Cytokine biomarkers and chronic pain: association of genes, transcription, and circulating proteins with temporomandibular disorders and widespread palpation tenderness

Applications of hydrogels in tissue-engineered repairing of temporomandibular joint diseases

Epidemiological studies reveal that symptoms of temporomandibular joint disorders (TMDs) occur in 60-70% of adults. The inflammatory damage caused by TMDs can easily lead to defects in the articular disc, condylar cartilage, subchondral bone and muscle of the temporomandibular joint (TMJ) and cause pain. Despite the availability of various methods for treating TMDs, few existing treatment schemes can achieve permanent recovery. This necessity drives the search for new approaches. Hydrogels, polymers with high water content, have found widespread use in tissue engineering and regeneration due to their excellent biocompatibility and mechanical properties, which resemble those of human tissues. In the context of TMD therapy, numerous experiments have demonstrated that hydrogels show favorable effects in aspects such as articular disc repair, cartilage regeneration, muscle repair, pain relief, and drug delivery. This review aims to summarize the application of hydrogels in the therapy of TMDs based on recent research findings. It also highlights deficiencies in current hydrogel research related to TMD therapy and outlines the broad potential of hydrogel applications in treating TMJ diseases in the future.

A mouse model of chronic primary pain that integrates clinically relevant genetic vulnerability, stress, and minor injury

Chronic primary pain conditions (CPPCs) affect over 100 million Americans, predominantly women. They remain ineffectively treated, in large part because of a lack of valid animal models with translational relevance. Here, we characterized a CPPC mouse model that integrated clinically relevant genetic (catechol-O-methyltransferase; COMT knockdown) and environmental (stress and injury) factors. Compared with wild-type mice, Comt+/- mice undergoing repeated swim stress and molar extraction surgery intervention exhibited pronounced multisite body pain and depressive-like behavior lasting >3 months. Comt+/- mice undergoing the intervention also exhibited enhanced activity of primary afferent nociceptors innervating hindpaw and low back sites and increased plasma concentrations of norepinephrine and pro-inflammatory cytokines interleukin-6 (IL-6) and IL-17A. The pain and depressive-like behavior were of greater magnitude and longer duration (≥12 months) in females versus males. Furthermore, increases in anxiety-like behavior and IL-6 were female-specific. The effect of COMT genotype × stress interactions on pain, IL-6, and IL-17A was validated in a cohort of 549 patients with CPPCs, demonstrating clinical relevance. Last, we assessed the predictive validity of the model for analgesic screening and found that it successfully predicted the lack of efficacy of minocycline and the CB2 agonist GW842166X, which were effective in spared nerve injury and complete Freund's adjuvant models, respectively, but failed in clinical trials. Yet, pain in the CPPC model was alleviated by the beta-3 adrenergic antagonist SR59230A. Thus, the CPPC mouse model reliably recapitulates clinically and biologically relevant features of CPPCs and may be implemented to test underlying mechanisms and find new therapeutics.

Fibromyalgia Animal Models Using Intermittent Cold and Psychological Stress

Fibromyalgia (FM) is a chronic pain condition characterized by widespread musculoskeletal pain and other frequent symptoms such as fatigue, sleep disturbance, cognitive impairment, and mood disorder. Based on the view that intermittent stress would be the most probable etiology for FM, intermittent cold- and intermittent psychological stress-induced generalized pain (ICGP and IPGP) models in mice have been developed and validated as FM-like pain models in terms of the patho-physiological and pharmacotherapeutic features that are shared with clinical versions. Both models show long-lasting and generalized pain and female-predominant sex differences after gonadectomy. Like many other neuropathic pain models, ICGP and IPGP were abolished in lysophosphatidic acid receptor 1 (LPAR1) knock-out mice or by LPAR1 antagonist treatments, although deciding the clinical importance of this mechanism depends on waiting for the development of a clinically available LPAR1 antagonist. On the other hand, the nonsteroidal anti-inflammatory drug diclofenac with morphine did not suppress hyperalgesia in these models, and this is consistent with the clinical findings. Pharmacological studies suggest that the lack of morphine analgesia is associated with opioid tolerance upon the stress-induced release of endorphins and subsequent counterbalance through anti-opioid NMDA receptor mechanisms. Regarding pharmacotherapy, hyperalgesia in both models was suppressed by pregabalin and duloxetine, which have been approved for FM treatment in clinic. Notably, repeated treatments with mirtazapine, an α2 adrenergic receptor antagonist-type antidepressant, and donepezil, a drug for treating Alzheimer's disease, showed potent therapeutic actions in these models. However, the pharmacotherapeutic treatment should be carried out 3 months after stress, which is stated in the FM guideline, and many preclinical studies, such as those analyzing molecular and cellular mechanisms, as well as additional evidence using different animal models, are required. Thus, the ICGP and IPGP models have the potential to help discover and characterize new therapeutic medicines that might be used for the radical treatment of FM, although there are several limitations to be overcome.

The role of inflammatory markers in Temporomandibular Myalgia: A systematic review

Approximately 10 % of the general population is affected by temporomandibular disorder (TMD) pain. Diagnosis of myogenous TMD pain (i.e., TM myalgia) may be challenging, while an adequate assessment of this pain is crucial to establish an adequate management strategy. We aim to analyze if there is a relation between inflammation and TM myalgia, and if we can identify and measure inflammatory markers in patients suffering from this condition. An electronic literature search was conducted from inception up to July 14 2022 through the databases PubMed, Cochrane Library, Web of Science, and Embase in collaboration with a medical information specialist. Studies on patients with masticatory muscle inflammation and/or pain were included. After a screening procedure, only nine full-text articles met the criteria for inclusion. In the included studies 9-131 patients showed TM myalgia, and presence of inflammation was reported with analysis of interleukines IL-1, IL-6, IL-10, tumor necrosis factor alpha, and prostaglandins from blood, saliva, and extracellular fluid of masseter muscle using microdialysis. Our results contributed to the identification of the relation between inflammation and TM myalgia and established that measurement of inflammatory cytokines may be a valid diagnostic tool, which is an essential step towards finding a better treatment.

Heart rate monitoring to detect acute pain in non-verbal patients: a study protocol for a randomized controlled clinical trial

BACKGROUND

Autism entails reduced communicative abilities. Approximately 30% of individuals with autism have intellectual disability (ID). Some people with autism and ID are virtually non-communicative and unable to notify their caregivers when they are in pain. In a pilot study, we showed that heart rate (HR) monitoring may identify painful situations in this patient group, as HR increases in acutely painful situations.

OBJECTIVES

This study aims to generate knowledge to reduce the number of painful episodes in non-communicative patients' everyday lives. We will 1) assess the effectiveness of HR as a tool for identifying potentially painful care procedures, 2) test the effect of HR-informed changes in potentially painful care procedures on biomarkers of pain, and 3) assess how six weeks of communication through HR affects the quality of communication between patient and caregiver.

METHODS

We will recruit 38 non-communicative patients with autism and ID residing in care homes.

ASSESSMENTS

HR is measured continuously to identify acutely painful situations. HR variability and pain-related cytokines (MCP-1, IL-1RA, IL-8, TGFβ1, and IL-17) are collected as measures of long-term pain. Caregivers will be asked to what degree they observe pain in their patients and how well they believe they understand their patient's expressions of emotion and pain. Pre-intervention: HR is measured 8 h/day over 2 weeks to identify potentially painful situations across four settings: physiotherapy, cast use, lifting, and personal hygiene.

INTERVENTION

Changes in procedures for identified painful situations are in the form of changes in 1) physiotherapy techniques, 2) preparations for putting on casts, 3) lifting techniques or 4) personal hygiene procedures.

DESIGN

Nineteen patients will start intervention in week 3 while 19 patients will continue data collection for another 2 weeks before procedure changes are introduced. This is done to distinguish between specific effects of changes in procedures and non-specific effects, such as caregivers increased attention.

DISCUSSION

This study will advance the field of wearable physiological sensor use in patient care.

TRIAL REGISTRATION

Registered prospectively at ClinicalTrials.gov (NCT05738278).

Pathogenesis and Differential Diagnosis of Temporomandibular Joint Disorders

Temporomandibular disorders (TMDs) are an umbrella term including disorders of the temporomandibular joint and muscles of the masticatory system. They are the most common nonodontogenic cause of pain in the orofacial region. A clear understanding of various conditions, underlying mechanisms, clinical presentation, and examination skills is required to effectively diagnose and manage these patients.

Classification and Diagnosis of Temporomandibular Disorders and Temporomandibular Disorder Pain

Designing classification systems and developing diagnostic criteria for temporomandibular disorders is difficult. An appreciation of the utility and applicability of these entities requires an understanding of the importance of each, the differences between the two, and how they may be optimally operationalized for both clinical and research activities in light of their inherent advantages and limitations. In addition, consideration for adopting newer approaches, such as following ontological and precision-based medicine principles, accounting for genetics/epigenetic and neurobiological factors, and the inclusion of biomarkers will potentially result in more thorough and comprehensive classification systems and diagnostic criteria.

