Juxtametallic Bipolar Bone Radiofrequency Ablation: Thermal Monitoring in an Ex-Vivo Model with Specimen MRI and Histopathologic Correlation.

PURPOSE: To measure the ablation zone temperature and nontarget tissue temperature during radiofrequency (RF) ablation in bone containing metal instrumentation versus no metal instrumentation (control group). MATERIALS AND METHODS: Ex vivo experiments were performed on 15 swine vertebrae (control, n = 5; titanium screw, n = 5; stainless steel screw, n = 5). Screws and RF ablation probe were inserted identically under fluoroscopy. During RF ablation (3 W, 5 minutes), temperature was measured 10 mm from RF ablation centerpoint and in muscle contacting the screw. Magnetic resonance (MR) imaging, gross pathologic, and histopathologic analyses were performed on 1 specimen from each group. RESULTS: Ablation zone temperatures at 2.5 and 5 minutes increased by 12.2 °C ± 2.6 °C and 21.5 °C ± 2.1 °C (control); 11.0 °C ± 4.1 °C and 20.0 °C ± 2.9 °C (juxta-titanium screw), and 10.0 °C ± 3.4 °C and 17.2 °C ± 3.5 °C (juxta-stainless steel) screw; differences among groups did not reach significance by analysis of variance (P = .87). Mixed-effects linear regression revealed a statistically significant increase in temperature over time in all 3 groups (4.2 °C/min ± 0.4 °C/min, P < .001). Compared with the control, there was no significant difference in the temperature change over time for titanium (-0.3 °C/min ± 0.5 °C/min, P = .53) or steel groups (-0.4 °C/min ± 0.5 °C/min, P = .38). The mean screw temperature at the final time point did not show a statistically significant change compared with baseline in either the titanium group (-1.2 °C ± 2.3 °C, P = .50) or steel group (2.6 °C ± 2.9 °C, P = .11). MR imaging and pathologic analyses revealed homogeneous ablation without sparing of the peri-hardware zones. CONCLUSIONS: Adjacent metallic instrumentation did not affect the rate of or absolute increase in temperature in the ablation zone, did not create peri-metallic ablation inhomogeneities, and did not result in significant nontarget heating of muscle tissue in contact with the metal instrumentation.

Association of cystic fibrosis transmembrane conductance regulator with epithelial sodium channel subunits carrying Liddle's syndrome mutations.

The association of the cystic fibrosis transmembrane conductance regulator (CFTR) and epithelial sodium channel (ENaC) in the pathophysiology of cystic fibrosis (CF) is controversial. Previously, we demonstrated a close physical association between wild-type (WT) CFTR and WT ENaC. We have also shown that the F508del CFTR fails to associate with ENaC unless the mutant protein is rescued pharmacologically or by low temperature. In this study, we present the evidence for a direct physical association between WT CFTR and ENaC subunits carrying Liddle's syndrome mutations. We show that all three ENaC subunits bearing Liddle's syndrome mutations (both point mutations and the complete truncation of the carboxy terminus), could be coimmunoprecipitated with WT CFTR. The biochemical studies were complemented by fluorescence lifetime imaging microscopy (FLIM), a distance-dependent approach that monitors protein-protein interactions between fluorescently labeled molecules. Our measurements revealed significantly increased fluorescence resonance energy transfer between CFTR and all tested ENaC combinations as compared with controls (ECFP and EYFP cotransfected cells). Our findings are consistent with the notion that CFTR and ENaC are within reach of each other even in the setting of Liddle's syndrome mutations, suggestive of a direct intermolecular interaction between these two proteins.

Stellate Ganglion Blockade: an Intervention for the Management of Ventricular Arrhythmias.

