Multiphase/Anisotropic Scaffolds With Spatiotemporal Delivery for TMJ Disc Regeneration

Objectives: Over 10 million Americans experience signs or symptoms of temporomandibular joint disorders (TMJDs), with an annual cost for treatment estimated at ~$4B per NIDCR. The TMJ disc, an inhomogeneous/anisotropic fibrocartilaginous tissue, is highly associated with onset and progression of TMJDs, leading to the emerging need for TMJ disc regeneration. This study was designed to develop a biomaterials-based 3D-scaffold with spatiotemporal delivery of multiple growth factors to regenerate a multiphase TMJ disc from human mesenchymal stem/progenitor cells (MSCs).
Methods: Anatomically shaped human TMJ disc scaffolds were fabricated with poly-ε-caprolactone using 3D Bioplotter® (EnvisionTec; Germany) and consisted of interlaid microstrands and interconnecting microchannels. Microstrands were aligned in the circumferential and anterioposterior directions in the outer ring and intermediate zone, respectively, mimicking collagen alignment in the native TMJ disc. To induce multiphase fibrocartilaginous matrix formation, poly(lactic-co-glycolic acids) (PLGA) microspheres (µS)-encapsulating connective tissue growth factor (CTGF) and transforming growth factor β3 (TGFβ3) were incorporated in overall regions of disc and intermediate zone, respectively, per our prior methods. Human bone marrow MSCs were then delivered into microchannels of the scaffolds via infusion with collagen type I gel (2 mg/mL). After 6 weeks in vitro culture, samples were harvested and tissue formation was assessed using immunofluorescence and histochemical analyses.
Results: After 6 weeks, immunofluorescence analysis using Maestro™ imaging system revealed collagen I (COL-I) matrix throughout the scaffolds and aggrecan (AGC)⁺ cartilaginous matrix in the intermediate zone when compared against scaffolds with empty μS. Histologically, anterior and posterior bands showed dense collagen structure and anteroposterior alignment in the intermediate zone, as demonstrated by Picrosirious red (PR) staining. Alcian blue (AB)-positive cartilaginous matrix was only observed in intermediate zone and was not present in the outer band regions. Scaffolds with empty μS resulted in suboptimal matrix deposition.
Conclusions: These findings demonstrate potential for regeneration of the TMJ disc using bioscaffolds and stem cells.