Influence of Alginate Polysaccharide Composition and Culture Conditions on Chondrocytes in Three-Dimensional Culture

Alginate-embedded chondrocytes have been used for experimental analysis of cartilage matrix metabolism and as a potential bioartificial system for repairing cartilage defects. Alginates are linear copolymers composed of 1,4-linked β -n-mannuronic acid and 1,4 linked α -L-guluronic acid, which occur as regions made up exclusively of one unit or the other, or as regions in which the monomers approximate an alternating sequence. Data presented here demonstrate that the mannuronic to guluronic acid (M/G) ratio and molecular weight of the alginate utilized effects the tissue-culture handling properties of the resultant gel and the activity of embedded chondrocytes. In experiments comparing chondrocyte survival and matrix synthesis, optimal conditions were obtained with an alginate of both high mannuronic acid content and high molecular weight. Chondrocytes survived and proliferated when maintained in unsupplemented media, in media supplemented with fetal calf serum, and in media supplemented with the defined serum replacement ITS+ (6.25 µ g/ml insulin, 6.25 µ g/ml transferrin, 6.25 ng/ml selenous acid, 1.25 mg/ml bovine serum albumin, 5.35 µ g/ml linoleic acid). High cell survival rate and increase in cell number was obtained in the absence of serum. In contrast, long-term matrix synthesis and deposition required media supplementation as indicated by uptake of [ 35 S]sulfate into glycosaminoglycans and by immunofluorescence using antibodies specific for cartilage matrix molecules.