Evaluation of PLLA–collagen hybrid sponge as a scaffold for cartilage tissue engineering

Bovine chondrocytes were isolated from the shoulder and knee articular joints of a calf, seeded in biodegradable porous polymer scaffolds, and implanted subcutaneously in the dorsa of athymic nude mice to tissue engineer articular cartilage in vivo. Hybrid sponge of poly l-lactic acid (PLLA) and collagen was used as the porous scaffold with PLLA sponge as the control. Chondrocytes were seeded in the sponges at a density of 5×107 cells/ml. PLLA–collagen hybrid sponge was easily seeded, but PLLA sponge required prewetting of the sponge before cell seeding. The scaffold-cell constructs were cultured in vitro for 1 week and implanted subcutaneously in the dorsa of athymic nude mice. The implants were harvested after in vivo incubation for 2, 4 and 8 weeks. The PLLA–collagen hybrid sponge implants maintained their original shapes, as did the PLLA sponge. The implants were examined histochemically by Hematoxylin/eosin and Safranin O/fast green staining, and immunohistochemically by anti-bovine type II collagen antibody. The presence of cartilaginous extracellular matrices indicated by positive staining of Safranin O and anti-bovine type II collagen antibody increased, while neovascularization decreased with an increased implantation period. Cartilaginous tissue was more widely formed and more homogeneously distributed in the PLLA–collagen hybrid sponge than in the PLLA sponge throughout implantation period. Hybridization of PLLA sponge and collagen sponge facilitated cell seeding, prevented the scaffold from collapsing and promoted the formation of cartilaginous tissue in vivo.