In Vitro Cartilage Tissue Engineering Using Adipose-Derived Extracellular Matrix Scaffolds Seeded with Adipose-Derived Stem Cells

Extracellular matrix (ECM) secreted from the resident cell of tissue is an ideal biomaterial evolved by nature. Cartilage is also built from well-organized ECM components in a gel-like structure with a high collagen and proteoglycan content. Here, we explored cartilage tissue engineering using ECM scaffolds seeded with stem cells. Both scaffolds and stem cells were isolated from human adipose tissue, which is abundant and easily harvested in the human body. The human ECM scaffolds contained various endogenous bioactive factors, including transforming growth factor-beta1 (TGF-beta 1, 8782 +/- 4989 pg/g, dry ECM), insulin growth factor-1 (13319 +/- 1388 pg/g, dry ECM), basic fibroblast growth factor (82373 +/- 9572 pg/g, dry ECM), and vascular endothelial growth factor (25647 +/- 2749 pg/g, dry ECM). A composite of ECM and stem cells was prepared and cultured in chondrogenic medium (with 10 ng/mL TGF-beta 1 or not) for 45 days. The volumes and weights of the composites increased during culture and the surface gradually became smooth. Cell viability remained high throughout the 45 days of in vitro culture. Composites showed the formation of cartilage-like tissue with the synthesis of cartilage-specific proteins such as collagen and glycosaminoglycan. Important chondrogenic markers were expressed including Sox-9, aggrecan, and collagen type II and XI. These results demonstrate that a cell/ECM composite containing endogenous bioactive factors could provide biochemical cues for the promotion of cartilage formation.