Three-dimensional seeding of chondrocytes encapsulated in collagen gel into PLLA scaffolds.

Tissue engineering approaches have been clinically tried to repair damaged articular cartilages. It is an essential step to uniformly seed chondrocytes into 3D scaffolds in order to reconstruct tissue-engineered cartilages in vitro, but the tissue engineering could not have been provided with efficient cell seeding methods. Type I collagen is clinically used and known as a cytocompatible material, having recognition sites for integrins. Collagen gel encapsulating chondrocytes has been tried for making regenerated cartilages, but it is found difficult to have the gel keep its original shape after long-term culture, because of shrinking. On the other hand, 3D scaffolds, either of a nonwoven structure or a sponge-like structure, involve difficulty in that chondrocytes could not be uniformly seeded, although they have adequate initial mechanical properties. In this study, by combining collagen gelation with a nonwoven PLLA scaffold, we achieved uniform cell seeding into the 3D scaffold. Bovine articular chondrocytes were mixed with type I collagen solution, and the solution was poured into the nonwoven PLLA scaffold (1.5 mm thick, diameter 15 mm). The collagen-chondrocyte mixture was made into gel at 37 degrees C for 1 h. The 0.39% collagen mixture was viscous enough to prevent cells from precipitating during gelation. Almost all chondrocytes were able to be incorporated into the PLLA scaffolds by mixing with collagen solution and subsequently making into gel, while 30-40% of the chondrocytes seeded as a cell suspension were not trapped into the PLLA scaffolds. The method presented, where chondrocytes were mixed with collagen solution, and the mixture was incorporated into a 3D scaffold, then made into gel in the scaffold, could serve as an alternative for in vitro cartilage regeneration, also simultaneously having the advantages of both materials.