Tissue Engineering of Articular Cartilage: Perichondrial Cells in Osteochondral Repair

Efforts to expand treatment options for articular cartilage repair have increasingly focused on the implantation of cell polymer constructs. Primary cells cultured from perichondrium, a chondrogenic tissue, were found to survive in vitro within a biodegradable porous polylactic acid matrix. These perichondrocyte-polylactic acid composite grafts were then implanted within osteochondral defects drilled into 3.7 x 5 mm of the left medial femoral condyles of 82 adult New Zealand white rabbits. The repair tissue was evaluated grossly, histologically, histomorphologically, biochemically, and biomechanical-ly at 6 weeks, 12 weeks, 6 months, and 1 year after implantation. On gross evaluation, cartilaginous material appeared to fill the defect in 70 experimental knees, for an overall repair frequency of 85%. None of the specimens were completely normal at 1 year. Only specimens with subchondral bone formation displayed a definable hyaline cartilage appearing surface with chondrocytes surrounded by dense matrix. Subchondral bone reformation was inconsistent, reaching 50% at 1 year. Biochemically, the repair tissue matured during a 1-year period into a hyaline Type II collagen dominant tissue, whereas glycosaminoglycan content remained low at all periods. The measured compressive properties of the repair tissue at 1 year were not significantly different from those of the contralateral knee that was not surgically treated. The treatment of osteochondral defects in the rabbit knee with allogenic perichondrium cell polylactic acid composite grafts yielded a high percentage of grossly successful repairs that showed inconsistent subchondral bone reformation.