PURPOSE OF REVIEW: To highlight the indications, procedural considerations, and data supporting the use of stellate ganglion blockade (SGB) for management of refractory ventricular arrhythmias. RECENT FINDINGS: In patients with refractory ventricular arrhythmias, unilateral or bilateral SGB can reduce arrhythmia burden and defibrillation events for 24-72 h, allowing time for use of other therapies like catheter ablation, surgical sympathectomy, or heart transplantation. The efficacy of SGB appears to be consistent despite the type (monomorphic vs polymorphic) or etiology (ischemic vs non-ischemic cardiomyopathy) of the ventricular arrhythmia. Ultrasound-guided SGB is safe with low risk for complications, even when performed on anticoagulation. SGB is effective and safe and could be considered for patients with refractory ventricular arrhythmias.

Stellate ganglion blockade for the treatment of refractory ventricular arrhythmias: A systematic review and meta-analysis.

INTRODUCTION: Treatment refractory ventricular arrhythmias (VAs) are often driven and exacerbated by heightened sympathetic tone. We aim to conduct a systematic review and meta-analysis of published studies of a temporary percutaneous stellate ganglion block (SGB) on VA burden and defibrillation episodes in patients with treatment refractory VAs. METHODS: Relevant studies from January 1960 through May 2017 were identified in PubMed and Google Scholar. We performed a patient-level analysis using Student's t-test to compare outcomes before and after SGB. RESULTS: We identified 22 unique case series with a total of 35 patients. Patients were 57 ± 17 years old and 69% were males with a high burden of VA. A unilateral (left)-sided SGB was used in 85.7% (30 of 35) of cases and the remaining were bilateral SGB. The use of a unilateral or bilateral SGB resulted in a significant reduction of VA episodes (24-hours pre: mean 16.5 [CI 9.7-23.1] events vs. post: mean 1.4 [CI 0.85-2.01] events; P = 0.0002) and need for defibrillation (24-hours pre: mean 14.2 [CI 6.8-21.6] vs. post: mean 0.6 [CI 0.3-0.9]; P = 0.0026). Furthermore, SGB was significantly associated with a reduction of VA burden regardless of etiology of cardiomyopathy, type of ventricular rhythm, and degree of contractile dysfunction. SGB was followed by surgical sympathectomy in 21% of cases. CONCLUSIONS: Early experience suggests that SGB is associated with an acute reduction in the VA burden and offers potential promise for a broader use in high-risk populations. Randomized controlled studies are needed to confirm the safety and efficacy of this therapy.

5-Hydroxymethylcytosine (5hmC) and Ten-eleven translocation 1-3 (TET1-3) proteins in the dorsal root ganglia of mouse: Expression and dynamic regulation in neuropathic pain.

Epigenetic mechanisms are increasingly implicated in chronic pain pathology. In this study, we demonstrate that the novel epigenetic mark 5-hydroxymethylcytosine (5hmC) is present in dorsal root ganglia (DRG) neurons and glia, and its levels increase following nerve injury. Furthermore, we show that the 5hmC-generating Ten-eleven translocation 1-3 (TET1-3) proteins are expressed in a cell-type specific manner in the DRG, with Tet3 displaying differential upregulation after injury, suggesting a potential role in neuropathic pain.

A Multicenter Study of Stellate Ganglion Block as a Temporizing Treatment for Refractory Ventricular Arrhythmias.

BACKGROUND: Ventricular tachycardia (VT) and ventricular fibrillation (VF) are life-threatening conditions and can be refractory to conventional drug and device interventions. Stellate ganglion blockade (SGB) has been described as an adjunct, temporizing intervention in patients with refractory ventricular arrhythmia. We examined the association of SGB with VT/VF in a multicenter registry. OBJECTIVES: This study examined the efficacy of SGB for treatment/temporization of refractory VT/VF. METHODS: The authors present the first analysis from a multicenter registry of patients treated for refractory ventricular arrhythmia at a clinical site in the Czech Republic and the United States. Data were collected between 2016 and 2022. SGB was performed at the bedside by anesthesiologists and/or cardiologists. Outcomes of interest were VT/VF burden and defibrillations at 24 hours before and after SGB. RESULTS: In total, there were 117 patients with refractory ventricular arrhythmias treated with SGB at Duke (n = 49) and the Institute for Clinical and Experimental Medicine (n = 68). The majority of patients were male (94.0%), were White (87.2%), and had an implantable cardioverter-defibrillator (70.1%). The most common etiology of heart disease was ischemic cardiomyopathy (52.1%), and monomorphic VT was the most common morphology (70.1%). Within 24 hours before SGB (0-24 hours), the median episodes of VT/VF were 7.5 (Q1-Q3: 3.0-27.0), and 24 hours after SGB, the median decreased to 1.0 (Q1-Q3: 0.0-4.5; P < 0.001). At 24 hours before SGB, the median defibrillation events were 2.0 (Q1-Q3: 0.0-8.0), and 24 hours after SGB, the median decreased to 0.0 (Q1-Q3: 0.0-1.0; P < 0.001). CONCLUSIONS: In the largest cohort of patients with treatment-refractory ventricular arrhythmia, we demonstrate that SGB use was associated with a reduction in the ventricular arrhythmia burden and need for defibrillation therapy.

