Residual pain in rheumatoid arthritis: Is it a real problem?

"Inflammatory or non-inflammatory pain in inflammatory arthritis - How to differentiate it?"

Pain is a significant issue in rheumatoid arthritis (RA) and psoriatic arthritis (PSA) and can have a negative impact on patients' quality of life. Despite optimal control of inflammatory disease, residual chronic pain remains a major unmet medical need in RA. Pain in RA can be secondary to inflammation but can also generate neuroendocrine responses that initiate neurogenic inflammation and enhance cytokine release, leading to persistent hyperalgesia. In addition to well-known cytokines such as TNFα and IL-6, other cytokines and the JAK-STAT pathway play a role in pain modulation and inflammation. The development of chronic pain in RA involves processes beyond inflammation or structural damage. Residual pain is often observed in patients even after achieving remission or low disease activity, suggesting the involvement of non-inflammatory and central sensitization mechanisms. Moreover, fibromyalgia syndrome (FMS) is prevalent in RA patients and may contribute to persistent pain. Factors such as depression, sleep disturbance, and pro-inflammatory cytokines may contribute to the development of fibromyalgia in RA. It is essential to identify and diagnose concomitant FMS in RA patients to better manage their symptoms. Further research is needed to unravel the complexities of pain in RA. Finally, recent studies have shown that JAK inhibitors effectively reduce residual pain in RA patients, suggesting pain-reducing effects independent of their anti-inflammatory properties.

People with osteoarthritis have a higher component of neuropathic pain as compared to those with rheumatoid arthritis: A cross-sectional study

Neuropathic pain may be present in a proportion of patients with osteoarthritis (OA) and rheumatoid arthritis (RA). Its presence may lead to the requirement of altered management approaches in these conditions. This study investigated the prevalence of neuropathic pain in OA as compared to that in RA. Patients with OA and RA were included cross-sectionally if they had no other known neuropathic disorder. The PainDETECT questionnaire was used to assess neuropathic pain. WOMAC and CDAI scores were used to assess disease severity in OA and RA respectively. 69 patients with OA with a mean WOMAC score of 53.30 ± 16.39 and 98 patients with RA with a mean CDAI of 25.48 ± 16.99 were compared. The median PainDETECT score for OA was 13 (0-30) and RA was 5 (0-37) [p<0.001]. 15 patients with OA and six patients with RA were highly likely to have neuropathic pain, while 15 patients with OA and 30 patients with RA were classified as possibly having neuropathic pain. Thus, the proportion of patients free from neuropathic pain was higher in the RA group (63.3%) than in the OA group (39.1%) [p = 0.003]. Both the prevalence and the severity of neuropathic pain were significantly higher in OA than in RA. These findings suggest that neuropathic pain is an important factor in OA, as in RA, and must be considered in management as well as in future research in both these conditions.

Transcriptome Analysis of Rheumatoid Arthritis Uncovers Genes Linked to Inflammation-Induced Pain

Autoimmune diseases such as rheumatoid arthritis (RA) can promote states of chronic Inflammation with accompanying tissue destruction and pain. RA can cause inflammatory synovitis in peripheral joints, particularly within the hands and feet, but can also sometimes trigger temporomandibular joint (TMJ) arthralgia. To better understand the effects of ongoing Inflammation-induced pain signaling, dorsal root ganglia (DRGs) were acquired from individuals with RA for transcriptomic study. We conducted RNA sequencing from the L5 DRGs because it contains the soma of the sensory neurons that innervate the affected joints in the foot. DRGs from 5 RA patients were compared with 9 non-arthritic controls. RNA-seq of L5 DRGs identified 128 differentially expressed genes (DEGs) that were dysregulated in the RA subjects as compared to the non-arthritic controls. The DRG resides outside the blood brain barrier and, as such, our initial transcriptome analysis detected signs of an autoimmune disorder including the upregulated expression of immunoglobulins and other immunologically related genes within the DRGs of the RA donors. Additionally, we saw the upregulation in genes implicated in neurogenesis that could promote pain hypersensitivity. overall, our DRG analysis suggests that there are upregulated inflammatory and pain signaling pathways that can contribute to chronic pain in RA.

Can we achieve pain stratification in musculoskeletal conditions? Implications for clinical practice

In the last few years there has been an increased appreciation that pain perception in rheumatic and musculoskeletal diseases (RMDs) has several mechanisms which include nociceptive, inflammatory, nociplastic and neuropathic components. Studies in specific patient groups have also demonstrated that the pain experienced by people with specific diagnoses can present with distinctive components over time. For example, the pain observed in rheumatoid arthritis has been widely accepted to be caused by the activation of nociceptors, potentiated by the release of inflammatory mediators, including prostaglandins, leukotrienes and cytokine networks in the joint environment. However, people with RA may also experience nociplastic and neuropathic pain components, particularly when treatments with disease modifying anti-rheumatic drugs (DMARDs) have been implemented and are insufficient to control pain symptoms. In other RMDs, the concept of pain sensitisation or nociplastic pain in driving ongoing pain symptoms e.g. osteoarthritis and fibromyalgia, is becoming increasingly recognised. In this review, we explore the hypothesis that pain has distinct modalities based on clinical, pathophysiological, imaging and genetic factors. The concept of pain stratification in RMD is explored and implications for future management are also discussed.

