Chondrocytes from different zones exhibit characteristic differences in high density culture

Superficial and middle/deep zone chondrocytes were isolated from goat femoral cartilage by a zonal abrasion method. The cells were expanded 100-fold through two passages, then seeded into agarose wells to form high-density constructs through a self-assembling process. After 4 weeks in culture, the superficial zone constructs contracted into a dense cell mass, while middle/deep zone chondrocytes formed constructs with four distinct regions. Middle/deep zone chondrocytes produced 250% more glycosaminoglycans per dry weight and more collagen per dry weight than superficial zone chondrocytes. The superficial and middle/deep zone chondrocytes were found to retain characteristic differences even after 100-fold expansion, as evidenced by construct morphology and extracellular matrix content. This study uniquely demonstrated the ability of expanded superficial and middle/deep zone chondrocytes to form constructs of distinct characteristics without a scaffold. The goal of tissue engineering different zones of cartilage is to eventually replicate the specific function of each zone.