Regenerative Potential of Mandibular Condyle Cartilage and Bone Cells Compared to Costal Cartilage Cells When Seeded in Novel Gelatin Based Hydrogels

The field of temporomandibular joint (TMJ) condyle regeneration is hampered by a limited understanding of the phenotype and regeneration potential of cells in mandibular condyle cartilage. It has been shown that chondrocytes derived from hyaline and costal cartilage exhibit a greater chondro-regenerative potential in vitro than those from mandibular condylar cartilage. However, our recent in vivo studies suggest that mandibular condyle cartilage cells do have the potential for cartilage regeneration in osteochondral defects, but that bone regeneration is inadequate. The objective of this study was to determine the regeneration potential of cartilage and bone cells from goat mandibular condyles in two different photocrosslinkable hydrogel systems, PGH and methacrylated gelatin, compared to the well-studied costal chondrocytes. PGH is composed of methacrylated poly(ethylene glycol), gelatin, and heparin. Histology, biochemistry and unconfined compression testing was performed after 4 weeks of culture. For bone derived cells, histology showed that PGH inhibited mineralization, while gelatin supported it. For chondrocytes, costal chondrocytes had robust glycosaminoglycan (GAG) deposition in both PGH and gelatin, and compression properties on par with native condylar cartilage in gelatin. However, they showed signs of hypertrophy in gelatin but not PGH. Conversely, mandibular condyle cartilage chondrocytes only had high GAG deposition in gelatin but not in PGH. These appeared to remain dormant in PGH. These results show that mandibular condyle cartilage cells do have innate regeneration potential but that they are more sensitive to hydrogel material than costal cartilage cells.