Sensory neurons derived from human induced pluripotent stem cells (hiPSCs) are a promising model. One limitation posed by the use of monocultures is the loss of cellular heterogeneity found in tissues. Here we make use of high-throughput RNA sequencing to quantify gene expression in hiPSC-derived mono-cultured and co-cultured sensory neurons. The following groups were compared: human induced pluripotent stem cells (hiPSCs) prior to differentiation, mature hiPSC-derived sensory neurons, mature co-cultures containing hiPSC-derived astrocytes and sensory neurons, mouse dorsal root ganglion (DRG) tissues, and mouse DRG cultures. We find that co-culture of sensory neurons and astrocytes enhances expression of transcripts enriched in native DRG tissues. Numerous well-established genes linked to pain and most translation factors are consistently expressed in both hiPSC and mouse samples. Marker genes for various neuronal subtypes are also present in the hiPSC cultures. As a proof of concept for the potential use of the dataset for hypothesis generation, we validated the expression of eukaryotic initiation factor 5A (eIF5A) in DRG tissue and hiPSC samples. eIF5A is a unique translation factor in that it requires a post-translational hypusine modification to be active. We show that inhibition of hypusine synthesis prevents hyperalgesic priming by inflammatory mediators in vivo and diminishes hiPSC neuronal firing in vitro. In total, we present the transcriptomes of hiPSC sensory neuron models and evaluate the requirement of a functional translation factor. This work was supported by NIH grants R01NS100788 (ZTC), R01NS114018 (ZTC), and 1UG3TR003149 (BJB).

Keratinocytes are closely juxtaposed to cutaneous nerve terminals, enabling communication between keratinocytes and cutaneous nerves. We investigated potential mechanisms that mediate this communication. We genetically expressed stimulatory DREADDs (hM3Dq) into K14 basal keratinocytes (K14) in mice as a tool for mimicking the activation of Gq-linked G protein-coupled receptors (GPCRs) in K14 expressing cells. We have shown that activation of these DREADDs reduced innervation of the epidermis indicating that activation of K-14 Gq-linked GPCRs can regulate nerve fiber degeneration in the epidermis. We used bulk and single-cell RNA (scRNA-seq) sequencing from the skin and Dorsal Root Ganglion (DRG) taken from mice expressing hM3Dq into K14 keratinocytes comparing control mice receiving saline and mice receiving CNO to activate K14 keratinocytes expressing hM3Dq. Bulk RNA sequencing of the epidermis revealed changes in a set of genes associated with neurite outgrowth, including class III semaphorins, potentially impacting cutaneous nerve degeneration. Using RNAScope we found dramatic changes in the expression of semaphorins and their receptors in distinct DRG neurons subtypes. Using single-cell RNA-seq from lumbar DRG we profiled the transcriptome of 10,000 individual DRG cells and found that hM3Dq mediated stimulation of keratinocytes induced changes in DRG single-cell gene expression profile resulting in the identification of a novel DRG neuronal subtype among the nonpeptidergic nociceptors (NP1.2). Our findings indicate that activation of basal keratinocytes Gq-linked GPCRs can result in profound changes in DRG neuronal transcriptomic profile resulting in a phenotypical switch (plasticity) of DRG neurons. Furthermore, our results suggest possible therapeutic effects of activating or blocking specific keratinocyte Gq-linked GPCRs for promoting axon regeneration in small fiber neuropathy. Grant support from 1R01AR77691-01.

Painful diabetic neuropathy (PDN) is one of the most common and intractable complications of diabetes. PDN is characterized by small-fiber degeneration, which can progress to complete loss of cutaneous innervation and is accompanied by neuropathic pain. Uncovering the mechanisms underlying axonal degeneration in PDN remains a major challenge to finding effective and disease-modifying therapies. Sensory nerve afferents normally extend into the epidermis in close juxtaposition to keratinocytes but degenerate in diabetic skin. Our aim is to identify the changes in gene expression profiles and the interactions between dorsal root ganglion (DRG) neurons and keratinocytes to explore the mechanisms by which keratinocytes communicate with cutaneous afferents and how this communication impacts axonal degeneration underlying neuropathic pain in PDN. We used a mouse model of PDN where mice were fed a regular diet (RD, 11% fat) or a high-fat diet (HFD, 42% fat) for 10 weeks during which these mice develop glucose intolerance, mechanical allodynia, small fiber neuropathy. Using a single-cell RNA (scRNA-seq) sequencing approach we captured DRG and keratinocytes gene expression profiles and generated interactome maps. scRNA-seq identified both neuronal and non-neuronal clusters and several differentially expressed genes between RD and HFD from the DRG. We were able to identify several clusters of immune cells and keratinocytes at different stages of differentiation. scRNA-seq results were validated using RNAscope on DRG and skin frozen sections. Moreover, we generated interactome maps between DRG neurons and the peripheral cells to highlight ligand-receptor interactions and we looked to identify genes that were differentially expressed in these interactions. Taken together our data highlights the importance of studying neurons in conjunction with the cells in the tissues with which they interact to identify ligand-receptor interactions that may lead to the identification of neuron signaling in a chronic pain state such as PDN. Grant support from 1R01AR77691-01.