Rationale and design of a multicenter randomized clinical trial of vestibulodynia: understanding pathophysiology and determining appropriate treatments (vestibulodynia: UPDATe)

BACKGROUND

Limited data are available to establish evidence-based management protocols for vestibulodynia (VBD), a chronic vulvar pain condition that affects approximately 14 million women in the U.S. For the purposes of the study, our group subdivided VBD subtypes that may benefit from different types of treatment: 1) VBD peripheral (VBD-p), characterized by pain localized to the vulvar vestibule and 2) VBD central (VBD-c), characterized by VBD alongside one or more other chronic overlapping pain conditions (e.g. irritable bowel syndrome, temporomandibular disorder, and fibromyalgia syndrome) that affect remote body regions. Here, we describe the rationale and design of an NIH-funded multicenter clinical trial comparing the effectiveness of topical and/or systemic medication for alleviating pain and normalizing pain- relevant biomarkers among women with VBD-p and VBD-c.

METHODS

Participants will be randomly assigned to one of four parallel arms: peripheral treatment with 5% lidocaine + 0.5 mg/ml 0.02% oestradiol compound cream + oral placebo pill, 2) central treatment with the tricyclic antidepressant nortriptyline + placebo cream, 3) combined peripheral cream and central pill treatments, or 4) placebo cream and placebo pill. The treatment phase will last 16 weeks, with outcome measures and biomarkers assessed at 4 time points (0, 8, 16, and 24 weeks). First, we will compare the efficacy of treatments in alleviating pain using standardized tampon insertion with a numeric rating scale and self-reported pain on the short form McGill Pain Questionnaire. Next, we will compare the efficacy of treatments in improving perceived physical, mental, and sexual health using standardized questionnaires. Finally, we will measure cytokines and microRNAs in local vaginal and circulating blood samples using multiplex assays and RNA sequencing, and determine the ability of these biomarkers to predict treatment response.

CONCLUSION

This is the first multicenter randomized controlled trial to evaluate the efficacy of peripherally and centrally acting medications currently used in clinical practice for treating unique VBD subtypes based on distinct clinical and biological signatures.

ADMINISTRATIVE INFORMATION

Vestibulodynia UPDATe is a multi-centre, two-by-two factorial designed randomized, double-blind, placebo-controlled trial registered at clinical trials.gov (NCT03844412). This work is supported by the R01 HD096331 awarded to Drs. Nackley, Rapkin, Geller and Carey by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD).Key messagesPeripheral lidocaine and oestradiol and centrally-targeted nortriptyline medications are used for the treatment of pain in women with VBD, but there is a lack of data from well-powered RCTs.This two-by-two factorial RCT will test the efficacy of these medications in VBD subtypes characterized by distinct clinical characteristics and biomarker profiles.We hope that results will provide clinicians with scientific evidence of therapeutic efficacy in distinct VBD subtypes in an effort to direct and optimize treatment approaches.

Association of climacterium with temporomandibular disorders at the age of 46 years – a cross-sectional study

OBJECTIVE

Hormonal factors have been suggested to contribute to female dominance among subjects with temporomandibular disorders (TMD). Aim of the study was to examine the association of climacteric status with TMD amongst female participants in the Northern Finland Birth Cohort (NFBC) 1966 at 46 years of age.

MATERIAL AND METHODS

Among female subjects in NFBC1966, climacteric status was determined based on menstrual anamnesis and measurement of blood follicle-stimulating hormone (FSH) levels. Women with FSH > 25 IU/L and amenorrhoea > 4 months were defined as climacteric (case group, n = 71); women not diagnosed as climacteric were defined as preclimacteric (control group, n = 656). Differences between cases and controls were evaluated on self-reported TMD pain, clinical TMD signs and TMD diagnoses using modified Diagnostic Criteria for TMD (DC/TMD) protocol. Crosstabulation and logistic regression models were used to analyse differences between cases and controls.

RESULTS

Compared to preclimacteric women, climacteric women had significantly more often pain on palpation in temporomandibular joints (TMJs) (OR = 2.64, 95% CI 1.12-6.21, p= .026) and more crepitus in TMJs (OR = 2.92, 95% CI 1.13-7.56, p= .027). Degenerative joint disease diagnoses were more common in climacteric than preclimacteric women (OR = 2.27, 95% CI 1.05-4.91, p= .037). Differences were statistically significant after adjusting for confounding factors (body mass index (BMI), smoking, parity). No statistically significant differences in self-reported TMD pain were noted between groups.

CONCLUSION

Among females at the age of 46 years, climacterium seems associated with TMD by increasing pain on palpation in TMJs, subjective symptoms, and clinical signs indicating degenerative changes in TMJs when using DC/TMD.

Triad Multisystem Phenotype with High-risk for Developing Temporomandibular Disorders- Characteristics and Potential Pathophysiology Results from the OPPERA Dataset

ABSTRACT

A multisystem phenotype with the Triad of bodily pain, psychological distress, and sleep disturbance was found to have high risk for developing initial onset of painful temporomandibular disorders (TMDs) in the multicenter Orofacial Pain: Prospective Evaluation and Risk Assessment (OPPERA) dataset. In this study, we systemically examined phenotypic characteristics and explored potential pathophysiology in quantitative sensory testing (QST) and autonomic nervous system (ANS) domains in this multisystem Triad phenotype. Secondary analysis was performed on 1199 non-Triad and 154 Triad TMD-free OPPERA enrollees at baseline. Results indicate that prior to developing TMDs, the Triad phenotype demonstrated both orofacial and systemic signs and symptoms that can only be captured through multisystem assessment. In addition, we found significantly lower resting heart rate variability and higher resting heart rate in the Triad phenotype as compared to the non-Triad group. However, pain sensitivity measured by QST was not different between groups. These findings highlight the importance of whole-person multisystem assessment at the stage prior to developing complex pain conditions such as TMDs, and suggest that, in addition to a "tissue damage monitor", pain should be considered in a broader context, such as a component within a "distress monitoring system" at the whole-person level when multisystem issues co-present. Therefore, the presence or absence of multisystem issues may carry critical information when searching for disease mechanisms and developing mechanism-based intervention and prevention strategies for TMDs and related pain conditions. Cardiovascular autonomic function should be further researched when multisystem issues co-present prior to developing TMDs.

The level pro-inflammatory and anti-inflammatory biomarkers in patients with chronic mechanical low back pain under pulse radiofrequency therapy

Low back pain is a frequent and recurrent condition, often with a non-specific cause. Conventional treatment methods are generally insufficient in the treatment of chronic low back pain. The aim of the study was to estimate the level of IFN, IL-1, IL-6 (proinflammatory), IL-10, IL-4 (anti-inflammatory) and VEGF proteins in the serum of patients with chronic mechanical low back pain under Pulse radiofrequency (PRF) therapy. The study was carried out on 40 patients 20-60 years old, diagnosed with chronic low back pain for at least 4 months, primary complaint on lumbosacral low back pain, pain intensity VAS (visual analog scale) score of 5 and above, not responding well to conservative treatment (analgesic drugs, physiotherapy, etc.). Therapeutic Radiofrequency applications were carried out with an RF generator (RFG 3C Plus, Radionics). Blood samples were taken 1 day before interventional treatment (control), then 1 day (group1) and 15 days (group 2) after. The serum level of IFN, IL-1, IL-6, IL-10, IL-4 and VEGF l was analyzed with ELISA test. It was shown that as a result of PRF treatment the level of IL-1 was decreased while the levels of IL-4 and IL-6 were increased. It was concluded that the increase in serum levels of proinflammatory cytokines may be correlated with the severity of pain and that the increase in the level of anti-inflammatory cytokines reduces pain by reducing inflammation. Keywords: chronic low back pain, cytokines, radiofrequency therapy

Training-induced hypoalgesia and its potential underlying mechanisms

It is well-established that a single bout of exercise can reduce pain sensitivity (i.e., exercise-induced hypoalgesia) in healthy individuals. However, exercise-induced hypoalgesia is often impaired in individuals with chronic pain. This might suggest that repeated bouts of exercise (i.e., exercise training) are needed in order to induce a reduction in pain sensitivity (i.e., training-induced hypoalgesia) among individuals with chronic pain, given that a single bout of exercise seems to be insufficient to alter pain. However, the effect of repeated bouts of exercise on pain sensitivity and its underlying mechanisms remain poorly understood. Therefore, the purpose of this review was to provide an overview of the existing literature on training-induced hypoalgesia, as well as discuss potential mechanisms of training-induced hypoalgesia and offer considerations for future research. Existing literature suggests that training interventions may induce hypoalgesic adaptations potentially driven by central nervous system and immune system factors. However, the limited number of randomized controlled trials available, along with the lack of understanding of underlying mechanisms, provides a rationale for future research.

