Nerve growth factor in rheumatic diseases

Sex-dependent effects of the targeted nerve growth factor mutation (R100E) on pain behavior, joint inflammation, and bone erosion in mice

ABSTRACT

Nerve growth factor (NGF)-R100E is a mutated form of human recombinant NGF that reduces the binding of NGF to its p75NTR receptor while retaining its affinity toward the TrkA receptor. Here, we used human wild type NGF and NGF-R100E knock-in mice to investigate the effects of this NGF mutation on inflammation-induced pain-related behaviors and bone loss. The hNGF-R100E mutation did not alter the nerve fiber density in the sciatic nerve, ankle joint synovium, and skin of naïve mice. Withdrawal responses to mechanical, thermal, and cold stimuli before and after joint inflammation induced by intra-articular injection of complete Freund adjuvant (CFA) were similar between human recombinant nerve growth factor-wild type and hNGF-R100E male and female mice while weight bearing and gait analysis revealed significant differences. Intriguingly, hNGF-R100E male and female mice showed only mild changes, indicating lower degrees of deep joint-related pain compared to their wild type counterparts. Furthermore, micro-CT analysis demonstrated that hNGF-R100E female mice, but not males, were protected from CFA-induced bone loss, and mRNA analysis showed a different gene regulation indicating a sex-dependent relationship between NGF, inflammation, and bone loss. In conclusion, our study reveals that the hNGF-R100E mutation renders mice insensitive to inflammation-induced impact on joint loading and gait while preserving the development of the peripheral nociceptive neurons and sensitivity to punctate stimulation of the skin. Notably, the mutation uncovers a sex-dependent relationship between NGF and inflammation-induced bone loss. These findings offer valuable insights into NGF as a target for pain management and the interplay between NGF and bone architecture.

CCL19-Positive Lymph Node Stromal Cells Govern the Onset of Inflammatory Arthritis via Tropomyosin Receptor Kinase

OBJECTIVE

The study objective was to assess the role of CCL19+ lymph node stromal cells of the joint-draining popliteal lymph node (pLN) for the development of arthritis.

METHODS

CCL19+ lymph node stromal cells were spatiotemporally depleted for five days in the pLN before the onset of collagen-induced arthritis (CIA) using Ccl19-Cre × iDTR mice. In addition, therapeutic treatment with recombinant CCL19-immunoglobulin G (IgG), locally injected in the footpad, was used to confirm the results. RNA sequencing of lymph node stromal cells combined with T cell coculture assays using tropomyosin receptor kinase (Trk) family inhibitors together with in vivo local pLN small interfering RNA (siRNA) treatments were used to elucidate the pathway by which CCL19+ lymph node stromal cells initiate the onset of arthritis.

RESULTS

Spatiotemporal depletion of CCL19+ lymph node stromal cells prevented disease onset in CIA mice. These inhibitory effects could be mimicked by local CCL19-IgG treatment. The messenger RNA sequencing analyses showed that CCL19+ lymph node stromal cells down-regulated the expression of the tropomyosin receptor kinase A (TrkA) just before disease onset. Blocking TrkA in lymph node stromal cells led to increased T cell proliferation in in vitro coculture assays. Similar effects were observed with the pan-Trk inhibitor larotrectinib in cocultures of lymph node stromal cells of patients with rheumatoid arthritis and T cells. Finally, local pLN treatment with TrkA inhibitor and TrkA siRNA led to exacerbated arthritis scores.

CONCLUSION

CCL19+ lymph node stromal cells are crucially involved in the development of inflammatory arthritis. Therefore, targeting of CCL19+ lymph node stromal cells via TRK could provide a tool to prevent arthritis.

NGF facilitates ICAM-1-dependent monocyte adhesion and M1 macrophage polarization in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disorder in which monocytes adhering to synovial tissue differentiate into the pro-inflammatory M1 macrophage phenotype. Nerve growth factors (NGF) referred to as neurotrophins have been associated with inflammatory events; however, researchers have yet to elucidate the role of NGF in RA. Our examination of clinical tissue samples and analysis of data sourced from the Gene Expression Omnibus dataset unveiled elevated expression levels of M1 macrophage markers in human RA synovial tissue samples compared to normal tissue, with no such distinction observed for M2 markers. Furthermore, immunofluorescence data depicted increased expression levels of NGF and M1 macrophages in RA mice in contrast to normal mice. It appears that NGF stimulation facilitates macrophage polarization from the M0 to the M1 phenotype. It also appears that NGF promotes ICAM-1 production in human RA synovial fibroblasts, which enhances monocyte adhesion through the TrkA, MEK/ERK, and AP-1 signaling cascades. Our findings indicate NGF/TrkA axis as a novel target for the treatment of RA.

Salivary Biomarkers and Temporomandibular Disorders: A Systematic Review conducted according to PRISMA guidelines and the Cochrane Handbook for Systematic Reviews of Interventions

BACKGROUND

The present review aimed to investigate the association between salivary biomarkers and temporomandibular disorders (TMD). TMD is a multifactorial condition characterised by pain and dysfunction in the temporomandibular joint (TMJ) and surrounding structures. Salivary biomarkers have emerged as potential diagnostic tools due to their non-invasiveness and easy accessibility. However, the literature on salivary biomarkers in relation to TMD is limited and inconsistent.

METHODS

Electronic databases of Pubmed, Embase, Web of Science, Scopus, Cochrane Library, PsychINFO, CINAHL and Medline were searched using specific search terms and Boolean operators. The search was limited to articles published in English that assessed salivary biomarkers in individuals diagnosed with TMD. Two reviewers independently screened the articles and extracted data. ROB-2 was used to assess the risk of bias.

RESULTS

Eleven clinical papers met the inclusion criteria and were included in the review. The findings provided consistent evidence of a clear association between salivary biomarkers and TMD. Various biomarkers, including cortisol, IL-1, glutamate and several others, were assessed. Some studies reported higher levels of cortisol and IL-1 in TMD patients, indicating potential involvement in stress and inflammation. Glutamate levels were found to be elevated, suggesting a role in pain modulation. Other biomarkers also showed alterations in TMD patients compared to controls: CONCLUSION: The findings from the included studies suggest that salivary biomarkers may play a role in TMD pathophysiology. Though a definitive conclusion can be drawn regarding the specific salivary biomarkers and their association with TMD, the results must be interpreted with caution considering the heterogeneity of the biomarkers assessed. Further research with larger sample sizes, standardised methodology and rigorous study designs is needed to elucidate the role of salivary biomarkers in TMD.

Nerve Growth Factor and Autoimmune Diseases

NGF plays a crucial immunomodulatory role and increased levels are found in numerous tissues during autoimmune states. NGF directly modulates innate and adaptive immune responses of B and T cells and causes the release of neuropeptides and neurotransmitters controlling the immune system activation in inflamed tissues. Evidence suggests that NGF is involved in the pathogenesis of numerous immune diseases including autoimmune thyroiditis, chronic arthritis, multiple sclerosis, systemic lupus erythematosus, mastocytosis, and chronic granulomatous disease. Furthermore, as NGF levels have been linked to disease severity, it could be considered an optimal early biomarker to identify therapeutic approach efficacy. In conclusion, by gaining insights into how these molecules function and which cells they interact with, future studies can devise targeted therapies to address various neurological, immunological, and other disorders more effectively. This knowledge may pave the way for innovative treatments based on NGF manipulation aimed at improving the quality of life for individuals affected by diseases involving neurotrophins.

Salivary biomarkers and temporomandibular disorders: A systematic review

Temporomandibular disorders (TMD) are a common condition affecting the musculoskeletal group evoking clinical signs such as pain, restricted mouth opening, and disability in the temporomandibular joint (TMJ), masticatory musculature, and the osseous structures in the surroundings. Saliva is a strong proponent of a diagnostic and prognostic tool for TMDs. Hence, a systematic review was undertaken to answer the research question "What is the role of salivary biomarkers in the identification of TMD?" A thorough literature search was performed in databases of PubMed, Embase, and Google Scholar till February 2022. Every included study was characterized by Study ID, location, sample size, demographic information, biomarker analysis, assessment method, and results. Newcastle-Ottawa scale was used to assess the methodological quality of all qualifying research. A total of eight articles were included for the review after screening the titles, abstracts, and full-text articles. The review included articles of observational design with a control group. TMD disorders were confirmed both clinically and radiographically in the study of Shoukri et al. TMDs are commonly prevalent in maxillofacial conditions. Despite the availability of various diagnostic techniques, certain limitations are remarkable. The researchers are yet to ascertain a gold standard biomarker to identify TMD.

