Bioreactor cultivation conditions modulate the composition and mechanical properties of tissue‐engineered cartilage

TLDR

Cartilaginous constructs have been grown in vitro using isolated cells, biodegradable polymer scaffolds, and bioreactors. The study investigates how static, mixed, and rotating bioreactor environments affect the composition and mechanical properties of engineered cartilage. Bovine calf articular chondrocytes were seeded on 5‑mm diameter, 2‑mm thick, 97 % porous polyglycolic acid scaffolds and cultured for six weeks in static flasks, mixed flasks, or rotating vessels. Static and mixed cultures yielded small, fragile constructs with poor mechanical properties, whereas rotating vessel culture produced the largest, ECM‑rich constructs with the highest glycosaminoglycan and collagen content and superior mechanical performance, and mechanical metrics correlated with wet‑weight fractions of GAG, collagen, and water, indicating that bioreactor hydrodynamics modulate engineered cartilage composition, morphology, mechanics, and electromechanical function.

Abstract

Cartilaginous constructs have been grown in vitro with use of isolated cells, biodegradable polymer scaffolds, and bioreactors. In the present work, the relationships between the composition and mechanical properties of engineered cartilage constructs were studied by culturing bovine calf articular chondrocytes on fibrous polyglycolic acid scaffolds (5 mm in diameter, 2-mm thick, and 97% porous) in three different environments: static flasks, mixed flasks, and rotating vessels. After 6 weeks of cultivation, the composition, morphology, and mechanical function of the constructs in radially confined static and dynamic compression all depended on the conditions of in vitro cultivation. Static culture yielded small and fragile constructs, while turbulent flow in mixed flasks yielded constructs with fibrous outer capsules; both environments resulted in constructs with poor mechanical properties. The constructs that were cultured freely suspended in a dynamic laminar flow field in rotating vessels were the largest, contained continuous cartilage-like extracellular matrices with the highest fractions of glycosaminoglycan and collagen, and had the best mechanical properties. The equilibrium modulus, hydraulic permeability, dynamic stiffness, and streaming potential correlated with the wet-weight fractions of glycosaminoglycan, collagen, and water. These findings suggest that the hydrodynamic conditions in tissue-culture bioreactors can modulate the composition, morphology, mechanical properties, and electromechanical function of engineered cartilage.