Epigenetics of chronic pain after thoracic surgery

Effects of epidural anesthesia and analgesia on the incidence of chronic pain after thoracoscopic lung surgery: A retrospective cohort study

Objective

Chronic postoperative pain (CPSP) is common after thoracic surgery, even after the less invasive video-assisted thoracoscopic surgery (VATS). This study investigated the effect of thoracic epidural anesthesia (TEA) on the development of CPSP.

Materials

We retrospectively analyzed the data of patients who underwent VATS at our center between 2020 and 2022. The enrolled patients were divided into the epidural block (EPI) and patient-controlled intravenous analgesia (PCIA) groups. A telephone questionnaire was used to collect information regarding CPSP, which was defined as a numerical rating scale (VAS) score ≥1 at 3 or 6 months postoperatively. Additionally, statistical analyses were performed to identify the risk factors for CPSP in the two groups.

Results

Overall, 894 patients completed the follow-up interviews at 3 and 6 months, with 325 and 569 patients in the PCIA and EPI groups, respectively. The incidence rates of CPSP in the PCIA group at 3 and 6 months were 16.9 % (95 % confidence interval [CI]: 9.3-32.7 %) and 13.5 % (95 % CI: 8.7-33.4 %), and 10.3 % (95 % CI: 8.1-30.5 %) and 3.6 % (95 % CI: 3.5-21.5 %) in EPI group, respectively. The incidence of CPSP at 3 months (P = 0.0048) and 6 months (P < 0.005) was statistically significant in both groups. Age and lymph node dissection were significantly associated with CPSP.

Conclusions

Compared to PCIA, TEA was associated with a lower incidence of CPSP after VATS, and should be considered an important part of the analgesia regimen for patients with VATS.

Opioid use disorder in pediatric populations: considerations for perioperative pain management and precision opioid analgesia

INTRODUCTION

Opioids are commonly used for perioperative analgesia, yet children still suffer high rates of severe post-surgical pain and opioid-related adverse effects. Persistent and severe acute surgical pain greatly increases the child's chances of chronic surgical pain, long-term opioid use, and opioid use disorder.

AREAS COVERED

Enhanced recovery after surgery (ERAS) protocols are often inadequate in treating a child's severe surgical pain. Research suggests that 'older' and longer-acting opioids such as methadone are providing better methods to treat acute post-surgical pain. Studies indicate that lower repetitive methadone doses can decrease the incidence of chronic persistent surgical pain (CPSP). Ongoing research explores genetic components influencing severe surgical pain, inadequate opioid analgesia, and opioid use disorder. This new genetic research coupled with better utilization of opioids in the perioperative setting provides hope in personalizing surgical pain management, reducing pain, opioid use, adverse effects, and helping the fight against the opioid pandemic.

EXPERT OPINION

The opioid and analgesic pharmacogenomics approach can proactively 'tailor' a perioperative analgesic plan to each patient based on underlying polygenic risks. This transition from population-based knowledge of pain medicine to individual patient knowledge can transform acute pain medicine and greatly reduce the opioid epidemic's socioeconomic, personal, and psychological strains globally.

Maintaining quality of life after major lung resection for carcinoid tumor

BACKGROUND

Pulmonary carcinoid is a rare diagnosis with surgery remaining the standard treatment of choice. However, resection may impact patients' daily activities due to decreased lung volume reserve and postoperative pain. Our study aims to compare the impact of different types of surgical resection on the post-operative quality of life with the application of a strict peri-operative pulmonary care program.

METHODS

Patients who underwent surgery for bronchopulmonary carcinoid tumors in a tertiary cancer center between August, 2017 and March, 2020 were identified and demographic data was collected. Patients were contacted via phone for the qualitative and quantitative assessment of pain and quality of life, utilizing the Arabic version of Short-form McGill Pain Questionnaire and Activity of Daily Living (ADL) instrument respectively. Lung reserve was assessed before and after surgery. Statistical analysis used Chi-Square for categorical variables and ANOVA for continuous variables.

