Glucose Concentration and Medium Volume Influence Cell Viability and Glycosaminoglycan Synthesis in Chondrocyte-Seeded Alginate Constructs

Abstract

Increasing the thickness of tissue-engineered cartilage is associated with loss of chondrocyte viability and biosynthetic activity at the tissue center. Exceptionally high volumes of culture medium, however, can maintain cellularity and glycosaminoglycan synthesis throughout 4-mm-thick constructs. We hypothesized that glucose supplementation could replicate the augmentation of tissue formation achieved by medium volume. Chondrocyte-alginate constructs (40×10⁶ cells/mL) were cultured for 14 days in 0.4–6.4 mL/10^–6 cells of either low- (5.1mM) or high- (20.4mM) glucose medium. Glucose was critical to chondrocyte viability, and glucose uptake increased significantly (P < .001) with both medium volume and glucose supplementation. After 14 days, constructs cultured in 0.4 mL/10^–6 cells of low-glucose medium had a mass of 172 ± 6.1mg and glycosaminoglycan (GAG) content of 0.32 ± 0.03mg (mean ± standard deviation). A 4-fold increase in medium volume increased the final construct mass by 44% and GAG content by 207%. An equivalent increase in glucose supply in the absence of volume change increased these parameters by just 10% and 73%, respectively. A similar trend was observed from 0.8 to 3.2mL/10^–6 cells, when maximal values of construct GAG content and mass were obtained. Therefore, medium volume remains an important consideration for the optimal culture of tissue-engineered cartilage.