Physiological levels of hydrocortisone maintain an optimal chondrocyte extracellular matrix metabolism

Abstract

Objective: To investigate the effects of physiological doses of hydrocortisone on synthesis and turnover of cell associated matrix (CAM) by human chondrocytes obtained from normal articular cartilage.

Methods: Human articular cartilage cells were obtained from visually intact cartilage of the femoral condyles of five donors and maintained in culture for one week to reach equilibrium in accumulated CAM compounds. 0, 0.05, 0.20, and 1.0 micro g/ml hydrocortisone was added to the nutrient media during the entire culture period. Cells were liberated and levels of CAM aggrecan, type II collagen, and fibronectin, of intracellular IGF-1, IL1alpha and beta, and of their respective plasma membrane bound receptors IGFR1, IL1RI, and the decoy receptor IL1RII, were assayed by flow cytometry.

Results: In comparison with controls, hydrocortisone treated chondrocytes, at all concentrations, expressed significantly higher plasma membrane bound IGFR1. Intracellular IGF-1 levels remained unchanged. Together with these changes, reflecting an increased ability to synthesise extracellular matrix (ECM) macromolecules, hydrocortisone treated cells expressed significantly higher amounts of the plasma membrane bound decoy IL1RII. Concurrently, intracellular IL1alpha and beta levels and membrane bound IL1RI were down regulated. Levels of CAM aggrecan, type II collagen, and fibronectin were significantly up regulated in the chondrocytes treated with hydrocortisone.

Conclusion: 0.05 micro g/ml hydrocortisone treated chondrocytes had decreased catabolic signalling pathways and showed an enhanced ability to synthesise ECM macromolecules. Because IL1 activity was decreased and the expression of IL1RII decoy receptor enhanced, more of the ECM macromolecules produced remained accumulated in the CAM of the chondrocytes. The effects were obtained at doses comparable with physiological plasma levels of hydrocortisone in humans.

Figure 1

Effects of increasing doses of hydrocortisone on the IGF-1/IGFR1 autocrine pathway and on plasma membrane IL1RII. Percentage changes in chondrocyte MFI due to the binding of monoclonal antibodies specific for IGFR1 (A), IGF-1 (B), and IL1RII (C) are shown for varying doses of hydrocortisone in the culture medium. Each dot represents the mean value of the three results obtained in a single donor. Median values are indicated for each dose of hydrocortisone. Results of paired samples t test (p values) are given in the figure.

Figure 2

Effects of increasing doses of hydrocortisone on the IL1/IL1RI autocrine pathway. Percentage changes in chondrocyte MFI due to the binding of monoclonal antibodies specific for IL1α (A), IL1ß (B), and IL1RI (C) are shown for varying doses of hydrocortisone in the culture medium. Each dot represents the mean value of the three results obtained in a single donor. Median values are indicated for each dose of hydrocortisone. Results of paired samples t test (p values) are given in the figure.

Figure 3

Effects of increasing doses of hydrocortisone on the levels of CAM aggrecan, type II collagen, and fibronectin. Percentage changes in chondrocyte MFI due to the binding of monoclonal antibodies specific for aggrecan (A), type II collagen (B), and fibronectin (C) are shown for varying doses of hydrocortisone in the culture medium. Each dot represents the mean value of the three results obtained in a single donor. Median values are indicated for each dose of hydrocortisone. Results of paired samples t test (p values) are given in the figure.