Pain Phenotypes Research Articles

Pain mechanisms in the transgender individual: a review.

Provide an overview of the literature addressing major areas pertinent to pain in transgender persons and to identify areas of primary relevance for future research. A team of scholars that have previously published on different areas of related research met periodically though zoom conferencing between April 2021 and February 2023 to discuss relevant literature with the goal of providing an overview on the incidence, phenotype, and mechanisms of pain in transgender patients. Review sections were written after gathering information from systematic literature searches of published or publicly available electronic literature to be compiled for publication as part of a topical series on gender and pain in the Frontiers in Pain Research. While transgender individuals represent a significant and increasingly visible component of the population, many researchers and clinicians are not well informed about the diversity in gender identity, physiology, hormonal status, and gender-affirming medical procedures utilized by transgender and other gender diverse patients. Transgender and cisgender people present with many of the same medical concerns, but research and treatment of these medical needs must reflect an appreciation of how differences in sex, gender, gender-affirming medical procedures, and minoritized status impact pain. While significant advances have occurred in our appreciation of pain, the review indicates the need to support more targeted research on treatment and prevention of pain in transgender individuals. This is particularly relevant both for gender-affirming medical interventions and related medical care. Of particular importance is the need for large long-term follow-up studies to ascertain best practices for such procedures. A multi-disciplinary approach with personalized interventions is of particular importance to move forward.

Satellite Glial Cells in Human Disease.

Satellite glial cells (SGCs) are the main type of glial cells in sensory ganglia. Animal studies have shown that these cells play essential roles in both normal and disease states. In a large number of pain models, SGCs were activated and contributed to the pain behavior. Much less is known about SGCs in humans, but there is emerging recognition that SGCs in humans are altered in a variety of clinical states. The available data show that human SGCs share some essential features with SGCs in rodents, but many differences do exist. SGCs in DRG from patients suffering from common painful diseases, such as rheumatoid arthritis and fibromyalgia, may contribute to the pain phenotype. It was found that immunoglobulins G (IgG) from fibromyalgia patients can induce pain-like behavior in mice. Moreover, these IgGs bind preferentially to SGCs and activate them, which can sensitize the sensory neurons, causing nociception. In other human diseases, the evidence is not as direct as in fibromyalgia, but it has been found that an antibody from a patient with rheumatoid arthritis binds to mouse SGCs, which leads to the release of pronociceptive factors from them. Herpes zoster is another painful disease, and it appears that the zoster virus resides in SGCs, which acquire an abnormal morphology and may participate in the infection and pain generation. More work needs to be undertaken on SGCs in humans, and this review points to several promising avenues for better understanding disease mechanisms and developing effective pain therapies.

Risk factors and related miRNA phenotypes of chronic pain after thoracoscopic surgery in lung adenocarcinoma patients.

Chronic postsurgical pain may have a substantial impact on patient's quality of life, and has highly heterogenous presentation amongst sufferers. We aimed to explore the risk factors relating to chronic pain and the related miRNA phenotypes in patients with lung adenocarcinoma after video-assisted thoracoscopic lobectomy to identify potential biomarkers. Our prospective study involved a total of 289 patients with early invasive adenocarcinoma undergoing thoracoscopic lobotomy and a follow-up period of 3 months after surgery. Blood was collected the day before surgery for miRNA detection and patient information including operation duration, duration of continuous drainage of the chest, leukocyte count before and after operation, and postoperative pain scores were recorded. Using clinical and biochemical information for each patient, the risk factors for chronic postsurgical pain and related miRNA phenotypes were screened. We found that chronic postsurgical pain was associated with higher body mass index; greater preoperative history of chronic pain; longer postoperative drainage tube retention duration; higher numerical rating scale scores one, two, and three days after surgery; and changes in miRNA expression, namely lower expression of miRNA 146a-3p and higher expression of miRNA 550a-3p and miRNA 3613-3p in peripheral blood (p < 0.05). Of these factors, patient body mass index, preoperative history of chronic pain, average numerical rating scale score after operation, and preoperative peripheral blood miRNA 550a-3P expression were independent risk factors for the development of chronic postsurgical pain. Identification of individual risk markers may aid the development and selection of appropriate preventive and control measures.