RESULTS

A total of 16 patients underwent different type of resection. The majority were male (n = 10; 63%) with a mean age of 44 years (19-81). Most common clinical stage was stage I (n = 12, 75%) with typical carcinoid features recorded in more than half of the cases (n = 11, 69%). Almost all patients underwent surgical excision (n = 15, 94%) with negative resection margin and no major post-operative complications. Bilobectomy was the most frequent procedure (n = 6, 40%) and video-assisted thoracoscopic surgery (VATS) was utilized in 8 patients (50%). Expected changes were recorded in pre- and postoperative pulmonary function test with an average drop of 10 in FEV1 and 14 mL/min/mmHg in DLCO. The majority of patients (n = 15, 94%) were totally independent doing daily activities. Mild intermittent pain was found in 7 patients (44%) who scored an average intensity of 1.6 out of 10.

CONCLUSIONS

Excellent long-term outcomes can be achieved following surgical resection of pulmonary carcinoid tumors with little to no effect on patients' lung function and quality of life in regard to performance status and post-operative pain when a good peri-operative pulmonary, physical rehabilitation, and pain management programs are adopted and strictly implemented.

Prevalence and Characteristics of Persistent Postoperative Pain After Thoracic Surgery: A Systematic Review and Meta-Analysis

BACKGROUND

A systematic review and meta-analysis was conducted to investigate the prevalence and characteristics of persistent (≥3 months) postoperative pain (PPP) after thoracic surgery.

METHODS

For this purpose, Medline, Embase, and CINAHL databases were searched for the prevalence and characteristics of PPP after thoracic surgery from their inception to May 1, 2022. Random-effect meta-analysis was used to estimate pooled prevalence and characteristics.

RESULTS

We included 90 studies with 19,001 patients. At a median follow-up of 12 months, the pooled overall prevalence of PPP after thoracic surgery was 38.1% (95% confidence interval [CI], 34.1-42.3). Among patients with PPP, 40.6% (95% CI, 34.4-47.2) and 10.1% (95% CI, 6.8-14.8) experienced moderate-to-severe (rating scale ≥4/10) and severe (rating scale ≥7/10) PPP, respectively. Overall, 56.5% (95% CI, 44.3-67.9) of patients with PPP required opioid analgesic use, and 33.0% (95% CI, 22.5-44.3) showed a neuropathic component.

CONCLUSIONS

One in 3 thoracic surgery patients developed PPP. There is a need for adequate pain treatment and follow-up in patients undergoing thoracic surgery.

Epigenetic Factors Related to Low Back Pain: A Systematic Review of the Current Literature

Low back pain (LBP) is one of the most common causes of pain and disability. At present, treatment and interventions for acute and chronic low back pain often fail to provide sufficient levels of pain relief, and full functional restoration can be challenging. Considering the significant socio-economic burden and risk-to-benefit ratio of medical and surgical intervention in low back pain patients, the identification of reliable biomarkers such as epigenetic factors associated with low back pain could be useful in clinical practice. The aim of this study was to review the available literature regarding the epigenetic factors associated with low back pain. This review was carried out in accordance with Preferential Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The search was carried out in October 2022. Only peer-reviewed articles were considered for inclusion. Fourteen studies were included and showed promising results in terms of reliable markers. Epigenetic markers for LBP have the potential to significantly modify disease management. Most recent evidence suggests that epigenetics is a more promising field for the identification of factors associated with LBP, offering a rationale for further investigation in this field with the long-term goal of finding epigenetic biomarkers that could constitute biological targets for disease management and treatment.

Pain predict genetics: protocol for a prospective observational study of clinical and genetic factors to predict the development of postoperative pain

INTRODUCTION

Postoperative pain remains a challenging medical condition impacting the quality of life of every patient. Although several predictive factors for postoperative pain have been identified, an adequate prediction of postoperative pain in patients at risk has not been achieved yet.The primary objective of this study is to identify specific genetic risk factors for the development of acute and chronic postoperative pain to construct a prediction model facilitating a more personalised postoperative pain management for each individual. The secondary objectives are to build a databank enabling researchers to identify other risk factors for postoperative pain, for instance, demographic and clinical outcome indicators; provide insight into (genetic) factors that predict pharmacological pain relief; investigate the relationship between acute and chronic postoperative pain.

