Optimization of Protocol for Isolation of Chondrocytes from Human Articular Cartilage

Cartilage tissue engineering has evolved as one of the therapeutic strategies for cartilage defect, which relies on a large number of viable chondrocytes. Because of limited availability of cartilage and low chondrocytes yield from cartilage, the need for an improve isolation protocol for maximum yield of viable cells is a key to achieving successful clinical constructs. This study optimizes and compares different protocols for isolation of chondrocytes from cartilage.

We employed enzymatic digestion of cartilage using collagenase II and trypsin. The chondrocytes yield, growth kinetics, aggrecan, and collagen type 2 (COL2) expression were evaluated. Collagen type 1 (COL1) mRNA expression was assessed to monitor the possibility of chondrocytes dedifferentiation.

Chondrocyte yield per gram of cartilage was significantly higher (P < 0.05) using collagenase II in Hank's balanced salt solution (HBSS) compared with 0.25% trypsin. The number of chondrocyte yield per gram was higher in cartilage digested with collagenase in HBSS compared with Dulbecco's modified Eagle medium/F12; however, the difference was not statistically significant. Chondrocytes seeded at lower densities had shorter population doubling time compared to those seeded at higher density. Protein and gene expression of chondrocyte phenotype indicates the expression of aggrecan and COL2. The expression of COL1 was significantly increased (P < 0.05) in passage 3 compared with primary chondrocytes. The mRNA expression of chondrocyte phenotype was similar in primary and passaged one cells.

Collagenase in HBSS yield the highest number of viable chondrocytes and the isolated cells expressed chondrocyte phenotype. This protocol can be employed to generate large number of viable chondrocytes, particularly with limited cartilage biopsies.