African Americans have been found to receive less medication and experience more pain than Caucasians. Unfortunately, many studies simply highlight the disparities that exist between African Americans and Caucasian in pain management, but there is a lack of understanding at the etiology of these disparities. The purpose of this study was to determine the adequacy of analgesia that was prescribed for African Americans with cancer pain and elucidate any potential characteristics that contributed to receiving appropriate analgesia. This was a secondary analysis of baseline data of an intervention study of African Americans with cancer pain. In order to determine the adequacy of analgesics received, the Pain Management Index (PMI) was calculated for 302 African Americans with cancer pain. Structure equation modeling was utilized to determine which patient factors (age, gender, presence of caregiver, employment status, educational level, perceived control over pain, pain-related distress, pain intensity, functional status) led to adequate analgesia. Forty percent of African Americans with cancer pain did not receive adequate analgesia based on the drug class alone. African Americans with cancer pain who reported higher levels of pain received higher levels of analgesics. Cancer metastasis (p = .03) was the only significant predictor of an increased likelihood of receiving adequate analgesia. Despite national attention to racial disparities, African Americans with cancer pain continue to receive inadequate analgesia. Forty percent of African Americans did not get the appropriate drug based on their reported pain score. The only significant predictor of receiving appropriate analgesia was cancer metastasis. Ensuing studies testing whether these results would be the same for other races will clarify if this disparity was due to race alone. Interventions should then be created and utilized to decrease these disparities.

Emerging literature suggests that experiences of discrimination negatively influence health and well-being. It is unfortunately common for people living with HIV (PLWH) to be stigmatized and discriminated against because of their HIV status and other marginalized identities (e.g., ethnicity/race, sexual identity and orientation). To date, little research has specifically examined discrimination in PWLH and its associations with pain and other pain-relevant factors such as mood and sleep. The purpose of this ongoing study was to preliminarily analyze associations among daily experiences of discrimination, pain severity and interference, depressive symptoms, and sleep in PLWH. Participants included 24 PLWH recruited from a local HIV treatment center. Participants completed The Everyday Discrimination Scale (TEDS) followed by the Brief Pain Inventory - Short Form (BPI-SF), the Insomnia Severity Index (ISI), and the Center for Epidemiologic Studies - Depression Scale (CES-D). Initial findings tentatively suggest that more frequent daily experiences of discrimination may be significantly associated with greater pain interference on the BPI-SF (p = .030) and greater severity of insomnia symptoms on the ISI (p = .059). However, it appears that daily experiences of discrimination may not be meaningfully associated with pain severity on the BPI-SF (p = .401) or depressive symptoms on the CES-D (p = .235). Our findings highlight the potentially deleterious effects of daily discrimination experiences on pain and sleep in in PLWH. As this ongoing study recruits a larger sample of PLWH, data will need to be reanalyzed to better determine the durability of these preliminary findings. However, there is potential that findings from this study may assist in elucidating causal pathways linking discrimination to pain and pain relevant health behaviors like sleep in PLWH. Grant support from The Impact of Insomnia on Pain, Physical Function, and Inflammation in HIV (3R01HL147603-03S1).