Circulating Omega-6 and Omega-3 Polyunsaturated Fatty Acids in Painful Temporomandibular Disorder and Low Back Pain

Preclinical studies demonstrate opposing effects of long-chain polyunsaturated fatty acid (PUFA) metabolites on inflammation and nociception. Omega-6 (n-6) PUFAs amplify both processes while omega-3 (n-3) PUFAs inhibit them. This cross-sectional study examined relationships between PUFAs in circulating erythrocytes and 2 chronic idiopathic pain conditions: temporomandibular disorder (TMD) and low back pain in a community-based sample of 503 U.S. adults. Presence or absence of TMD and low back pain, respectively, were determined by clinical examination and by responses to established screening questions. Liquid chromatography-tandem mass spectrometry quantified PUFAs. In multivariable logistic regression models, a higher ratio of n-6/n-3 long-chain PUFAs was associated with greater odds of TMD (odds ratio ((OR) = 1.75, 95% confidence limits (CL): 1.16, 2.64) and low back pain (OR = 1.63, 95% CL: 1.07, 2.49). Higher levels of the pronociceptive n-6 long-chain arachidonic acid (AA) were associated with a greater probability of both pain conditions for women, but not men. Higher levels of the antinociceptive long-chain n-3 PUFAs eicosapentaenoic and docosahexaenoic acids were associated with a lower probability of both pain conditions for men, but not women. As systemic inflammation is not a hallmark of these conditions, PUFAs may influence idiopathic pain through other mechanisms. PERSPECTIVE: This cross-sectional clinical study found that a higher ratio of circulating n-6/n-3 long-chain PUFAs was associated with greater odds of 2 common chronic overlapping pain conditions. This suggests that the pro and antinociceptive properties of n-6 and n-3 PUFAs, respectively, influence pain independently of their well-established inflammatory pathways.

Neurophysiological Markers for Monitoring Exercise and Recovery Cycles in Endurance Sports

The current study analyzes the suitability and reliability of selected neurophysiological and vegetative nervous system markers as biomarkers for exercise and recovery in endurance sport. Sixty-two healthy men and women, endurance trained and moderately trained, performed two identical acute endurance tests (running trial 1 and running trial 2) followed by a washout period of four weeks. Exercise protocol consisted of an acute running trial lasting 60 minutes. An intensity corresponding to 95% of the heart rate at individual anaerobic threshold for 40 minutes was followed by 20 minutes at 110%. At pre-exercise, post-exercise, three hours post-exercise and 24 hours post-exercise, experimental diagnostics on Brain-derived neurotrophic factor (BDNF), heart rate variability (HRV), Stroop Color and Word Test (SCWT), and Short-Form McGill Pain Questionnaire (SF-MPQ) were performed. Significant changes over time were found for all parameters (p < .05). Furthermore, there was an approached statistical significance in the interaction between gender and training status in BDNF regulation (F₍₃₎ = 2.43; p = 0.06), while gender differences were found only for LF/HF-ratio (3hPoEx, F₍₃₎ = 3.40; p = 0.002). Regarding the reliability, poor ICC-values (< 0.5) were found for BDNF, Stroop sensitivity and pNN50, while all other parameters showed moderate ICC-values (0.5-0.75). Plasma-BDNF, SCWT performance, pain perception and all HRV parameters are suitable exercise-sensitive markers after an acute endurance exercise. Moreover, pain perception, SCWT reaction time and all HRV parameters show a moderate reliability, others rather poor. In summary, a selected neurophysiological and vegetative marker panel can be used to determine exercise load and recovery in endurance sports, but its repeatability is limited due to its vaguely reliability.

Altered Plasma Proteins in Myogenous Temporomandibular Disorders

The aims of this study were (1) to compare the levels and interactions of several plasma proteins in patients with myogenous temporomandibular disorders (TMDM) compared to healthy and pain-free controls, (2) to compare the levels and interactions in two TMDM subgroups, myalgia (MYA) and myofascial pain (MFP), and (3) to explore associations between the proteins and clinical data. Thirty-nine patients with TMDM (MFP, n = 25, MYA, n = 14), diagnosed according to the diagnostic criteria for TMD (DC/TMD), aged 38 years, and sex-matched pain-free controls completed an extended DC/TMD Axis II questionnaire and the plasma concentration of 87 biomarkers were analyzed. Nine proteins separated TMDM from controls (p = 0.0174) and 12 proteins separated MYA from MFP (p = 0.019). Pain duration, characteristic pain intensity, pain catastrophizing, perceived stress, and insomnia severity were significantly associated with protein markers (p < 0.001 to p < 0.022). In conclusion, several plasma proteins were upregulated in TMDM and either upregulated or downregulated in MYA compared to MFP. Some proteins in TMDM were associated with pain variables, sleep disturbance, and emotional function. These results show that systemic differences in protein expression exist in patients with TMDM and that altered levels of specific plasma proteins are associated with different clinical variables.

Is Chronic Pain a Disease?

It was not until the twentieth century that pain was considered a disease. Before that it was managed medically as a symptom. The motivations for declaring chronic pain a disease, whether of the body or of the brain, include increasing its legitimacy as clinical problem and research focus worthy of attention from healthcare and research organizations alike. But 1 problem with disease concepts is that having a disease favors medical solutions and tends to reduce patient participation. We argue that chronic pain, particularly chronic primary pain (recently designated a first tier pain diagnosis in International Diagnostic Codes 11), is a learned state that is not intransigent even if it has biological correlates. Chronic pain is sometimes a symptom, and may sometimes be its own disease. But here we question the value of a disease focus for much of chronic pain for which patient involvement is essential, and which may need a much broader societal approach than is suggested by the disease designation. PERSPECTIVE: This article examines whether designating chronic pain a disease of the body or brain is helpful or harmful to patients. Can the disease designation help advance treatment, and is it needed to achieve future therapeutic breakthrough? Or does it make patients over-reliant on medical intervention and reduce their engagement in the process of recovery?

Sleep, Positive Affect, and Circulating Interleukin-6 in Women With Temporomandibular Joint Disorder

OBJECTIVE

Systemic inflammation is commonly observed in idiopathic chronic pain conditions, including temporomandibular joint disorder (TMD). Trait positive affect (PA) is associated with lower inflammation in healthy controls, but those effects may be threatened by poor sleep. The associations between PA with proinflammatory cytokine activity and potential moderation by sleep in chronic pain are not known. We thus investigated the association between PA and circulating interleukin-6 (IL-6) and moderation of that association by sleep in a sample of women with TMD and sleep difficulties.

METHODS

Participants (n = 110) completed the insomnia severity index and provided blood samples at five intervals throughout an evoked pain testing session. They then completed a 14-day diary assessing sleep and affect, along with wrist actigraphy.

RESULTS

There was not a significant main effect of PA on resting or pain-evoked IL-6 (b = 0.04, p = .33). Diary total sleep time (b = -0.002, p = .008), sleep efficiency (b = -0.01, p = .005), sleep onset latency (b = 0.006, p = .010), and wake after sleep onset (b = 0.003, p = .033) interacted with PA to predict IL-6, such that PA inversely predicted IL-6 at higher levels of total sleep time and sleep efficiency and at lower levels of sleep onset latency and wake after sleep onset. Surprisingly, when sleep was poor, PA predicted greater IL-6.

CONCLUSIONS

The potential salutary effects of PA on resting IL-6 erode when sleep is poor, underscoring the importance of considering sleep in conceptual and intervention models of TMD.

Action of Hyaluronic Acid as a Damage-Associated Molecular Pattern Molecule and Its Function on the Treatment of Temporomandibular Disorders

The temporomandibular joint is responsible for fundamental functions. However, mechanical overload or microtraumas can cause temporomandibular disorders (TMD). In addition to external factors, it is known that these conditions are involved in complex biological mechanisms, such as activation of the immune system, activation of the inflammatory process, and degradation of extracellular matrix (ECM) components. The ECM is a non-cellular three-dimensional macromolecular network; its most studied components is hyaluronic acid (HA). HA is naturally found in many tissues, and most of it has a high molecular weight. HA has attributed an essential role in the viscoelastic properties of the synovial fluid and other tissues. Additionally, it has been shown that HA molecules can contribute to other mechanisms in the processes of injury and healing. It has been speculated that the degradation product of high molecular weight HA in healthy tissues during injury, a low molecular weight HA, may act as damage-associated molecular patterns (DAMPs). DAMPs are multifunctional and structurally diverse molecules that play critical intracellular roles in the absence of injury or infection. However, after cellular damage or stress, these molecules promote the activation of the immune response. Fragments from the degradation of HA can also act as immune response activators. Low molecular weight HA would have the ability to act as a pro-inflammatory marker, promoting the activation and maturation of dendritic cells, the release of pro-inflammatory cytokines such as interleukin 1 beta (IL-1β), and tumor necrosis factor α (TNF-α). It also increases the expression of chemokines and cell proliferation. Many of the pro-inflammatory effects of low molecular weight HA are attributed to its interactions with the activation of toll-like receptors (TLRs 2 and 4). In contrast, the high molecular weight HA found in healthy tissues would act as an anti-inflammatory, inhibiting cell growth and differentiation, decreasing the production of inflammatory cytokines, and reducing phagocytosis by macrophages. These anti-inflammatory effects are mainly attributed to the interaction of high-weight HA with the CD44 receptor. In this study, we review the action of the HA as a DAMP and its functions on pain control, more specifically in orofacial origin (e.g., TMD).

