TGFß signaling pathway is altered by HLA-B27 expression, resulting in pathogenic consequences relevant for spondyloarthritis.

BACKGROUND: Association of HLA-B27 with spondyloarthritis (SpA) has been known for 50 years, but still remains unexplained. We recently showed that HLA-B27 expressed in wing imaginal disc from HLA-B27/human-ß2 microglobulin (hß2m) transgenic Drosophila deregulated bone morphogenetic protein (BMP) pathway by interacting physically with type I BMP receptor (BMPR1) Saxophone (Sax), leading to crossveinless phenotype. METHODS: Genetic interaction was studied between activin/transforming growth factor ß (TGFß) pathway and HLA-B27/hß2m in transgenic Drosophila wings. The HLA-B27-bound peptidome was characterized in wing imaginal discs. In mesenteric lymph node (mLN) T cells from HLA-B27/hß2m rat (B27 rat), physical interaction between HLA-B27 and activin receptor-like kinase-2 (ALK2), ALK3 and ALK5 BMPR1s, phosphorylation of small mothers against decapentaplegic (SMADs) and proteins of the non-canonical BMP/TGFß pathways induced by its ligands, and the transcript level of target genes of the TGFß pathway, were evaluated. RESULTS: In HLA-B27/hß2m transgenic Drosophila, inappropriate signalling through the activin/TGFß pathway, involving Baboon (Babo), the type I activin/TGFß receptor, contributed to the crossveinless phenotype, in addition to deregulated BMP pathway. We identified peptides bound to HLA-B27 with the canonical binding motif in HLA-B27/hß2m transgenic Drosophila wing imaginal disc. We demonstrated specific physical interaction, between HLA-B27/hß2m and mammalian orthologs of Sax and Babo, i.e. ALK2 and ALK5 (i.e. TGFß receptor I), in the mLN cells from B27 rat. The magnitude of phosphorylation of SMAD2/3 in response to TGFß1 was increased in T cells from B27 rats, showing evidence for deregulated TGFß pathway. Accordingly, expression of several target genes of the pathway was increased in T cells from B27 rats, in basal conditions and/or after TGFß exposure, including Foxp3, Rorc, Runx1 and Maf. Interestingly, Tgfb1 expression was reduced in naive T cells from B27 rats, even premorbid, an observation consistent with a pro-inflammatory pattern. CONCLUSIONS: This study shows that HLA-B27 alters the TGFß pathways in Drosophila and B27 rat. Given the importance of this pathway in CD4 + T cells differentiation and regulation, its disturbance could contribute to the abnormal expansion of pro-inflammatory T helper 17 cells and altered regulatory T cell phenotype observed in B27 rats.

Unmet needs in axial spondyloarthritis. Proceedings of the French spondyloarthritis taskforce workshop.

The progress observed over the last 30 years in the field of axial spondyloarthritis (axSpA) has not made it possible to answer all the current questions. This manuscript represents the proceedings of the meeting of the French spondyloArthitiS Task force (FAST) in Besançon on September 28 and 29, 2023. Different points of discussion were thus individualized as unmet needs: biomarkers for early diagnosis and disease activity, a common electronic file dedicated to SpA nationwide, a better comprehension of dysbiosis in the disease, a check-list for addressing to the rheumatologist, adapt patient reported outcomes thresholds for female gender, implementation of comorbidities screening programs, new imaging tools, in research cellular and multi omics approaches, grouping, at a nationwide level, different cohorts and registries, therapeutic strategy studies, consensual definition of difficult to treat disease and management, preclinical stage of the disease, mastering AI as a tool in the various aspects of research. These elements may represent a framework for the research agenda in axSpA for the years to come.

How to translate genetic findings into clinical applications in spondyloarthritis?

Spondyloarthritis (SpA) is characterized by a strong genetic predisposition evidenced by the identification of up to 50 susceptibility loci, in addition to HLA-B27, the major genetic factor associated with the disease. These loci have not only deepened our understanding of disease pathogenesis but also offer the potential to improve disease management. Diagnostic delay is a major issue in SpA. HLA-B27 testing is widely used as diagnostic biomarker in SpA but its predictive value is limited. Several attempts have been made to develop more sophisticated polygenic risk score (PRS). However, these scores currently offer very little improvement as compared to HLA-B27 and are still difficult to implement in clinical routine. Genetics might also help to predict disease outcome including treatment response. Several genetic variants have been reported to be associated with radiographic damage or with poor response to TNF blockers, unfortunately with lack of coherence across studies. Large-scale studies should be conducted to obtain more robust findings. Genetic and genomic evidence in complex diseases can be further used to support the identification of new drug targets and to repurpose existing drugs. Although not fully driven by genetics, development of IL-17 blockers has been facilitated by the discovery of the association between IL23R variants and SpA. Development of recent approaches combining GWAS findings with functional genomics will help to prioritize new drug targets in the future. Although very promising, translational genetics in SpA remains challenging and will require a multidisciplinary approach that integrates genetics, genomics, immunology, and clinical research.

Risk of cardiovascular disease decreases over time in psoriatic arthritis but not in spondylarthritis: meta-analysis of longitudinal studies.

OBJECTIVES: Spondyloarthritis (SpA) and psoriatic arthritis (PsA) represent two frequent inflammatory rheumatic disorders, characterized by an increased burden on quality of life, due to the association of several comorbidities, especially cardiovascular diseases (CVD). The estimated prevalence of CVD ranges from 12-19% and differ between the two diseases, however, its incidence is not completely known. We aimed to systematically review the literature (SLR) and perform a meta-analysis of controlled observational studies to assess the incidence rate of CVD over time, separately in SpA and PsA. METHODS: We performed a SLR of longitudinal studies with a study period of at least 5 years, including SpA/PsA patients and general population. The main outcome was the occurrence of CVD, including ischemic heart disease, stroke, and death from CV cause. We then performed a random-effect model for meta-analysis. RESULTS: The SLR included 34 articles, mainly focused on the association between SpA/PsA and CVD. Twenty-four articles were then selected for the meta-analysis. The overall incidence of CVD was increased in PsA (HR: 1.28, 95%CI: 1.15-1.43), and in SpA (HR: 1.45, 95%CI: 1.22-1.72) compared with the general population, with consistency across the different types of CVD; Interestingly the incidence tended to decrease over time in PsA, but not in SpA. CONCLUSION: The SLR and meta-analysis confirmed the increased incidence of CVD in both SpA and PsA patients compared with the general population during the last years, although such increase seems to be less prominent in PsA than in SpA. Future studies are needed to confirm such tendence.