Combined Experiments with in Vivo Fiber Photometry and Behavior Tests Can Facilitate the Measurement of Neuronal Activity in the Primary Somatosensory Cortex and Hyperalgesia in an Inflammatory Pain Mice Model.

The pain matrix, which includes several brain regions that respond to pain sensation, contribute to the development of chronic pain. Thus, it is essential to understand the mechanism of causing chronic pain in the pain matrix such as anterior cingulate (ACC), or primary somatosensory (S1) cortex. Recently, combined experiment with the behavior tests and in vivo calcium imaging using fiber photometry revealed the interaction between the neuronal function in deep brain regions of the pain matrix including ACC and the phenotype of chronic pain. However, it remains unclear whether this combined experiment can identify the interaction between neuronal activity in S1, which receive pain sensation, and pain behaviors such as hyperalgesia or allodynia. In this study, to examine whether the interaction between change of neuronal activity in S1 and hyperalgesia in hind paw before and after causing inflammatory pain was detected from same animal, the combined experiment of in vivo fiber photometry system and von Frey hairs test was applied. This combined experiment detected that amplitude of calcium responses in S1 neurons increased and the mechanical threshold of hind paw decreased from same animals which have an inflammatory pain. Moreover, we found that the values between amplitude of calcium responses and mechanical thresholds were shifted to negative correlation after causing inflammatory pain. Thus, the combined experiment with fiber photometry and the behavior tests has a possibility that can simultaneously consider the interaction between neuronal activity in pain matrix and pain induced behaviors and the effects of analgesics or pain treatments.

World Endometriosis Research Foundation Endometriosis Phenome and Biobanking Harmonization Project: V. Physical examination standards in endometriosis research

The World Endometriosis Research Foundation established the Endometriosis Phenome and Biobanking Harmonisation Project (EPHect) to create standardized documentation tools (with common data elements) to facilitate the comparison and combination of data across different research sites and studies. In 2014, 4 data research standards were published: clinician-reported surgical data, patient-reported clinical data, and fluid and tissue biospecimen collection. Our current objective is to create an EPHect standard for the clinician-reported physical examination (EPHect-PE) for research studies. An international consortium involving 26 clinical and academic experts and patient partners from 11 countries representing 25 institutions and organizations. Two virtual workshops, followed by the development of the physical examination standards underwent multiple rounds of iterations and revisions. N/A MAIN OUTCOME MEASURE(S): N/A RESULT(S): The EPHect-PE tool provides standardized assessment of physical examination characteristics and pain phenotyping. Data elements involve examination of back and pelvic girdle; abdomen including allodynia and trigger points; vulva including provoked vestibulodynia; pelvic floor muscle tone and tenderness; tenderness on unidigital pelvic examination; presence of pelvic nodularity; uterine size and mobility; presence of adnexal masses; presence of incisional masses; speculum examination; tenderness and allodynia at an extra-pelvic site (e.g., forearm); and recording of anthropometrics. The EPHect-PE standards will facilitate the standardized documentation of the physical examination, including the assessment and documentation of examination phenotyping of endometriosis-associated pelvic pain.

A multi-ancestry genetic study of pain intensity in 598,339 veterans.

Chronic pain is a common problem, with more than one-fifth of adult Americans reporting pain daily or on most days. It adversely affects the quality of life and imposes substantial personal and economic costs. Efforts to treat chronic pain using opioids had a central role in precipitating the opioid crisis. Despite an estimated heritability of 25-50%, the genetic architecture of chronic pain is not well-characterized, in part because studies have largely been limited to samples of European ancestry. To help address this knowledge gap, we conducted a cross-ancestry meta-analysis of pain intensity in 598,339 participants in the Million Veteran Program, which identified 126 independent genetic loci, 69 of which are new. Pain intensity was genetically correlated with other pain phenotypes, level of substance use and substance use disorders, other psychiatric traits, education level and cognitive traits. Integration of the genome-wide association studies findings with functional genomics data shows enrichment for putatively causal genes (n = 142) and proteins (n = 14) expressed in brain tissues, specifically in GABAergic neurons. Drug repurposing analysis identified anticonvulsants, β-blockers and calcium-channel blockers, among other drug groups, as having potential analgesic effects. Our results provide insights into key molecular contributors to the experience of pain and highlight attractive drug targets.

