Microfracture surgery may be improved by the implantation of unidirectional
collagen scaffolds that provide a template for mesenchymal stem cells to regenerate cartilage. Incorporation of
growth factors in unidirectional scaffolds may further enhance cartilage regeneration. In scaffolds, immobilization of
growth factors is required to prolong in vivo activity, to limit diffusion and to reduce the amount of
growth factor needed for safe clinical application. We investigated the immobilization of
bone morphogenetic protein 2 (BMP2) to unidirectional
collagen scaffolds and the effect on in vitro chondrogenesis. C3H10T1/2 cells were seeded on unidirectional
collagen scaffolds with and without covalently attached
heparin, and with and without incubation with BMP2 (1 and 10 μg), or with BMP2 present in the culture medium (10-200 ng ml-1). Culturing was for 2 weeks and readout parameters included histology, immunohistochemistry, biochemical analysis and molecular
biological analysis. The unidirectional pores facilitated the distribution of C3H10T1/2 cells and matrix formation throughout scaffolds. The effective dose of medium supplementation with BMP2 was 100 ng ml-1 (total exposure 1 μg BMP2), and similar production of cartilage-specific molecules
chondroitin sulfate (CS) and
type II collagen was found for scaffolds pre-incubated with 10 μg BMP2. Pre-incubation with 1 μg BMP2 resulted in less cartilage matrix formation. The conjugation of
heparin to the scaffolds resulted in more CS and less
type II collagen deposition compared to scaffolds without
heparin. In conclusion, unidirectional
collagen scaffolds pre-incubated with 10 μg BMP2 supported chondrogenesis in vitro and may be suitable for prolonged cartilage matrix synthesis in vivo.