A High Interleukin 1 Receptor Antagonist/IL-1ß Ratio Occurs Naturally in Knee Osteoarthritis

PASCAL RICHETTE, MATHIAS FRANÇOIS, ERIC VICAUT, CATHERINE FITTING, THOMAS BARDIN, MAÏTÉ CORVOL, JEAN-FRANÇOIS SAVOURET, and FRANÇOIS RANNOU

ABSTRACT.

Objective. To assess the interleukin 1 receptor antagonist (IL-1Ra)/IL-1ß ratio in synovial fluid (SF) of patients with knee osteoarthritis (OA) or rheumatoid arthritis (RA) to determine a possible relation between cytokine level and disease activity.

Methods. IL-1ß and IL-1Ra concentrations were measured by ELISA in knee SF from patients with OA (n = 42) or RA (n = 11). For OA patients, pain and disability were assessed by a visual analog scale (VAS) and the Lequesne index. RA disease activity was assessed using the Disease Activity Score 28 Joint Count (DAS28).

Results. Patients with OA showed lower median levels of IL-1ß and IL-1Ra in SF than patients with RA (p < 0.001) but a higher IL-1Ra/IL-1ß ratio: 1793 (584–6221) versus 773.5 (187.64–1570.5) (p = 0.05). For patients with OA, the IL-1Ra/IL-1ß ratio was not associated with pain or disability. For patients with RA, the IL-1Ra/IL-1ß ratio and IL-1Ra and IL-1ß levels were related to SF white blood cell count.

Conclusion. High endogenous IL-1Ra/IL-1ß ratio occurs in SF from knee OA and does not correlate with pain or Lequesne index. Our results suggest that intraarticular injection of IL-1Ra might be self-limited in patients with knee OA and a naturally high SF ratio. (First Release July 1 2008; J Rheumatol 2008;35:1650–4)

Key Indexing Terms:

OSTEOARTHRITIS
SYNOVIAL FLUID
INTERLEUKIN 1
INTERLEUKIN 1 RECEPTOR ANTAGONIST
PAIN

---

From Université Paris 7, UFR médicale, Assistance Publique-Hôpitaux de Paris, Hôpital Lariboisière, Fédération de Rhumatologie; INSERM-UMR-747, UFR médicale, Université Paris Descartes; Université Paris 7, UFR médicale, Assistance Publique-Hôpitaux de Paris, Hôpital Fernand Widal, Unité de recherche clinique; Unité cytokines et inflammation, Institut Pasteur; and Université Paris Descartes, Assistance Publique-Hôpitaux de Paris, Groupe Hospitalier Cochin, Service de rééducation, Paris, France.

Supported by INSERM and by the Association Rhumatisme et Travail (Centre Viggo Petersen, Hôpital Lariboisière, service de Rhumatologie). Dr. Rannou is supported by Université Paris Descartes (soutien à équipe en émergence).

P. Richette, MD, PhD, Université Paris 7, UFR médicale, Assistance Publique-Hôpitaux de Paris, Hôpital Lariboisière, Fédération de Rhumatologie and INSERM-UMR-747, UFR médicale, Université Paris Descartes; M. François, PhD; M. Corvol, MD, PhD; J-F. Savouret, PhD, INSERM-UMR-747, UFR médicale, Université Paris Descartes; E. Vicaut, MD, PhD, Université Paris 7, UFR médicale, Assistance Publique-Hôpitaux de Paris, Hôpital Fernand Widal, Unité de recherche clinique; C. Fitting, PhD, Unité cytokines et inflammation, Institut Pasteur; T. Bardin, MD, Université Paris 7, UFR médicale, Assistance Publique-Hôpitaux de Paris, Hôpital Lariboisière, Fédération de Rhumatologie; F. Rannou, MD, PhD, INSERM-UMR-747, UFR médicale, Université Paris Descartes and Assistance Publique-Hôpitaux de Paris, Groupe Hospitalier Cochin, Service de rééducation.

Drs. Richette and François contributed equally to this work.

Address reprint requests to Dr. P. Richette, Fédération de Rhumatologie, Hôpital Lariboisière, 2 Rue Ambroise Paré, 75475 Paris cedex 10, France. E-mail: pascal.richette@lrb.aphp.fr

Accepted for publication March 10, 2008.

---