Time course of 3D fibrocartilage formation by expanded human meniscus fibrochondrocytes in hypoxia.

Adult human meniscus fibrocartilage is avascular and non-healing after injury. Meniscus tissue engineering aims to replace injured meniscus with lab grown fibrocartilage. Dynamic culture systems may be necessary to generate fibrocartilage of sufficient mechanical properties for implantation; however, the optimal static pre-culture conditions prior to initiation of dynamic culture are unknown. This study thus investigated the time course of fibrocartilage formation by human meniscus fibrochondrocytes on a 3D biomaterial scaffold under various static conditions. Human meniscus fibrochondrocytes from partial meniscectomy were expanded to P1 or P2 (3.0±0.4 or 6.5±0.6 population doublings), seeded onto type I collagen scaffolds, and grown in hypoxia (HYP, 3% O2 ) or normoxia (NRX, 20% O2 ) for 3, 6, or 9 weeks. Mechanical properties were not different between P1 and P2 cell-based constructs. Mechanical properties were lower in HYP, increased continually in NRX only, and were positively correlated with glycosaminoglycan content and accumulation of hyaline cartilage-like matrix components. The most mechanically competent tissues (NRX/9 weeks) reached 1/5 of the native meniscus instantaneous compression modulus but had an increasingly hypertrophic matrix-forming phenotype. HYP consistently suppressed the hypertrophic phenotype. The results provide baselines of engineered meniscus fibrocartilage properties under static conditions, which can be used to select a pre-culture strategy for dynamic culture depending on the desired combination of mechanical properties, hyaline cartilage-like matrix abundance, and hypertrophic phenotype. This article is protected by copyright. All rights reserved.