METHODS AND ANALYSIS

In this prospective, observational study, patients who undergo elective surgery will be recruited to a sample size of approximately 10 000 patients. Postoperative acute and chronic pain outcomes will be collected through questionnaires at different time points after surgery in the follow-up of 6 months. Potential genetic, demographic and clinical risk factors for prediction model construction will be collected through blood, questionnaires and electronic health records, respectively.Genetic factors associated with acute and/or chronic postoperative pain will be identified using a genome-wide association analysis. Clinical risk factors as stated in the secondary objectives will be assessed by multivariable regression. A clinical easy-to-use prediction model will be created for postoperative pain to allow clinical use for the stratification of patients.

ETHICS AND DISSEMINATION

The Institutional Review Board of the Radboud university medical centre approved the study (authorisation number: 2012/117). The results of this study will be made available through peer-reviewed scientific journals and presentations at relevant conferences, which will finally contribute to personalised postoperative pain management.

TRIAL REGISTRATION NUMBER

NCT02383342.

Methylome of skeletal muscle tissue in patients with hypertension and diabetes undergoing cardiopulmonary bypass

Background: Epigenomic changes occurring during surgery have been neglected in research; diabetes and hypertension can affect the epigenome but little is known about the epigenetics of skeletal muscle (SKM). Methods: DNA methylation was profiled via Illumina MethylationEPIC arrays in SKM samples obtained at the beginning and end of heart surgery with cardiopulmonary bypass. Results: Methylation in patients with hypertension and diabetes was significantly different, more so for uncontrolled diabetes; hypertension alone produced minimal effect. The affected pathways involved IL-1, IL-12, IL-18, TNF-α, IFN-γ, VEGF, NF-κB and Wnt signaling, apoptosis and DNA damage response. Significant changes occurred during surgery and included loci in the Hippo-YAP/TAZ pathway. Conclusion: Cardiopulmonary bypass surgery affects the SKM methylome, and the combination of hypertension and diabetes induces changes in the SKM epigenome in contrast to hypertension alone.

Epigenetics and postsurgical pain: A scoping review

OBJECTIVE

Multiple factors are involved in the physiology and variability of postsurgical pain, a great part of which can be explained by genetic and environmental factors and their interaction. Epigenetics refers to the mechanism by which the environment alters the stability and expression of genes. We conducted a scoping review to examine the available evidence in both animal models and clinical studies on epigenetic mechanisms involved in regulation of postsurgical and chronic postsurgical pain.

METHODS

The Arksey & ÓMalley framework and the PRISMA-ScR (Preferred Reporting Items for Systematic Review and Meta-Analysis, scoping reviews extension) guidelines were used. The PubMed, Web of Science and Google Scholar databases were searched, and the original articles cited in reviews located through the search were also reviewed. English-language articles without time limits were retrieved. Articles were selected if the abstract addressed information on the epigenetic or epigenomic mechanisms, histone, or DNA methylation and microribonucleic acids involved in postsurgical and chronic postsurgical pain in animal models and clinical studies.

RESULTS

The initial search provided 174 articles, and 81 were used. The available studies to date, mostly in animal models, have shown that epigenetics contributes to regulation of gene expression in the pathways involved in postsurgical pain and in maintaining long-term pain.

CONCLUSION

Research on possible epigenetic mechanisms involved in postsurgical pain and chronic postsurgical pain in humans is scarce. In view of the evidence available in animal models, there is a need to evaluate epigenetic pain mechanisms in the context of human and clinical studies.

Implementation of the Uniformed Services University Pain Registry Biobank: A Military and Veteran Population Focused Biobank and Registry

OBJECTIVE

The objective of this overview is to discuss the development, implementation, data content, and structure of the Uniformed Services University Pain Registry Biobank. Additionally, procedures and policies for accessing samples for pain-related research purposes are detailed.

DESIGN

Cross-sectional overview.