Office-Based Intraosseous Infiltrations of PRGF as an Effective Treatment for Knee Osteoarthritis: A Retrospective Observational Clinical Study

The aim of this study was to explore and assess office-based ultrasound-guided intraosseous and intra-articular infiltrations of plasma rich in growth factors (PRGF) in patients with moderate and severe knee osteoarthritis (KOA). Seventy-nine patients (30 women and 49 men) with grade 3-4 KOA according to the Kellgren-Lawrence classification participated in the study. All patients were treated with a minimally invasive technique using local anesthesia WALANT (wide-awake local anesthesia no tourniquet) in the ambulatory setting. A PRGF intra-articular infiltration and two intraosseous infiltrations in the tibial plateau and femoral condyle were performed weekly for a total of three sessions. The evaluation of the results was carried out using knee injury and osteoarthritis outcome score (KOOS) at baseline and post-treatment. After a follow-up period of 11 months (median) [interquartile range, 7-14], all the KOOS domains showed statistically significant improvement (p < 0.001). Moreover, 88% of the patients showed a pain reduction of at least 10 points (minimally clinically important improvement) from pre- to post-treatment. Our retrospective study using the in-office procedure of ultrasound-guided combination of intra-articular and intraosseous infiltrations of PRGF is a safe and efficacious approach for the treatment of grade 3-4 knee osteoarthritis.

Nerve growth factor mediates activation of transient receptor potential vanilloid 1 in neurogenic pruritus of psoriasis

Pruritus is a common and painful symptom in psoriasis with profoundly negative impacts on quality of life. The underlying mechanisms of pruritus are complex and multifactorial, and accumulating evidence suggests that pruritus induced by neurogenic inflammation predominates in psoriasis. Nerve growth factor (NGF) -mediated transient receptor potential vanilloid receptor 1(TRPV1) pathway has emerged as a crucial node in the regulation of neurogenic pruritus. TRPV1 appears coupled to most pruritus-specific molecules via the neuro-immune axis. While the modes of regulation differ for each axis, TRPV1 is involved in substantial biochemical crosstalk-causing feedback loops with significant effects on neurogenic pruritus. Therefore, TRPV1 has emerged as a target molecular in drug development for pruritus in psoriasis. However, no significant clinical progress occurred in the development of systemic TRPV1 antagonists due to elevated core temperature. Thus, topical application of TRPV1 antagonists and interference with mediators linked to the TRPV1 activation pathway may be promising therapeutic options to ameliorate pruritus. This Review focuses on recent advances in complicated regulation of NGF-mediated TRPV1 pathway in psoriatic neurogenic pruritus, as well as the therapeutic options that arise from the dissection of the pathway.

Does anti-nerve growth factor monoclonal antibody treatment have the potential to replace nonsteroidal anti-inflammatory drugs and opioids in treating hip or knee osteoarthritis? A systematic review of randomized controlled trials

Purpose

Considering the adverse effects of nonsteroidal anti-inflammatory drugs (NSAIDs) and opioids for treating osteoarthritis (OA), development of drugs that are more effective and better tolerated than existing treatments is urgently needed. This systematic review aimed to evaluate the efficacy and safety of anti-nerve growth factor (NGF) monoclonal antibodies vs active comparator therapy, such as NSAIDs and oxycodone, in treating hip or knee OA.

Methods

Databases were comprehensively searched for randomized controlled trials (RCTs) published before January 2022. Efficacy and safety outcomes were assessed.

Results

Six RCTs that included 4325 patients were identified. Almost all the RCTs indicated that moderate doses of anti-NGF monoclonal antibody treatment significantly improved efficacy outcomes based on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain score, the WOMAC physical function score and the Patient's Global Assessment compared with those of the active comparator. At least half of the RCTs indicated that the incidence of severe adverse events, withdrawals due to adverse events (AEs) and total joint replacement were not significantly different between anti-NGF monoclonal antibody treatment and active comparator therapy, but the outcomes of some studies may have been limited by a short duration of follow-up. Most RCTs suggested that anti-NGF monoclonal antibody treatment had a lower incidence of gastrointestinal and cardiovascular AEs. However, the majority of RCTs reported a higher incidence of abnormal peripheral sensation with anti-NGF monoclonal antibody treatment. Furthermore, the higher incidence of rapidly progressive osteoarthritis (RPOA) with anti-NGF monoclonal antibody treatment should also not be overlooked, and the identification of patient characteristics that increase the risk of RPOA is critical in further studies.

Conclusion

Based on the current research evidence, anti-NGF monoclonal antibodies are not yet a replacement for analgesic drugs such as NSAIDs but might be a new treatment option for hip or knee OA patients who are intolerant or unresponsive to nonopioid or opioid treatment. Notably, however, considering the inconsistency and inconclusive evidence on the safety outcomes of recent studies, more research is needed, and long-term follow-up is required.

Peripheral nerves in the tibial subchondral bone : the role of pain and homeostasis in osteoarthritis

Osteoarthritis (OA) is a highly prevalent degenerative joint disorder characterized by joint pain and physical disability. Aberrant subchondral bone induces pathological changes and is a major source of pain in OA. In the subchondral bone, which is highly innervated, nerves have dual roles in pain sensation and bone homeostasis regulation. The interaction between peripheral nerves and target cells in the subchondral bone, and the interplay between the sensory and sympathetic nervous systems, allow peripheral nerves to regulate subchondral bone homeostasis. Alterations in peripheral innervation and local transmitters are closely related to changes in nociception and subchondral bone homeostasis, and affect the progression of OA. Recent literature has substantially expanded our understanding of the physiological and pathological distribution and function of specific subtypes of neurones in bone. This review summarizes the types and distribution of nerves detected in the tibial subchondral bone, their cellular and molecular interactions with bone cells that regulate subchondral bone homeostasis, and their role in OA pain. A comprehensive understanding and further investigation of the functions of peripheral innervation in the subchondral bone will help to develop novel therapeutic approaches to effectively prevent OA, and alleviate OA pain.

Cite this article: Bone Joint Res 2022;11(7):439–452.

Localization of Nerve Growth Factor Expression to Structurally Damaged Cartilaginous Tissues in Human Lumbar Facet Joint Osteoarthritis

Purpose

Nerve Growth Factor (NGF) is a pivotal mediator of chronic pain and plays a role in bone remodelling. Through its high affinity receptor TrkA, NGF induces substance P (SP) as key downstream mediator of pain and local inflammation. Here we analysed NGF, TrkA and SP tissue distribution in facet joint osteoarthritis (FJOA), a major cause of chronic low back pain.

Methods

FJOA specimens (n=19) were harvested from patients undergoing intervertebral fusion surgery. Radiologic grading of FJOA and spinal stenosis, followed by immunohistochemistry for NGF, TrkA and SP on consecutive tissue sections, was performed in ten specimens. Explant cultures (n=9) were used to assess secretion of NGF, IL-6, and SP by FJOA osteochondral tissues under basal and inflammatory conditions.

Results

NGF was predominantly expressed in damaged cartilaginous tissues (80%), occasionally in bone marrow (20%), but not in osteochondral vascular channels. NGF area fraction in cartilage was not associated with the extent of proteoglycan loss or radiologic FJOA severity. Consecutive sections showed that NGF and SP expression was localized at structurally damaged cartilage, in absence of TrkA expression. SP and TrkA were expressed in subchondral bone marrow in both presence and absence of NGF. Low level NGF, but not SP secretion, was detected in four out of eighteen FJOA explants under both basal or inflammatory conditions (n=2 each).

Conclusion

NGF is associated with SP expression and structural cartilage damage in osteoarthritic facet joints, but not with radiologic disease severity. NGF tissue distribution in FJOA differs from predominant subchondral bone expression reported for knee OA.

Fitness Levels and Gender Are Related With the Response of Plasma Adipokines and Inflammatory Cytokines in Prepubertal Children

Background and Aim

Changes in adipokines have been related with the development of metabolic syndrome, frequently associated with obesity, and other risk factors. Fitness seems to promote a healthy cardiovascular status and could be a protector factor, just from childhood. Therefore, the present study aimed to evaluate the relationship between fitness levels with plasma adipokines and inflammatory biomarkers in prepubertal children.

