OP0100 IL-17A BLOCKADE MODULATES DISEASE SPECIFIC IMMUNE AND STROMAL PATHWAYS IN PERIPHERAL SPONDYLOARTHRITIS SYNOVITIS

Background

The cellular and molecular mechanisms driving inflammation and structural remodelling in spondyloarthritis (SpA) remain largely unknown, though the IL-23/IL-17 pathway can contribute to synovial inflammation and radiographic progression.

Objectives

To investigate the molecular pathways affected by IL-17A blockade (IL-17Ai) with secukinumab in SpA synovitis, and assess if this response is tissue- and/or treatment-specific.

Methods

Synovial biopsies were obtained from peripheral SpA patients by needle arthroscopy before and after 12 weeks of IL-17Ai with secukinumab (n=12), and analyzed by RNA-sequencing and qPCR. We performed pathway enrichment analysis of the differentially expressed genes (DEGs) to identify pathways modulated after treatment. We compared the synovial tissue response in patients with psoriatic arthritis (PsA) in our cohort (n=7) with open source gene expression data of skin biopsies of psoriasis patients receiving secukinumab (n=22)[1] and of synovial biopsies of PsA patients receiving IL-12p40/IL-23p40 blockade (n=7)[2].

Results

IL-17Ai significantly modulated the expression of 1255 genes (549 up- and 706 down-regulated, FDR 0.1) in the synovium at week 12 compared to baseline (Figure 1). Genes downregulated upon IL-17Ai were significantly enriched in GO terms and KEGG pathways related to immune and inflammatory responses, including neutrophil and monocyte chemotaxis, TNF-mediated, NF-κB-, Wnt-, and JAK-STAT signalling pathways, and, importantly, bone-remodelling responses, such as osteoblast and osteoclast differentiation. Upregulated genes are enriched in JNK-, MAPK-, Wnt-, and PI3K-Akt signalling and negative regulation of osteoblast differentiation. We validated differential expression of selected genes from several pathways by qPCR, including: IL1B, p=0.027; CXCL6, p=0.020; ADAMTS4, p=0.002; MMP3, p=0.020; and CHRDL2, p= 0.039.

Figure 1.

Heatmap of differentially expressed genes (DEGs) and pathway enrichment analyses of changes in peripheral SpA synovium 12 weeks after anti-IL-17A treatment (IL-17Ai). A. Hierarchical cluster analysis of the top 100 most significant DEGs (FDR < 0.1) modulated by IL-17Ai separates pre- and post-treated groups. Normalized and scaled log2 gene expression levels are shown. B. Pathway enrichment analysis through DAVID. Enriched (p < 0.05) gene ontology terms from IL-17Ai-induced up- and down-regulated DEGs in peripheral SpA synovium are shown.

To assess if this response is tissue- and/or treatment-specific, we compared changes in gene expression by IL-17Ai in PsA synovium versus psoriatic skin, and in the PsA synovium after IL-17Ai versus IL-12p40/IL-23p40 blockade. While many inflammation-related GO terms and KEGG pathways were over-represented in both tissues and treatments, NF-κB-, JAK-STAT-, and PI3K-Akt-signaling were enriched in DEGs in both skin and synovium after IL-17Ai, whereas JNK cascade, IL-17 signalling pathway and Th17 cell differentiation were overrepresented in DEGs after IL-17Ai in the synovium specifically. Remarkably, IL-17Ai, but not IL-12p40/IL-23p40 blockade, modulated multiple bone-remodelling related pathways. Also, IL-17Ai modulated ossification and collagen catabolic process terms in PsA synovium and psoriatic skin in the opposite direction: these terms were over-represented in downregulated genes in synovium, but in upregulated genes in skin. Accordingly, genes upregulated after IL-17Ai were enriched in negative regulation of osteoblast differentiation in the synovium, but in positive regulation of osteoblast differentiation in the skin.

Conclusion

These first in vivo human data provide molecular confirmation of previously reported animal data[3] that demonstrated down-modulation of disease-relevant immune and stromal pathways in the synovium in response to IL-17Ai.

