Funded Projects

Neuropathic pain is a debilitating affliction present in 26% of diabetic patients, with substantial impact on the quality of life. Despite this significant impact and prevalence, current therapies for painful diabetic neuropathy (PDN) are only partially effective, and the molecular mechanisms underlying neuropathic pain in diabetes are not well understood. Our long-term goal is to elucidate the molecular mechanisms responsible for PDN in order to provide targets for the development of therapeutic agents. Our objective is to identify the molecular cascade linking CXCR4/SDF-1 chemokine signaling to DRG nociceptor hyper-excitability, neuropathic pain, and small fiber degeneration. Our aims will determine: 1) the ion-channel current profile of the nociceptor hyper-excitable state produced by CXCR4/SDF-1 signaling in PDN; 2) the gene expression profile of the nociceptor hyper-excitable state produced by CXCR4/SDF-1 signaling in PDN; and 3) the specific features of nociceptor mitochondrial dysfunction produced by CXCR4/SDF-1 signaling in PDN.

This project aims to develop a next-generation noninvasive neuromodulation system for non-addictive pain treatments. The research team will build an integrated system that uses magnetic resonance image-guided focused ultrasound (MRgFUS) stimulation to target pain regions and circuits in the brain with high precision. The system will use MR imaging to locate three pain targets commonly used in clinical pain treatments, to stimulate those targets with ultrasound, and to monitor responses of nociceptive pain circuits using a functional MRI readout. Three collaborating laboratories will tackle the goals of this project: (Aim 1) Develop focused ultrasound technology for neuromodulation in humans, compatible with the high magnetic fields in an MRI scanner. (Aim 2) Develop MRI technology to find neuromodulation targets, compatible with focused ultrasound transducers. (Aim 3) Validate the complete MRgFUS neuromodulation system in brain pain regions in nonhuman primates. By the end of the project, the research team will have a fully developed and validated MRgFUS system that is ready for pilot clinical trials in pain management.

Masticatory and spontaneous pain associated with temporomandibular joint disorders (TMJD) is a significant contributor to orofacial pain, and current treatments for TMJD pain are unsatisfactory. Pain-related transient receptor potential (TRP) channels, expressed by trigeminal ganglion (TG) sensory neurons, have been implicated in both acute and chronic pain and represent possible targets for anti-pain strategies. Using bite force metrics, we found TMJ inflammation-induced masticatory pain to be significantly, but not fully, reversed in Trpv4 knockout mice, suggesting the residual pain might be mediated by other pain-TRPs. Our gene expression studies demonstrated that TRPV1 and TRPA1 were up-regulated in the TG in response to TMJ inflammation in a Trpv4-dependent manner. We hypothesize that TRPV1 and TRPA1, like TRPV4, contribute to TMJ pain. Our specific aims will examine the contribution of TRPV1, TRPV4, and TRPA1 to pathogenesis of TMJD pathologic pain including assessment of the role of neurogenic inflammation.

Up to 5 percent of adolescents suffer from high-impact chronic musculoskeletal (MSK) pain, and only about 50 percent with chronic MSK pain who present for treatment recover. Current treatments for chronic MSK pain are suboptimal and have been tied to the opioid crisis. Discovery of robust markers of the recovery versus persistence of pain and disability is essential to develop more resourceful and patient-specific treatment strategies, requiring measurements across multiple dimensions in the same patient cohort in combination with a suitable computational analysis pipeline. Preliminary data has implicated novel candidates for neuroimaging, immune, quantitative sensory, and psychological markers for discovery. In addition, a standardized specimen collection, processing, storage, and distribution system is in place, along with expertise in machine learning approaches to extract reliable and prognostic bio-signatures from a large and complex data set. This project will facilitate risk stratification and a resourceful selection of patients who are likely to respond to current multidisciplinary pain treatment approaches.

