Table 1.

Summary of the Vocal Fold Mechanobiological in vitro Studies (in chronological orders).

Study	Mechanobiological Device	Cell Type	Stimulation Condition	Major Gene/ Protein Measures	Results
Titze et al. (2004)	Mechanically driven bioreactor. Cells were seeded on Tecoflex porous substrates.	Human VFF	20% static or cyclic axial strain (at 100 Hz) for 6 hours	mRNA expressions of elastin, procollagen I, fibronectin, fibromodulin, decorin, hyaluronic acid synthase 2 (HAS2), receptor for hyaluronan-mediated motility (RHAMM), CD44, matrix metalloprotease-1 (MMP-1), and hyaluronidase.	Compared to no-tension controls, elastin, procollagen I and fibronectin levels were significantly increased under the static axial strain condition. Cyclic axial strains further increased fibronectin and MMP-1 levels but significantly decreased procollagen I level. No significant changes were found in proteoglycan and HA-associated gene levels under the static axial strain condition. Cyclic axial strain produced significant increases in HAS2, CD 44, fibromodulin, and decorin levels.
Webb et al. (2006)	Mechanically driven bioreactor. Cells were seeded on Tecoflex porous substrates.	Human tracheal fibroblasts	10% static or cyclic axial strain (at 0.25 Hz) for up to 8 hrs per day over 7 days	DNA content; mRNA expressions of procollagen I, fibronectin, MMP-1, transforming growth factor-beta 1 (TGF-β1) and connective tissue growth factor (CTGF)	Compared to static strain controls, cyclic strain significantly increased fibroblast DNA content after 7 days as well as levels of procollagen I, TGF-β1, and CTGF after 6 hrs of stimulation.
Branski et al. (2007)	Collagen type- I coated Bioflex II plates	Rabbit VFF with or without IL-1β treatment	3–18% static or cyclic equibiaxial tensile strain (at 0.005–0.5 Hz) for up to 36 hrs	mRNA expressions of interleukin- 1beta (IL-1β), Inducible nitric oxide synthase (iNOS), cyclo-oxygenase-2 (COX-2), prostaglandin E (PGE-2), MMP-1 procollagen I	Compared to the CTS (6% and 0.5 Hz) alone condition, COX-2, MMP-1 and PGE2 expressions decreased up to 24 hrs and NO up to 36 hrs in the IL-1β-treated and CTS- stimulated cultures. Compared to IL-1β plus static conditions, procollagen I expression was significantly increased in the CTS only and CTS plus IL-1β conditions at 24 hrs and 48 hrs.
Wolchok et al. (2009)	Mechanically driven bioreactor. Cells were seeded on Tecoflex porous substrates.	Human laryngeal fibroblasts	100 Hz vibration with 15 min over a 6-hr period followed by 18- hr rest for up 21 days.	DNA microarray and protein expression of TGF-β1 and monocyte chemotactic protein-1 (MCP-1).	After 3 days of vibration, the gene expression ratios (vibrated: static control) ranged from 1.5 to 4.2 in collagen I and IX, syndecan, laminin, tissue inhibitor of metalloproteinase (TIMP) 1 and 3, CTGF and platelet-derived growth factor (PDGF). Compared to static controls, TGF-β1 and MCP-1 protein levels were significantly increased and decreased, respectively, after 24 hrs of vibration.
Kutty et al. (2010)	Mechanically driven bioreactor. Cells were encapsulated in hyaluronic acid hydrogels crosslinked with Tecoflex films.	Human dermal fibroblasts	100 Hz in a 2s on- 2s off regimen for 4 hrs per day for up to 10 days	mRNA expressions of collagen I, elastin, HAS2, decorin, fibromodulin and MMP-1. Protein expression of sulphated glycosaminoglycan (GAG) and hydroxyproline.	Compared to static controls, gene expressions of HAS2, decorin and MMP-1 were significantly increased whereas collagen and elastin were significantly decreased in the vibration group at Day 5. Compared to static controls, protein expressions of GAG and hydroxyproline were significantly increased and decreased respectively at both Day 5 and Day 10 in the vibration group.
Farran et al. (2011)	Aerodynamically driven bioreactor. Cells were seeded on silicone membranes.	Human neonatal foreskin fibroblasts	60, 110 or 300 Hz with varying vibration amplitude (1, 5, 10 and 30µm) for 1 hr followed by a 6-hr rest	mRNA expressions of collagen type I, fibronectin, MMP-1, TIMP-1, HAS3, hyaluronidase 1 (HYAL1) and CD44	At 60 Hz, collagen I level was significantly higher at 1µm than 10µm. HYAL1 level was significantly lower at 1µm than 5µm. At 110 Hz/ 30µm, levels of collagen I, MMP-1 was lower than the static controls. CD44 level was significantly lower at 1µm than 30µm.
Gaston et al. (2012)	Mechanically driven bioreactor. Cells were seeded on Tecoflex porous substrates	Human VFF and BM-MSC	200 Hz vibration at 20% strain for 8 hrs	mRNA expressions of collagen type I, fibronectin, TGF-β1 and α-smooth muscle actin (SMA)	Expressions of all genes were not significantly different between vibrated and non-vibrated controls in either cell types.

VFF = vocal fold fibroblasts; BM-MSC = bone marrow mesenchymal stem cells.