Head and neck squamous cell carcinoma (HNSCC) induces severe pain due in part to activation of primary afferent neurons by cancer-secreted mediators. Local neurotransmitter release (e.g., calcitonin gene-related peptide (CGRP)) from trigeminal neurons innervating the cancer has been linked to tumorigenesis. We hypothesize that CGRP exerts a dual effect on both cancer-associated pain and tumor progression, suggesting that CGRP may be a promising therapeutic target in HNSCC treatment. We used human tumor tissue and patient-reported outcomes to explore the relationship between CGRP+ sensory nerve innervation and cancer pain in patients. To determine CGRP receptor expression on tumor cells, immunohistochemistry and PCR were performed on human and mouse oral cancer cell lines. We used a syngeneic tongue tumor transplant mouse model of oral cancer and a global Calca knockout mouse (i.e. CGRP-KO) to investigate the impact of CGRP signaling on tumor growth and the associate immune response in vivo. We found prominent CGRP-immunoreactive sensory nerve presence innervating human HNSCC tumor tissue, which positively correlated to patient-reported pain (r2=0.357). Furthermore, human HNSCC cell lines expressed 3-fold more CGRP receptor, RAMP1, compared to a non-tumorigenic keratinocyte cell line. In tumor-bearing CGRP-KO mice, we found a significant reduction in tumor size at post-inoculation days 7 and 14 compared to wildtype. We also found a 4-fold increase in tumor infiltrating RAMP1-expressing CD4+ T cells, as well as a 5-fold increase cytotoxic CD8+ T cells and NK1.1+ NK cells in tumor tissue CGRP-KO mice compared to wildtype. This preliminary data suggests that CGRP signaling from sensory neurons may increase cancer associated pain and tumor progression. Further knowledge regarding the relationship between sensory neurons and cancer could allow for the repurposing clinically available nervous system drugs (e.g., anti-CGRP antibodies) for the treatment of cancer and cancer pain. Grant support from the Rita Allen Foundation.

Neuropathic pain is a chronic condition which can arise following damage to the somatosensory system and often involves both hyperalgesia and allodynia. The molecular mechanisms of neuropathic pain remain incompletely understood but require enduring alterations in specific gene programs and protein synthesis affecting neuronal signaling and excitability. We investigate non-coding RNA and RNA-binding protein regulatory pathways in impacting hyperalgesia and neuropathic pain using the mouse spared nerve injury model. Nerve injury alters the expression of many miRNAs, including the highly conserved let-7 family miRNAs, which repress pro-growth mRNAs and are implicated in axon growth, neuronal plasticity, and brain circuit development. The Lin28 RNA binding protein can prevent maturation of let-7 precursor RNAs; consequently, increased Lin28 signaling promotes pro-growth gene expression. The regulation and potential roles of Lin28/let-7 pathway in neuropathic pain remain largely unexplored. In preliminary data, we find that Lin28a loss of function in some, but not other, sensory neuron populations can result in a deficit in mechanical hypersensitivity post-injury. In the SNI mouse model, we evaluate molecular mechanisms underlying pain using single molecule detection. A specific RNA imaging assay, RNAscope in situ hybridization (ISH), is used to amplify single RNA target signals in fixed tissues to allow mapping of the spatiotemporal patterns and cell type specificity of changes. We find that Lin28 mRNAs are elevated in classes of injured neurons relative to uninjured neurons in dorsal route ganglia (DRG) which are ipsilateral at early, 3 day, timepoints post-SNI surgery. In contrast, Lin28 mRNAs are highly elevated following a more protracted time courses post-surgery in the compartment of injured neuronal processes. The spatiotemporal differences in Lin28 mRNA levels across compartments of the nervous system following nerve injury could indicate potential trafficking or local stabilization of Lin28 mRNAs and are the subject of ongoing investigations. Grant support from NIH NS103974.

Many patients with sickle cell disease (SCD) suffer from chronic pain, the underlying causes of which are unclear. Recent 16s ribosomal RNA sequencing studies revealed differences in the number and types of bacteria in the gastrointestinal tract of patients and mouse models of SCD relative to controls, but it is unclear if or how these changes contribute to symptomology. In these experiments, we used transgenic SCD mice to determine the extent to which disease related gut dysbiosis contributes to persistent pain. Reflexive pain behaviors were first measured in SCD mice following longitudinal probiotic or antibiotic treatment. Vehicle-treated SCD mice displayed significant mechanical allodynia relative to vehicle-treated wildtype mice, and antibiotic treatment further exacerbated mechanical allodynia in both genotypes. In contrast, probiotic treatment completely reversed persistent touch hypersensitivity in SCD mice. Persistent touch pain was also transiently reversed in SCD mice following fecal material transplant from healthy mice. In complementary experiments, wildtype recipient mice developed cold and touch hypersensitivity that persisted for several weeks after fecal material transplant from SCD donors. Using whole-cell patch clamp recordings, we further determined that these behavioral observations were accompanied by altered intrinsic plasticity in a select class of nodose ganglia sensory neurons, the peripheral terminals of which are well positioned to detect sensory information in the gut. Nodose ganglia neurons isolated from animals that received sickle cell fecal material transplants were hyperexcitable relative to those isolated from animals that received control fecal material transplants. These data are the first to suggest that disease-related gut dysbiosis induces pain through changes in vagal nerve activity. Ongoing studies are examining specific bacterial populations and/or metabolites responsible for these functional changes in order to develop novel therapeutics for chronic SCD pain management. Grant support from National Institutes of Health grants K99HL155791 and R01NS070711.

