Mechanistic pain profiling as a tool to predict the efficacy of 3-week nonsteroidal anti-inflammatory drugs plus paracetamol in patients with painful knee osteoarthritis

Update on pain in arthritis

PURPOSE OF REVIEW

Osteoarthritis is a degenerative joint disease that features pain as a hallmark symptom. This review summarises progress and obstacles in our understanding of pain mechanisms in arthritis.

RECENT FINDINGS

Pain phenotypes in osteoarthritis are poorly characterized in clinical studies and animal studies are largely carti-centric. Different animal models incur variable disease progression patterns and activation of distinct pain pathways, but studies reporting both structural and pain outcomes permit better translational insights. In patients, classification of osteoarthritis disease severity is only based on structural integrity of the joint, but pain outcomes do not consistently correlate with joint damage. The complexity of this relationship underlines the need for pain detection in criteria for osteoarthritis classification and patient-reported outcome measures.

SUMMARY

Variable inflammatory and neuropathic components and spatiotemporal evolution underlie the heterogeneity of osteoarthritis pain phenotypes, which must be considered to adequately stratify patients. Revised classification of osteoarthritis at different stages encompassing both structural and pain outcomes would significantly improve detection and diagnosis at both early and late stages of disease. These are necessary advancements in the field that would also improve trial design and provide better understanding of basic mechanisms of disease progression and pain in osteoarthritis.

Undenatured Type II Collagen Ameliorates Inflammatory Responses and Articular Cartilage Damage in the Rat Model of Osteoarthritis

Osteoarthritis (OA) is an age-related joint disease that includes gradual disruption of the articular cartilage and the resulting pain. The present study was designed to test the effects of undenatured type II collagen (UC-II®) on joint inflammation in the monoiodoacetate (MIA) OA model. We also investigated possible mechanisms underlying these effects. Female Wistar rats were divided into three groups: (i) Control; (ii) MIA-induced rats treated with vehicle; (iii) MIA-induced rats treated with UC-II (4 mg/kg BW). OA was induced in rats by intra-articular injection of MIA (1 mg) after seven days of UC-II treatment. UC-II reduced MIA-induced Kellgren-Lawrence scoring (53.3%, P < 0.05). The serum levels of inflammatory cytokines [IL-1β (7.8%), IL-6 (18.0%), TNF-α (25.9%), COMP (16.4%), CRP (32.4%)] were reduced in UC-II supplemented group (P < 0.0001). In the articular cartilage, UC-II inhibited the production of PGE2 (19.6%) and the expression of IL-1β, IL-6, TNF-a, COX-2, MCP-1, NF-κB, MMP-3, RANKL (P < 0.001). The COL-1 and OPG levels were increased, and MDA decreased in UC-II supplemented rats (P < 0.001). UC-II could be useful to alleviate joint inflammation and pain in OA joints by reducing the expression of inflammatory mediators.

Expression profiles of long non-coding RNAs in the cartilage of patients with knee osteoarthritis and normal individuals

Knee osteoarthritis is caused by a multifactorial imbalance in the synthesis and degradation of knee chondrocytes, subchondral bone and extracellular matrix. Abnormal expression of long non-coding RNAs (lncRNAs) affects the metabolism, synovitis, autophagy and apoptosis of chondrocytes, as well as the production of cartilage matrix. The aim of the present study was to identify novel targets for the treatment of osteoarthritis and to examine the pathogenesis of the disease. The lncRNA expression profiles of seven patients with knee osteoarthritis and six healthy controls were examined by RNA-sequencing. Differentially expressed lncRNAs were selected for bioinformatics analyses, including Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment. Reverse transcription-quantitative PCR (RT-qPCR) was used to further investigate the differential expression of the lncRNAs. A total of 23,583 lncRNAs were identified in osteoarthritis cartilage, including 5,255 upregulated and 5,690 downregulated lncRNAs, compared with normal cartilage. Although there were more downregulated lncRNAs compared with upregulated lncRNAs, among the changed lncRNAs (fold-change >6), there were more upregulated lncRNAs compared with downregulated lncRNAs. Several lncRNAs exhibiting differences were identified as potential therapeutic targets in knee osteoarthritis. GO and KEGG pathway analyses were performed for the target genes of the differentially expressed lncRNAs. RT-qPCR validation was performed on three randomly selected upregulated and downregulated lncRNAs. The results of RT-qPCR were consistent with the findings obtained by RNA-sequencing analysis. The findings from the present study may contribute to the diagnosis of osteoarthritis and may predict the development of osteoarthritis. Furthermore, the differentially expressed lncRNAs may aid in the identification of novel candidate targets for the treatment of knee osteoarthritis.

Recent advances in understanding the phenotypes of osteoarthritis

Recent research in the field of osteoarthritis (OA) has focused on understanding the underlying molecular and clinical phenotypes of the disease. This narrative review article focuses on recent advances in our understanding of the phenotypes of OA and proposes that the disease represents a diversity of clinical phenotypes that are underpinned by a number of molecular mechanisms, which may be shared by several phenotypes and targeted more specifically for therapeutic purposes. The clinical phenotypes of OA supposedly have different underlying etiologies and pathogenic pathways and they progress at different rates. Large OA population cohorts consist of a majority of patients whose disease progresses slowly and a minority of individuals whose disease may progress faster. The ability to identify the people with relatively rapidly progressing OA can transform clinical trials and enhance their efficiency. The identification, characterization, and classification of molecular phenotypes of rapidly progressing OA, which represent patients who may benefit most from intervention, could potentially serve as the basis for precision medicine for this disabling condition. Imaging and biochemical markers (biomarkers) are important diagnostic and research tools that can assist with this challenge.

