Injecting partially digested cartilage fragments into a biphasic scaffold to generate osteochondral composites in a nude mice model.

This study proposed a novel scaffold with heterogeneous morphology that mimics the natural tissue. Its upper part contains a hollow cavity surrounded by a wall of poly(L-lactic-co-glycolic acid) (PLGA) porous membrane for injecting cartilage tissue and cells. An interconnecting porous structure located under the hollow cavity was made of composite materials that combined PLGA and beta-tricalcium phosphate (beta-TCP) to simulate the subchondral bone. Adult pig articular cartilage was cut and sieved into small fragments. The tissue fragments was partially digested by 0.1% collagenase for 0, 2, 4, and 6 h and injected into the hollow cavity of the biphasic scaffold. The biphasic scaffolds were then implanted into the subcutaneous pocket of nude mice for 4 weeks. No tissue bonding or new cartilaginous tissue formation was identified in the cartilage fragment without enzymatic treatment. The cartilage fragments digested with 2 h of collagenase digestion were partially integrated after implantation. The integrative properties of the cartilage fragment depended on the extent of enzymatic digestion. Releasing cells at the tissue surface enhanced confluence and bonding of the cartilage fragment matrix. Complete integration of the cartilage fragments and cartilage remodeling were achieved by digestion of the tissue fragments with 4 h of enzymatic treatment. The neocartilage grew from the upper hollow cavity into the lower PLGA/beta-TCP porous structure, forming an interface similar to that formed between cartilage and subchondral bone. This study combined the osteochondral scaffold and limited cartilage tissues to generate cartilage tissue in vivo intending for repairing full-thickness articular cartilage defects.