Effect of initial cell seeding density on 3D-engineered silk fibroin scaffolds for articular cartilage tissue engineering.

The repair of articular cartilage defects poses a continuing challenge. Cartilage tissue engineering through the culture of chondrocytes seeded in 3D porous scaffolds has the potential for generating constructs that repair successfully. It also provides a platform to study scaffold-cell and cell-cell interactions. The scaffold affects the growth and morphology of cells growing on it, and concomitantly, cells affect the properties of the resultant tissue construct. Silk fibroin protein from Antheraea mylitta, a non-mulberry Indian tropical tasar silkworm, is a potential biomaterial for diverse applications due to its widespread versatility as a mechanically robust, biocompatible, tissue engineering material. Analysis of silk fibroin scaffolds seeded with varying initial densities (25, 50 and 100 million cells/ml) and cultured for 2 weeks showed that thickness and wet weight increased by 60-70% for the highest cell density, and DNA, GAG and collagen content of the cartilaginous constructs increased with increasing cell density. Mechanical characterization of the constructs elucidated that the highest density constructs had compressive stiffness and modulus 4-5 times that of cell-free scaffolds. The present results indicate the importance of cell seeding density in the rapid formation of a functional cartilaginous tissue.