Microneurography as a minimally invasive method to assess target engagement during neuromodulation.

Peripheral neural signals recorded during neuromodulation therapies provide insights into local neural target engagement and serve as a sensitive biomarker of physiological effect. Although these applications make peripheral recordings important for furthering neuromodulation therapies, the invasive nature of conventional nerve cuffs and longitudinal intrafascicular electrodes (LIFEs) limit their clinical utility. Furthermore, cuff electrodes typically record clear asynchronous neural activity in small animal models but not in large animal models.

Spatially selective stimulation of the pig vagus nerve to modulate target effect versus side effect.

Electrical stimulation of the cervical vagus nerve using implanted electrodes (VNS) is FDA-approved for the treatment of drug-resistant epilepsy, treatment-resistant depression, and most recently, chronic ischemic stroke rehabilitation. However, VNS is critically limited by the unwanted stimulation of nearby neck muscles-a result of non-specific stimulation activating motor nerve fibers within the vagus. Prior studies suggested that precise placement of small epineural electrodes can modify VNS therapeutic effects, such as cardiac responses.

Visualization of Pig Vagus Nerve "Vagotopy" Using Ultrasound.

Placement of the clinical vagus nerve stimulating cuff is a standard surgical procedure based on anatomical landmarks, with limited patient specificity in terms of fascicular organization or vagal anatomy. As such, the therapeutic effects are generally limited by unwanted side effects of neck muscle contractions, demonstrated by previous studies to result from stimulation of (1) motor fibers near the cuff in the superior laryngeal and (2) motor fibers within the cuff projecting to the recurrent laryngeal. Conventional non-invasive ultrasound, where the transducer is placed on the surface of the skin, has been previously used to visualize the vagus with respect to other landmarks such as the carotid and internal jugular vein.

Segment-Specific Orientation of the Dorsal and Ventral Roots for Precise Therapeutic Targeting of Human Spinal Cord.

Objective: To provide precise description of the dorsal and ventral roots orientation along with the main spinal cord anatomical measurements and their segment-specific variations.

Patients And Methods: We collected and analyzed the measurements of the spines, spinal cords, and dorsal and ventral roots (C2-L5) of nine adult cadavers (five males and four females).

Results: This study for the first time provides analysis of the dorsal and ventral roots orientation along with spinal cord anatomical measurements and their segment-specific distribution.

Changes in spinal cord hemodynamics reflect modulation of spinal network with different parameters of epidural stimulation.

In this study functional ultrasound (fUS) imaging has been implemented to explore the local hemodynamics response induced by electrical epidural stimulation and to study real-time in vivo functional changes of the spinal cord, taking advantage of the superior spatiotemporal resolution provided by fUS. By quantifying the hemodynamics and electromyographic response features, we tested the hypothesis that the temporal hemodynamics response of the spinal cord to electrical epidural stimulation could reflect modulation of the spinal circuitry and accordingly respond to the changes in parameters of electrical stimulation. The results of this study for the first time demonstrate that the hemodynamics response to electrical stimulation could reflect a neural-vascular coupling of the spinal cord.

Sources of off-target effects of vagus nerve stimulation using the helical clinical lead in domestic pigs.

Objective: Clinical data suggest that efficacious vagus nerve stimulation (VNS) is limited by side effects such as cough and dyspnea that have stimulation thresholds lower than those for therapeutic outcomes. VNS side effects are putatively caused by activation of nearby muscles within the neck, via direct muscle activation or activation of nerve fibers innervating those muscles. Our goal was to determine the thresholds at which various VNS-evoked effects occur in the domestic pig—an animal model with vagus anatomy similar to human—using the bipolar helical lead deployed clinically.

Functional vagotopy in the cervical vagus nerve of the domestic pig: implications for the study of vagus nerve stimulation.

Objective: Given current clinical interest in vagus nerve stimulation (VNS), there are surprisingly few studies characterizing the anatomy of the vagus nerve in large animal models as it pertains to on-and off-target engagement of local fibers. We sought to address this gap by evaluating vagal anatomy in the pig, whose vagus nerve organization and size approximates the human vagus nerve.