Methods

One hundred and thirty-seven healthy normal-weight prepubertal children were recruited from local schools and divided after performing the fitness tests, into two groups according to fitness level—low cardiovascular fitness group (LF) and equal or higher cardiovascular fitness group (HF). Anthropometric variables, blood pressure (BP) and plasma insulin, and leptin, resistin, adiponectin, tumor necrosis factor-alpha, hepatic growth factor, interleukin (IL)-8, monocyte chemoattractant protein-1, nerve growth factor (NGF), and plasminogen activator inhibitor-1 (PAI-1) were measured fasting in both groups to be compared. Univariate analysis of variance, comparative analysis, binary logistic regression, stepwise linear regression, and principal component analysis were conducted to evaluate the association between fitness, BMI, gender, and the biochemical parameters.

Results

Girls and boys with HF presented lower waist circumference Z-score, BMI Z-score, systolic BP (only boys) as well as lower levels of leptin and NGF compared with their respective LF group. Regarding the association between variables, fitness showed an inverse relationship with BMI Z-score, leptin, PAI-1, HOMA-IR, resistin, IL-8, and NGF.

Conclusion

An adequate level of fitness seems to protect against risk factors related to low-grade inflammation and altered adipokines that are related to the onset of obesity just from the prepubertal stage.

Based on minimal clinically important difference values, a moderate dose of tanezumab may be a better option for treating hip or knee osteoarthritis: a meta-analysis of randomized controlled trials

Background:

Tanezumab is a nerve growth factor monoclonal antibody that may regulate pain in hip or knee osteoarthritis (OA). This meta-analysis was performed to evaluate the efficacy and safety of low and moderate doses of tanezumab in treating hip or knee OA.

Methods:

PubMed, EMBASE, the Cochrane Library, and Web of Science were comprehensively searched for clinical trials published before 1 May 2021. Patients were assessed via efficacy and safety outcomes.

Results:

Twelve randomized controlled trials including 6022 patients were identified. Both low and moderate doses of tanezumab significantly improved efficacy outcomes. However, only the point estimates (mean difference, MD) of moderate-dose tanezumab significantly exceeded the minimal clinically important differences (MCIDs). There were no significant differences in the incidence of treatment-related adverse events (AEs), withdrawals due to AEs, serious AEs, and total joint replacement between the tanezumab and placebo groups, whereas the incidence of AEs was higher in the tanezumab group (relative risk, RR = 1.10; 95% confidence interval, 95% CI = 1.04–1.17). The incidence of rapidly progressive OA was significantly higher in the combined low- and moderate-dose tanezumab groups than in the placebo group (RR = 5.01; 95% CI = 1.17–21.33). Furthermore, both low and moderate doses of tanezumab significantly increased the incidence of abnormal peripheral sensation (RR = 1.99, 95% CI = 1.21–3.28; RR = 2.64, 95% CI = 1.91–3.67, respectively). Compared with nonsteroidal anti-inflammatory drugs (NSAIDs) and opioids, tanezumab showed significantly improved efficacy outcomes (p < 0.05). However, the point estimates (MD) of tanezumab were not greater than the MCID. Pooled analysis showed no significant differences between tanezumab and NSAIDs and opioids in safety outcomes (p > 0.05).

Conclusion:

Tanezumab is efficacious in patients with hip or knee OA. Tanezumab is relatively well tolerated and safe but increases the incidence of AEs and reversible abnormal peripheral sensation. Additional studies on the occurrence of rapidly progressive OA are needed. A moderate dose of tanezumab may maximize the benefits for hip or knee OA.

Neuropathic pain in primary knee osteoarthritis patients: correlation with physical function, quality of life, disease severity, and serum beta nerve growth factor levels

Background

Neuropathic mechanisms are thought to play a role in knee osteoarthritis (KOA) pain. Neuropathic pain questionnaires can promote diagnosis of a neuropathic component. Thus, we aimed to assess the frequency of neuropathic pain in primary KOA patients (using clinical questionnaires) and to investigate its correlation with socio-demographic factors, physical function, quality of life, disease severity, and serum beta nerve growth factor (β-NGF) levels.

Results

Seventy primary KOA patients were included. Neuropathic pain was detected in 52.9% of patients based on Douleur Neuropathique en 4 Questions (DN4) questionnaire and in 38.6% of patients based on Leeds assessment neuropathic pain symptoms and signs questionnaire (LANSS). Serum β-NGF levels were significantly higher in KOA patients than controls (P<0.0001), and in KOA patients with neuropathic pain compared with patients with non-neuropathic pain. DN4 score was positively correlated with Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain, stiffness, and physical function, and it was also negatively correlated with Osteoarthritis knee hip quality of life questionnaire (OAKHQOL) pain scores (rs=0.459, P<0.001; rs= 0.258, P= 0.031; rs= 0.307, P= 0.010; rs = −0.337, P= 0.004, respectively), while LANSS scale was positively correlated with symptom duration, WOMAC stiffness, Lequesne pain, and Lequesne index (rs= 0.260, P= 0.020; rs= 0.343, P= 0.004; rs= 0.344, P= 0.004; rs= 0.322, P= 0.007) and negatively correlated with OAKHQOL physical, OAKHQOL mental health, OAKHQOL social support, and total OAKHQOL scores (rs= −0.258, P= 0.031;rs= −0.254, P= 0.034; rs= −0.283, P= 0.018; rs= −0.261, P= 0.029 respectively).

Conclusions

Neuropathic pain symptoms are frequent in primary KOA patients. KOA patients with neuropathic pain have worse quality of life, extreme disability, and higher serum β-NGF levels. Nerve growth factor inhibitors could have a potential role for not only relieving pain in KOA patients but also improving functional disability and quality of life in these patients.

Neuroimmune interactions in painful TMD: Mechanisms and treatment implications

The underlying mechanisms and treatment of painful temporomandibular disorders (TMDs) are important but understudied topics in craniofacial research. As a group of musculoskeletal diseases, the onset of painful TMD is proved to be a result of disturbance of multiple systems. Recently, emerging evidence has revealed the involvement of neuroimmune interactions in painful TMD. Inflammatory factors play an important role in peripheral sensitization of temporomandibular joint (TMJ), and neurogenic inflammation in turn enhances TMJs dysfunction in TMD. Furthermore, centralized neuroimmune communications contribute to neuron excitability amplification, leading to pain sensitization, and is also responsible for chronic TMD pain and other CNS symptoms. Therapeutics targeting neuroimmune interactions may shed light on new approaches for treating TMD. In this review, we will discuss the role of neuroimmune interactions in the onset of painful TMD from the peripheral and centralized perspectives, and how understanding this mechanism could provide new treatment options. Insights into the neuroimmune interactions within TMJs and painful TMD would broaden the knowledge of mechanisms and treatments of this multifactorial disease.

Deregulation of the Kallikrein Protease Family in the Salivary Glands of the Sjögren's Syndrome ERdj5 Knockout Mouse Model

Introduction

The purpose of this study was to identify differentially expressed proteins in salivary glands of the ERdj5 knockout mouse model for Sjögren's syndrome and to elucidate possible mechanisms for the morbid phenotype development. At the same time, we describe for the first time the sexual dimorphism of the murine submandibular salivary gland at the proteome level.

Methods

We performed Liquid Chromatography/Mass Spectrometry in salivary gland tissues from both sexes of ERdj5 knockout and 129SV wildtype mice. The resulting list of proteins was evaluated with bioinformatic analysis and selected proteins were validated by western blot and immunohistochemistry and further analyzed at the transcription level by qRT-PCR.

Results

We identified 88 deregulated proteins in females, and 55 in males in wildtype vs knockout comparisons. In both sexes, Kallikrein 1b22 was highly upregulated (fold change>25, ANOVA p<0.0001), while all other proteases of this family were either downregulated or not significantly affected by the genotype. Bioinformatic analysis revealed a possible connection with the downregulated NGF that was further validated by independent methods. Concurrently, we identified 416 proteins that were significantly different in the salivary gland proteome of wildtype female vs male mice and highlighted pathways that could be driving the strong female bias of the pathology.

Conclusion

Our research provides a list of novel targets and supports the involvement of an NGF-mediating proteolytic deregulation pathway as a focus point towards the better understanding of the underlying mechanism of Sjögren's syndrome.