Phenotypes of osteoarthritis-related knee pain and their transition over time: data from the osteoarthritis initiative

BackgroundIdentification of knee osteoarthritis (OA) pain phenotypes, their transition patterns, and risk factors for worse phenotypes, may guide prognosis and targeted treatment; however, few studies have described them. We aimed to investigate different pain phenotypes, their transition patterns, and potential risk factors for worse pain phenotypes.MethodsUtilizing data from the Osteoarthritis Initiative (OAI), pain severity was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscale. We identified the activity-related pain phenotypes and estimated the transition probabilities of pain phenotypes from baseline to the 24-month using latent transition analysis. We examined the risk factors at baseline with the 24-month pain phenotypes and the transition of pain phenotypes.ResultsIn 4796 participants, we identified four distinct knee pain phenotypes at both baseline and 24-month follow-up: no pain, mild pain during activity (Mild P-A), mild pain during both rest and activity (Mild P-R-A), and moderate pain during both rest and activity (Mod P-R-A). 82.9% knees with no pain at baseline stayed the same at 24-month follow-up, 17.1% progressed to worse pain phenotypes. Among “Mild P-A” at baseline, 32.0% converted to no-pain, 12.8% progressed to “Mild P-R-A”, and 53.2% remained. Approximately 46.1% of “Mild P-R-A” and 54.5% of “Mod P-R-A” at baseline experienced remission by 24-month. Female, non-whites, participants with higher depression score, higher body mass index (BMI), higher Kellgren and Lawrence (KL) grade, and knee injury history were more likely to be in the worse pain phenotypes, while participants aged 65 years or older and with higher education were less likely to be in worse pain phenotypes at 24-month follow-up visit. Risk factors for greater transition probability to worse pain phenotypes at 24-month included being female, non-whites, participants with higher depression score, higher BMI, and higher KL grade.ConclusionsWe identified four distinct knee pain phenotypes. While the pain phenotypes remained stable in the majority of knees over 24 months period, substantial proportion of knees switched to different pain phenotypes. Several socio-demographics as well as radiographic lesions at baseline are associated with worse pain phenotypes at 24-month follow-up visit and transition of pain phenotypes.

Moderating effects of preoperative knee pain and pain catastrophizing on the relation between COMT rs4680 genotypes and chronic postsurgical pain in total knee arthroplasty patients

BackgroundThe Catechol-O-methyltransferase (COMT) gene, responsible for encoding an enzyme crucial in the metabolism of catecholamines, is known to play a significant role in pain perception. Polymorphisms within this gene, particularly the COMT rs4680 genotypes, have been linked to various acute pain phenotypes. This prospective cohort study examines interactions among the genetic polymorphism COMT rs4680 genotypes, preoperative knee pain, and pain catastrophizing in chronic postsurgical pain (CPSP) at 3, 6, and 12 months post-total knee arthroplasty (TKA). Study designA total of 280 patients undergoing primary unilateral TKA participated, sharing demographic details, preoperative knee pain levels, psychological variables (pain catastrophizing), and COMT rs4680 genotyping via venous blood samples. Telephone interviews at specified intervals enabled the application of binary logistic regressions and interaction models. ResultsSignificant influences of preoperative knee pain and pain catastrophizing on postsurgical outcomes were observed. Specifically, at the first time point (T1, 3 months post-TKA), a notable moderation effect was identified in preoperative knee pain (R2 change = 0.026, p = 0.026). The Johnson–Neyman regions of significance (RoS) indicated these moderation effects were significant above a threshold of 17.18 (p = 0.05), accounting for 26.4%. At the third time point (T3, 12 months post-TKA), a complex three-way interaction among genotypes (GG, GA, and AA carriers) was evident, resulting in an R2 change of 0.051 (p = 0.009). Here, the RoS for pain catastrophizing was above 32.74 for 30.5% of GG genotype carriers, above 22.38 for 50.8% of GA carriers, and below 11.94 for 63.2% of AA carriers. ConclusionThis study illuminates the significant role of the COMT Val158Met rs4680 polymorphism in susceptibility to prolonged pain following TKA. It also elucidates how these genetic genotypes interplay with preoperative knee pain and pain catastrophizing. Such intricate genetic-psychological-pain relationships necessitate additional investigation to confirm these findings and potentially guide post-TKA pain management strategies.