Low temperature and chemical rescue affect molecular proximity of DeltaF508-cystic fibrosis transmembrane conductance regulator (CFTR) and epithelial sodium channel (ENaC).

An imbalance of chloride and sodium ion transport in several epithelia is a feature of cystic fibrosis (CF), an inherited disease that is a consequence of mutations in the cftr gene. The cftr gene codes for a Cl(-) channel, the cystic fibrosis transmembrane conductance regulator (CFTR). Some mutations in this gene cause the balance between Cl(-) secretion and Na(+) absorption to be disturbed in the airways; Cl(-) secretion is impaired, whereas Na(+) absorption is elevated. Enhanced Na(+) absorption through the epithelial sodium channel (ENaC) is attributed to the failure of mutated CFTR to restrict ENaC-mediated Na(+) transport. The mechanism of this regulation is controversial. Recently, we have found evidence for a close association of wild type (WT) CFTR and WT ENaC, further underscoring the role of ENaC along with CFTR in the pathophysiology of CF airway disease. In this study, we have examined the association of ENaC subunits with mutated ΔF508-CFTR, the most common mutation in CF. Deletion of phenylalanine at position 508 (ΔF508) prevents proper processing and targeting of CFTR to the plasma membrane. When ΔF508-CFTR and ENaC subunits were co-expressed in HEK293T cells, we found that individual ENaC subunits could be co-immunoprecipitated with ΔF508-CFTR, much like WT CFTR. However, when we evaluated the ΔF508-CFTR and ENaC association using fluorescence resonance energy transfer (FRET), FRET efficiencies were not significantly different from negative controls, suggesting that ΔF508-CFTR and ENaC are not in close proximity to each other under basal conditions. However, with partial correction of ΔF508-CFTR misprocessing by low temperature and chemical rescue, leading to surface expression as assessed by total internal reflection fluorescence (TIRF) microscopy, we observed a positive FRET signal. Our findings suggest that the ΔF508 mutation alters the close association of CFTR and ENaC.

ENaCs and ASICs as therapeutic targets.

The epithelial Na(+) channel (ENaC) and acid-sensitive ion channel (ASIC) branches of the ENaC/degenerin superfamily of cation channels have drawn increasing attention as potential therapeutic targets in a variety of diseases and conditions. Originally thought to be solely expressed in fluid absorptive epithelia and in neurons, it has become apparent that members of this family exhibit nearly ubiquitous expression. Therapeutic opportunities range from hypertension, due to the role of ENaC in maintaining whole body salt and water homeostasis, to anxiety disorders and pain associated with ASIC activity. As a physiologist intrigued by the fundamental mechanics of salt and water transport, it was natural that Dale Benos, to whom this series of reviews is dedicated, should have been at the forefront of research into the amiloride-sensitive sodium channel. The cloning of ENaC and subsequently the ASIC channels has revealed a far wider role for this channel family than was previously imagined. In this review, we will discuss the known and potential roles of ENaC and ASIC subunits in the wide variety of pathologies in which these channels have been implicated. Some of these, such as the role of ENaC in Liddle's syndrome are well established, others less so; however, all are related in that the fundamental defect is due to inappropriate channel activity.