Sexual Dimorphism in the Expression of Pain Phenotype in Preclinical Models of Rheumatoid Arthritis

Rheumatoid arthritis is one of most frequent rheumatic diseases, affecting around 1% of the population worldwide. Pain impacting the quality of life for the patient with rheumatoid arthritis, is often the primary factor leading them to seek medical care. Although sex-related differences in humans and animal models of rheumatoid arthritis are described, the correlation between pain and sex in rheumatoid arthritis has only recently been directly examined. Here we review the literature and explore the mechanisms underlying the expression of the pain phenotype in females and males in preclinical models of rheumatoid arthritis.

Interaction of pain and chronic inflammation

Rheumatic diseases are characterized by chronic inflammation of synovial joints and are often associated with persistent pain and increased pain sensitivity. The inflammatory process is a complex cascade of events involving several mediators, which can lead to a chronic condition of pain. Inflammation can stimulate angiogenesis, and angiogenesis can facilitate inflammation. Inflammatory pain arises from tissue damage via the sensitization of pain receptors (nociceptors). The main peripheral mechanism underlying nociceptive pain is a change in the activity of the nociceptors located in the affected anatomical structures (joints, tendons, and ligaments), which renders them more sensitive to normally painful stimuli (hyperalgesia) or normally non-painful stimuli (allodynia). Neuroimmune interaction has been considered to play an essential role in rheumatic disease. Neurogenic inflammation, which influences normal central nervous system signaling, leads to insufficient signaling/bioavailability of various cytokines. These central mechanisms play an important role in the increased pain sensitivity following inflammation and are responsible for the development of secondary hyperalgesia in regions beyond the injured tissue. Reduction of pain in rheumatic disease requires familiarity with various pain mechanisms.

The evolution of nerve growth factor inhibition in clinical medicine

Nerve growth factor (NGF) is a neurotrophin that activates nociceptive neurons to transmit pain signals from the peripheral to the central nervous system and that exerts its effects on neurons by signalling through tyrosine kinase receptors. Antibodies that inhibit the function of NGF and small molecule inhibitors of NGF receptors have been developed and tested in clinical studies to evaluate the efficacy of NGF inhibition as a form of analgesia in chronic pain states including osteoarthritis and chronic low back pain. Clinical studies in individuals with painful knee and hip osteoarthritis have revealed that NGF inhibitors substantially reduce joint pain and improve function compared with NSAIDs for a duration of up to 8 weeks. However, the higher tested doses of NGF inhibitors also increased the risk of rapidly progressive osteoarthritis in a small percentage of those treated. This Review recaps the biology of NGF and the studies that have been performed to evaluate the efficacy of NGF inhibition for chronic musculoskeletal pain states. The adverse events associated with NGF inhibition and the current state of knowledge about the mechanisms involved in rapidly progressive osteoarthritis are also discussed and future studies proposed to improve understanding of this rare but serious adverse event.

Circulating miRNA-181b-5p, miRNA-223-3p, miRNA-210-3p, let 7i-5p, miRNA-21-5p and miRNA-29a-3p in patients with localized scleroderma as potential biomarkers

Localized scleroderma (LoSc) is a rare disease manifested by an inflammation and sclerosis of the skin. The latest studies focused on glycoprotein Krebs von den Lungen-6, surfactant protein-D, chemokine ligand 18 and dipeptidylpeptidase 4 as potential biomarkers of skin fibrosis in systemic scleroderma. Our study aimed to identify 6 miRNAs with elevated or decreased levels in 38 LoSc patients (31 females, 7 males) compared to healthy volunteers (HVs) and to correlate the selected miRNAs' serum levels with the severity and the clinical symptoms of LoSc and some laboratory parameters with the selected miRNAs' serum levels. The serum levels of miRNAs, i.e. miRNA-181b-5p, miRNA-223-3p, miRNA-21-5p, let 7i-5p, miRNA-29a-3p and miRNA-210-3p were significantly increased in the LoSc patients compared to the HVs. The level of let-7i increase in the female LoSc patients correlated negatively with BSA (r =  - 0.355, p = 0.049) and mLoSSI (r =  - 0.432, p = 0.015). Moreover, the female patients with inactive LoSc had significantly higher level of let-7i (2.68-fold on average) in comparison to those with active disease (p = 0.045). The exact role of those molecules has not been revealed in LoSc and a long-term longitudinal research is pivotal to confirm their prognostic value.

Emerging pharmaceutical therapies for osteoarthritis

The prevalence of osteoarthritis (OA) and the burden associated with the disease are steadily increasing worldwide, representing a major public health challenge for the coming decades. The lack of specific treatments for OA has led to it being recognized as a serious disease that has an unmet medical need. Advances in the understanding of OA pathophysiology have enabled the identification of a variety of potential therapeutic targets involved in the structural progression of OA, some of which are promising and under clinical investigation in randomized controlled trials. Emerging therapies include those targeting matrix-degrading proteases or senescent chondrocytes, promoting cartilage repair or limiting bone remodelling, local low-grade inflammation or Wnt signalling. In addition to these potentially disease-modifying OA drugs (DMOADs), several targets are being explored for the treatment of OA-related pain, such as nerve growth factor inhibitors. The results of these studies are expected to considerably reshape the landscape of OA management over the next few years. This Review describes the pathophysiological processes targeted by emerging therapies for OA, along with relevant clinical data and discussion of the main challenges for the further development of these therapies, to provide context for the latest advances in the field of pharmaceutical therapies for OA.

Efficacy of tocilizumab in patients with hand osteoarthritis: double blind, randomised, placebo-controlled, multicentre trial

OBJECTIVE

To evaluate the efficacy of tocilizumab, an antibody against IL-6 receptor, in patients with hand osteoarthritis.

METHODS

This was a multicentre, 12-week, randomised, double-blind, placebo-controlled study from November 2015 to October 2018. Patients with symptomatic hand osteoarthritis (pain ≥40 on a 0-100 mm visual analogue scale (VAS) despite analgesics and non-steroidal anti-inflammatory drugs; at least three painful joints, Kellgren-Lawrence grade ≥2) were randomised to receive two infusions 4 weeks apart (weeks 0 and 4) of tocilizumab (8 mg/kg intravenous) or placebo. The primary endpoint was changed in VAS pain at week 6. Secondary outcomes included the number of painful and swollen joints, duration of morning stiffness, patients' and physicians' global assessment and function scores.

RESULTS

Of 104 patients screened, 91 (45 to tocilizumab and 46 to placebo; 82% women; mean age 64.4 (SD 8.7) years) were randomly assigned and 79 completed the 12-week study visit. The mean change between baseline and week 6 on the VAS for pain (primary outcome) was -7.9 (SD 19.4) and -9.9 (SD 20.1) in the tocilizumab and placebo groups (p=0.7). The groups did not differ for any secondary outcomes at weeks 4, 6, 8 or 12. Overall, adverse events were slightly more frequent in the tocilizumab than placebo group.

CONCLUSION

Tocilizumab was no more effective than placebo for pain relief in patients with hand osteoarthritis.

Altered levels of salivary and plasma pain related markers in temporomandibular disorders

Background

Different pain syndromes may be characterized by different profiles of mediators reflecting pathophysiological differences, and these alterations may be measured in a simple saliva sample. The aims of the current study were to compare concentration of glutamate, serotonin (5-HT), nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and substance P (SP) in saliva and plasma from a well-defined group of patients with chronic temporomandibular disorders myalgia (TMD-myalgia) with a group of pain-free controls, and further investigate the relationship between these markers and clinical characteristics.

Methods

Patients diagnosed according to the diagnostic criteria for TMD (n = 39), and matched healthy pain-free controls (n = 39) were included. Stimulated whole saliva and plasma samples were collected in the morning. Glutamate was analysed using a colorimetric assay, and 5-HT and SP were analysed by commercially available ELISA. Levels of NGF and BDNF were determined using multiplex electrochemiluminescence assay panel.