Different pain phenotypes are associated with anti-Caspr2 autoantibodies

Autoantibodies against contactin-associated protein 2 (Caspr2) not only induce limbic autoimmune encephalitis but are also associated with pain conditions. Here, we analyzed clinical data on pain in a large cohort of patients included into the German Network for Research in Autoimmune Encephalitis. Out of 102 patients in our cohort, pain was a frequent symptom (36% of all patients), often severe (63.6% of the patients with pain) and/or even the major symptom (55.6% of the patients with pain). Pain phenotypes differed between patients. Cluster analysis revealed two major phenotypes including mostly distal-symmetric burning pain and widespread pain with myalgia and cramps. Almost all patients had IgG4 autoantibodies and some additional IgG1, 2, and/or 3 autoantibodies, but IgG subclasses, titers, and presence or absence of intrathecal synthesis were not associated with the occurrence of pain. However, certain pre-existing risk factors for chronic pain like diabetes mellitus, peripheral neuropathy, or preexisting chronic back pain tended to occur more frequently in patients with anti-Caspr2 autoantibodies and pain. Our data show that pain is a relevant symptom in patients with anti-Caspr2 autoantibodies and support the idea of decreased algesic thresholds leading to pain. Testing for anti-Caspr2 autoantibodies needs to be considered in patients with various pain phenotypes.

Incidence of Different Characters of Neuropathic Pain in Cancer Patients Coming to Tertiary Care Centre in North India Over A Period of 1 Year - An Observational Study.

Pain is classified as nociceptive, neuropathic, or nociplastic. Neuropathic pain presents as variable phenotypes (characters) based on specific aetiology and pathophysiology. This study aimed to find out among cancer patients the incidence of different phenotypes of neuropathic pain and form specific phenotypic clusters based on the underlying neurophysiology and association of sensory profile with various organ systems - A prospective observational study. The Institutional Ethical Committee clearance (IEC code: 2020-49-MD-EXP-15) https://ctri.nic.in/Clinicaltrials/showallp.php?mid1=44886&EncHid=88651.15716&userName=CTRI/2020/09/027964 approval was obtained. After written and informed consent, patients of age group 18-80 years, registering in the pain and palliative outpatient department or radiotherapy department with complaints of pain and not taking any anti-neuropathic pain medications, were enrolled. They were assessed using Leeds assessment of neuropathic symptoms and signs (LANSS) pain score, and a score of >12 was eligible for assessment of neuropathic pain phenotypes. Out of 210 cancer patients complaining of pain, a neuropathic component with LANSS >12 was found in 73 (34.76%). The most predominant phenotypes, allodynia> tingling> pricking = burning, were found in 72.60%, 56.16%, and 43.84% of patients, respectively. Phenotypes were clustered into Nodes 1 and 2 based on clinically significant separation of phenotypes. Node 1 had neuropathic pain of spontaneous origin found predominantly in gastrointestinal tract (GIT) and genitourinary tract (GUT) cancers. Node 2 had stimulus-evoked negative and positive characters which occurred in head and neck, thoracic, and spinal metastatic cancers. Careful patient assessment reveals the incidence of neuropathic pain in 34.76%; allodynia and tingling astable the most prominent phenotypes. Broadly, sensory characters were clustered into spontaneous and stimulus-evoked sensations with GIT and GUT cancers presenting with Node 1 symptoms.

Rethinking Sjögren Beyond Inflammation: Considering the Role of Nerves in Driving Disease Manifestations.

Sjögren syndrome (SS) is a chronic inflammatory autoimmune disease characterized by destruction of mucosal glands resulting in dry eye and dry mouth. Ocular presentations can be heterogenous in SS with corneal nerves abnormalities that are structural, functional, or both. Some individuals present with corneal hyposensitivity, with a phenotype of decreased tear production and epithelial disruption. Others present with corneal hypersensitivity, with a phenotype of neuropathic pain including light sensitivity and pain out of proportion to signs of tear dysfunction. A similar correlate can be found outside the eye, with dry mouth predominating in some individuals while pain conditions predominate in others. Understanding how nerve status affects SS phenotype is an important first step to improving disease management by targeting nerve abnormalities, as well as inflammation.