Interventional Radiology Regional Anesthesia Approaches for Intra- and Postprocedural Pain Control.

Effective pain control enables procedural success and improved patient satisfaction in interventional radiology. Regional anesthesia techniques are now established for intraoperative and postoperative anesthesia during major surgery, and interventional radiologists (IRs) can readily apply these injections for intraprocedural nerve blocks that can reduce anesthetic requirements and ensure durable analgesia postprocedure. Moreover, IR is poised to advance this field with novel blocks unique to IR needs and by blocking deep plexi safely reachable with CT guidance (e.g., hepatic hilar plexus, aorticorenal plexus blocks). This report aims to provide a succinct IR-directed primer for image-guided nerve blocks usable in the interventional radiology suite.

Amiloride docking to acid-sensing ion channel-1.

Amiloride is a small molecule diuretic, which has been used to dissect sodium transport pathways in many different systems. This drug is known to interact with the epithelial sodium channel and acid-sensing ion channel proteins, as well as sodium/hydrogen antiporters and sodium/calcium exchangers. The exact structural basis for these interactions has not been elucidated as crystal structures of these proteins have been challenging to obtain, though some involved residues and domains have been mapped. This work examines the interaction of amiloride with acid-sensing ion channel-1, a protein whose structure is available using computational and experimental techniques. Using molecular docking software, amiloride and related molecules were docked to model structures of homomeric human ASIC-1 to generate potential interaction sites and predict which analogs would be more or less potent than amiloride. The predictions made were experimentally tested using whole-cell patch clamp. Drugs previously classified as NCX or NHE inhibitors are shown to also inhibit hASIC-1. Potential docking sites were re-examined against experimental data to remove spurious interaction sites. The voltage sensitivity of inhibitors was also examined. Using the aggregated data from these computational and experimental experiments, putative interaction sites for amiloride and hASIC-1 have been defined. Future work will experimentally verify these interaction sites, but at present this should allow for virtual screening of drug libraries at these putative interaction sites.

Procedural Treatments for Knee Osteoarthritis: A Review of Current Injectable Therapies.

Knee osteoarthritis is a common painful degenerative condition affecting the aging Canadian population. In addition to pain and disability, osteoarthritis is associated with depression, comorbid conditions such as diabetes, and increased caregiver burden. It is predicted to cost the Canadian healthcare system $7.6 billion dollars by 2031. Despite its high cost and prevalence, controversy persists in the medical community regarding optimal therapies to treat knee osteoarthritis. A variety of medications like nonsteroidal anti-inflammatories and opioids can cause severe side effects with limited benefits. Total knee arthroplasty, although a definitive management, comes with risk such as postoperative infections, revisions, and chronic pain. Newer injectable therapies are gaining attention as alternatives to medications because of a safer side effect profile and are much less invasive than a joint replacement. Platelet-rich plasma is beginning to replace the more common injectable therapies of intra-articular corticosteroids and hyaluronic acid, but larger trials are needed to confirm this effect. Small studies have examined prolotherapy and stem cell therapy and demonstrate some benefits. Trials involving genicular nerve block procedures have been successful. As treatments evolve, injectable therapies may offer a safe and effective pathway for patients suffering from knee osteoarthritis.

Implications for Neuromodulation Therapy to Control Inflammation and Related Organ Dysfunction in COVID-19.

COVID-19 is a syndrome that includes more than just isolated respiratory disease, as severe acute respiratory syndrome-coronavirus 2 (SARS-CoV2) also interacts with the cardiovascular, nervous, renal, and immune system at multiple levels, increasing morbidity in patients with underlying cardiometabolic conditions and inducing myocardial injury or dysfunction. Emerging evidence suggests that patients with the highest rate of morbidity and mortality following SARS-CoV2 infection have also developed a hyperinflammatory syndrome (also termed cytokine release syndrome). We lay out the potential contribution of a dysfunction in autonomic tone to the cytokine release syndrome and related multiorgan damage in COVID-19. We hypothesize that a cholinergic anti-inflammatory pathway could be targeted as a therapeutic avenue. Graphical Abstract .

