(219b) Peg-Based Hydrogels as Vocal Fold Regeneration Matrices

Voice loss or chronic voice impairment due to scarring of the vocal fold lamina propria (LP) can be debilitating in terms of quality of life. Currently, little can be done to treat patients affected by vocal fold scarring. Due to the size of the patient population suffering from voice impairment secondary to scarring, alternate treatment methods are currently being investigated. An implant-based approach is one potential strategy for treating LP scarring. Due to the dependence of vocal fold vibration on proper fold geometry, an implant inserted to restore appropriate shape and pliability to scarred LP should ideally maintain its insertion-dimensions while being replaced by newly synthesized extracellular matrix (ECM). Several materials have previously been examined in vivo as possible replacements for the SLP, including collagen (1) and hylan B (2), a derivative of hyaluronan (HA). Although both of these materials resulted in some degree of improvement in vocal fold function post-implantation, gel resorption and/or compaction has generally limited the longer term success of these materials, in particular of collagen. In the present study, polyethylene-glycol (PEG)-based hydrogels are examined as potential vocal fold regeneration matrices. PEG has several properties desirable in a vocal fold regeneration template. Diacrylate-derivatized PEG (PEGDA) macromers readily dissolve in aqueous solution, forming an injectable mixture that is photopolymerizable through epithelial layers, a feature critical for a vocal fold regeneration scaffold, since vocal fold tissue is highly susceptible to scarring induced by surgical procedures (3). In addition, the photoactivity of PEGDA combined with its intrinsic resistance to cell and protein adhesion results in a biological ?blank slate? which can be modified in a controlled manner to contain bioactive moieties (4). PEG hydrogels are also highly elastic, which is important to the vocal folds which must sustain prolonged high frequency stresses, and their mechanical properties are tunable, meaning that their properties can be tailored to patient needs. This study demonstrates the ability of PEGDA hydrogels to stimulate ECM synthesis and accumulation by vocal fold fibroblasts (VFFs) in 3D culture while inhibiting the matrix compaction/volume loss detrimental to vocal fold restoration. Pig VFFs were encapsulated at ~0.5x106 cells/mL in the following precursor solutions, each containing 2 µmol/mL acryloyl-PEG-RGDS: (1) 10 (w/v) % 10000 Da PEGDA, (2) 20 (w/v) % 10000 Da, (3) 30 (w/v) % 10000 Da and cultured in the DMEM supplemented with 10% FBS, 100 mg/L, 100 mU/mL penicillin, and 100 mg/L streptomycin composites in a humidified incubator maintained at 5% CO2 / 37 ºC. After 4 weeks and 8 weeks of culture, the constructs were examined biochemically, biomechanically, and histologically. All matrices tested successfully resisted fibroblast-mediated matrix compaction. Moreover, we demonstrate that can tune VFF matrix production by altering the mechanical properties of the scaffold. PEG-based hydrogels appear to be promising materials for vocal fold restoration, warranting further investigation.

References 1. C. A. Rosen, Otolaryngologic Clinics Of North America 33, 1087 (Oct, 2000). 2. S. Hertegard, A. Dahlqvist, C. Laurent, A. Borzacchiello, L. Ambrosio, Otolaryngology-Head and Neck Surgery 128, 401 (Mar, 2003). 3. C. A. Rosen, Otolaryngologic Clinics Of North America 33, 1081 (Oct, 2000). 4. W. R. Gombotz, G. H. Wang, T. A. Horbett, A. S. Hoffman, Journal of Biomedical Materials Research 25, 1547 (1991).