Results

Patients expressed higher salivary and plasma levels of glutamate (saliva: 40.22 ± 13.23 μmol/L; plasma: 30.31 ± 18.73 μmol/L) than controls (saliva: 33.24 ± 11.27 μmol/L; plasma: 20.41 ± 15.96 μmol/L) (p < 0.05). Salivary NGF (0.319 ± 0.261 pg/ml) and BDNF (3.57 ± 1.47 pg/ml) were lower in patients compared to controls (NGF: 0.528 ± 0.477 pg/ml; BDNF 4.62 ± 2.51 pg/ml)(p’s < 0.05). Contrary, plasma BDNF, was higher in patients (263.33 ± 245.13 pg/ml) than controls (151.81 ± 125.90 pg/ml) (p < 0.05). 5-HT was undetectable in saliva. Neither plasma 5-HT, nor SP levels differed between groups. BDNF and NGF concentrations correlated to levels of psychological distress (p < 0.0005).

Conclusion

The higher levels of salivary and plasma glutamate in patients with TMD-myalgia compared to controls strengthens its importance in the pathophysiology of TMD-myalgia. However, the lack of correlation to pain levels question its role as a putative biomarker. Patients with TMD-myalgia further had lower levels of salivary NGF and BDNF, but higher plasma BDNF. These results and their correlations to psychological distress warrant further investigations.

Key Milestones Contributing to the Understanding of the Mechanisms Underlying Fibromyalgia

The promulgation of the American College of Rheumatology (ACR) 1990 criteria for fibromyalgia (FM) classification has significantly contributed to an era of increased research into mechanisms that underlie the disorder. The previous emphasis on putative peripheral nociceptive mechanisms has advanced to identifying of changes in central neural networks that modulate pain and other sensory processes. The influences of psychosocial factors on the dynamic and complex neurobiological mechanisms involved in the fibromyalgia clinical phenotype are now better defined. This review highlights key milestones that have directed knowledge concerning the fundamental mechanisms contributing to fibromyalgia.

Disease activity-dependent expression of nerve growth factor TRKA and P75 receptors on elevated dendritic cells and peripheral leucocytes in patients with systemic lupus erythematosus

INTRODUCTION

The nervous system modulates rheumatic diseases in neurogenic inflammation (NI). Nerve growth factor (NGF) plays a pivotal role in NI and chronic nociceptive pain. However, the role of NGF in autoimmune inflammatory diseases is not well understood. The aim of this study was to analyse NGF high- (TrkA) and low-affinity (p75) receptors on all major leucocyte subsets of patients with systemic lupus erythematosus (SLE) as a potential indicator of NI.

METHODS

A total of 13 patients were analysed by fluorescence-activated cell sorting and compared to 13 healthy control (HC) subjects. Patients were also stratified for high or low disease activity (CRP, ESR, SLEDAI, ANA, anti-dsDNA and C3/C4). Statistics included the Kruskal-Wallis test and Mann-Whitney U-test.

RESULTS

When comparing patients and HC, TrkA was not differentially expressed. In contrast, p75 was increased on CD16+ and CD56+ leucocytes in patients. CD11c+ dendritic cells (DC) were in total increased in SLE. DCs were also significantly elevated in active patients. Furthermore, we found an intermediate CD11b+ population strongly expressing TrkA in patients and HC.

CONCLUSION

We demonstrate for the first time differential NGF receptor expression in SLE. The increased CD11c+ DCs might indicate additional activation in SLE.

Nerve growth factor promotes ASIC1a expression via the NF-κB pathway and enhances acid-induced chondrocyte apoptosis

Nerve growth factor (NGF) is a neurotrophic factor that is thought to have a broad role in the nervous system and tumors, and has recently been described as a mediator of inflammation. It is not clear whether or not NGF participates in apoptosis of articular chondrocytes. In this study, we determined if NGF affects ASIC1a expression and NF-κB P65 activation in rat chondrocytes, and measured the effectiveness of NGF on apoptotic protein expression in acid-induced chondrocytes. NGF was shown to up-regulate the level of ASIC1a in a dose- and time-dependent fashion. Simultaneously, NGF activated NF-κB P65 in chondrocytes. Additionally, the elevated ASIC1a expression induced by NGF was eliminated by the NF-κB inhibitor (PDTC) in chondrocytes. Moreover, NGF reduced cell viability and induced LDH release under the premise of acid-induced articular chondrocytes. Furthermore, NGF could enhance cleaved-caspase 9 and cleaved-PARP expression in acid-pretreated chondrocytes, and which could be inhibited by using psalmotoxin 1(PcTX1) or PDTC. Together, these results indicated that NGF may up-regulate ASIC1a expression through the NF-κB signaling pathway, and further promote acid-induced apoptosis of chondrocytes.

IL-1-dependent electrophysiological changes and cardiac neural remodeling in a mouse model of Kawasaki disease vasculitis

Kawasaki disease (KD) is the leading cause of acquired heart disease in children. In addition to coronary artery abnormalities, aneurysms and myocarditis, acute KD is also associated with echocardiogram (ECG) abnormalities in 40-80% of patients. Here, we show that these ECG changes are recapitulated in the Lactobacillus casei cell wall extract (LCWE)-induced KD vasculitis mouse model. LCWE-injected mice developed elevated heart rate and decreased R wave amplitude, with significant differences in prolonged ventricular repolarization. LCWE-injected mice developed cardiac ganglion inflammation, that may affect the impulse-conducting system in the myocardium. Furthermore, serum nerve growth factor (NGF) was significantly elevated in LCWE-injected mice, similar to children with KD vasculitis, associated with increased neural remodeling of the myocardium. ECG abnormalities were prevented by blocking interleukin (IL)-1 signaling with anakinra, and the increase in serum NGF and cardiac neural remodeling were similarly blocked in Il1r1-/- mice and in wild-type mice treated with anakinra. Thus, similar to clinical KD, the LCWE-induced KD vasculitis mouse model also exhibits electrophysiological abnormalities and cardiac neuronal remodeling, and these changes can be prevented by blocking IL-1 signaling. These data support the acceleration of anti-IL-1 therapy trials to benefit KD patients.

Efficacy and safety of intra-articular injection of tropomyosin receptor kinase A inhibitor in painful knee osteoarthritis: a randomized, double-blind and placebo-controlled study

OBJECTIVE

This trial evaluated the efficacy and safety of GZ389988A, a tropomyosin receptor kinase A (TrkA) inhibitor, in subjects with painful knee osteoarthritis (OA).

METHOD

In this single center, double-blind, placebo-controlled and randomized trial, 104 subjects with moderate-to-severe knee OA pain were enrolled to receive a single intra-articular (IA) injection of either GZ389988A or placebo. Efficacy measures were assessed over 12 weeks and included walking pain (Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC] A1), overall knee pain, WOMAC A, B, C and total score, Patient Global Impression of Change (PGIC), OMERACT-OARSI responder rate and rescue medication use. Adverse events (AEs) were monitored up to 24 weeks.

RESULTS

The primary efficacy endpoint was met with a between-group difference of -7.49 (VAS 0-100) on WOMAC A1 changes over 4 weeks (P < 0.05 favoring GZ389988A). The secondary outcome on WOMAC A1 changes over 12 weeks had a between-group difference of -6.78 (P = 0.064). Among weekly assessments, statistically significant greater improvement in the GZ389988A group was observed in WOMAC A1, overall knee pain and/or WOMAC A at weeks 2-5. Although not statistically significant, improvements over placebo on pain and WOMAC C persisted over 12 weeks. Greater AE incidence was observed in the GZ389988A group including transient and self-limited injection joint inflammatory reactions with a spike of acetaminophen intake within the first week post-injection.

CONCLUSION

IA injection of TrkA inhibitor GZ389988A in knee OA subjects reduced pain with a numerically functional gain and an acceptable safety profile. (ClinicalTrials.gov, NCT02845271).

The COX-2 inhibitor etoricoxib reduces experimental osteoarthritis and nociception in rats: The roles of TGF-β1 and NGF expressions in chondrocytes

BACKGROUND

Osteoarthritis (OA) is the most common joint disease, especially affecting the knee joint. Etoricoxib, a highly selective cyclooxygenase (COX)-2 inhibitor which can reduce postoperative pain after orthopaedic surgery. The aim of this study was to investigate the effects of oral etoricoxib on the development of OA and to examine concomitant changes in the nociceptive behaviour of rats.

METHOD

OA was induced in wistar rats by anterior cruciate ligament transection (ACLT) of the right knee. The ACLT + etoricoxib groups received 6.7 or 33.3 mg/kg of oral etoricoxib three times a week for 12 consecutive weeks, starting at week 8 after ACLT. Nociceptive behaviours and changes in knee joint width during OA development were analyzed. Histopathological studies were then performed on the cartilage. Immunohistochemical analysis was performed to examine the effect of etoricoxib on the expression of transforming growth factor-beta (TGF-β) and nerve growth factor (NGF) in articular cartilage chondrocytes.

