Cell-Cell Interaction of Chondrocytes in Porous Alginate Hydrogels With Different Spatial Cell Distributions and Its...

Cell-cell interactions play a critical role in regulating chondrocyte functions and cell fate. However, how the transition from single-cell dispersion to multicellular aggregation affects chondrocyte functions has not yet been systematically investigated. In this study, we developed a simple and cell-friendly method to modulate the spatial distribution of chondrocytes within porous alginate hydrogels to control cell-cell interactions. Cell-loaded or cell-free micropores were successfully generated within cell-embedded or cell-free alginate hydrogels by injecting calcium chloride solution droplets into the alginate solution. The cell-cell interaction was controlled to different degrees by encapsulating bovine articular chondrocytes in the hydrogel matrix or micropores. Chondrocytes in the hydrogel matrix were distributed individually, whereas chondrocytes in the micropores formed spheroids. Individual and spheroid cell-cell interactions showed different effects on chondrocyte proliferation, expression of cartilaginous genes, and secretion of cartilaginous extracellular matrices. Spheroids in the micropores more effectively promoted these cell functions than the individual chondrocytes in the hydrogel matrix. Direct comparison within the same hydrogel system demonstrated that spheroid-mediated cell-cell interactions were more effective than individual cell-cell interactions in maintaining chondrocyte functions. These results provide useful insights into cartilage tissue engineering.