Approach: Here we combined microdissection, histology, and immunohistochemistry to provide data on key features across the cervical vagus nerve in a swine model, and compare our results to other animal models (mouse, rat, dog, non-human primate) and humans.

An Injectable Neural Stimulation Electrode Made from an In-Body Curing Polymer/Metal Composite.

Implanted neural stimulation and recording devices hold vast potential to treat a variety of neurological conditions, but the invasiveness, complexity, and cost of the implantation procedure greatly reduce access to an otherwise promising therapeutic approach. To address this need, a novel electrode that begins as an uncured, flowable prepolymer that can be injected around a neuroanatomical target to minimize surgical manipulation is developed. Referred to as the Injectrode, the electrode conforms to target structures forming an electrically conductive interface which is orders of magnitude less stiff than conventional neuromodulation electrodes.

Single-Dose Neoadjuvant AKT Pathway Inhibitor Reduces Growth of Hepatocellular Carcinoma after Laser Thermal Ablation in Small-Animal Model.

BackgroundLocal recurrence following thermal ablation of hepatocellular carcinoma (HCC) larger than 2-3 cm remains a challenging clinical problem. Prior studies suggest that phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR)-dependent protein kinase B (AKT) signaling mediates HCC cell survival caused by moderate heat stress in vitro but these findings need in vivo validation.PurposeTo test the hypothesis that neoadjuvant inhibition of PI3K/mTOR/AKT signaling reduces HCC tumor growth in vivo after laser ablation and to evaluate the effects of moderate heat stress on molecular signaling and cellular function in HCC cells in vitroMaterials and MethodsHCC tumor-bearing mice were randomized to neoadjuvant PI3K/mTOR inhibitor (BEZ235) or control groups followed by an intentional partial laser ablation or sham ablation; there were at least nine mice per group.

Functional Ultrasound Imaging of Spinal Cord Hemodynamic Responses to Epidural Electrical Stimulation: A Feasibility Study.

This study presents the first implementation of functional ultrasound (fUS) imaging of the spinal cord to monitor local hemodynamic response to epidural electrical spinal cord stimulation (SCS) on two small and large animal models. SCS has been successfully applied to control chronic refractory pain and recently was evolved to alleviate motor impairment in Parkinson's disease and after spinal cord injury. At present, however, the mechanisms underlying SCS remain unclear, and current methods for monitoring SCS are limited in their capacity to provide the required sensitivity and spatiotemporal resolutions to evaluate functional changes in response to SCS.

Heat Stress and Thermal Ablation Induce Local Expression of Nerve Growth Factor Inducible (VGF) in Hepatocytes and Hepatocellular Carcinoma: Preclinical and Clinical Studies.

The purposes of this study were to test the hypothesis that heat stress and hepatic thermal ablation induce nerve growth factor inducible (VGF) and to determine intrahepatic versus systemic VGF expression induced by thermal ablation in vivo and in patients. Hepatocytes and HCC cells were subjected to moderate (45°C) or physiologic (37°C) heat stress for 10 min and assessed for VGF expression at 0-72 h post-heat stress ( ≥ 3 experiments). Orthotopic N1S1 HCC-bearing rats were randomized to sham or laser thermal ablation (3 W × 90 s), and liver/serum was harvested at 0-7 days postablation for analysis of VGF expression ( ≥ 6 per group).

Heat Stress and Hepatic Laser Thermal Ablation Induce Hepatocellular Carcinoma Growth: Role of PI3K/mTOR/AKT Signaling.

Purpose To determine if heat stress and hepatic laser thermal ablation induce hepatocellular carcinoma (HCC) growth and to identify growth factors induced by heat stress. Materials and Methods Non-heat-stressed HCC cells were cocultured with HCC cells or hepatocytes that were heat stressed at 37°C (physiologic), 45°C (moderate), or 50°C (severe) for 10 minutes and proliferation monitored with bioluminescence imaging for up to 6 days after heat stress (three experiments). Rats bearing orthotopic N1S1 HCC were randomly assigned to undergo immediate sham or laser thermal (3 W for 60 or 90 seconds; hereafter, 3W×60s and 3W×90s, respectively) ablation of the median (local) or left (distant) hepatic lobe, and tumor growth was monitored with magnetic resonance imaging for up to 18 days after ablation (six or more rats per group).

