Effects of Co-cultures of Meniscus Cells and Articular Chondrocytes on PLLA Scaffolds

The knee meniscus, a fibrocartilaginous tissue located in the knee joint, is characterized by heterogeneity in extracellular matrix and biomechanical properties. To recreate these properties using a tissue engineering approach, co-cultures of meniscus cells (MCs) and articular chondrocytes (ACs) were seeded in varying ratios (100:0, 75:25, 50:50, 25:75, and 0:100) on poly-L-lactic acid (PLLA) scaffolds and cultured in serum-free medium for 4 weeks. Histological, biochemical, and biomechanical tests were used to assess constructs at the end time point. Strong staining for collagen and glycosaminoglycan (GAG) was observed in all groups. Constructs with 100% MCs were positive for collagen I and constructs cultured with 100% ACs were positive for collagen II, while a mixture of collagen I and II was observed in other co-culture groups. Total collagen and GAG per construct increased as the percentage of ACs increased (27 +/- 8 microg, 0% AC to 45 +/- 8 microg, 100% ACs for collagen and 12 +/- 4 microg, 0% ACs to 40 +/- 5 microg, 100% ACs for GAG). Compressive modulus (instantaneous and relaxation modulus) of the constructs was significantly higher in the 100% ACs group (63 +/- 12 and 22 +/- 9 kPa, respectively) when compared to groups with higher percentage of MCs. No differences in tensile properties were noted among groups. Specific co-culture ratios were identified mimicking the GAG/DW of the inner (0:100, 25:75, and 50:50) and outer regions (100:0) of the meniscus. Overall, it was demonstrated that co-culturing MCs and ACs on PLLA scaffolds results in functional tissue engineered meniscus constructs with a spectrum of biochemical and biomechanical properties.