Increased chondrocyte seeding density has no positive effect on cartilage repair in an MPEG-PLGA scaffold

Purpose

This study investigates the effect of cell seeding density on cartilage repair in matrix-assisted chondrocyte implantation in vitro and in vivo.

Methods

In vitro: Four different cell seeding densities of human chondrocytes were seeded onto a porous methoxy-polyethylene glycol-polylactic-co-glycolic acid scaffold (MPEG-PLGA) polymer scaffold ASEED? (1.2 × 10⁶, 4.0 × 10⁶, 1.2 × 10⁷ and 2.0 × 10⁷ cells/cm³). The cartilage repair response was evaluated by relative gene expression of the chondrogenic markers sox9, collagen types I, II and X, and aggrecan, total DNA content and sulphated glycosaminoglycan synthesis. In vivo: Using a New Zealand white rabbit intercondylar osteochondral defect model, three different cell seeding densities (1.2 × 10⁶, 4.0 × 10⁶ and 1.2 × 10⁷ cells/cm³) were tested with an empty scaffold as control. The cartilage repair response was evaluated using O’Driscoll score.

Results

In vitro: A significant difference (p < 0.05) in total DNA content was found at day 2 but not at day 7. The low cell seeding densities yielded the highest GAG content (p < 0.001) at day 7. Collagen type I was highest (p < 0.01) at the lowest density at day 7. In vivo: No significant difference was found between the 4 groups.

Conclusions

No positive effect on cartilage repair was found using increased cell seeding density.

Level of evidence

Controlled experimental study, Level II.