SETTING

Multiple military treatment facilities.

SUBJECTS

Adult beneficiaries seeking care within the Military Health System.

METHODS

Participants complete a baseline battery of biopsychosocial survey measures, including PROMIS® measures, provide biologic samples (e.g. blood and saliva), and relevant health history, including medications and surgical history, is extracted from medical records. During the course of the next year, enrolled participants complete surveys and provide biologic samples at 3-months, 6-months, and 12-months. Thereafter, participants are contacted once annually to complete self-reported assessments and provide biologic samples.

RESULTS

In the first year alone 86 subjects have participated in the Uniformed Services University Pain Registry Biobank and provided 390 observations (e.g. biological samples and biopsychosocial patient-reported outcomes). The Uniformed Services University Pain Registry Biobank's integration of biological samples, patient-reported outcomes, and health record data over a longitudinal period across a diverse sample recruited from multiple military facilities addresses many of the limitations faced by other pain-related registries or biorepositories.

CONCLUSIONS

The Uniformed Services University Pain Registry Biobank will serve as a platform for conducting research closely aligned with the Federal Pain Research Strategy. The inclusion of active duty service members, beneficiaries, and civilians living with and without acute or chronic pain provides a unique data repository for all investigators interested in advancing pain science.

Chronic Pain After Lung Resection: Risk Factors, Neuropathic Pain, and Quality of Life

CONTEXT

Chronic postsurgical pain (CPSP) can occur frequently after thoracic surgery.

OBJECTIVES

This retrospective study aimed to determine CPSP prevalence, risk factors, neuropathic pain (NP) occurrence, and its impact on quality of life.

METHODS

About 200 patients who underwent lung resection via minithoracotomy or thoracoscopy between January 2017 and December 2017 were assessed 4-12 months postoperatively via phone interview for chronic pain by a 0-10 Numeric Rating Scale, for NP using the Douleur Neuropathique 4 test, and for quality of life using a Short Form-36 (SF-36) Health Survey (Italian version).

RESULTS

CPSP incidence was 35% (n = 70 of 200; 95% CI 41-28) of which 31.5% (n = 22 of 70; 95% CI 41-21) was with NP. Only 10% of patients with CPSP reported severe chronic pain. According to univariate analysis, CPSP was associated to moderate and severe acute postoperative pain (P < 0.001), open surgery (P = 0.001), and female gender (P = 0.044). According to multivariable analysis, independent risk factors for CPSP development included moderate-to-severe acute postoperative pain occurrence (odds ratio 32.61; 95% CI 13.37-79.54; P < 0.001) and open surgery (odds ratio 6.78; 95% CI, 2.18-21.03; P = 0.001). NP incidence was higher in female patients (16% in women and 6% in men, respectively; P = 0.040). A significant decrease in all SF-36 Health Survey domain scores was recorded for patients with CPSP and NP (P < 0.001).

CONCLUSION

More than one of three patients who underwent lung resection could develop CPSP, frequently showing neuropathic component. Female gender reported a higher CPSP and NP incidence. Moderate-to-severe acute postoperative pain occurrence and open surgery seem to be independent risk factors for CPSP. Chronic pain and NP have a negative impact on quality of life, decreasing the SF-36 scores of all domains.

Sex differences in negative affect and postoperative pain in patients undergoing total knee arthroplasty

Background

Knee osteoarthritis (OA) is among the most common and disabling persistent pain conditions, with increasing prevalence in the developed world, and affects women to a greater degree than men. In the USA, the growth of knee OA has been paralleled by an increase in rates of total knee arthroplasty (TKA), a surgical treatment option for late-stage knee OA. While TKA outcomes are generally good, postoperative trajectories of pain vary widely, with some patients reporting a complete absence of pain, but with a significant minority reporting worsening pain. Biopsychosocial factors, including anxiety and depression, are known to contribute importantly to the experience of joint pain, with women reporting a higher degree of negative affective symptoms.