Severe Persistent Pain and Inflammatory Biomarkers in Sickle Cell Disease: An Exploratory Study

BACKGROUND

Severe pain is among the most common and deleterious symptoms experienced by individuals with sickle cell disease (SCD), of whom more than 50% report chronic pain. Despite this, the understanding of the biological contributors to persistent severe SCD pain is limited. This exploratory study sought to describe pain phenotypes based on frequency of severe pain experienced over 6 months and identify inflammatory biomarkers associated with pain phenotypes among individuals with SCD.

METHODS

This study used self-report and electronic health record data collected from 74 individuals enrolled in the Duke Sickle Cell Disease Implementation Consortium Registry. Plasma from previously collected blood specimens was used to generate inflammatory biomarker data using the Inflammation 20-plex ProcartaPlexTM panel. Descriptive statistics were used to describe the occurrence of severe pain over the past 6 months, and bi-variate analyses were used to evaluate the relationship between inflammatory biomarkers and pain phenotypes.

RESULTS

Among the 74 participants included in this study, 33.8% reported severe pain occurring never or rarely, 40.5% reported severe pain occurring sometimes, and 25.7% reported severe pain occurring often or always. Soluble E-selectin (sE-selectin) was the only inflammatory biomarker significantly associated with the pain phenotype groups (p = 0.049). Post hoc comparisons identified that participants in the often/always severe pain group had significantly higher plasma concentrations of sE-selectin compared to those in the sometimes severe pain group (p = 0.040).

CONCLUSIONS

Our findings provide preliminary evidence of the frequent occurrence of severe pain and that sE-selectin may be an objective biomarker for the frequent occurrence of severe pain in this population.

Presence of widespread pain predicts comorbidities and treatment response in temporomandibular disorders patients

OBJECTIVES

Investigate the presence of widespread pain in a well-defined TMD group and analyze its interrelationship with various comorbidities. Also, longitudinally seek the difference in treatment response according to the presence of widespread pain.

SUBJECTS AND METHODS

The observational study involved 45 female TMD patients in their 20s. Patients were grouped into localized and widespread pain groups based on the widespread pain index (WPI ≥ 4). Clinical characteristics and levels of comorbidities were analyzed through physical examination and validated questionnaires. Differences between the groups and the power of pre-treatment WPI in predicting pre-treatment comorbidities and post-treatment pain level improvement were statistically analyzed.

RESULTS

Patients with widespread pain showed higher somatization and anxiety levels. SF-36 scores were significantly lower and more patients complained of gastrointestinal symptoms. Conventional treatment significantly reduced pain intensity in both groups but less in the widespread pain group. WPI showed significant chances to predict patients showing improvement in pain levels with treatment with a cutoff value of 4. WPI was also effective in differentiating patients that showed a higher level of somatization.

CONCLUSION

Widespread pain index could be effectively applied in differentiating those with a higher level of psychological distress and predicting TMD treatment response with further investigations into its reliability.

A comprehensive review on biomarkers associated with painful temporomandibular disorders

Pain of the orofacial region is the primary complaint for which patients seek treatment. Of all the orofacial pain conditions, one condition that possess a significant global health problem is temporomandibular disorder (TMD). Patients with TMD typically frequently complaints of pain as a symptom. TMD can occur due to complex interplay between peripheral and central sensitization, endogenous modulatory pathways, and cortical processing. For diagnosis of TMD pain a descriptive history, clinical assessment, and imaging is needed. However, due to the complex nature of pain an additional step is needed to render a definitive TMD diagnosis. In this review we explicate the role of different biomarkers involved in painful TMD. In painful TMD conditions, the role of biomarkers is still elusive. We believe that the identification of biomarkers associated with painful TMD may stimulate researchers and clinician to understand the mechanism underlying the pathogenesis of TMD and help them in developing newer methods for the diagnosis and management of TMD. Therefore, to understand the potential relationship of biomarkers, and painful TMD we categorize the biomarkers as molecular biomarkers, neuroimaging biomarkers and sensory biomarkers. In addition, we will briefly discuss pain genetics and the role of potential microRNA (miRNA) involved in TMD pain.

Identification of key candidate genes in local dorsal root ganglion inflammation by integrated bioinformatics analysis

The purpose of the present study was to identify potential markers of local dorsal root ganglion (DRG) inflammation to aid diagnosis, treatment and prognosis evaluation of DRG pain. A localized inflammation of the DRG (LID) rat model was used to study the contribution of inflammation to pain. The dataset GSE38859 was obtained from the Gene Expression Omnibus database. Pre-treatment standardization of gene expression data for each experiment was performed using the R/Bioconductor Limma package. Differentially expressed genes (DEGs) were identified between a LID model and a sham surgery control group. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses of DEGs and gene set enrichment analysis (GSEA) were carried out using the ‘clusterProfiler’ package in R. Using the Search Tool for Retrieval of Interacting Genes, a protein-protein interaction network was constructed and visualized. Candidate genes with the highest potential validity were validated using reverse transcription-quantitative PCR and western blotting. In total, 66 DEGs were enriched in GO terms related to inflammation and the immune response processes. KEGG analysis revealed 14 associated signaling pathway terms. Protein-protein interaction network analysis revealed 9 node genes, 3 of which were among the top 10 DEGs. Matrix metallopeptidase 9, chemokine CXCL9, and complement component 3 were identified as key regulators of DRG inflammatory pain progression.

Long-term evaluation of temporomandibular disorders in association with cytokine and autoantibody status in young women

Temporomandibular disorders (TMD) is a chronic pain disease affecting 4-60% of general population. Its suggested etiology includes mechanical overloading to related structures, psychosocial factors, and genetic vulnerability. However, its pathogenesis is yet to be fully understood, especially in cases with a higher level of pain and more associated comorbidities. Recently chronic systemic inflammation and possible autoimmunity has been indicated in several pain conditions as the underlying mechanism of chronicity but this aspect has not been rigorously investigated in TMD. This article focuses on analyzing the levels of cytokines, chemokines, autoantibodies and nonspecific inflammatory markers and comparing their levels according to pain severity and duration in 66 female TMD patients in their 20 s and investigating their association with clinical indices of TMD and comorbidities. The high pain disability group showed decreased range of jaw function and more pain on palpation of capsule areas compared to the low pain disability group. Comorbidities such as anxiety and sleep disturbance were also significantly more prevalent. The level of IL-8 and IgG were significantly higher in the high pain disability group. IL-2, -8, -13, IFN- γ, RANTES, PGE2, and thrombopoietin levels showed a significant effect on indices reflecting jaw function, generalized pain intensity, and health related quality of life. Such results imply that longer pain duration and higher pain intensity is associated with higher levels of systemic inflammation suggesting the possible role of immunologic disturbance as an underlying factor of chronic TMD pain and warranting further investigation for its consideration in diagnosis and treatment.

Fibromyalgia: Pathogenesis, Mechanisms, Diagnosis and Treatment Options Update

Fibromyalgia is a syndrome characterized by chronic and widespread musculoskeletal pain, often accompanied by other symptoms, such as fatigue, intestinal disorders and alterations in sleep and mood. It is estimated that two to eight percent of the world population is affected by fibromyalgia. From a medical point of view, this pathology still presents inexplicable aspects. It is known that fibromyalgia is caused by a central sensitization phenomenon characterized by the dysfunction of neuro-circuits, which involves the perception, transmission and processing of afferent nociceptive stimuli, with the prevalent manifestation of pain at the level of the locomotor system. In recent years, the pathogenesis of fibromyalgia has also been linked to other factors, such as inflammatory, immune, endocrine, genetic and psychosocial factors. A rheumatologist typically makes a diagnosis of fibromyalgia when the patient describes a history of pain spreading in all quadrants of the body for at least three months and when pain is caused by digital pressure in at least 11 out of 18 allogenic points, called tender points. Fibromyalgia does not involve organic damage, and several diagnostic approaches have been developed in recent years, including the analysis of genetic, epigenetic and serological biomarkers. Symptoms often begin after physical or emotional trauma, but in many cases, there appears to be no obvious trigger. Women are more prone to developing the disease than men. Unfortunately, the conventional medical therapies that target this pathology produce limited benefits. They remain largely pharmacological in nature and tend to treat the symptomatic aspects of various disorders reported by the patient. The statistics, however, highlight the fact that 90% of people with fibromyalgia also turn to complementary medicine to manage their symptoms.

