Cartilage Regeneration in the Head and Neck Area: Combination of Ear or Nasal Chondrocytes and Mesenchymal Stem Cells Improves Cartilage Production

Background: Cartilage tissue engineering can offer promising solutions for restoring cartilage defects in the head and neck area and has the potential to overcome limitations of current treatments. However, to generate a construct of reasonable size, large numbers of chondrocytes are required, which limits its current applicability. Therefore, the authors evaluate the suitability of a combination of cells for cartilage regeneration: bone marrow–derived mesenchymal stem cells and ear or nasal chondrocytes. Methods: Human bone marrow–derived mesenchymal stem cells were encapsulated in alginate hydrogel as single-cell–type populations or in combination with bovine ear chondrocytes or nasal chondrocytes at an 80:20 ratio. Constructs were either cultured in vitro or implanted directly subcutaneously into mice. Cartilage formation was evaluated with biochemical and biomechanical analyses. The use of a xenogeneic coculture system enabled the analyses of the contribution of the individual cell types using species-specific gene-expression analyses. Results: In vivo, human bone marrow–derived mesenchymal stem cells/bovine ear chondrocytes or human bone marrow–derived mesenchymal stem cells/bovine nasal chondrocytes contained amounts of cartilage components similar to those of constructs containing chondrocytes only (i.e., bovine ear and nasal chondrocytes). In vitro, species-specific gene-expression analyses demonstrated that aggrecan was expressed by the chondrocytes only, which suggests a more trophic role for human bone marrow–derived mesenchymal stem cells. Furthermore, the additional effect of human bone marrow–derived mesenchymal stem cells was more pronounced in combination with bovine nasal chondrocytes. Conclusions: By supplementing low numbers of bovine ear or nasal chondrocytes with human bone marrow–derived mesenchymal stem cells, the authors were able to engineer cartilage constructs with properties similar to those of constructs containing chondrocytes only. This makes the procedure more feasible for future applicability in the reconstruction of cartilage defects in the head and neck area because fewer chondrocytes are required