Methods

This study investigated sex differences in TKA outcomes in age-matched groups of men and women at two academic medical centers. Pain and physical function were assessed in 100 patients (50 men and 50 women) during the perioperative period (preoperative visit—6 weeks postsurgical). The association of preoperative negative affect (anxiety and depression scores) to postoperative pain and function was evaluated, with specific attention to sex differences in this relationship.

Results

Overall, women reported more baseline pain-related physical dysfunction (although not higher baseline pain scores), as well as higher acute postoperative pain scores during the 2 weeks following TKA than their male counterparts. By 6 weeks postoperatively, sex differences in reported pain were no longer evident. Interestingly, although women reported higher preoperative levels of emotional distress than men, preoperative anxiety and depression scores were better predictors of severe postoperative pain among men than women, throughout the postoperative test period.

Conclusions

This study underlines the importance of considering sex and psychosocial factors, as well as their interaction, in understanding postsurgical pain trajectories.

Targeting epigenetic mechanisms for chronic visceral pain: A valid approach for the development of novel therapeutics

BACKGROUND

Chronic visceral pain is persistent pain emanating from thoracic, pelvic, or abdominal origin that is poorly localized with regard to the specific organ affected. The prevalence can range up to 25% in the adult population as chronic visceral pain is a common feature of many visceral disorders, which may or may not be accompanied by distinct structural or histological abnormalities within the visceral organs. Mounting evidence suggests that changes in epigenetic mechanisms are involved in the top-down or bottom-up sensitization of pain pathways and the development of chronic pain. Epigenetic changes can lead to long-term alterations in gene expression profiles of neurons and consequently alter functionality of peripheral neurons, dorsal root ganglia, spinal cord, and brain neurons. However, epigenetic modifications are dynamic, and thus, detrimental changes may be reversible. Hence, external factors/therapeutic interventions may be capable of modulating the epigenome and restore normal gene expression for extended periods of time.

PURPOSE

The goal of this review is to highlight the latest discoveries made toward understanding the epigenetic mechanisms that are involved in the development or maintenance of chronic visceral pain. Furthermore, this review will provide evidence supporting that targeting these epigenetic mechanisms may represent a novel approach to treat chronic visceral pain.

MBD1 Contributes to the Genesis of Acute Pain and Neuropathic Pain by Epigenetic Silencing of Oprm1 and Kcna2 Genes in Primary Sensory Neurons

The transmission of normal sensory and/or acute noxious information requires intact expression of pain-associated genes within the pain pathways of nervous system. Expressional changes of these genes after peripheral nerve injury are also critical for neuropathic pain induction and maintenance. Methyl-CpG-binding domain protein 1 (MBD1), an epigenetic repressor, regulates gene transcriptional activity. We report here that MBD1 in the primary sensory neurons of DRG is critical for the genesis of acute pain and neuropathic pain as DRG MBD1-deficient mice exhibit the reduced responses to acute mechanical, heat, cold, and capsaicin stimuli and the blunted nerve injury-induced pain hypersensitivities. Furthermore, DRG overexpression of MBD1 leads to spontaneous pain and evoked pain hypersensitivities in the WT mice and restores acute pain sensitivities in the MBD1-deficient mice. Mechanistically, MDB1 represses Oprm1 and Kcna2 gene expression by recruiting DNA methyltransferase DNMT3a into these two gene promoters in the DRG neurons. DRG MBD1 is likely a key player under the conditions of acute pain and neuropathic pain.SIGNIFICANCE STATEMENT In the present study, we revealed that the mice with deficiency of methyl-CpG-binding domain protein 1 (MBD1), an epigenetic repressor, in the DRG displayed the reduced responses to acute noxious stimuli and the blunted neuropathic pain. We also showed that DRG overexpression of MBD1 produced the hypersensitivities to noxious stimuli in the WT mice and rescued acute pain sensitivities in the MBD1-deficient mice. We have also provided the evidence that MDB1 represses Oprm1 and Kcna2 gene expression by recruiting DNA methyltransferase DNMT3a into these two gene promoters in the DRG neurons. DRG MBD1 may participate in the genesis of acute pain and neuropathic pain likely through regulating DNMT3a-controlled Oprm1 and Kcna2 gene expression in the DRG neurons.

