ab1902

Interleukin-10 and interleukin-10 receptor in human osteoarthritic and healthy chondrocytes

F. Iannone, C. De Bari, F. Dell'Accio, M. Covelli, F.P. Cantatore, V. Patella¹, G. Lo Bianco¹, G. Lapadula

Cattedra di Reumatologia, ¹Clinica Ortopedica II, Università degli Studi di Bari, Italy.

ABSTRACT
Objective
To evaluate the expression of interleukin-10 (IL-10) and interleukin-10 receptor (IL-10R) on chondrocytes from healthy, osteoarthritic, and foetal cartilage from human subjects.

Methods
Articular cartilage was obtained from 12 patients with osteoarthritis (OA) undergoing surgical knee replacement. Chondrocytes were isolated from the two zones of cartilage showing macroscopically and histologically the lowest (MIN) and highest (MAX) extent of osteoarthritic damage. Additional specimens of cartilage were obtained from 3 healthy donors and 3 human foetuses.
IL-10 mRNA expression was determined by a reverse transcriptase-polymerase chain reaction (RT-PCR). For detection of intracellular IL-10 protein, chondrocytes were permeabilized and then incubated with R-phycoerythrin (PE) conjugated rat anti-human IL-10 mAb. Cell surface IL-10R was detected by incubation with biotinylated recombinant human IL-10; after washing, bound IL-10 was revealed by fluorescein (FITC) conjugated streptavidin. Positive chondrocytes were analysed by flowcytometry.

Results
IL-10 mRNA expression was higher in osteoarthrtic than in normal chondrocytes. IL-10 protein intracellular levels were significantly higher in MAX than in MIN osteoarthritic cartilage or in healthy cartilage. Cell surface IL-10R was expressed on osteoarthritic chondrocytes with no difference in the degree of cartilage damage. The highest levels of IL-10 protein and IL-10R were found in foetal cartilage.

Conclusion
Human chondrocytes synthesise IL-10 and express on their surface IL-10R. Since IL-10 inhibits IL-1 and TNF-a expression, its upregulation in osteoarthritic chondrocytes may counteract the detrimental effects
of these catabolic cytokines. However, the functions of IL-10 in cartilage may go beyond those activities established in the immunological setting. The high levels of IL-10 and IL-10R in foetal cartilage, an active growing tissue, suggest that IL-10 may play a role in controlling chondrocyte metabolism under physiological conditions.

Key words
IL-10, IL-10R, cartilage, foetal cartilage.

This work was partially supported by CNR Italy (grant no. 97.4164.04).
Please address correspondence and reprint requests to: Prof. Giovanni Lapadula, Cattedra di Reumatologia, Piazza G. Cesare 11, 70124 Policlinico, Bari, Italy.
E-mail: pa1@reumbari.uniba.it