Pain in axial spondyloarthritis: role of the JAK/STAT pathway

Axial spondyloarthritis (axSpA) is a chronic inflammatory disease that is characterized by new bone formation in the axial musculoskeletal system, with X-ray discriminating between radiographic and non-radiographic forms. Current therapeutic options include non-steroidal anti-inflammatory drugs in addition to biological disease-modifying anti-rheumatic drugs that specifically target tumor necrosis factor-alpha (TNFα) or interleukin (IL)-17. Pain is the most critical symptom for axSpA patients, significantly contributing to the burden of disease and impacting daily life. While the inflammatory process exerts a major role in determining pain in the early phases of the disease, the symptom may also result from mechanical and neuromuscular causes that require complex, multi-faceted pharmacologic and non-pharmacologic treatment, especially in the later phases. In clinical practice, pain often persists and does not respond further despite the absence of inflammatory disease activity. Cytokines involved in axSpA pathogenesis interact directly/indirectly with the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling cascade, a fundamental component in the origin and development of spondyloarthropathies. The JAK/STAT pathway also plays an important role in nociception, and new-generation JAK inhibitors have demonstrated rapid pain relief. We provide a comprehensive review of the different pain types observed in axSpA and the potential role of JAK/STAT signaling in this context, with specific focus on data from preclinical studies and data from clinical trials with JAK inhibitors.

Potential mechanism of tea for treating osteoporosis, osteoarthritis, and rheumatoid arthritis

Osteoporosis (OP), osteoarthritis (OA), and rheumatoid arthritis (RA) are common bone and joint diseases with a high incidence and long duration. Thus, these conditions can affect the lives of middle-aged and elderly people. Tea drinking is a traditional lifestyle in China, and the long-term intake of tea and its active ingredients is beneficial to human health. However, the mechanisms of action of tea and its active ingredients against OP, OA, and RA are not completely elucidated. This study aimed to assess the therapeutic role and related mechanisms of tea and its active ingredients in OP, OA, and RA. Moreover, it expanded the potential mechanisms of tea efficacy based on network pharmacology and molecular docking. Results showed that tea has potential anti-COX properties and hormone-like effects. Compared with a single component, different tea components synergize or antagonize each other, thereby resulting in a more evident dual effect. In conclusion, tea has great potential in the medical and healthcare fields. Nevertheless, further research on the composition, proportion, and synergistic mechanism of several tea components should be performed.

Sex-related differences in patient characteristics, and efficacy and safety of advanced therapies in randomised clinical trials in psoriatic arthritis: a systematic literature review and meta-analysis

BACKGROUND

Sex-related differences in clinical manifestations and disease outcomes exist in psoriatic arthritis, however, there is limited information on sex-related differences in randomised controlled trials of psoriatic arthritis. We aimed to compare patient characteristics and efficacy and safety of advanced therapies (including biological and targeted synthetic therapies) between male and female patients with psoriatic arthritis participating in randomised controlled trials.

METHODS

In this systematic review and meta-analysis, we searched Medline, Embase, and Central databases, and conference abstract archives, from their inception to June 10, 2022, for randomised controlled trials that assessed the efficacy of advanced therapies in psoriatic arthritis. Two reviewers extracted information on participants' characteristics and rates of American College of Rheumatology (ACR) 20 and ACR50 response and minimal disease activity (MDA) by sex. Random-effects models were used to calculate pooled effects of ACR20, ACR50, and MDA in male versus female patients by drug class.

FINDINGS

We included 54 trials (11 514 [50·9%] of 22 621 participants were female and 11 107 [49·1%] were male). Sex-disaggregated results were reported in a minority of studies (nine [17%] of 54 reported baseline characteristics by sex, 18 [33%] reported efficacy by sex, and two [4%] reported safety endpoints by sex). At baseline, male patients had lower baseline tender joint count (mean difference -3·01 [95% CI -3·83 to -2·18], health assessment questionnaire scores (-0·28 [-0·33 to -0·24]), pain scores (-4·58 [-6·86 to -2·30]), patient global assessment (-3·22 [-5·27 to -1·17]), and physician global assessment (-1·34 [-2·08 to -0·08]) than did female patients. Male patients had higher baseline psoriasis area and severity index scores (mean difference 1·95 [95% CI 0·78 to 3·11]) and C-reactive protein concentrations (2·57 [0·40 to 4·74]) than did female patients. ACR20 response by sex varied across drug classes, with higher rates in males than females with interleukin (IL)-17 inhibitors (odds ratio [OR] 1·70 [95% CI 1·38-2·11]), IL-23 inhibitor (1·46 [1·20-1·78]), IL-12 and IL-23 inhibitor (2·67 [1·39-5·09]), and tumour necrosis factor (TNF) inhibitors (1·55 [1·11-2·18]), but no difference with JAK and TYK2 inhibitors (1·10 [0·87-1·38]). Similarly, ACR50 response rates were higher in male patients versus female patients in all drug classes, with exception of JAK and TYK2 inhibitors (TNF inhibitors, OR 2·17 [95% CI 1·62-2·90]; IL-17 inhibitors, 1·93 [1·56-2·38]; IL-23 inhibitor, 1·71 [1·25-2·34]; IL-12 and 23 inhibitor, 2·43 [1·14-5·20]; and JAK and TYK2 inhibitors, 1·09 [0·73-1·62]). Male patients were more likely to reach MDA with most drug classes, including IL-17 inhibitors (OR 1·99 [95% CI 1·50-2·63]), IL-23 inhibitors (1·79 [1·29-2·50]), TNF inhibitors (2·62 [1·54-4·44]), and JAK and TYK2 inhibitors (1·77 [1·15-2·73]). Risk of bias was low for most studies.

INTERPRETATION

Biological sex of patients with psoriatic arthritis influences their response to advanced therapies, but the effect varies by drug class. Selective reporting might have influenced these results. Future trials should report baseline characteristics and endpoint results by sex.

FUNDING

Canadian Rheumatology Association.