RESULTS

OA rats receiving etoricoxib showed a significantly lower degree of cartilage degeneration than the rats receiving placebo. Nociceptive behaviour studies showed significant improvement in the ACLT + etoricoxib groups compared to that in the ACLT group. Moreover, etoricoxib attenuated NGF expression, but increased TGF-β expression, in OA-affected cartilage.

CONCLUSIONS

Oral etoricoxib in a rat OA model (a) attenuates the development of OA, (b) concomitantly reduces nociception, and (c) modulates chondrocyte metabolism, possibly by inhibiting NGF expression and increasing TGF-β expression.

SIGNIFICANCE

Oral administration of etoricoxib can attenuate the development of OA, with an associated attenuation of nociceptive behaviour in an experimental rat OA model. Moreover, etoricoxib attenuated NGF expression, but enhanced TGF-β expression in OA-affected chondrocytes. These findings may pave the way for further investigations of etoricoxib as a potential therapeutic target for the treatment of the inflammatory component in OA.

[Inflammation and osteoarthritis-related pain]

Osteoarthritis (OA) is one of the major causes of chronic pain. Although OA has long been considered a non-inflammatory "wear and tear" disease leading to loss of articular cartilage, recent findings provide convincing evidence that inflammatory mechanisms play a pivotal role in the pathophysiology of OA. In OA mononuclear cells (e. g. T‑cells and macrophages) infiltrate the synovial membrane and the levels of pro-inflammatory cytokines in peripheral blood and synovial fluid samples are elevated. Increased release of inflammatory mediators including interleukin (IL) IL-1β, IL-6, IL-8, IL-15 und tumor necrosis factor alpha (TNF‑α) induces the expression of proteolytic enzymes such as matrix metalloproteinases resulting in cartilage breakdown. Molecular and cellular interactions between the immune and nervous system are also involved in the development of OA-related pain. Inflammatory mediators including IL-6 und TNF‑α lead to peripheral sensitization of joint nociceptors and growth factors (e. g. NGF) trigger the expression of TRPV1 channels in primary afferents. Moreover, neuropeptides reduce the threshold of nociceptors of OA joints. The current review highlights the role of inflammatory mechanisms in OA-induced joint pain considering clinical signs of inflammation and major inflammatory pathways.

A diagnosis of rheumatoid arthritis, endometriosis or IBD is associated with later onset of fibromyalgia and chronic widespread pain

BACKGROUND

Widespread pain is a common comorbidity in several chronic diseases and is suspected to be caused by pain resulting from the underlying disease that has provoked a state of central sensitization. However, this argument is currently limited by evidence that has insufficiently captured the temporal nature of the relationship between diagnosis of the underlying disease and onset of widespread pain. The aim of this study was to investigate if patients with rheumatoid arthritis (RA), endometriosis or inflammatory bowel disease (IBD), have a higher risk of developing widespread pain (fibromyalgia or chronic widespread pain [CWP]).

METHODS

Using the Swedish Skåne Healthcare register on health care consultation, a cohort of 889,938 adult patients were followed from 2007 to 2016 and incident cases of RA, endometriosis or IBD and of fibromyalgia and CWP were identified by registered diagnoses. Using Poisson regression, we calculated incidence rate ratios (IRR) adjusted for sex, age, education and propensity to seek health care.

RESULTS

For patients with RA the IRR for later fibromyalgia was 3.64 (95% CI: 2.75-4.81) compared to patients without RA, for CWP it was 2.96 (95% CI: 1.81-4.86). For endometriosis patients the IRR for fibromyalgia was 2.83 (95% CI: 1.96-4.08) and for CWP 5.02 (95% CI: 3.10-8.13). IBD patients had an IRR = 2.32 (95% CI: 1.58-3.42) for fibromyalgia and 1.42 (95% CI: 0.93-2.17) for CWP.

CONCLUSIONS

This study shows that RA, endometriosis and IBD are all risk factors for later fibromyalgia and CWP, consistent with a hypothesis of central sensitization as an effect of a painful underlying condition.

SIGNIFICANCE

We show that RA, endometriosis and IBD predisposes for later fibromyalgia and CWP, a common hypothesis previously difficult to verify due to lack of longitudinal data. The results inform further research regarding the aetiology of fibromyalgia and CWP and stress the need of clinical focus on the pain itself in chronic diseases with pain as a symptom.

Treating Severe Knee Osteoarthritis with Combination of Intra-Osseous and Intra-Articular Infiltrations of Platelet-Rich Plasma: An Observational Study

OBJECTIVE

Assessing the therapeutic effects of a combination of intra-articular and intra-osseous infiltrations of platelet-rich plasma (PRP) to treat severe knee osteoarthritis (KOA) using intra-articular injections of PRP as the control group.

DESIGN

In this observational study, 60 patients suffering from severe KOA were treated with intra-articular infiltrations of PRP (IA group) or with a combination of intra-osseous and intra-articular infiltrations of PRP (IO group). Both groups were matched for sex, age, body mass index, and radiographic severity (III and IV degree according to Ahlbäck scale). Clinical outcome was evaluated at 2, 6, and 12 months, using the Knee injury and Osteoarthritis Outcome Score (KOOS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaires.

RESULTS

At 2, 6 and 12 months after treatment, IO group had a significant improvement in all KOOS and WOMAC subscales ( P < 0.05). On the contrary, patients of the IA group did not improve in any of the scores. Sixteen out of 30 IO group patients showed minimal clinically important improvement (MCII) whereas 8 out of 30 IA group patients showed this response at 6 months (26.7%; 95% CI -0.4 to 49.9; P = 0.037). At 12 months, 14 patients of IO group and 5 patients of the IA group showed MCII (30%; 95% CI 4.3 to 51.9; P = 0.013). No differences between groups were observed at 2 months.

CONCLUSIONS

PRP intra-articular injections in severe KOA were not effective and did not provide any benefit. Combination of intra-articular and intra-osseous infiltrations of PRP was not clinically superior at 2 months, but it showed superior clinical outcomes at 6 and 12 months when compared with intra-articular injections of PRP.

Anti-nerve growth factor monoclonal antibodies for the control of pain in dogs and cats

Nerve growth factor (NGF) is essential for the survival of sensory and sympathetic neurons during development. However, in the adult, NGF and its interaction with tropomyosin receptor kinase A receptor (TrkA) has been found to play a critical role in nociception and nervous system plasticity in pain conditions. Thus, various monoclonal antibody (mAb) therapies targeting this pathway have been investigated in the development of new pharmacotherapies for chronic pain. Although none of the mAbs against NGF are yet approved for use in humans, they look very promising for the effective control of pain. Recently, species-specific anti-NGF mAbs for the management of osteoarthritis (OA)-associated pain in dogs and cats has been developed, and early clinical trials have been conducted. Anti-NGF therapy looks to be both very effective and very promising as a novel therapy against chronic pain in dogs and cats. This review outlines the mechanism of action of NGF, the role of NGF in osteoarthritis, research in rodent OA models and the current status of the development of anti-NGF mAbs in humans. Furthermore, we describe and discuss the recent development of species-specific anti-NGF mAbs for the treatment of OA-associated pain in veterinary medicine.

Peripheral Synthesis of an Atypical Protein Kinase C Mediates the Enhancement of Excitability and the Development of Mechanical Hyperalgesia Produced by Nerve Growth Factor

Nerve growth factor (NGF) plays a key role in the initiation as well as the prolonged heightened pain sensitivity of the inflammatory response. Previously, we showed that NGF rapidly augmented both the excitability of isolated rat sensory neurons and the mechanical sensitivity of the rat's hind paw. The increase in excitability and sensitivity was blocked by the myristoylated pseudosubstrate inhibitor of atypical PKCs (mPSI), suggesting that an atypical PKC may play a key regulatory role in generating this heightened sensitivity. Our findings raised the question as to whether NGF directs changes in translational control, as suggested for long-lasting long-term potentiation (LTP), or whether NGF leads to the activation of an atypical PKC by other mechanisms. The current studies demonstrate that enhanced action potential (AP) firing produced by NGF was blocked by inhibitors of translation, but not transcription. In parallel, in vitro studies showed that NGF elevated the protein levels of PKMζ, which was also prevented by inhibitors of translation. Intraplantar injection of NGF in the rat hind paw produced a rapid and maintained increase in mechanical sensitivity whose onset was delayed by translation inhibitors. Established NGF-induced hypersensitivity could be transiently reversed by injection of rapamycin or mPSI. These results suggest that NGF produces a rapid increase in the synthesis of PKMζ protein in the paw that augments neuronal sensitivity and that the ongoing translational expression of PKMζ plays a critical role in generating as well as maintaining the heightened sensitivity produced by NGF.

