Effect of media mixing on ECM assembly and mechanical properties of anatomically-shaped tissue engineered meniscus

This study investigated the hypothesis that controlled media mixing will enhance tissue formation and increase mechanical properties of anatomically-shaped tissue engineered menisci. Bovine meniscal fibrochondrocytes were seeded in 2% w/v alginate, cross-linked with 0.02 g/mL CaSO4, and injected into molds of menisci. Engineered menisci were incubated for up to 6 weeks. A mixing media bioreactor was designed to ensure proper mixing of culture medium while protecting constructs from the spinning impeller. Impeller speeds were calibrated to produce Reynolds number (Re) of 0.5, 2.9, 5.8, 10.2, and 21.8. Constructs were divided a tested in confined compression and in tension to determine the equilibrium and tensile moduli, respectively. Media stimulation resulted in a 2–5 fold increase in mechanical properties and a 2–3 fold increase in matrix accumulation in constructs over 6 weeks in culture. Benefits from mixing stimulation for collagen accumulation and compressive modulus appeared to peak near Re 2.9, and decreased with increased mixing intensity. This study suggests that fluid mixing can be optimized to enhance mechanical properties of anatomically-shaped engineered constructs.