Association between psychological factors and temporomandibular disorders in adolescents of rural and urban zones

Background

Temporomandibular disorders (TMD) are related to psychological factors. Adolescence is one of the stages in life with more psychosocial vulnerability, which is dissimilar in rural and urban zones. Thus, the aim of this investigation was to evaluate the association between psychological factors (symptoms of anxiety, depression and somatization) and TMD in adolescents between 12 and 15 years, belonging to urban and rural zones of Colombia.

Methods

180 subjects aged 12–15 years (mean 13.8, SD 1.2), enrolled in public schools in the rural (n = 90) and urban (n = 90) zones were included. All subjects were evaluated using the DC/TMD instrument; the Axis I was applied for the clinical examination and the Axis II for the psychological evaluation. Data were analyzed by means of T-student, Mann–Whitney, Kruskall–Wallis tests, Pearson Chi square and multiple-variable analysis with logistic regression.

Results

Forty percent of the included subjects presented some type of TMD. TMD related to pain were the most common (25.5% of the studied adolescents), being myalgia the most common (20% of the adolescents in urban zone and 31.1% of the adolescents in the rural zone). There was no difference between the TMD present in males and females, but there were differences in the symptoms of Anxiety, and Somatization (p < 0.05). TMD and psychological factors were more prevalent in children with 13 years of age. A statistically significant association between TMD and symptoms of Anxiety (Pearson Chi squared 25.57, p = 0.04), depression (Pearson Chi squared 33.28, p = 0.03) and somatization (Pearson Chi squared 25.79, p = 0.04) was found in subjects from rural zones. No associations between psychological aspects and TMD were found in subjects from urban zones, but overall all psychological factors significantly influenced TMD.

Conclusion

This study indicates Myalgia to be the most prevalent TMD in studied Colombian adolescents. Pain-related TMDs are associated with psychological factors in the adolescent population of rural Colombia. Symptoms of anxiety, depression and somatization were found to be associated to TMD, even when the frequency was not necessarily severe.

Mechanical Stress Induce PG-E2 in Murine Synovial Fibroblasts Originating from the Temporomandibular Joint

Genetic predisposition, traumatic events, or excessive mechanical exposure provoke arthritic changes in the temporomandibular joint (TMJ). We analysed the impact of mechanical stress that might be involved in the development and progression of TMJ osteoarthritis (OA) on murine synovial fibroblasts (SFs) of temporomandibular origin. SFs were subjected to different protocols of mechanical stress, either to a high-frequency tensile strain for 4 h or to a tensile strain of varying magnitude for 48 h. The TMJ OA induction was evaluated based on the gene and protein secretion of inflammatory factors (Icam-1, Cxcl-1, Cxcl-2, Il-1ß, Il-1ra, Il-6, Ptgs-2, PG-E2), subchondral bone remodelling (Rankl, Opg), and extracellular matrix components (Col1a2, Has-1, collagen and hyaluronic acid deposition) using RT-qPCR, ELISA, and HPLC. A short high-frequency tensile strain had only minor effects on inflammatory factors and no effects on the subchondral bone remodelling induction or matrix constituent production. A prolonged tensile strain of moderate and advanced magnitude increased the expression of inflammatory factors. An advanced tensile strain enhanced the Ptgs-2 and PG-E2 expression, while the expression of further inflammatory factors were decreased. The tensile strain protocols had no effects on the RANKL/OPG expression, while the advanced tensile strain significantly reduced the deposition of matrix constituent contents of collagen and hyaluronic acid. The data indicates that the application of prolonged advanced mechanical stress on SFs promote PG-E2 protein secretion, while the deposition of extracellular matrix components is decreased.

Temporomandibular disorders: a review of current concepts in aetiology, diagnosis and management

Temporomandibular disorders (TMD) is a collective term for a group of musculoskeletal conditions involving pain and/or dysfunction in the masticatory muscles, temporomandibular joints (TMJ) and associated structures. It is the most common type of non-odontogenic orofacial pain and patients can present with pain affecting the face/head, TMJ and or teeth, limitations in jaw movement, and sounds in the TMJ during jaw movements. Comorbid painful and non-painful conditions are also common among individuals with TMD. The diagnosis of TMD have significantly improved over time with the recent Diagnostic Criteria for TMD (DC/TMD) being reliable and valid for most common diagnoses, and an efficient way to communicate in multidisciplinary settings. This classification covers 12 most common TMD, including painful (myalgia, arthralgia and headache attributed to TMD) as well as the non-painful (disc displacements, degenerative joint disease and subluxation) TMD diagnoses. Recent studies have demonstrated that the pathophysiology of common painful TMD is biopsychosocial and multifactorial, where no one factor is responsible for its development. Importantly, research has suggested different predisposing, initiating and perpetuating factors, including both peripheral and central mechanisms. This is an active field of investigation and future studies will not only seek to clarify specific causal pathways but translate this knowledge into mechanism-directed diagnosis and treatment. In accordance with this complex aetiology, current evidence supports primarily conservative multidisciplinary treatment including self-management strategies, behavioural therapy, physical therapy and pharmacotherapy. The aim of this review is to present an overview of most recent developments in aetiology, pathophysiology, diagnosis and management of TMD.

Effects of Auricular Point Acupressure on Pain Relief: A Systematic Review

OBJECTIVES

This systematic review aimed to summarize and provide an update on clinical studies investigating the effects of auricular point acupressure (APA) on pain relief, in addition to the APA methods of delivery and operation.

DESIGN

A systematic review.

DATA SOURCES

A systematic review on literatures published on five English (PubMed, Web of Science, Embase, EBSCO, and Cochrane databases) and four major Chinese databases (China National Knowledge Infrastructure, Wan Fang Data, Chinese Scientific Journals Database [VIP], and SinoMed) was conducted.

METHOD

We screened nine electronic databases from the time of their respective establishment until December 20, 2019. Randomized controlled trials and studies that defined an APA intervention measure and evaluated pain intensity were considered. We individually categorized and analyzed 46 studies considering the following: (1) acute or chronic pain and (2) whether the outcomes positively or negatively support the effectiveness of APA on pain intensity. We also summarized the methods of delivery used (including the acupoint selection, stimulator selection, method of taping seeds on the ears, frequency of replacing seeds, suitability of acupressure intensity, acupressure frequency, and pressing time) and APA operator.

RESULTS

Regardless of pain intensity, APA effectively treated most acute pain when combined with other interventions. Although it was used alone to treat low back pain and dysmenorrhea, other chronic diseases typically underwent a combination of APA with other interventions. The 43 positive studies revealed that acute pain required shorter APA intervention periods than chronic pain. Corresponding acupoints and nervous system acupoints were chosen. Vaccaria seeds, the single-ear method (including the alternate-ear method), and daily seed replacement were commonly adopted. Deqi was considered an effective signal for appropriate acupressure intensity. Additionally, the patients could effectively apply acupressure.

CONCLUSION

This systematic review revealed important trends in APA treatments, which could be essential in determining treatment efficacy.

Temporomandibular disorder, body pain and systemic diseases: assessing their associations in adolescents

Painful temporomandibular disorders (TMD) in children and adolescents may impact negatively the individual´s life. The presence of comorbidities associated with TMD tends to increase the persistence of pain and to facilitate its chronification.

A novel cortical biomarker signature for predicting pain sensitivity: protocol for the PREDICT longitudinal analytical validation study

PREDICT will undertake analytical validation of a peak alpha frequency and corticomotor excitability biomarker, determining the sensitivity, specificity, and accuracy at predicting pain sensitivity.

Introduction:

Temporomandibular disorder is a common musculoskeletal pain condition with development of chronic symptoms in 49% of patients. Although a number of biological factors have shown an association with chronic temporomandibular disorder in cross-sectional and case control studies, there are currently no biomarkers that can predict the development of chronic symptoms. The PREDICT study aims to undertake analytical validation of a novel peak alpha frequency (PAF) and corticomotor excitability (CME) biomarker signature using a human model of the transition to sustained myofascial temporomandibular pain (masseter intramuscular injection of nerve growth factor [NGF]). This article describes, a priori, the methods and analysis plan.

Methods:

This study uses a multisite longitudinal, experimental study to follow individuals for a period of 30 days as they progressively develop and experience complete resolution of NGF-induced muscle pain. One hundred fifty healthy participants will be recruited. Participants will complete twice daily electronic pain diaries from day 0 to day 30 and undergo assessment of pressure pain thresholds, and recording of PAF and CME on days 0, 2, and 5. Intramuscular injection of NGF will be given into the right masseter muscle on days 0 and 2. The primary outcome is pain sensitivity.

Perspective:

PREDICT is the first study to undertake analytical validation of a PAF and CME biomarker signature. The study will determine the sensitivity, specificity, and accuracy of the biomarker signature to predict an individual's sensitivity to pain.

Registration details:

ClinicalTrials.gov: NCT04241562 (prospective).