Stellate Ganglion Blockade for the Treatment of Refractory Ventricular Arrhythmias.

OBJECTIVES: This study sought to describe our institutional experience with establishing a neurocardiology service in an attempt to provide autonomic modulation as a treatment for ventricular arrhythmias (VAs). BACKGROUND: Treatment-refractory VAs are commonly driven and exacerbated by heightened sympathetic tone. METHODS: Among patients referred to the neurocardiology service (August 2016 to December 2018), we performed ultrasound-based, bilateral, temporary stellate ganglion blockade (SGB) in 20 consecutive patients. We analyzed outcomes of interest including sustained VA or VA requiring defibrillation in the 24 and 48 h before and 24 and 48 h after SGB. RESULTS: The majority of patients were men (n = 19, 95%), with a mean age of 58 ± 14 years. At the time of SGB, 10 (50%) were on inotropic support and 9 (45%) were on mechanical circulatory support. Besides 1 case of hoarseness, there were no apparent procedural complications. SGB was associated with a reduction in the number of VA episodes from the 24 h before (median 5.5 [interquartile range (IQR): 2.0 to 15.8]) to 24 h after SGB (median 0 [IQR: 0 to 3.8]) (p < 0.001). The number of defibrillation events decreased from 2.5 (IQR: 0 to 10.3) to 0 (IQR: 0 to 2.5) (p = 0.002). Similar findings were observed over the 48-h period before and after the SGB. Overall, 9 of 20 (45%) patients had a complete response with no recurrence of ventricular tachycardia (VT) or ventricular fibrillation (VF) for 48 h after SGB. Four (20%) patients had no recurrent VT or VF following SGB through discharge. Similar response rates were observed in those with ischemic (median 6 [IQR: 1.8 to 18.8] to 0.5 [IQR: 0 to 5.3] events; p = 0.031) and nonischemic (median 3.5 [IQR: 1.8 to 6.8] to 0 [IQR: 0 to 1.3] events; p = 0.012) cardiomyopathy. CONCLUSIONS: Minimally invasive, ultrasound-guided bilateral SGB appears safe and provides substantial reduction in VA burden with approximately 1 in 2 patients exhibiting complete suppression of VT or VF for 48 h.

Erythromyeloid progenitors give rise to a population of osteoclasts that contribute to bone homeostasis and repair.

Osteoclasts are multinucleated cells of the monocyte/macrophage lineage that degrade bone. Here, we used lineage tracing studies-labelling cells expressing Cx3cr1, Csf1r or Flt3-to identify the precursors of osteoclasts in mice. We identified an erythromyeloid progenitor (EMP)-derived osteoclast precursor population. Yolk-sac macrophages of EMP origin produced neonatal osteoclasts that can create a space for postnatal bone marrow haematopoiesis. Furthermore, EMPs gave rise to long-lasting osteoclast precursors that contributed to postnatal bone remodelling in both physiological and pathological settings. Our single-cell RNA-sequencing data showed that EMP-derived osteoclast precursors arose independently of the haematopoietic stem cell (HSC) lineage and the data from fate tracking of EMP and HSC lineages indicated the possibility of cell-cell fusion between these two lineages. Cx3cr1+ yolk-sac macrophage descendants resided in the adult spleen, and parabiosis experiments showed that these cells migrated through the bloodstream to the remodelled bone after injury.

Two PKC consensus sites on human acid-sensing ion channel 1b differentially regulate its function.