Nerve growth factor concentrations in the synovial fluid from healthy dogs and dogs with secondary osteoarthritis

Objective: To measure the concentrations of nerve growth factor (NGF) in the synovial fluid from normal dogs and dogs with osteoarthritis (OA) secondary to common joint disorders.

Methods: Nerve growth factor synovial concentrations were measured by ELISA assay in 50 dogs divided into three groups: 12 healthy, 16 affected by acute lameness within seven days before enrolment, and 22 with chronic lameness persisting by more than one month before enrolment and accompanied by radiological signs of OA. Both acute and chronic lameness were secondary to orthopaedic diseases involving the shoulder, elbow and stifle joints. Nerve growth factor synovial concentrations were compared between means for healthy and acute groups and between the three groups using an F-test. Significance level was set at p ±0.05.

Results: Nerve growth factor was detected in all canine synovial fluid samples. However, the mean synovial NGF concentration of healthy dogs (3.65 ± 2.18 pg/ml) was not significantly different from the mean value in dogs with acute lameness (6.45 ± 2.45 pg/ml) (p ± 0.79). Conversely, the mean synovial NGF concentration in dogs with chronic lameness (20.19 ± 17.51 pg/ml) was found to be significantly higher than that found in healthy dogs (p ±0.01).

Clinical significance: This study demonstrates for the first time the presence of NGF in canine synovial fluid and its increased concentrations in dogs with chronic lameness compared to healthy dogs and dogs with acute lameness. The association between chronic lameness and raised synovial concentrations may suggest an involvement of NGF in OA inflammation and chronic pain.

Trophic and neurotrophic factors in human pituitary adenomas (Review)

The pituitary gland is an organ that functionally connects the hypothalamus with the peripheral organs. The pituitary gland is an important regulator of body homeostasis during development, stress, and other processes. Pituitary adenomas are a group of tumors arising from the pituitary gland: they may be subdivided in functional or non-functional, depending on their hormonal activity. Some trophic and neurotrophic factors seem to play a key role in the development and maintenance of the pituitary function and in the regulation of hypothalamo-pituitary-adrenocortical axis activity. Several lines of evidence suggest that trophic and neurotrophic factors may be involved in pituitary function, thus suggesting a possible role of the trophic and neurotrophic factors in the normal development of pituitary gland and in the progression of pituitary adenomas. Additional studies might be necessary to better explain the biological role of these molecules in the development and progression of this type of tumor. In this review, in light of the available literature, data on the following neurotrophic factors are discussed: ciliary neurotrophic factor (CNTF), transforming growth factors β (TGF‑β), glial cell line-derived neurotrophic factor (GDNF), nerve growth factor (NGF), vascular endothelial growth factor (VEGF), vascular endothelial growth inhibitor (VEGI), fibroblast growth factors (FGFs) and epidermal growth factor (EGF) which influence the proliferation and growth of pituitary adenomas.

β-NGF and β-NGF receptor upregulation in blood and synovial fluid in osteoarthritis

Osteoarthritis (OA) of the knee is the most common form of non-traumatic joint disease. Previous studies have shown the involvement of β-NGF and its receptors TrKA and p75NTR in OA-related pain, but their role in its pathogenesis is still unclear. The aim of our study was to investigate the amount of β-NGF and the expression levels of its receptors on cells isolated from synovial fluid and blood from OA patients who had undergone total knee arthroplasty, in order to check any possible correlation with the disease staging. Our results show a progressive stage-related increase of β-NGF and its receptors both in serum and synovial fluid. Furthermore, with respect to control subjects, OA patients show an increased amount of inflammatory monocytes along with an increased expression of β-NGF, TrKA and p75NTR. In conclusion, our study suggests a stage-related modulation of β-NGF and its receptors in the inflammatory process of OA.

Mechanism and therapeutic effectiveness of nerve growth factor in osteoarthritis pain

Osteoarthritis (OA) is the most common form of articular joint arthritis and a cause of significant morbidity. In this review, we present the role of nerve growth factor (NGF) in pain generation, relationship between NGF and OA pain, and pathogenic factors (interleukin-1β, transforming growth factor-β1, mechanical loading, and adipokines) involved in OA development. Since NGF blocking is an efficient way to inhibit OA-associated pain, we summarize four categories of drugs that target NGF/tropomyosin receptor kinase A (TrkA) signaling. In addition, we discuss the future of NGF/TrkA antagonists and underline their potential for use in OA pain relief. A better understanding of the causes and treatment of OA will facilitate the development of more effective methods of OA pain management.

RAPID COMMUNICATION: Nerve growth factor influences cleavage rate and embryo development in sheep

Recent information about Nerve growth factor (NGF), a protein traditionally associated to the nervous system that regulates survival and maturation of developing neurons, suggests that it may exert action also on different levels in the reproductive system. The aim of this study was to evaluate the effect of NGF added during in vitro oocyte maturation, fertilization or in vitro embryo development in sheep. Nerve growth factor was supplemented to the culture medium at 0, 100, or 1,000 ng/mL, during either in vitro maturation (Exp. 1), in vitro fertilization (Exp. 2), or in vitro culture (Exp. 3). In addition, NGF mRNA expression was determined in cumulus cells and oocytes. Nerve growth factor induced early cleavage when added during oocyte maturation or fertilization, improved embryo development when added during fertilization, and had no significant effect when added during embryo culture. In general, the effect was more evident with 100 rather than 1,000 ng/mL (P < 0.05). Expression of endogenous NGF was not detected in oocytes, and increased in cumulus cells when 1,000 ng/mL of NGF was added during fertilization, but not during maturation and embryo culture. In conclusion, the addition of NGF during oocyte maturation and fertilization affects in vitro cleavage and embryo development in sheep. We suggest a possible effect of this growth factor on oocyte maturation and mainly on the fertilization process.

Patients with Rheumatoid Arthritis and Chronic Pain Display Enhanced Alpha Power Density at Rest

Patients with chronic pain due to neuropathy or musculoskeletal injury frequently exhibit reduced alpha and increased theta power densities. However, little is known about electrical brain activity and chronic pain in patients with rheumatoid arthritis (RA). For this purpose, we evaluated power densities of spontaneous electroencephalogram (EEG) band frequencies (delta, theta, alpha, and beta) in females with persistent pain due to RA. This was a cross-sectional study of 21 participants with RA and 21 healthy controls (mean age = 47.20; SD = 10.40). EEG was recorded at rest over 5 min with participant's eyes closed. Twenty electrodes were placed over five brain regions (frontal, central, parietal, temporal, and occipital). Significant differences were observed in depression and anxiety with higher scores in RA participants than healthy controls (p = 0.002). Participants with RA exhibited increased average absolute alpha power density in all brain regions when compared to controls [F_(1.39) = 6.39, p = 0.016], as well as increased average relative alpha power density [F_(1.39) = 5.82, p = 0.021] in all regions, except the frontal region, controlling for depression/anxiety. Absolute theta power density also increased in the frontal, central, and parietal regions for participants with RA when compared to controls [F_{(1, 39)} = 4.51, p = 0.040], controlling for depression/anxiety. Differences were not exhibited on beta and delta absolute and relative power densities. The diffuse increased alpha may suggest a possible neurogenic mechanism for chronic pain in individuals with RA.

Tanezumab for Patients with Osteoarthritis of the Knee: A Meta-Analysis

OBJECTIVE

Tanezumab is a new therapeutic intervention for patients with osteoarthritis (OA) of the knee. We performed the present meta-analysis to appraise the efficacy and safety of tanezumab for patients with knee OA.

