Revisiting the Role of Interleukin-1 Pathway in Osteoarthritis: Interleukin-1α and -1β, and NLRP3 Inflammasome Are Not Involved in the Pathological Features of the Murine Menisectomy Model of Osteoarthritis

Abstract

Background: Innate immune response components such as toll-like receptors (TLRs) and NLRP3-inflammasome act in concert to increase IL-1α/β secretion by synovial macrophages. Previous results suggest that IL-1α/β could be an important mediator involved in the pathogenesis of osteoarthritis (OA).Objectives: The aim of our study was to evaluate the role of NLRP3, IL-1β, and IL-1α in the menisectomy (MNX) model of murine OA.Methods: Murine chondrocytes (CHs) and bone marrow-derived machrophages (BMDM) were stimulated with hydroxyapatite (HA) crystals, a form of calcium-containing crystal found in human OA, and IL-1β and IL-6 secretion assayed by ELISA.Conversely, the ability of IL-1β and IL-6 to induce CHs calcification was assessed in vitro by Alizarin red staining. Knees from 8 to 10 weeks old C57Bl/6J wild-type (WT) (n = 7), NLRP3−/− (n = 9), IL-1α−/− (n = 5), and IL-1β−/− (n = 5) mice were menisectomized, using the sham-operated contralateral knee as control. 8 weeks later, knee cartilage degradation and synovial inflammation were evaluated by histology. In addition, apoptotic chondrocytes, metalloproteases activity, and collagen-type 2 expression were evaluated in all mice. Joint calcification and subchondral bone parameters were quantified by CT-scan in WT and IL-1β−/− menisectomized knees.Results: In vitro, HA crystals induced significant increased IL-6 secretion by CHs, while IL-1β remained undetectable.Conversely, both IL-6 and IL-1β were able to increase chondrocytes mineralization. In vivo, operated knees exhibited OA features compared to sham-operated knees as evidenced by increased cartilage degradation and synovial inflammation. In menisectomized KO mice, severity and extent of cartilage lesions were similar (IL-1α−/− mice) or exacerbated (IL-1β−/− and NLRP3−/− mice) compared to that of menisectomized WT mice. Metalloproteases activity, collagen-type 2 expression, chondrocytes apoptosis, and synovial inflammation were similar between KO and WT mice menisectomized knees. Moreover, the extent of joint calcification in osteoarthritic knees was comparable between IL-1β−/− and WT mice.Conclusions: MNX knees recapitulated features of OA, i.e, cartilage destruction, synovial inflammation, cell death, and joint calcification. Deficiency of IL-1α did not impact on the severity of these features, whereas deficiency of IL-1β or of NLRP3 led to increased cartilage erosion. Our results suggest that IL-1α and IL-1β are not key mediators in this murine OA model and may explain the inefficiency of IL-1 targeted therapies in OA.

A Phase II Trial of Lutikizumab, an Anti–Interleukin‐1α/β Dual Variable Domain Immunoglobulin, in Knee Osteoarthritis Patients With Synovitis

“…The IL‐1 pathway may mediate OA pain through pathways in the peripheral and central nervous systems . In some, but not all, animal models of OA, blocking of the IL‐1 pathway improves disease manifestations . However, in clinical trials in knee OA patients not selected for synovitis, an IL‐1R antagonist (anakinra) or an antibody to IL‐1R1 (AMG 108) did not meet the primary symptom‐based study end points.…”

Current perspectives on biological approaches for osteoarthritis

“…In fact, Nasi et al recently demonstrated that the two forms of IL-1 (IL-1␤ and IL-1␣) were not key mediators in the progression of OA. 60 These results highlight the potential gaps in our understanding of the etiology of OA. Despite these major challenges, several other agents that target inflammatory diseases are clinically available and have demonstrated positive clinical results for the treatment of cardiovascular disease (IL-1␤ monoclonal antibody, Canakinumab), 62 psoriasis (IL-17 antibody, Ixekizumab), 63 and psoriatic arthritis (IL-17, Secukinumab), [64][65][66] but longitudinal observations to elucidate their clinical potential for the treatment of OA-related inflammation are necessary.…”

“…In fact, Nasi et al . recently demonstrated that the two forms of IL‐1 (IL‐1β and IL‐1α) were not key mediators in the progression of OA . These results highlight the potential gaps in our understanding of the etiology of OA.…”

“…Even though the pathophysiological mechanisms are not fully understood, several observations suggest that the presence of upregulated immune processes, and specifically inflammatory factors, may predispose the articular structures to OA . IL‐1 is one such proinflammatory cytokine that is responsible for stimulating catabolic factors and, ultimately, predisposing intracapsular structures to degenerative processes …”

“…59 IL-1 is one such proinflammatory cytokine that is responsible for stimulating catabolic factors and, ultimately, predisposing intracapsular structures to degenerative processes. 60 One first-line pharmacological treatment modality that targets IL-1 is a recombinant form of its receptor IL-1R␣ (i.e., Anakinra), and it has been shown to be clinically safe; however, an RCT for the treatment of knee OA found little to no difference in outcomes between treated and placebo groups, in spite of effective IL-1 neutralization. 61 These results reinforce the notion that OA is a multifactorial disease and that there may not be a single factor or pathway propagating OA-induced inflammation and degradation.…”