Tissue-engineered cartilage by in vivo culturing of chondrocytes in PLGA–collagen hybrid sponge

Bovine chondrocytes were isolated from the shoulder articular joints of a calf, seeded in biodegradable porous polymer scaffolds, and implanted subcutaneously in the dorsum of athymic nude mice to tissue engineer articular cartilage in vivo. Hybrid sponge of poly(dl-lactic-co-glycolic acid) (PLGA) and collagen was used as the porous scaffold with PLGA sponge and collagen sponge used as the controls. Chondrocytes were seeded in low (1×107 cells/ml) and high (5×107 cells/ml) densities. Before implantation, the scaffold-cell constructs were cultured in vitro for 1 week. The implants were harvested after in vivo incubation of 2, 4, 6, and 8 weeks. The PLGA–collagen hybrid sponge implants maintained their original shapes, as did the PLGA sponge, whereas the collagen sponge collapsed. The mechanically strong PLGA sponge functioned as a skeleton and prevented the embedded collagen sponge from collapsing. The implants were examined histochemically by haematoxylin and eosin staining, by safranin O/fast green staining, and immunohistochemically by anti-collagen type II antibody. The percent of cartilaginous extracellular matrices increased, while neovascularization decreased with an increased implantation period. A greater amount of homogeneous cartilaginous tissue formed when chondrocytes were seeded at a higher density. The morphology of chondrocytes, the expression of cartilaginous matrices in the PLGA–collagen hybrid sponge, was similar to those in collagen sponge. The cartilaginous matrices were more homogeneously distributed in the PLGA–collagen hybrid sponge and collagen sponge than in the PLGA sponge. Hybridization of the PLGA sponge and collagen sponge facilitated cell seeding and promoted the in vivo formation of cartilaginous tissue.