Total sleep deprivation increases pain sensitivity, impairs conditioned pain modulation and facilitates temporal summation of pain in healthy participants

Chronic pain patients often suffer from insomnia or impaired sleep which has been associated with increased pain sensitivity, but a limited amount of studies have investigated the effects of total sleep deprivation on central pain mechanisms. Therefore, the aim of this study was to determine the effects of total sleep deprivation on temporal summation, conditioned pain modulation, thermal and pressure pain sensitivity in healthy participants. Twenty-four healthy participants took part in this two-session trial. The measurements were conducted after a night of habitual sleep (baseline) and following 24 hours of total sleep deprivation. Detection thresholds for cold and warmth and pain thresholds for cold and heat were assessed. Cuff induced pressure pain detection and tolerance thresholds, temporal summation and conditioned pain modulation were assessed with user-independent, computer-controlled cuff algometry. Conditioned pain modulation was significantly impaired, temporal summation was significantly facilitated and pain sensitivity to pressure and cold pain were significantly increased at follow-up compared with baseline. In conclusion, this study found that one night of total sleep deprivation impaired descending pain pathways, facilitated spinal excitability and sensitized peripheral pathways to cold and pressure pain. Future studies are encouraged to investigate if sleep therapy might normalize pain sensitivity in sleep-deprived chronic pain patients.

Best Evidence Rehabilitation for Chronic Pain Part 5: Osteoarthritis

Osteoarthritis (OA) is a leading cause of chronic pain and disability in older adults, which most commonly affects the joints of the knee, hip, and hand. To date, there are no established disease modifying interventions that can halt or reverse OA progression. Therefore, treatment is focused on alleviating pain and maintaining or improving physical and psychological function. Rehabilitation is widely recommended as first-line treatment for OA as, in many cases, it is safer and more effective than the best-established pharmacological interventions. In this article, we describe the presentation of OA pain and give an overview of its peripheral and central mechanisms. We then provide a state-of-the-art review of rehabilitation for OA pain—including self-management programs, exercise, weight loss, cognitive behavioral therapy, adjunct therapies, and the use of aids and devices. Next, we explore several promising directions for clinical practice, including novel education strategies to target unhelpful illness and treatment beliefs, methods to enhance the efficacy of exercise interventions, and innovative, brain-directed treatments. Finally, we discuss potential future research in areas, such as treatment adherence and personalized rehabilitation for OA pain.

Pretreatment with AM1241 Enhances the Analgesic Effect of Intrathecally Administrated Mesenchymal Stem Cells

Mesenchymal stem cells have cannabinoid (CB) receptors type 1 and type 2 and can alleviate a variety of neuropathic pains, including chronic constriction injury (CCI). A selective CB2 receptor agonist is AM1241. In the present study, it was found that mice with CCI displayed a longer duration of mechanical and thermal analgesia when intrathecally (i.t.) injected with AM1241-treated mesenchymal stem cells, compared to those injected with untreated mesenchymal stem cells or AM1241 alone. Moreover, CCI-induced upregulation of the phosphorylated extracellular signal-regulated kinase (ERK) 1/2 (p-ERK1/2) was inhibited following i.t. injection of AM1241-treated mesenchymal stem cells and this inhibition was noticeably higher compared to injection with untreated mesenchymal stem cells. The expression of transforming growth factor-β1 (TGF-β1) was also analyzed in the dorsal root ganglion (DRGs) and spinal cord of CCI mice. In untreated CCI mice, expression of TGF-β1 was increased, whereas pretreatment with AM1241-treated mesenchymal stem cells regulated the expression of TGF-β1 on 10 days and 19 days after surgery. In addition, i.t. injection of exogenous TGF-β1 slightly alleviated neuropathic pain whilst neutralization of TGF-β1 potently blocked the effect of AM1241-treated mesenchymal stem cells on thermal hyperalgesia and mechanical allodynia of CCI mice. In an in vitro experiment, AM1241 could enhance the release of TGF-β1 in the supernatant of BMSCs after lipopolysaccharide (LPS) simulation. Taken together, the findings of the current study show that i.t. administration of AM1241-treated mesenchymal stem cells has a positive effect on analgesia and that TGF-β1 and p-ERK1/2 may be the molecular signaling pathway involved in this process.

[What factors affect the effectiveness of long - term analgesic therapy for osteoarthritis? Data analysis of the multi - center 3-month PARACELSUS study]

There are factors that can affect the effectiveness of treatment of osteoarthritis (OA). Aim to identify factors affecting the effectiveness of long - term analgesic therapy in OA. Materials and methods. The study included 6448 patients (70.9% female and 29.1% male), middle age 57.8±10.2 years, with severe pain [≥40 mm on the visual analog scale]. All patients received the preparation of avocado - soybean unsaponifiables (ASU) 300 mg/day. For pain relief at the beginning and during the study, the drug Ketoprofen lysine salt (KLS) 320 mg/day was used. The efficiency criterion was pain reduction ≥50% and satisfaction with treatment ≥4 on a 5-point scale. The influence of a number of factors on the result of treatment was evaluated. Results. For 3 months of treatment, the pain decreased from 63.7±12.0 to 14.2±11.7 mm VAS. The result was evaluated as "good" or "excellent" 81.7% of patients. Adverse reactions were rare. In total, a good response to therapy was noted in 87.4% of patients. Gender, body mass index ≥30 kg/m2, type 2 diabetes mellitus, poor effect of non - steroidal anti - inflammatory drugs (NSAIDs) and Symptomatic Slow-Acting Drugs in Osteoarthritis (SYSADOA) in history did not affect the result. The effect was lower in persons >65 years [odds ratio (OR) 0.418; 95% confidence interval (CI) 0.342-0.509, p2 by Kellgren-Lawrence (OR 0.556; 95% CI 0.298-0.738, p.