Poly(ethylene-glycol) Scaffold System for Temporomandibular Joint Tissue Engineering with Fibrochondrocytes

Objective: Two major indications of temporomandibular joint (TMJ) disorders are anterior displacement and deterioration of the TMJ disc. While a scaffoldless approach has been used for TMJ disc tissue engineering (TE), a scaffold material would provide control over the shape of the TMJ disc analog. In order to identify a potential system for TMJ disc TE, this study aims to study the characteristics of poly(ethylene glycol) (PEG) hydrogel scaffold system using fibrochondrocytes.

Method: Costal fibrochondrocytes isolated from three young female goats were photoencapulated in PEG at 0.5 million cells per scaffold (7 mm Diameter X 1 mm) using 3.2 J/cm² UV-A exposure. Initial cell viability was quantified at 60 minutes (Live/Dead Assay). Cell/PEG constructs were cultured for four weeks (chondrogenic medium), then assessed for matrix deposition and biomechanical behavior using the transverse isotropic biphasic theory. The matrix assays included glycosaminoglycan (GAG, 1,9-dimethylmethylene blue assay), collagen (hydroxyproline assay), and DNA content (Pico Green assay). Data are shown as mean±Standard Error.

Result: Live/Dead assay showed an average of 82.4% viability on the first day. The biomechanical test indicated that cell/PEG constructs fit the transversely isotropic biphasic model well. At four weeks, the compression tangent modulus was 46.0±8.7 kPa. The percentage stress relaxation was 37.4±2.6%. Cell/PEG constructs exhibited a permeability value of 2.15x10^-13m⁴/N s. The biochemical results indicated an average of 0.15±0.01 million cells per PEG construct. Cell/PEG constructs had an average of 440.4±52.2 μg per construct for total GAG, and 69.2±12.7 μg per construct for total collagen.

Conclusion: The data showed that PEG encapsulation promoted GAG and collagen production. PEG scaffold resulted in slightly higher GAG and collagen production and similar permeability when comparing with a previous study using poly-glycolic acid (PGA) scaffold seeded with TMJ disc cells. With appropriate modifications, cell/PEG scaffold is a promising material for TMJ disc TE.