Sensitivity of anulus fibrosus cells to interleukin 1 beta - Comparison with articular chondrocytes

Study Design, Anulus fibrosus cells from rabbits were grown in primary cult ure 1) to study their ability to produce prostaglandin E2 and Type II phosp holipase A2, and to express stromelysin-1 messenger ribonucleic acid; and 2 ) to study the effect of interleukin 1 beta on this production and on prote oglycan aggregation. Objectives. To investigate the potency of anulus fibrosus cells to respond to interleukin 1 beta by producing degradative and inflammatory agents as c ompared with the potency of articular chondrocytes in the same animal. Summary of Background Data. Interleukin 1 beta has been implicated in the d egradation of intervertebral discs. The way anulus fibrosus cells differ fr om articular chondrocytes in their responses to interleukin 1 beta remains to be established. Methods. Anulus fibrosus cells and articular chondrocytes were obtained fro m young rabbits, grown in primary culture, and incubated with interleukin 1 beta. The newly synthesized proteoglycan was measured by labeling with [S- 35]-sulfate. Proteoglycan aggregation was analyzed by the elution profile o n Sepharose 2B columns. The contents of collagen Type II and stromelysin-1 messenger ribonucleic acid were assessed by Northern blot analysis. The Typ e II phospholipase A2 activity was measured using a fluorometric substrate. Prostaglandin E2 production was evaluated by radioimmunoassay. Results. Anulus fibrosus cells had 2.5-fold less Type II collagen messenger ribonucleic acid than articular chondrocytes, and interleukin 1 beta had n o significant effect on this. Anulus fibrosus cells synthesized and secrete d fourfold less proteoglycan than articular chondrocytes. Interleukin 1 bet a reduced the anulus fibrosus content of total [S-3S]-sulfated proteoglycan by 35% (P< 0.01), and that of articular cells by 41% and decreased proteog lycan aggregation. Interleukin 1 beta induced the production of stromelysin -1 messenger ribonucleic acid in both cell types. The stromelysin-1 messeng er ribonucleic acid content of anulus fibrosus cells was one half that of a rticular cells. Interleukin 1 beta increased the production of prostaglandi n 52 and caused a dose-dependent secretion of Type II phospholipase A2 acti vity in both cell types. Its effect was 2.5-fold lower in anulus fibrosus c ells than in articular chondrocytes. Conclusion. Anulus fibrosus cells can be stimulated by interleukin 1 beta t o produce factors implicated in local degradative and inflammatory processe s. This production is associated with decreased proteoglycan aggregation. A nulus fibrosus cells respond slightly less well to interleukin 1 beta in vi tro than do articular cells.