The influence of hydrocortisone on aggrecan metabolism in human articular chondrocyte cultures: Comparison of two different matrices

Objective Numerous reports of negative effects as well as protective effects of gluco corticoids on articular cartilage convinced us to study the influence of hy drocortisone on aggrecan synthesis of isolated phenotypically stable human articular chondrocytes cultured in two different matrices. Methods Macroscopically normal human articular cartilage was obtained from femoral condyles within 24 hours postmortem. Chondrocytes were isolated and culture d in gelled agarose or in alginate. After 14 days in culture, hydrocortison e was added for 5 days at concentrations ranging from 0.005 mug to 1 mg/ml for the agarose cultures and from 0.005 mug to 1 mug/ml for the alginate cu lture system. Aggrecan synthesis was measured by the incorporation of (35)S ulphate, and the proportion of neosynthesized aggrecan that bound to hyalur onan to form aggrecan aggregates was analyzed by gel chromatography. Results At concentrations from 0.005 to 1 mug/ml, hydrocortisone was found to produ ce a similar dose-dependent stimulation of aggrecan synthesis in both matri ces. The synthesis of aggrecans remained at the same level for concentratio ns of 1 mug/ml up to 100 mug/ml of hydrocortisone. When supraphysiological concentrations of hydrocortisone were added the aggrecan synthesis rate pla teau declined. Simultaneously with the increase in aggrecan synthesis, the proportion of low-molecular weight S-35-proteoglycans decreased in favour o f S-35-aggrecan aggregates and monomers in the agarose system. The chondroc ytes cultured in alginate showed this increase of aggrecan aggregates and m onomeric aggrecans in both the cell-associated and the inter-territorial ma trix. Conclusion Hydrocortisone is a stimulator of aggrecan synthesis by normal human articu lar chondrocytes cultured in vitro. The two culture systems (agarose and al ginate) tested in this experiment showed a comparable aggrecan synthesis ra te, increasing under the influence of hydrocortisone at concentrations up t o 1 mug/ml. The proportions of (35)Sulphate incorporated in aggrecan aggreg ates and monomeric aggrecan were also higher under the influence of hydroco rtisone.