References

[1]Krueger JG et al. J Allergy Clin Immunol. 2019. Sep;144(3):750-763

[2]Fiechter RH et al. Front Immunol. 2021. Mar 4;12:611656

[3]Van Tok MN et al. Arthritis Rheumatol. 2019. Apr;71(4):612-625

Disclosure of Interests

Renée Fiechter: None declared, Leonieke van Mens: None declared, Ihsan Hammoura: None declared, Henriëtte de Jong: None declared, Desire Pots: None declared, Inka Fluri: None declared, Sander Tas: None declared, Dominique Baeten Employee of: Current employee of UCB Pharma, Marleen G.H. van de Sande Consultant of: Novartis and AbbVie, Grant/research support from: Janssen, Novartis and Eli Lilly, Nataliya Yeremenko: None declared.

Transmembrane TNF drives osteoproliferative joint inflammation reminiscent of human spondyloarthritis

TNF plays a key role in immune-mediated inflammatory diseases including rheumatoid arthritis (RA) and spondyloarthritis (SpA). It remains incompletely understood how TNF can lead to different disease phenotypes such as destructive peripheral polysynovitis in RA versus axial and peripheral osteoproliferative inflammation in SpA. We observed a marked increase of transmembrane (tm) versus soluble (s) TNF in SpA versus RA together with a decrease in the enzymatic activity of ADAM17. In contrast with the destructive polysynovitis observed in classical TNF overexpression models, mice overexpressing tmTNF developed axial and peripheral joint disease with synovitis, enthesitis, and osteitis. Histological and radiological assessment evidenced marked endochondral new bone formation leading to joint ankylosis over time. SpA-like inflammation, but not osteoproliferation, was dependent on TNF-receptor I and mediated by stromal tmTNF overexpression. Collectively, these data indicate that TNF can drive distinct inflammatory pathologies. We propose that tmTNF is responsible for the key pathological features of SpA.

mTOR Blockade by Rapamycin in Spondyloarthritis: Impact on Inflammation and New Bone Formation in vitro and in vivo

Introduction: Spondyloarthritis (SpA) is characterized by inflammation, articular bone erosions and pathologic new bone formation. Targeting TNFα or IL-17A with current available therapies reduces inflammation in SpA, however, treatment of the bone pathology in SpA remains an unmet clinical need. Activation of the mammalian target Of rapamycin (mTOR) promotes IL-17A expression and osteogenesis. Therefore, the inhibition of mTOR (with rapamycin) could be a promising therapeutic avenue in SpA.

Objectives: To investigate the effect of blocking mTOR on inflammation, bone erosions and new bone formation in SpA.

Methods: Peripheral blood mononuclear cells (PBMCs) from patients with SpA were stimulated with anti-CD3/CD28 in the presence or absence of rapamycin and the resulting cytokine expression was assessed. Fibroblast-like synoviocytes (FLS) from SpA patients were assessed for osteogenic differentiation potential in conditions with TNFα, IL-17A, or TNFα plus IL-17A, in the presence or absence of rapamycin. HLA-B27/Huβ2m transgenic rats were immunized with low dose heat-inactivated Mycobacterium tuberculosis (M. tub), treated with 1.5 mg/kg rapamycin prophylactically or therapeutically and monitored for arthritis and spondylitis. Histology and mRNA analysis were performed after 5 weeks of treatment to assess inflammation and bone pathology.

Results:In vitro TNFα and IL-17A protein production by SpA PBMCs was inhibited in the presence of rapamycin. Rapamycin also inhibited osteogenic differentiation of human SpA FLS. Ex vivo analysis of SpA synovial biopsies indicated activation of the mTOR pathway in the synovial tissue of SpA patients. In vivo, prophylactic treatment of HLA-B27/Huβ2m transgenic rats with rapamycin significantly inhibited the development and severity of inflammation in peripheral joints and spine (arthritis and spondylitis), with histological evidence of reduced bone erosions and new bone formation around peripheral joints. In addition, therapeutic treatment with rapamycin significantly decreased severity of arthritis and spondylitis, with peripheral joint histology showing reduced inflammation, bone erosions and new bone formation. IL-17A mRNA expression was decreased in the metacarpophalangeal joints after rapamycin treatment.

Conclusion: mTOR blockade inhibits IL-17A and TNFα production by PBMCs, and osteogenic differentiation of FLS from patients with SpA in vitro. In the HLA-B27 transgenic rat model of SpA, rapamycin inhibits arthritis and spondylitis development and severity, reduces articular bone erosions, decreases pathologic new bone formation and suppresses IL-17A expression. These results may support efforts to evaluate the efficacy of targeting the mTOR pathway in SpA patients.