Xanthan gum protects temporomandibular chondrocytes from IL‑1β through Pin1/NF‑κB signaling pathway

Temporomandibular disorder (TMD) is a complicated and multi-factorial disease related to inflammation and cartilage destruction. Intra-articular injection of xanthan gum (XG) has been demonstrated to protect the joint cartilage and reduce osteoarthritis progression. However, the role and mechanism of XG in TMD is still unclear. In the present study, chondrocytes were isolated from rats and identified by immunofluorescence. Cells were stimulated by XG or interleukin (IL)-1β. Cell viability was analyzed by MTT assay. Tumor necrosis factor α (TNF-α) and IL-6 levels were determined by ELISA. The expression of monocyte chemoattractive protein-1 (MCP-1), inducible nitric oxide synthase (iNOS), collagens, matrix metalloproteinases (MMPs), peptidyl-prolyl isomerase 1 (Pin1) and phosphorylated nuclear factor κB (NF-κB) p65 (p-p65) was analyzed by quantitative PCR or western blotting. MMP activity was assessed by gelatin zymography. Compared with the control, XG treatment partially reversed the IL-1β-reduced cell viability. In addition, IL-1β stimulation increased inflammatory cytokine expression, including TNF-α, IL-6 secretion, MCP-1 and iNOS expression, whereas XG treatment reduced the expression of these inflammatory cytokines compared with that of the IL-1β-stimulated cells. Additionally, XG increased the expression of collagen, but reduced MMP expression and activity as compared with that in the IL-1β group. In addition, XG treatment prevented the IL-1β-increased Pin1 and p-p65 expression. These data suggested that XG reduced the expression of inflammatory cytokines and may maintain the balance between collagens and MMPs partially through the Pin1/NF-κB signaling pathway in IL-1β-stimulated temporomandibular chondrocytes. Therefore, XG may be useful in the treatment of TMD.

Genetic Polymorphisms of Cytokines Might Affect Postoperative Sufentanil Dosage for Analgesia in Patients

Objective

To explore the effect of genetic polymorphisms of cytokines on the dosage of sufentanil for patient-controlled intravenous analgesia (PCIA) after radical lung cancer surgery.

Methods

A total of 100 patients, aged 18 years and above, with ASA grade Ⅰ-Ⅱ and body mass index (BMI) 18.5 to 30, and who were scheduled for radical lung cancer surgery under total intravenous anaesthesia with PCIA of sufentanil from September 2015 to March 2016, were selected. DNA was collected from peripheral blood samples before surgery, and the iMLDRTM multiple single-nucleotide polymorphism typing kit was used to detect 16 related single-nucleotide polymorphism (SNP) sites of interleukin-1A (IL-1A), interleukin-1β (IL-1β), interleukin-1RN (IL-1RN), interleukin-6 (IL-6), C-X-C motif chemokine ligand 8 (CXCL8), interleukin-10 (IL-10), tumour necrosis factor (TNF), nuclear factor kappa-B1 (NFκB1), REL (REL proto-oncogene, NF-kB subunit), and nuclear factor kappa-B inhibitor alpha (NFκBIA). The general characteristics of patients, surgery and anaesthesia data, postoperative resting VAS pain scores, postoperative opioid dosages of sufentanil for PCIA and opioid-related adverse events were recorded. The effects of the examined genetic polymorphisms of the cytokines on the dosage of sufentanil were analysed.

Results

Eight of 100 patients withdrew for various reasons, and, eventually, 92 patients were included. The patients’ resting visual analogue scale (VAS) scores at 24 h, 48 h, and 72 h after surgery were 2.3 ± 1.2, 2.0 ± 0.9, and 1.9 ± 1.0, respectively. The total amounts of sufentanil used were 34.7 ± 10.5 μg, 65.2 ± 13.7 μg, and 94.7 ± 11.6 μg, respectively. We found that the TT genotype of NFκBIA rs696 had higher PCIA sufentanil dosages than the CC genotype and the CT genotype at 48–72 h postoperation (p=0.023, p=0.025, respectively).

Conclusion

The genetic polymorphisms of the cytokine NFκBIA rs696 might affect the dosage of sufentanil for PCIA after radical lung cancer surgery. The specific mechanism needs further study.

Central mechanisms of pain in orofacial pain patients: Implications for management

BACKGROUND

Central sensitization (CS) is a form of neuroplasticity characterized by changes in the neural sensitivity, responsiveness, and/or output that are not contingent on peripheral input nor activity-dependent. CS is characterized by activation of unmyelinated C-fibers resulting in a cascade of events at molecular and cellular levels which eventuate into generation of synaptic currents at rest. CS, therefore, contributes to heightened generalized pain sensitivity, further complicates the process of reaching a diagnosis, and increases the possibility of treatment failure. BODY: Trigeminal nerve is the main sensory supplier of the anterior part of the head, including the intraoral structures. Primary afferent nociceptors of the trigeminal nerve and low threshold mechanoreceptors synapse with wide dynamic range (WDR) neurons in the pons. This multifaceted network of nerve interactions which is further complicated by the modulatory circuits that can suppress or heighten the activity of WDR neurons is one of the main contributors to CS. The importance of CS in orofacial pain disorders is emphasized in the context of chronic pain development. As for all chronic pain conditions, it is crucial to consider the biopsychosocial aspects of chronic orofacial pain in managing this diverse group of conditions. This review highlights current understanding of the biopsychosocial model and central mechanisms contributing to the pathogenesis of chronic orofacial pain.

Ahmad WMA, Ahmed Asif J, Khoo SP, Husein A, Ab-Ghani Z, Kassim NK. Biomarkers for Temporomandibular Disorders: Current Status and Future Directions

Numerous studies have been conducted in the previous years with an objective to determine the ideal biomarker or set of biomarkers in temporomandibular disorders (TMDs). It was recorded that tumour necrosis factor (TNF), interleukin 8 (IL-8), IL-6, and IL-1 were the most common biomarkers of TMDs. As of recently, although the research on TMDs biomarkers still aims to find more diagnostic agents, no recent study employs the biomarker as a targeting point of pharmacotherapy to suppress the inflammatory responses. This article represents an explicit review on the biomarkers of TMDs that have been discovered so far and provides possible future directions towards further research on these biomarkers. The potential implementation of the interactions of TNF with its receptor 2 (TNFR2) in the inflammatory process has been interpreted, and thus, this review presents a new hypothesis towards suppression of the inflammatory response using TNFR2-agonist. Subsequently, this hypothesis could be explored as a potential pain elimination approach in patients with TMDs.

Osteoarthritis of the Temporomandibular Joint can be diagnosed earlier using biomarkers and machine learning

After chronic low back pain, Temporomandibular Joint (TMJ) disorders are the second most common musculoskeletal condition affecting 5 to 12% of the population, with an annual health cost estimated at $4 billion. Chronic disability in TMJ osteoarthritis (OA) increases with aging, and the main goal is to diagnosis before morphological degeneration occurs. Here, we address this challenge using advanced data science to capture, process and analyze 52 clinical, biological and high-resolution CBCT (radiomics) markers from TMJ OA patients and controls. We tested the diagnostic performance of four machine learning models: Logistic Regression, Random Forest, LightGBM, XGBoost. Headaches, Range of mouth opening without pain, Energy, Haralick Correlation, Entropy and interactions of TGF-β1 in Saliva and Headaches, VE-cadherin in Serum and Angiogenin in Saliva, VE-cadherin in Saliva and Headaches, PA1 in Saliva and Headaches, PA1 in Saliva and Range of mouth opening without pain; Gender and Muscle Soreness; Short Run Low Grey Level Emphasis and Headaches, Inverse Difference Moment and Trabecular Separation accurately diagnose early stages of this clinical condition. Our results show the XGBoost + LightGBM model with these features and interactions achieves the accuracy of 0.823, AUC 0.870, and F1-score 0.823 to diagnose the TMJ OA status. Thus, we expect to boost future studies into osteoarthritis patient-specific therapeutic interventions, and thereby improve the health of articular joints.

Pain Sensitivity Modifies Risk of Injury-Related Temporomandibular Disorder

This study evaluates contributions of jaw injury and experimental pain sensitivity to risk of developing painful temporomandibular disorder (TMD). Data were from the Orofacial Pain: Prospective Evaluation and Risk Assessment (OPPERA) nested case-control study of incident painful TMD. Injury and subsequent onset of painful TMD were monitored prospectively for ≤5 y in a community-based sample of 409 US adults who did not have TMD when enrolled. At baseline, thermal-pressure and pinprick pain sensitivity, as potential effect modifiers, were measured using quantitative sensory testing. During follow-up, jaw injury from any of 9 types of potentially traumatic events was determined using quarterly (3-monthly) health update questionnaires. Study examiners classified incident painful TMD, yielding 233 incident cases and 176 matched controls. Logistic regression models, estimated incidence odds ratios (IORs), and 95% confidence limits (CLs) were used for the association between injury and subsequent onset of painful TMD. During follow-up, 38.2% of incident cases and 13.1% of controls reported 1 or more injuries that were 4 times as likely to be intrinsic (i.e., sustained mouth opening or yawning) as extrinsic (e.g., dental visits, whiplash). Injuries due to extrinsic events (IOR = 7.6; 95% CL, 1.6–36.2), sustained opening (IOR = 5.4; 95% CL, 2.4–12.2), and yawning (IOR = 3.4; 95% CL, 1.6–7.3) were associated with increased TMD incidence. Both a single injury (IOR = 6.0; 95% CL, 2.9–12.4) and multiple injuries (IOR = 9.4; 95% CL, 3.4,25.6) predicted greater incidence of painful TMD than events perceived as noninjurious (IOR = 1.9; 95% CL, 1.1–3.4). Injury-associated risk of painful TMD was elevated in people with high sensitivity to heat pain (IOR = 7.4; 95% CL, 3.1–18.0) compared to people with low sensitivity to heat pain (IOR = 3.9; 95% CL, 1.7–8.4). Jaw injury was strongly associated with elevated painful TMD risk, and the risk was amplified in subjects who had enhanced sensitivity to heat pain at enrollment. Commonly occurring but seemingly innocuous events, such as yawning injury, should not be overlooked when judging prognostic importance of jaw injury.

