participants with initially poor VHI scores, the VH program failed to produce VHI benefits over the control condition. The addition of VT was required to optimize results for that cohort. CONCLUSIONS Preliminary data suggest that a minimalist, individually tailored VH program may be sufficient to prevent voice problems from teaching in healthy student teachers. However, for student teachers with existing voice problems, VT may be required to optimize results of intervention.

Translational systems biology and voice pathophysiology.

Personalized medicine has been called upon to tailor healthcare to an individuals needs. Evidence‐based medicine (EBM) has advocated using randomized clinical trials with large populations to evaluate treatment effects. However, due to large variations across patients, the results are likely not to apply to an individual patient. We suggest that a complementary, systems biology approach using computational modeling may help tackle biological complexity in order to improve ultimate patient care. The purpose of the article is: 1) to review the pros and cons of EBM, and 2) to discuss the alternative systems biology method and present its utility in clinical voice research.

Biosimulation of acute phonotrauma: An extended model†

Personalized, preemptive, and predictive medicine is a central goal of contemporary medical care. The central aim of the present study was to investigate the utility of mechanistic computational modeling of inflammation and healing to address personalized therapy for patients with acute phonotrauma.

Microstructural and mechanical characterization of scarred vocal folds

The goal of this study was to characterize the vocal folds microstructure and elasticity using nonlinear laser scanning microscopy and atomic force microscopy-based indentation, respectively. As a pilot study, the vocal folds of fourteen rats were unilaterally injured by full removal of lamina propria; the uninjured folds of the same animals served as controls. The area fraction of collagen fibrils was found to be greater in scarred tissues two months after injury than the uninjured controls. A novel mathematical model was also proposed to relate collagen concentration and tissue bulk modulus. This work presents a first step towards systematic investigation of microstructural and mechanical characteristics in scarred vocal fold tissue.

Role of steroids in acute phonotrauma: A basic science investigation.

Steroids are used for the treatment of laryngitis in vocal performers and other individuals despite the absence of evidence demonstrating their impact on vocal fold inflammation. Our objective was to examine laryngeal secretion cytokine inflammatory profile changes associated with corticosteroid treatment in a human phonotrauma model.

An In Vivo Study of Composite Microgels Based on Hyaluronic Acid and Gelatin for the Reconstruction of Surgically Injured Rat Vocal Folds

PURPOSE The objective of this study was to investigate local injection with a hierarchically microstructured hyaluronic acid-gelatin (HA-Ge) hydrogel for the treatment of acute vocal fold injury using a rat model. METHOD Vocal fold stripping was performed unilaterally in 108 Sprague-Dawley rats. A volume of 25 μl saline (placebo controls), HA-bulk, or HA-Ge hydrogel was injected into the lamina propria (LP) 5 days after surgery. The vocal folds were harvested at 3, 14, and 28 days after injection and analyzed using hematoxylin and eosin staining and immunohistochemistry staining for macrophages, myofibroblasts, elastin, collagen type I, and collagen type III. RESULTS The macrophage count was statistically significantly lower in the HA-Ge group than in the saline group (p < .05) at Day 28. Results suggested that the HA-Ge injection did not induce inflammatory or rejection response. Myofibroblast counts and elastin were statistically insignificant across treatment groups at all time points. Increased elastin deposition was qualitatively observed in both HA groups from Day 3 to Day 28, and not in the saline group. Significantly more elastin was observed in the HA-bulk group than in the uninjured group at Day 28. Significantly more collagen type I was observed in the HA-bulk and HA-Ge groups than in the saline group (p < .05) at Day 28. The collagen type I concentration in the HA-Ge and saline groups was found to be comparable to that in the uninjured controls at Day 28. The concentration of collagen type III in all treatment groups was similar to that in uninjured controls at Day 28. CONCLUSION Local HA-Ge and HA-bulk injections for acute injured vocal folds were biocompatible and did not induce adverse response.

Current Understanding and Future Directions for Vocal Fold Mechanobiology.

The vocal folds, which are located in the larynx, are the main organ of voice production for human communication. The vocal folds are under continuous biomechanical stress similar to other mechanically active organs, such as the heart, lungs, tendons and muscles. During speech and singing, the vocal folds oscillate at frequencies ranging from 20 Hz to 3 kHz with amplitudes of a few millimeters. The biomechanical stress associated with accumulated phonation is believed to alter vocal fold cell activity and tissue structure in many ways. Excessive phonatory stress can damage tissue structure and induce a cell-mediated inflammatory response, resulting in a pathological vocal fold lesion. On the other hand, phonatory stress is one major factor in the maturation of the vocal folds into a specialized tri-layer structure. One specific form of vocal fold oscillation, which involves low impact and large amplitude excursion, is prescribed therapeutically for patients with mild vocal fold injuries. Although biomechanical forces affect vocal fold physiology and pathology, there is little understanding of how mechanical forces regulate these processes at the cellular and molecular level. Research into vocal fold mechanobiology has burgeoned over the past several years. Vocal fold bioreactors are being developed in several laboratories to provide a biomimic environment that allows the systematic manipulation of physical and biological factors on the cells of interest in vitro. Computer models have been used to simulate the integrated response of cells and proteins as a function of phonation stress. The purpose of this paper is to review current research on the mechanobiology of the vocal folds as it relates to growth, pathogenesis and treatment as well as to propose specific research directions that will advance our understanding of this subject.

Dose-dependent effect of mitomycin C on human vocal fold fibroblasts

The purpose of this study was to evaluate in vitro cytotoxicity and antifibrotic effects of mitomycin C on normal and scarred human vocal fold fibroblasts.