Induction of cervical disc degeneration and discogenic pain by low concentration Propionibacterium acnes infection: an in vivo animal study

BackgroundAlthough cervical intervertebral disc (IVD) degeneration is closely associated with neck pain, its cause remains unclear. In this study, an animal model of cervical disc degeneration and discogenic neck pain induced by a low concentration of Propionibacterium acnes (P. acnes-L) is investigated to explore the possible mechanisms of cervical discogenic pain.MethodsCervical IVD degeneration and discitis was induced in 8-week-old male rats in C3–C6 IVDs through the anterior intervertebral puncture with intradiscal injections of low and high concentrations of P. acnes (P. acnes-L, n = 20 and P. acnes-H, n = 15) or Staphylococcus aureus (S. aureus, n = 15), compared to control (injection with PBS, n = 20). The structural changes in the cervical IVD using micro-CT, histological evaluation, and gene expression assays after MRI scans at 2 and 6 weeks post-modeling. The P. acnes-L induced IVD degeneration model was assessed for cervical spine MRI, histological degeneration, pain-like behaviors (guarding behavior and forepaw von Frey), nerve fiber growth in the IVD endplate region, and DRG TNF-α and CGRP.ResultsIVD injection with P. acnes-L induced IVD degeneration with decreased IVD height and MRI T2 values. IVD injection with P. acnes-H and S. aureus both lead to discitis-like changes on T2-weighted MRI, trabecular bone remodeling on micro-CT, and osseous fusion after damage in the cartilage endplate adjacent to the injected IVD. Eventually, rats in the P. acnes-L group exhibited significant nociceptive hypersensitivity, nerve fiber ingrowth was observed in the IVD endplate region, inflammatory activity in the DRG was significantly increased compared to the control group, and the expression of the pain neurotransmitter CGRP was significantly upregulated.ConclusionP. acnes-L was validated to induce cervical IVD degeneration and discogenic pain phenotype, while P. acnes-H induced was identified to resemble septic discitis comparable to those caused by S. aureus infection.

Interindividual variability in cold-pressor pain sensitivity is not explained by peripheral vascular responding and generalizes to a C-nociceptor-specific pain phenotype.

Pain sensitivity of healthy subjects in the cold-pressor (CP) test was proposed to be dichotomously distributed and to represent a pain sensitivity trait. Still, it has not been systematically explored which factors influence this pain sensitivity readout. The aim of this study was to distinguish potential contributions of local tissue-related factors such as perfusion and thermoregulation or gain settings in nociceptive systems. Cold-pressor-sensitive and CP-insensitive students screened from a medical student laboratory course were recruited for a CP retest with additional cardiovascular and bilateral local vascular monitoring. In addition, comprehensive quantitative sensory testing according to Deutscher Forschungsverbund Neuropathischer Schmerz standards and a sustained pinch test were performed. Cold pressor was reproducible across sessions (Cohen kappa 0.61 ± 0.14, P < 0.005). At 30 seconds in ice water, CP-sensitive subjects exhibited not only more pain (78.6 ± 26.3 vs 29.5 ± 17.5, P < 0.0001) but also significantly stronger increases in mean arterial blood pressure (12.6 ± 9.3 vs 5.6 ± 8.1 mm Hg, P < 0.05) and heart rate (15.0 ± 8.2 vs 7.1 ± 6.2 bpm, P < 0.005), and lower baroreflex sensitivity, but not local or vasoconstrictor reflex-mediated microcirculatory responses. Cold-pressor-sensitive subjects exhibited significantly lower pain thresholds also for cold, heat, and blunt pressure, and enhanced pain summation, but no significant differences in Aδ-nociceptor-mediated punctate mechanical pain. In conclusion, differences in nociceptive signal processing drove systemic cardiovascular responses. Baroreceptor activation suppressed pain and cardiovascular responses more efficiently in CP-insensitive subjects. Cold-pressor sensitivity generalized to a pain trait of C-fiber-mediated nociceptive channels, which was independent of local thermal and vascular changes in the ice-water-exposed hand. Thus, the C-fiber pain trait reflects gain setting of the nociceptive system.