Researchers will develop a novel transcranial focused ultrasound (tFUS) device for pain treatment and establish its effectiveness for treating sickle cell disease (SCD) pain in humanized mice. The tFUS will target the specific cortical regions involved in SCD pain using a novel non-invasive electrophysiological source imaging technique. The project’s goals have several aims. Aim 1: Develop tFUS devices for pain treatment. The mouse-scale system will be designed to validate the therapeutic effect of stimulating the anticipated cortical targets. This will inform development of the simpler human-scale system, which will use models of the skull to select cost-effective transducers to reach the targets. Aim 2: Evaluate tFUS effectiveness and optimize stimulation parameters in an SCD mice model. Researchers will determine effective tFUS parameters to chronically reduce SCD pain in mice and validate this using behavioral measures. Aim 3: Use electrophysiological source imaging to target and trigger closed-loop tFUS in animal models. This aim also includes performing safety studies to prepare for human trials. The project will develop a transformative, noninvasive tFUS device to effectively and safely treat pain in SCD. 

Debilitating neuropathic pain occurs in 40 percent to 70 percent of people who suffer from spinal cord injury (SCI). There are no distinguishing characteristics to identify who will develop neuropathic pain. The objective of this research is to develop a biomarker signature prognostic of SCI-induced neuropathic pain (NP). The aims of the project are to (1) identify autoantibodies in plasma samples from acute SCI patients to CNS autoantigens and determine the relationship between autoantibodies levels to the development of NP, (2) identify the autoantibody combination with maximal prognostic accuracy for the development of NP at six months after SCI, and (3) develop and optimize an assay to simultaneously measure several autoantibodies and independently validate the prognostic efficacy for NP using plasma samples collected prospectively. Establishing a panel will refine the prognostic value of these autoantibodies as biomarkers to detect who are vulnerable to NP and may be used to for development of nonaddictive pain therapeutics.

Identification of new targets and mechanisms underlying chronic neuropathic pain is essential for the discovery of novel treatments and preventative tactics for better neuropathic pain management. A recent exploration of next-generation RNA sequencing identified a large, native, full-length long noncoding RNA (lncRNA) in mouse and human dorsal root ganglion (DRG). It was named as nerve injury-specific lncRNA (NIS-lncRNA), since its expression was found increased in injured DRGs, in response to peripheral nerve injury, but not in response to inflammation. Preliminary findings revealed that blocking the nerve injury-induced increases in DRG NIS-lncRNA levels ameliorated neuropathic pain. This project will validate NIS-lncRNA as a therapeutic target in animal models of neuropathic pain and in cell-based functional assays utilizing human DRG neurons. Completion of this proposal will advance neuropathic pain management and might provide a novel, non-opioid pain therapeutic target.

This project will build overdose models for fentanyl, methadone, codeine, and morphine in a multi-organ system and evaluate the acute and repeat dose, or chronic effects, of overdose treatments as well as off-target toxicity. Researchers developed a system using human cells in a pumpless multi-organ platform that allows continuous recirculation of a blood surrogate for up to 28 days. They will develop two overdose models for male and female phenotypes based on pre-B?tzinger Complex neurons and will integrate functional immune components that enable organ-specific or systemic monocyte actuation. Models for cardiomyopathy and infection will be utilized. Researchers will establish a pharmacokinetic/pharmacodynamic model of overdose and treatment to enable prediction for a range of variables. We will use a serum-free medium with microelectrode arrays and cantilever systems integrated on chip that allow noninvasive electronic and mechanical readouts of organ function.

Severe tissue injury generates central sensitization. Latent sensitization (LS) is a silent form of central sensitization that persists after tissue has healed and overt signs of hyperalgesia have resolved. Pain remission during LS is likely maintained by tonic opioid receptor activity. The opioid receptor inverse agonist, naloxone, can reinstate experimental pain when delivered one week after the resolution of secondary hyperalgesia following first degree thermal injury. Our aims are to test: 1) the hypothesis that burn or surgery triggers LS and long-term opioid analgesia in humans; 2) the hypothesis that mu-opioid receptor (MOR) constitutive activity (MORCA) receptors by opioid peptides maintains endogenous analgesia and restricts LS to a state of pain remission; 3) the extent to which MORs inhibit neural activity in the DH and synaptic strength in presynaptic terminals of primary afferent nociceptors during LS; and 4) whether MORs inhibit spinal NMDA receptor subunits to block pain during LS.