MicroRNA-30b regulates expression of the sodium channel Nav1.7 in nerve injury-induced neuropathic pain in the rat

Voltage-gated sodium channels, which are involved in pain pathways, have emerged as major targets for therapeutic intervention in pain disorders. Nav1.7, the tetrodotoxin-sensitive voltage-gated sodium channel isoform encoded by SCN9A and predominantly expressed in pain-sensing neurons in the dorsal root ganglion, plays a crucial role in nociception. MicroRNAs are highly conserved, small non-coding RNAs. Through binding to the 3′ untranslated region of their target mRNAs, microRNAs induce the cleavage and/or inhibition of protein translation. Based on bioinformatics analysis using TargetScan software, we determined that miR-30b directly targets SCN9A. To investigate the roles of Nav1.7 and miR-30b in neuropathic pain, we examined changes in the expression of Nav1.7 in the dorsal root ganglion by miR-30b over-expression or knockdown in rats with spared nerve injury. Our results demonstrated that the expression of miR-30b and Nav1.7 was down-regulated and up-regulated, respectively, in the dorsal root ganglion of spared nerve injury rats. MiR-30b over-expression in spared nerve injury rats inhibited SCN9A transcription, resulting in pain relief. In addition, miR-30b knockdown significantly increased hypersensitivity to pain in naive rats. We also observed that miR-30b decreased Nav1.7 expression in PC12 cells. Taken together, our results suggest that miR-30b plays an important role in neuropathic pain by regulating Nav1.7 expression. Therefore, miR-30b may be a promising target for the treatment of chronic neuropathic pain.

DNA Methylation Modulates Nociceptive Sensitization after Incision

DNA methylation is a key epigenetic mechanism controlling DNA accessibility and gene expression. Blockade of DNA methylation can significantly affect pain behaviors implicated in neuropathic and inflammatory pain. However, the role of DNA methylation with regard to postoperative pain has not yet been explored. In this study we sought to investigate the role of DNA methylation in modulating incisional pain and identify possible targets under DNA methylation and contributing to incisional pain. DNA methyltranferase (DNMT) inhibitor 5-Aza-2′-deoxycytidine significantly reduced incision-induced mechanical allodynia and thermal sensitivity. Aza-2′-deoxycytidine also reduced hindpaw swelling after incision, suggesting an anti-inflammatory effect. Global DNA methylation and DNMT3b expression were increased in skin after incision, but none of DNMT1, DNMT3a or DNMT3b was altered in spinal cord or DRG. The expression of proopiomelanocortin Pomc encoding β-endorphin and Oprm1 encoding the mu-opioid receptor were upregulated peripherally after incision; moreover, Oprm1 expression was further increased under DNMT inhibitor treatment. Finally, local peripheral injection of the opioid receptor antagonist naloxone significantly exacerbated incision-induced mechanical hypersensitivity. These results suggest that DNA methylation is functionally relevant to incisional nociceptive sensitization, and that mu-opioid receptor signaling might be one methylation regulated pathway controlling sensitization after incision.

Epigenetic regulation of chronic pain

Chronic pain arising from peripheral inflammation and tissue or nerve injury is a common clinical symptom. Although intensive research on the neurobiological mechanisms of chronic pain has been carried out during previous decades, this disorder is still poorly managed by current drugs such as opioids and nonsteroidal anti-inflammatory drugs. Inflammation, tissue injury and/or nerve injury-induced changes in gene expression in sensory neurons of the dorsal root ganglion, spinal cord dorsal horn and pain-associated brain regions are thought to participate in chronic pain genesis; however, how these changes occur is still elusive. Epigenetic modifications including DNA methylation and covalent histone modifications control gene expression. Recent studies have shown that peripheral noxious stimulation changes DNA methylation and histone modifications and that these changes may be related to the induction of pain hypersensitivity under chronic pain conditions. This review summarizes the current knowledge and progress in epigenetic research in chronic pain and discusses the potential role of epigenetic modifications as therapeutic antinociceptive targets in this disorder.