Improving characterization and diagnosis quality of myofascial pain syndrome: a systematic review of the clinical and biomarker overlap with delayed onset muscle soreness

INTRODUCTION

Myofascial pain syndrome (MPS) is one of the most common conditions of chronic musculoskeletal pain, yet its mechanisms are still poorly understood. Delayed Onset Muscle Soreness (DOMS) is also a regional pain syndrome that has clinical similarities to MPS, but has been better investigated. Emerging research suggests that DOMS may be a valid experimental model for studying MPS; however, a comparison of the similarities and differences of these two conditions has previously not been performed. Herein, we aimed to identify the similarities and differences in the clinical features and biomarkers between DOMS and MPS in order to better define MPS and identify future areas of (DOMS-informed) MPS research.

EVIDENCE ACQUISITION

In order to identify similarities and differences in the clinical manifestation and biomarkers of DOMS and MPS, scoping literature searches were performed using Medline (1965-2019), Embase (1966-2019) and Central (1966-2019) databases. Fifty-three full-text articles were reviewed out of the 2836 articles retrieved in the search.

EVIDENCE SYNTHESIS

A scoping review of the literature demonstrated that DOMS and MPS similarly present as conditions of musculoskeletal pain that are associated with decreased strength and limited range of motion. However, while taut bands and discrete tender spots were described in DOMS, none of the studies reviewed have characterized whether these tender points represent the classic myofascial trigger point phenomenon observed in MPS. Certain systemic circulation biomarkers, including inflammatory cytokines and growth factors, were commonly elevated in MPS and DOMS; further research is needed to determine if other biomarkers that are currently characterized in DOMS are useful to enhance the clinical evaluation of MPS.

CONCLUSIONS

DOMS and MPS share clinical and biomarker similarities suggesting that DOMS may be a useful model for studying MPS.

Genome-wide association reveals contribution of MRAS to painful temporomandibular disorder in males

Painful temporomandibular disorders (TMDs) are the leading cause of chronic orofacial pain, but its underlying molecular mechanisms remain obscure. Although many environmental factors have been associated with higher risk of developing painful TMD, family and twin studies support a heritable genetic component as well. We performed a genome-wide association study assuming an additive genetic model of TMD in a discovery cohort of 999 cases and 2031 TMD-free controls from the Orofacial Pain: Prospective Evaluation and Risk Assessment (OPPERA) study. Using logistic models adjusted for sex, age, enrollment site, and race, we identified 3 distinct loci that were significant in combined or sex-segregated analyses. A single-nucleotide polymorphism on chromosome 3 (rs13078961) was significantly associated with TMD in males only (odds ratio = 2.9, 95% confidence interval: 2.02-4.27, P = 2.2 × 10). This association was nominally replicated in a meta-analysis of 7 independent orofacial pain cohorts including 160,194 participants (odds ratio = 1.16, 95% confidence interval: 1.0-1.35, P = 2.3 × 10). Functional analysis in human dorsal root ganglia and blood indicated this variant is an expression quantitative trait locus, with the minor allele associated with decreased expression of the nearby muscle RAS oncogene homolog (MRAS) gene (beta = -0.51, P = 2.43 × 10). Male mice, but not female mice, with a null mutation of Mras displayed persistent mechanical allodynia in a model of inflammatory pain. Genetic and behavioral evidence support a novel mechanism by which genetically determined MRAS expression moderates the resiliency to chronic pain. This effect is male-specific and may contribute to the lower rates of painful TMD in men.

Evaluation of Orofacial and General Pain Location in Patients With Temporomandibular Joint Disorder-Myofascial Pain With Referral

Introduction: Pain is an emotional experience. As a subjective feeling, it is associated with pathophysiological processes occurring in the central nervous system, which in turn may negatively affect the psychophysical function, cognitive abilities, level of functioning and quality of life.

The Aim: The aim of the study was to assess orofacial and general pain location in patients with temporomandibular joint disorder—myofascial pain with referral.

Materials and Methods: The study group consisted of 50 randomly selected, generally healthy people with complete natural dentition (37 women and 13 men) at the age of 23.36 ± 2.14 years, referred to the Department of Prosthodontics of the Medical University. All patients underwent clinical examination according to the Diagnostic Criteria for Temporomandibular Disorders (Axes I and II). The subjects were classified as people with myofascial pain with referral. The evaluation of severity of temporomandibular disorders was based on the Temporomandibular Disorder Pain Screener and the Graded Chronic Pain Scale. In order to assess orofacial and general pain location, a bodychart drawing of pain was used.

Results: The study group indicated 40 different areas of the body affected by pain. 2–3 isolated pain locations were declared by a total of six subjects. One person identified 17 affected areas. Forty four people reported pain in at least four regions of the body. 70% of patients suffered from pain within the right masseter muscle. Pain of the left masseter muscle was noted in 68% of cases. Cervical ailments were reported by 56% of people. Pain of the left temporomandibular joint was observed in 68% of patients, and of the right one in 54%.

Conclusion: The patients with myofascial pain with referral suffer from general ailments in different regions of the body. Only the frequency of pain in the right masseter muscle and right temporomandibular joint differed with respect to gender. The suggestion that the prevalence of pain in other areas of the body varies between men and women has not been confirmed. Due to a small sample size, such differences cannot be excluded. Further studies in this area are needed.

Sustained stimulation of β2- and β3-adrenergic receptors leads to persistent functional pain and neuroinflammation

Functional pain syndromes, such as fibromyalgia and temporomandibular disorder, are associated with enhanced catecholamine tone and decreased levels of catechol-O-methyltransferase (COMT; an enzyme that metabolizes catecholamines). Consistent with clinical syndromes, our lab has shown that sustained 14-day delivery of the COMT inhibitor OR486 in rodents results in pain at multiple body sites and pain-related volitional behaviors. The onset of COMT-dependent functional pain is mediated by peripheral β2- and β3-adrenergic receptors (β2- and β3ARs) through the release of the pro-inflammatory cytokines tumor necrosis factor α (TNFα), interleukin-1β (IL-1β), and interleukin-6 (IL-6). Here, we first sought to investigate the role of β2- and β3ARs and downstream mediators in the maintenance of persistent functional pain. We then aimed to characterize the resulting persistent inflammation in neural tissues (neuroinflammation), characterized by activated glial cells and phosphorylation of the mitogen-activated protein kinases (MAPKs) p38 and extracellular signal-regulated kinase (ERK). Separate groups of rats were implanted with subcutaneous osmotic mini-pumps to deliver OR486 (15 mg/kg/day) or vehicle for 14 days. The β2AR antagonist ICI118551 and β3AR antagonist SR59230A were co-administrated subcutaneously with OR486 or vehicle either on day 0 or day 7. The TNFα inhibitor Etanercept, the p38 inhibitor SB203580, or the ERK inhibitor U0126 were delivered intrathecally following OR486 cessation on day 14. Behavioral responses, pro-inflammatory cytokine levels, glial cell activation, and MAPK phosphorylation were measured over the course of 35 days. Our results demonstrate that systemic delivery of OR486 leads to mechanical hypersensitivity that persists for at least 3 weeks after OR486 cessation. Corresponding increases in spinal TNFα, IL-1β, and IL-6 levels, microglia and astrocyte activation, and neuronal p38 and ERK phosphorylation were observed on days 14-35. Persistent functional pain was alleviated by systemic delivery of ICI118551 and SR59230A beginning on day 0, but not day 7, and by spinal delivery of Etanercept or SB203580 beginning on day 14. These results suggest that peripheral β2- and β3ARs drive persistent COMT-dependent functional pain via increased activation of immune cells and production of pro-inflammatory cytokines, which promote neuroinflammation and nociceptor activation. Thus, therapies that resolve neuroinflammation may prove useful in the management of functional pain syndromes.