Human acid-sensing ion channel 1b (hASIC1b) is a H(+)-gated amiloride-sensitive cation channel. We have previously shown that glioma cells exhibit an amiloride-sensitive cation conductance. Amiloride and the ASIC1 blocker psalmotoxin-1 decrease the migration and proliferation of glioma cells. PKC also abolishes the amiloride-sensitive conductance of glioma cells and inhibits hASIC1b open probability in planar lipid bilayers. In addition, hASIC1b's COOH terminus has been shown to interact with protein interacting with C kinase (PICK)1, which targets PKC to the plasma membrane. Therefore, we tested the hypothesis that PKC regulation of hASIC1b at specific PKC consensus sites inhibits hASIC1b function. We mutated three consensus PKC phosphorylation sites (T26, S40, and S499) in hASIC1b to alanine, to prevent phosphorylation, and to glutamic acid or aspartic acid, to mimic phosphorylation. Our data suggest that S40 and S499 are critical sites mediating the modulation of hASIC1b by PKC. We expressed mutant hASIC1b constructs in Xenopus oocytes and measured acid-activated currents by two-electrode voltage clamp. T26A and T26E did not exhibit acid-activated currents. S40A was indistinguishable from wild type (WT), whereas S40E, S499A, and S499D currents were decreased. The PKC activators PMA and phorbol 12,13-dibutyrate inhibited WT hASIC1b and S499A, and PMA had no effect on S40A or on WT hASIC1b in oocytes pretreated with the PKC inhibitor chelerythrine. Chelerythrine inhibited WT hASIC1b and S40A but had no effect on S499A or S40A/S499A. PKC activators or the inhibitor did not affect the surface expression of WT hASIC1b. These data show that the two PKC consensus sites S40 and S499 differentially regulate hASIC1b and mediate the effects of PKC activation or PKC inhibition on hASIC1b. This will result in a deeper understanding of PKC regulation of this channel in glioma cells, information that may help in designing potentially beneficial therapies in their treatment.

Microglia in Pain: Detrimental and Protective Roles in Pathogenesis and Resolution of Pain.

The previous decade has seen a rapid increase in microglial studies on pain, with a unique focus on microgliosis in the spinal cord after nerve injury and neuropathic pain. Numerous signaling molecules are altered in microglia and contribute to the pathogenesis of pain. Here, we discuss how microglial signaling regulates spinal cord synaptic plasticity in acute and chronic pain conditions with different degrees and variations of microgliosis. We highlight that microglial mediators such as pro- and anti-inflammatory cytokines are powerful neuromodulators that regulate synaptic transmission and pain via neuron-glial interactions. We also reveal an emerging role of microglia in the resolution of pain, in part via specialized pro-resolving mediators including resolvins, protectins, and maresins. We also discuss a possible role of microglia in chronic itch.

Transcriptional Profiling of Somatostatin Interneurons in the Spinal Dorsal Horn.

The spinal dorsal horn (SDH) is comprised of distinct neuronal populations that process different somatosensory modalities. Somatostatin (SST)-expressing interneurons in the SDH have been implicated specifically in mediating mechanical pain. Identifying the transcriptomic profile of SST neurons could elucidate the unique genetic features of this population and enable selective analgesic targeting. To that end, we combined the Isolation of Nuclei Tagged in Specific Cell Types (INTACT) method and Fluorescence Activated Nuclei Sorting (FANS) to capture tagged SST nuclei in the SDH of adult male mice. Using RNA-sequencing (RNA-seq), we uncovered more than 13,000 genes. Differential gene expression analysis revealed more than 900 genes with at least 2-fold enrichment. In addition to many known dorsal horn genes, we identified and validated several novel transcripts from pharmacologically tractable functional classes: Carbonic Anhydrase 12 (Car12), Phosphodiesterase 11 A (Pde11a), and Protease-Activated Receptor 3 (F2rl2). In situ hybridization of these novel genes showed differential expression patterns in the SDH, demonstrating the presence of transcriptionally distinct subpopulations within the SST population. Overall, our findings provide new insights into the gene repertoire of SST dorsal horn neurons and reveal several novel targets for pharmacological modulation of this pain-mediating population and treatment of pathological pain.

The ups and downs of peer review.

This article traces the history of peer review of scientific publications, plotting the development of the process from its inception to its present-day application. We discuss the merits of peer review and its weaknesses, both perceived and real, as well as the practicalities of several major proposed changes to the system. It is our hope that readers will gain a better appreciation of the complexities of the process and, when serving as reviewers themselves, will do so in a manner that will enhance the utility of the exercise. We also propose the development of an international on-line training program for accreditation of potential referees.