The influence of donor and hypoxic conditions on the assembly of cartilage matrix by osteoarthritic human articular chondrocytes on Hyalograft matrices

Resurfacing of cartilage defects using cell-seeded, biomaterial grafts is a promising approach for articular cartilage repair and in this study we investigated the ability of human chondrocytes from osteoarthritic joints to generate cartilage tissue under standard conditions in cultured over 21 days on Hyalograft matrices under normoxic (20% O2) and hypoxic (5% O2) conditions. The results showed that constructs were more chondrogenic when cultured under hypoxic conditions, which resulted in greater production of sulphated glycosaminoglycan and collagen type II within the constructs and the cells expressed higher levels of genes encoding cartilage matrix proteins and chondrocyte transcription factors. However, there were very wide differences in the chondrogenic potential amongst donors as the weight ratio of total sulphated glycosaminoglycan to DNA in constructs varied from above 200 to below 10. These results establish that the generation of cartilage from human OA chondrocytes on biodegradable supports is favoured in lowered oxygen, but that under standard conditions, even at low passage, there is a large variation in the chondrogenic potential amongst chondrocytes from different donors. Further analysis of this variation suggested that the gene expression ratio of COL2A1/COL1A1 mRNA in the chondrocytes in monolayer culture may predict their subsequent performance in forming cartilage matrix on the Hyalograft scaffold.