An improved conflict avoidance assay reveals modality-specific differences in pain hypersensitivity across sexes.

Abnormal encoding of somatosensory modalities (ie, mechanical, cold, and heat) are a critical part of pathological pain states. Detailed phenotyping of patients' responses to these modalities have raised hopes that analgesic treatments could one day be tailored to a patient's phenotype. Such precise treatment would require a profound understanding of the underlying mechanisms of specific pain phenotypes at molecular, cellular, and circuitry levels. Although preclinical pain models have helped in that regard, the lack of a unified assay quantifying detailed mechanical, cold, and heat pain responses on the same scale precludes comparing how analgesic compounds act on different sensory phenotypes. The conflict avoidance assay is promising in that regard, but testing conditions require validation for its use with multiple modalities. In this study, we improve upon the conflict avoidance assay to provide a validated and detailed assessment of all 3 modalities within the same animal, in mice. We first optimized testing conditions to minimize the necessary amount of training and to reduce sex differences in performances. We then tested what range of stimuli produce dynamic stimulus-response relationships for different outcome measures in naive mice. We finally used this assay to show that nerve injury produces modality-specific sex differences in pain behavior. Our improved assay opens new avenues to study the basis of modality-specific abnormalities in pain behavior.

Therapeutic management of the painful nerve: a narrative review of common rehabilitation interventions

There are many ways that rehabilitation therapists, including occupational and physical therapists, treat nerve-related pain. Commonly used interventions include neurodynamic treatment, pain neuroscience education, desensitization, exercise, physical agent modalities, mirror box therapy, and Kinesio taping. Despite common practice and anecdotal support, it can be challenging to determine the appropriate intervention for each patient. In this article, each of these treatment approaches is discussed, including indicated pain phenotypes and diagnoses, timing, efficacy, mechanism, contraindications, and limitations.

Network analysis of monoamines involved in anxiety-like behavior in a rat model of osteoarthritis.

Chronic pain is a major health problem that affects a significant number of patients, resulting in personal suffering and substantial health care costs. One of the most commonly reported causal conditions is osteoarthritis (OA). In addition to sensory symptoms, chronic pain shares an inherent overlap with mood or anxiety disorders. The involvement of the frontal cortex, striatum and nucleus accumbens, in the affective processing of pain is still poorly understood. Male Wistar rats were divided into two groups: MIA (monoiodoacetate injected into the knee-model of OA) and sham (NaCl). Behavioral tests assessing pain, anxiety, and depressive behavior were performed at week 1, 3, 4, 6, 8, and 10. Neurochemical assays were conducted at weeks 3, 6, and 10 post-MIA injection, followed by the neurotransmitters and their metabolites correlation matrix and network analysis. OA animals developed rapid pain phenotype, whereas anxiety-like behavior accompanied the development of a pain phenotype from 6week post-MIA injection. We did not detect any depressive-like behavior. Instead, immobility time measured in the forced swimming test transiently decreased at 3weeks post-MIA in the OA group. We detected changes in noradrenaline and serotonin levels in analyzed structures at distinct time points. Network analysis revealed noradrenaline and serotonin neurotransmission changes in the nucleus accumbens, confirming it to be the key structure affected by chronic pain. Animals with chronic pain exhibit symptoms of anxiety-like behavior and we identified underlying neurochemical changes using network analysis.

Pain phenotypes in caregivers of children with cerebral palsy.

To determine the phenotypes of chronic pain seen in individuals caring for children with cerebral palsy (CP). A current classification system was used to determine the prevalence of predominant pain phenotypes in caregivers of children with CP. To this end, the Visual Analog Scale, Margolis pain diagram, Central Sensitization Inventory, and Short Form-36 questionnaire were administered to the participants. In addition, the participants underwent a quantitative sensory examination. This study was concluded with 60 individuals. The predominant pain phenotype was nociceptive pain in 30% of the participants, nociplastic pain in 25%, and neuropathic pain in 5%. The pain duration (p=0.365) and quality of life of the individuals did not significantly differ according to the predominant pain phenotypes (p>0.05). However, there was a statistically significant difference between the pain phenotypes in terms of pain severity (p=0.016) and the Central Sensitization Inventory scores (p<0.001). Nociceptive pain was the most common pain phenotype in caregivers of children with CP. We also concluded that among the pain phenotypes, pain intensity was highest in neuropathic pain. There is a need for further studies in this area to demonstrate the validity and reliability of the evaluated mechanism-based classification system in order for it to be included in clinical guidelines.