The Role of Functional Neuroanatomy of the Lumbar Spinal Cord in Effect of Epidural Stimulation.

In this study, the neuroanatomy of the swine lumbar spinal cord, particularly the spatial orientation of dorsal roots was correlated to the anatomical landmarks of the lumbar spine and to the magnitude of motor evoked potentials during epidural electrical stimulation (EES). We found that the proximity of the stimulating electrode to the dorsal roots entry zone across spinal segments was a critical factor to evoke higher peak-to-peak motor responses. Positioning the electrode close to the dorsal roots produced a significantly higher impact on motor evoked responses than rostro-caudal shift of electrode from segment to segment.

Heat stress induced, ligand-independent MET and EGFR signalling in hepatocellular carcinoma.

Purpose: The aims of the present study were 2-fold: first, to test the hypothesis that heat stress induces MET and EGFR signalling in hepatocellular carcinoma (HCC) cells and inhibition of this signalling decreases HCC clonogenic survival; and second, to identify signalling pathways associated with heat stress induced MET signalling.

Materials And Methods: MET and EGFR HCC cells were pre-treated with inhibitors to MET, EGFR, PI3K/mTOR or vehicle and subjected to heat stress or control ± HGF or EGF growth factors and assessed by colony formation assay, Western blotting and/or quantitative mass spectrometry. IACUC approved partial laser thermal or sham ablation was performed on orthotopic N1S1 and AS30D HCC tumours and liver/tumour assessed for phospho-MET and phospho-EGFR immunostaining.

Heat Stress-Induced PI3K/mTORC2-Dependent AKT Signaling Is a Central Mediator of Hepatocellular Carcinoma Survival to Thermal Ablation Induced Heat Stress.

Thermal ablative therapies are important treatment options in the multidisciplinary care of patients with hepatocellular carcinoma (HCC), but lesions larger than 2-3 cm are plagued with high local recurrence rates and overall survival of these patients remains poor. Currently no adjuvant therapies exist to prevent local HCC recurrence in patients undergoing thermal ablation. The molecular mechanisms mediating HCC resistance to thermal ablation induced heat stress and local recurrence remain unclear.

Blockade of CCR2 reduces macrophage influx and development of chronic renal damage in murine renovascular hypertension.

Renovascular hypertension (RVH) is a common cause of both cardiovascular and renal morbidity and mortality. In renal artery stenosis (RAS), atrophy in the stenotic kidney is associated with an influx of macrophages and other mononuclear cells. We tested the hypothesis that chemokine receptor 2 (CCR2) inhibition would reduce chronic renal injury by reducing macrophage influx in the stenotic kidney of mice with RAS.

Combined effect of hyperfiltration and renin angiotensin system activation on development of chronic kidney disease in diabetic db/db mice.

Background: Hypertension is a major risk factor for renal disease progression. However, the mechanisms by which hypertension aggravates the effects of diabetes on the kidney are incompletely understood. We tested the hypothesis that renovascular hypertension accelerates angiotensin-II-dependent kidney damage and inflammation in the db/db mouse, a model of type II diabetes.

Anatomy of hepatic arteriolo-portal venular shunts evaluated by 3D micro-CT imaging.

The liver differs from other organs in that two vascular systems deliver its blood - the hepatic artery and the portal vein. However, how the two systems interact is not fully understood. We therefore studied the microvascular geometry of rat liver hepatic artery and portal vein injected with the contrast polymer Microfil(®).

Heat stress induced cell death mechanisms in hepatocytes and hepatocellular carcinoma: in vitro and in vivo study.

Background And Objective: The aims of the present study were to investigate the thermal-dose dependent effect of heat stress on hepatocyte and HCC cell death mechanisms using clinically relevant experimental heat stress conditions in vitro and to investigate apoptotic cell death induced by laser thermal ablation in vivo.

Study Design/materials And Methods: Institutional Animal Care and Use Committee approved all studies. Hepatocyte and HCC cell lines were heat stressed from 37 to 60°C for 2 or 10 minutes and assessed for viability, cytotoxicity and caspase-3/7 activity at 6 and/or 24 hours post-treatment (N = 3).