Applications of sensory and physiological measurement in oral-facial dental pain

Dentists regularly employ a variety of self‐report and sensory techniques to aid in the diagnosis and treatment of tooth‐related disease. Many of these techniques leverage principles borrowed from psychophysics, the quantitative measurement of the relationship between stimuli and evoked sensations, which falls under the larger umbrella of quantitative sensory testing (QST). However, most clinicians fail to meet the bar for what could be considered quantitative sensory testing, and instead focus on qualitative and dichotomous “yes/no” aspects of sensory experience. With our current subjective measurements for pain assessments, diagnosis and treatment of dental pain in young children and individuals (any age) with severe cognitive impairment rely extensively on third‐party observations. Consequently, the limitation of inadequate pain diagnosis can lead to poor pain management. In this review, it discusses mechanisms that underlie acute and chronic dental pain. It details the measurement of somatosensory responses and pulpal blood flow as objective measures of tooth health and pain. It proposes that bridging these varied methodologies will significantly improve diagnosis and treatment of orofacial pain and pathology. It concludes that improving the precision of sensory measurements could yield important improvements in diagnostic challenges in pulpal pathology for noncommunicative and cognitively impaired individuals.

Relationships Between Temporomandibular Disorders, MSD Conditions, and Mental Health Comorbidities: Findings from the Veterans Musculoskeletal Disorders Cohort

Objective

Temporomandibular disorders (TMDs) have been associated with other chronic painful conditions (e.g., fibromyalgia, headache) and suicide and mood disorders. Here we examined musculoskeletal, painful, and mental health comorbidities in men vs women veterans with TMD (compared with non-TMD musculoskeletal disorders [MSDs] cases), as well as comorbidity patterns within TMD cases.

Design

Observational cohort.

Setting

National Veterans Health Administration.

Subjects

A cohort of 4.1 million veterans having 1+ MSDs, entering the cohort between 2001 and 2011.

Methods

Chi-square tests, t tests, and logistic regression were utilized for cross-sectional analysis.

Results

Among veterans with any MSD, those with TMD were younger and more likely to be women. The association of TMD with race/ethnicity differed by sex. Odds of TMD were higher in men of Hispanic ethnicity (OR = 1.38, 95% CI = 1.27-1.48) and nonwhite race/ethnicity other than black or Hispanic (OR = 1.29, 95% CI = 1.16-1.45) compared with white men. Odds of TMD were significantly lower for black (OR = 0.54, 95% CI = 0.49-0.60) and Hispanic women (OR = 0.84, 95% CI = 0.73-0.995) relative to white women. Non-MSD comorbidities (e.g., irritable bowel syndrome, mental health, headaches) were significantly associated with TMD in male veterans; their pattern was similar in women. Veterans with back pain, nontraumatic joint disorder, or osteoarthritis had more MSD multimorbidity than those with TMD.

Conclusions

Complex patterns of comorbidity in TMD cases may indicate different underlying mechanisms of association in subgroups or phenotypes, thereby suggesting multiple targets to improve TMD. Longitudinal comprehensive studies powered to look at sex and racial/ethnic groupings are needed to identify targets to personalize care.

Neuroinflammation and Central Sensitization in Chronic and Widespread Pain

Chronic pain is maintained in part by central sensitization, a phenomenon of synaptic plasticity, and increased neuronal responsiveness in central pain pathways after painful insults. Accumulating evidence suggests that central sensitization is also driven by neuroinflammation in the peripheral and central nervous system. A characteristic feature of neuroinflammation is the activation of glial cells, such as microglia and astrocytes, in the spinal cord and brain, leading to the release of proinflammatory cytokines and chemokines. Recent studies suggest that central cytokines and chemokines are powerful neuromodulators and play a sufficient role in inducing hyperalgesia and allodynia after central nervous system administration. Sustained increase of cytokines and chemokines in the central nervous system also promotes chronic widespread pain that affects multiple body sites. Thus, neuroinflammation drives widespread chronic pain via central sensitization. We also discuss sex-dependent glial/immune signaling in chronic pain and new therapeutic approaches that control neuroinflammation for the resolution of chronic pain.

Cytokine Gene Polymorphisms Associated With Various Domains of Quality of Life in Women With Breast Cancer

CONTEXT

Little is known about the phenotypic and molecular characteristics associated with various domains of quality of life (QOL) in women after breast cancer surgery.

OBJECTIVES

In a sample of women with breast cancer (n = 398), purposes were as follows: to identify latent classes with distinct trajectories of QOL from before surgery through six months after surgery and to evaluate for differences in demographic and clinical characteristics, as well as for polymorphisms in cytokine genes, between these latent classes.

METHODS

Latent class analyses were done to identify subgroups of patients with distinct QOL outcomes. Candidate gene analyses were done to identify cytokine gene polymorphisms associated with various domains of QOL (i.e., physical, psychological, spiritual, social).

RESULTS

One latent class was identified for the psychological and spiritual domains. Two latent classes were identified for the social domain and overall QOL scores. Three latent classes were identified for the physical domain. For the physical and social domains, as well as for the overall QOL scores, distinct phenotypic characteristics (i.e., younger age, poorer functional status, higher body mass index, and receipt of adjuvant chemotherapy) and a number of cytokine gene polymorphisms (CXCL8, NFKB2, TNFSF, IL1B, IL13, and NFKB1) were associated with membership in the lower QOL classes.

CONCLUSIONS

Findings suggest that women experience distinctly different physical well-being, social well-being, and total QOL outcomes during and after breast cancer surgery. The genetic associations identified suggest that cytokine dysregulation influences QOL outcomes. However, specific QOL domains may be impacted by different cytokines.

Differential expression of systemic inflammatory mediators in amputees with chronic residual limb pain

Chronic postsurgical pain impacts most amputees, with more than half experiencing neuralgic residual limb pain. The transition from normal acute postamputation pain to chronic residual limb pain likely involves both peripheral and central inflammatory mechanisms. As part of the Veterans Integrated Pain Evaluation Research study, we investigated links between systemic inflammatory mediator levels and chronic residual limb pain. Subjects included 36 recent active duty military traumatic amputees with chronic residual limb pain and 40 without clinically significant pain. Blood samples were obtained and plasma concentrations of an array of inflammatory mediators were analyzed. Residual limb pain intensity and pain catastrophizing were assessed to examine associations with inflammatory mediators. Pro-inflammatory mediators including tumor necrosis factor (TNF)-α, TNF-β, interleukin (IL)-8, ICAM-1, Tie2, CRP, and SAA were elevated in patients with chronic residual limb pain. Across all patients, residual limb pain intensity was associated positively with levels of several proinflammatory mediators (IL-8, TNF-α, IL-12, TNF-β, PIGF, Tie2, SAA, and ICAM-1), and inversely with concentrations of the anti-inflammatory mediator IL-13, as well as IL-2 and Eotaxin-3. Pain catastrophizing correlated positively with IL-8, IL-12, TNF-β, PIGF, and ICAM-1, and inversely with IL-13. Significant associations between catastrophizing and residual limb pain intensity were partially mediated by TNF-α, TNF- β, SAA, and ICAM-1 levels. Results suggest that chronic postamputation residual limb pain is associated with excessive inflammatory response to injury or to inadequate resolution of the postinjury inflammatory state. Impact of pain catastrophizing on residual limb pain may be because of part to common underlying inflammatory mechanisms.

Effects of JWH015 in cytokine secretion in primary human keratinocytes and fibroblasts and its suitability for topical/transdermal delivery

Background

JWH015 is a cannabinoid (CB) receptor type 2 agonist that produces immunomodulatory effects. Since skin cells play a key role in inflammatory conditions and tissue repair, we investigated the ability of JWH015 to promote an anti-inflammatory and pro-wound healing phenotype in human primary skin cells.

Methods

Human primary keratinocytes and fibroblasts were stimulated with lipopolysaccharide. The mRNA expression of cannabinoid receptors was determined using RT-PCR. The effects of JWH015 (0.05, 0.1, 0.5, and 1 µM) in pro- and anti-inflammatory factors were tested in lipopolysaccharide-stimulated cells. A scratch assay, using a co-culture of keratinocytes and fibroblasts, was used to test the effects of JWH015 in wound healing. In addition, the topical and transdermal penetration of JWH015 was studied in Franz diffusion cells using porcine skin and LC-MS.

Results

The expression of CB1 and CB2 receptors (mRNA) and the production of pro- and anti-inflammatory factors enhanced in keratinocytes and fibroblasts following lipopolysaccharide stimulation. JWH015 reduced the concentration of major pro-inflammatory factors (IL-6 and MCP-1) and increased the concentration of a major anti-inflammatory factor (TGF-β) in lipopolysaccharide-stimulated cells. JWH015 induced a faster scratch gap closure. These JWH015’seffects were mainly modulated through both CB1 and CB2 receptors. Topically administered JWH015 was mostly retained in the skin and displayed a sustained and low level of transdermal permeation.

Conclusions

Our findings suggest that targeting keratinocytes and fibroblasts with cannabinoid drugs could represent a therapeutic strategy to resolve peripheral inflammation and promote tissue repair.