Although opioid-based analgesics have been proven effective in reducing the intensity of pain for many neuropathic pain conditions, their clinical utility is grossly limited due to the substantial risks involved in such therapy, including nausea, constipation, physical dependence, tolerance, and respiratory depression. Cumulative evidence suggests that human Mas-related G protein-coupled receptor X1 (MRGPRX1) is a promising target for pain with limited side effects due to its restricted expression in nociceptors within the peripheral nervous system; however, direct activation of MRGPRX1 at peripheral terminals is expected to induce itch side effects, limiting the therapeutic utility of orthosteric MRGPRX1 agonists. This finding led to the exploration of positive allosteric modulators (PAMs) of MRGPRX1 to potentiate the effects of the endogenous agonists at the central terminals of sensory neurons without activating peripheral MRGPRX1. An intrathecal injection of a prototype MRGPRX1 PAM, ML382, effectively attenuated evoked, persistent, and spontaneous pain without causing itch side effects. The goal of this study is to develop a CNS-penetrant small-molecule MRGPRX1 PAM that can be given orally to treat neuropathic pain conditions.

Chronic pain is maintained, in part, by persistent changes in sensory neurons, including a pathological increase in peptides derived from the neurosecretory protein VGF (non-acronymic). Preliminary findings show that the C-terminal VGF peptide, TLQP-62, contributes to spinal cord neuroplasticity and that TLQP-62 immunoneutralization attenuates established mechanical hypersensitivity in a traumatic nerve injury model of neuropathic pain. This project will test the hypothesis that spinal cord TLQP-62 signaling can be targeted for the development of new chronic pain treatments through immunoneutralization and/or receptor inhibition. It will pursue discovery and validation of TLQP-62-based therapeutic interventions along two parallel lines: identification of TLQP-62 receptor(s) and validation of anti-TLQP-62 antibodies as a potential biological therapeutic option for chronic neuropathic pain conditions.

For patients with neuropathic pain refractory to therapy using small molecules, modulation of specific neural structures in the central or peripheral nervous system can provide effective alternative treatments. While current Food and Drug Administration–approved devices for dorsal root ganglion (DRG) stimulation are safe and effective, there have been an unfortunate number of adverse events associated with pulse generator infections and lead migration. The research team will develop a wireless, millimeter-sized nerve stimulator that can be delivered through the vasculature and stimulate the DRG to alleviate symptoms of neuropathic pain and the associated minimally invasive delivery method. This endovascular nerve stimulation (EVNS) system depends on development and integration of key novel technologies into an endovascular stent. The magnetoelectric transducers and electronic circuits will convert wireless power and data into stimulus patterns that can trigger neural activity in the DRG via miniature electrodes. After chronic demonstration of safety and functionality in large animal models, the team will prepare for regulatory discussions with the FDA. If successful, the EVNS will provide a technology platform for treating other neuropathic pain syndromes. 

This project focuses on identifying and validating a new central analgesic circuit in the brain, based on a highly innovative hypothesis that the strong analgesic effects of general anesthesia (GA) are in part carried out by GA-mediated activation of the endogenous analgesic circuits. Preliminary discovery studies found that a subset of GABAergic neurons located in the central amygdala (CeA) become strongly activated and express high levels of the immediate early gene Fos under GA (hereafter referred to as CeAGA neurons). Furthermore, activation of these neurons exert profound pain-suppressing effects in an acute pain model and a chronic orofacial neuropathic pain model in mice. Based on these exciting preliminary findings, this project will identify and validate CeAGA neurons’ analgesic functions utilizing multiple mouse pain models. Identification of these shared common pathways that need to be suppressed by specific subtypes of CeAGA analgesic neurons will be highly critical for developing precise CeAGA-targeted therapies to treat chronic pain.