Effect of perceived injustice-targeted pain neuroscience education compared with biomedically focused education in breast cancer survivors: a study protocol for a multicentre randomised controlled trial (BCS-PI trial)

IntroductionCurrent treatments for pain in breast cancer survivors (BCSs) are mostly biomedically focused rather than biopsychosocially driven. However, 22% of BCSs with pain are experiencing perceived injustice, which is a...

Reduced capsaicin-induced mechanical allodynia and neuronal responses in the dorsal root ganglion in the presence of protein tyrosine phosphatase non-receptor type 6 overexpression.

Transient Receptor Potential Vanilloid 1 (TRPV1) is a nonselective cation channel expressed by pain-sensing neurons and has been an attractive target for the development of drugs to treat pain. Recently, Src homology region two domain-containing phosphatase-1 (SHP-1, encoded by Ptpn6) was shown to dephosphorylate TRPV1 in dorsal root ganglia (DRG) neurons, which was linked with alleviating different pain phenotypes. These previous studies were performed in male rodents only and did not directly investigate the role of SHP-1 in TRPV-1 mediated sensitization. Therefore, our goal was to determine the impact of Ptpn6 overexpression on TRPV1-mediated neuronal responses and capsaicin-induced pain behavior in mice of both sexes. Twelve-week-old male and female mice overexpressing Ptpn6 (Shp1-Tg) and their wild type (WT) littermates were used. Ptpn6 overexpression was confirmed in the DRG of Shp1-Tg mice by RNA in situ hybridization and RT-qPCR. Trpv1 and Ptpn6 were found to be co-expressed in DRG sensory neurons in both genotypes. Functionally, this overexpression resulted in lower magnitude intracellular calcium responses to 200nM capsaicin stimulation in DRG cultures from Shp1-Tg mice compared to WTs. In vivo, we tested the effects of Ptpn6 overexpression on capsaicin-induced pain through a model of capsaicin footpad injection. While capsaicin injection evoked nocifensive behavior (paw licking) and paw swelling in both genotypes and sexes, only WT mice developed mechanical allodynia after capsaicin injection. We observed similar level of TRPV1 protein expression in the DRG of both genotypes, however, a higher amount of tyrosine phosphorylated TRPV1 was detected in WT DRG. These experiments suggest that, while SHP-1 does not mediate the acute swelling and nocifensive behavior induced by capsaicin, it does mediate a protective effect against capsaicin-induced mechanical allodynia in both sexes. The protective effect of SHP-1 might be mediated by TRPV1 dephosphorylation in capsaicin-sensitive sensory neurons of the DRG.

Protocol of a cross-sectional, multicentre and multidisciplinary study describing phenotype and burden of a midfacial segment pain

Background: Midfacial segment pain is a term used in the past in the diagnosis of patients mainly from ear, nose and throat clinics. This type of pain cannot be attributed to other primary or secondary facial pain, but is to a large extent similar to tension-type headache with midfacial location. The purpose of this study is to describe midfacial segment pain phenotype, burden and comorbidities in a multicentre and multidisciplinary setting. The ultimate goal is a comprehensive description of this type of pain allowing for its implementation in future classifications. Methods: This cross-sectional study is designed to describe midfacial segment pain in a clinical setting. Patients from rhinologic, headache and facial pain or oral medicine/dentistry secondary care centres will be recruited during a 1 year period. Individuals with other facial pain according to current classification such as sinonasal disorders, neoplasms, local infections, history of significant trauma associated with pain onset will be excluded. Data will be collected through a structured questionnaire covering pain characteristics, coexisting diagnoses, pain-related burden and consequences, physical examination and paranasal sinuses imaging.