METHODS

We systematically searched randomized controlled trials from PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials (CENTRAL). The primary outcomes were mean change in the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain, the WOMAC physical function and patient's global assessment (PGA). Outcomes were reported as the standard mean difference (SMD) or relative risk (RR) with 95% confidence interval (CI). We assessed the pooled data using a random-effects model.

RESULTS

Of the identified studies, four were eligible and were included in this meta-analysis (N = 1839 participants). Compared with the placebo groups, tanezumab yielded a significant reduction in mean change in the WOMAC pain (SMD = 0.51, 95% CI 0.34 to 0.69, P<0.00001), the WOMAC physical function (SMD = 0.56, 95% CI 0.38 to 0.74, P<0.00001) and PGA (SMD = 0.34, 95% CI 0.22 to 0.47, P<0.00001). There was no significant difference in serious adverse events (RR = 1.06, 95% CI 0.59 to 1.92, P = 0.84) between the tanezumab and placebo groups. Tanezumab significantly increased discontinuations due to adverse events (RR = 2.89, 95% CI 1.59 to 5.26, P = 0.0005), abnormal peripheral sensations (RR = 3.14, 95% CI 2.12 to 4.66, P<0.00001), and peripheral neuropathy (RR = 6.05, 95% CI 2.32 to 15.81, P = 0.0002).

CONCLUSION

Tanezumab can alleviate pain and improve function for patients with OA of the knee. However, considering the limited number of studies, this conclusion should be interpreted cautiously and more clinical randomized controlled trials are needed to verify the efficacy and safety of tanezumab for OA of the knee.

Emerging targets in treating pain

PURPOSE OF REVIEW

To provide an overview on drug targets and emerging pharmacological treatment options for chronic pain.

RECENT FINDINGS

Chronic pain poses an enormous socioeconomic burden for the more than 30% of people who suffer from it, costing over $600 billion per year in the USA. In recent years, there has been a surge in preclinical and clinical research endeavors to try to stem this epidemic. Preclinical studies have identified a wide array of potential targets, with some of the most promising translational research being performed on novel opioid receptors, cannabinoid receptors, selective ion channel blockers, cytokine inhibitors, nerve growth factor inhibitors, N-methyl-D-aspartate receptor antagonists, glial cell inhibitors, and bisphosphonates.

SUMMARY

There are many obstacles for the development of effective medications to treat chronic pain, including the inherent challenges in identifying pathophysiological mechanisms, the overlap and multiplicity of pain pathways, and off-target adverse effects stemming from the ubiquity of drug target receptor sites and the lack of highly selective receptor ligands. Despite these barriers, the number and diversity of potential therapies have continued to grow, to include disease-modifying and individualized drug treatments.

A new strategy to tackle severe knee osteoarthritis: Combination of intra-articular and intraosseous injections of Platelet Rich Plasma

INTRODUCTION

Knee osteoarthritis (KOA) is a mechanically induced, cytokine and enzyme-mediated disorder involving all the joint tissue of the knee. Rebuilding a physiological-homeostatic network at the tissue level following knee organ failure, such as in severe KOA, is a daunting task with therapeutic targets encompassing the articular cartilage, synovium and subchondral bone. Intraarticular infiltration of plasma rich in growth factors (PRP) has emerged as a promising symptomatic approach, although it is insufficient to reach the subchondral bone.

AREAS COVERED

This review addresses current molecular and cellular data in joint homeostasis and osteoarthritis pathophysiology. In particular, it focuses on changes that subchondral bone undergoes in knee osteoarthritis and evaluates recent observations on the crosstalk among articular cartilage, subchondral bone and synovial membrane. In addition, we review some mechanistic aspects that have been proposed and provide the rationale for using PRP intraosseously in KOA.

EXPERT OPINION

The knee joint is a paradigm of autonomy and connectedness of its anatomical structures and tissues from which it is made. We propose an innovative approach to the treatment of severe knee osteoarthritis consisting of a combination of intraarticular and intraosseous infiltrations of PRP, which might offer a new therapeutic tool in KOA therapy.

Safety, tolerability, pharmacokinetics, and efficacy of AMG 403, a human anti-nerve growth factor monoclonal antibody, in two phase I studies with healthy volunteers and knee osteoarthritis subjects

INTRODUCTION

Nerve growth factor plays a key role in the pathology of osteoarthritis (OA) related chronic pain. The aim of these studies was to evaluate the safety, tolerability, pharmacokinetics, and clinical response of AMG 403, a human anti-nerve growth factor monoclonal antibody, in healthy volunteers and subjects with knee OA.

METHODS

Two phase I, randomized, placebo-controlled, double-blind studies were conducted. The single-ascending dose study randomized healthy volunteers (n = 48) 3:1 to receive AMG 403 (1, 3, 10, or 30 mg intravenously; or 10 or 30 mg subcutaneously; n = 8 per group) or placebo. The multiple-ascending dose study randomized knee OA subjects (n = 18) 3:1 to receive AMG 403 (3, 10, or 20 mg subcutaneously once monthly for four doses) or placebo. Safety, tolerability, and pharmacokinetics (PK) were assessed for both studies. Patient's and physician's disease assessments and total WOMAC score were determined in knee OA subjects.

RESULTS

AMG 403 appeared to be well-tolerated after single and multiple doses, except for subject-reported hyperesthesia, pain, and paresthesia (mild to moderate severity). These treatment-emergent neurosensory events showed evidence of reversibility and a possible dose-dependence. Three serious adverse events were reported in AMG 403 treated subjects, but were not considered treatment related. AMG 403 PK was linear with an estimated half-life of 19.6 to 25.8 days. After multiple doses, AMG 403 PK showed modest accumulation (≤2.4-fold increase) in systemic exposure. Knee OA diagnosis, body weight, and anti-drug antibody development did not appear to affect AMG 403 PK. Patient's and physician's disease assessments and total WOMAC score showed improvement in AMG 403 treated knee OA subjects compared with placebo.

CONCLUSIONS

AMG 403 was generally safe and well-tolerated in both healthy volunteers and knee OA patients, and exhibited linear pharmacokinetics. Preliminary clinical efficacy was observed in knee OA subjects.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02348879 . Registered 23 December 2014. Clintrials.gov NCT02318407 . Registered 2 December 2014.

Effect of exercise on the expression of nerve growth factor in the spinal cord of rats with induced osteoarthritis

[Purpose] We examined the impact of exercise on the expression pattern of nerve growth factor in the spinal cord of rats with induced osteoarthritis of the knee joint. [Subjects and Methods] To produce monosodium iodoacetate-induced arthritis, rats were administered 3 mg/50 µL monosodium iodoacetate through the interarticular space of the right knee. The animals were randomly divided into four groups: rats sacrificed 3 weeks after 0.9% saline solution injection (shame group, n = 10), rats sacrificed 3 weeks after monosodium iodoacetate injection (control group, n = 10), rats with 4 weeks rest from 3 weeks after monosodium iodoacetate injection (no exercise group, n = 10), and rats with 4 weeks treadmill training from 3 weeks after monosodium iodoacetate injection (exercise group, n = 10). Serial coronal sections of the lumbar spine were cut and processed for immunohistochemistry. [Results] The expression of nerve growth factor was significantly increased in the EG compared with the SG, CG, and NEG. [Conclusion] Increased nerve growth factor expression in the spinal cord due to exercise-induced stimulation can be effective in treating chronic pain. Such treatment will contribute not only to improving the joint function of patients with chronic pain but also their quality of life.

Protein alterations in women with chronic widespread pain--An explorative proteomic study of the trapezius muscle

Chronic widespread pain (CWP) has a high prevalence in the population and is associated with prominent negative individual and societal consequences. There is no clear consensus concerning the etiology behind CWP although alterations in the central processing of nociception maintained by peripheral nociceptive input has been suggested. Here, we use proteomics to study protein changes in trapezius muscle from 18 female patients diagnosed with CWP compared to 19 healthy female subjects. The 2-dimensional gel electrophoresis (2-DE) in combination with multivariate statistical analyses revealed 17 proteins to be differently expressed between the two groups. Proteins were identified by mass spectrometry. Many of the proteins are important enzymes in metabolic pathways like the glycolysis and gluconeogenesis. Other proteins are associated with muscle damage, muscle recovery, stress and inflammation. The altered expressed levels of these proteins suggest abnormalities and metabolic changes in the myalgic trapezius muscle in CWP. Taken together, this study gives further support that peripheral factors may be of importance in maintaining CWP.