Visceral hypersensitivity (VH) is commonly cited as a major driver of chronic abdominal pain in “functional” gastrointestinal disorders (e.g., irritable bowel syndrome) where persistent and/or recurrent abdominal pain is the primary unifying symptom regardless of any alterations in bowel habits. The complexity of VH is in part influenced by genetic factors and individual differences in gut microbiome composition, yet specific mechanisms that generate VH remain incompletely understood. Correspondingly, current treatments to primarily focus on symptom management rather than targeting physiological mechanisms responsible for generating VH. We have begun to examine the role of genetic susceptibility and microbiome response dynamics in VH development using a preclinical model of intracolonic zymosan (ZYM) administration in which there are strain differences to VH susceptibility. Preliminary data reveals differential susceptibility between ZYM-induced VH in two closely related C57BL/6 sub strains, one from Taconic Biosciences (C57BL/6NTac) and the other from Jackson Laboratory (C57BL/6J). We have identified a VH candidate gene that encodes the arginine-vasopressin receptor 1A (AVPR1A) protein. We have further observed dynamic strain differences in the location and composition of the gut microbiome in response to ZYM corresponding to VH susceptibility. Ongoing studies are focused on teasing apart the potential bidirectional relationship(s) between genetic susceptibility and host-microbiome interactions in the etiology of VH. Identifying underlying mechanisms that drive VH would provide novel targets for pharmacological intervention and decrease reliance on opioids, which are prescribed at a significantly higher rate to patients who report abdominal pain with no accompanying structural disease. Grant support from R21 NS104789/NS/NINDS (KMB), R03 NS096454/NS/NINDS (KMB), Rita Allen Foundation Award in Pain (KMB), P20GM103418 (EEY and KMB), and a K-INBRE recruitment startup package.

Epidermal keratinocytes express various purinergic 2 receptors that play an essential role in cell growth, differentiation, and proliferation. In the conditions of injury, concentrations of extracellular adenosine triphosphate (ATP) may dramatically increase due to cell damage and inflammatory processes. In this situation activation of purinergic signaling in keratinocytes could act as a double-edged sword contributing to skin regeneration or cell apoptosis. As the role of keratinocytes in transducing and modulating nociceptive stimuli has been increasingly appreciated in recent years, the aim of the present study was to evaluate whether peripheral nerve injury affects purinergic signaling in keratinocytes. Spared nerve injury (SNI), a classical model of peripheral neuropathic pain, was induced in mice. The injury was induced by sparing of the tibial nerve, and ligation and cut of the sural and common peroneal nerves. Keratinocytes were isolated and cultured on Days 2-4 post-injury and ATP-mediated calcium responses in keratinocytes were examined by confocal imaging. On average, the number of keratinocytes that responded to ATP with an increase in intracellular calcium gradient as well as the magnitude of the peak response was not significantly different between sham and SNI groups. However, significantly less delay in ATP-induced increase in intracellular calcium concentration was observed in keratinocytes in SNI group compared to sham. Selective pharmacological inhibition of keratinocyte response to ATP indicated a major role of P2 × 4 receptors in the modulation of calcium homeostasis in SNI. Our results indicate that epidermal purinergic signaling undergoes dramatic changes following peripheral nerve injury that may contribute to injury-induced mechanical hypersensitivity.

As the global prototypical zoonotic hantavirus, Hantaan virus (HTNV) is prevalent in Asia and is the leading causative agent of severe hemorrhagic fever with renal syndrome (HFRS), which has profound morbidity and mortality. Macrophages are crucial components of the host innate immune system and serve as the first line of defense against HTNV infection. Previous studies indicated that the viral replication efficiency in macrophages determines hantavirus pathogenicity, but it remains unknown which factor manipulates the macrophage activation pattern and the virus-host interaction process. Here, we performed the transcriptomic analysis of HTNV-infected mouse bone marrow-derived macrophages and identified the long noncoding RNA (lncRNA) nuclear enriched abundant transcript 1 (NEAT1), especially the isoform NEAT1-2, as one of the lncRNAs that is differentially expressed at the early phase. Based on coculture experiments, we revealed that silencing NEAT1-2 hinders inflammatory macrophage activation and facilitates HTNV propagation, while enhancing NEAT1-2 transcription effectively restrains viral replication. Furthermore, sterol response element binding factor-2 (SREBP2), which controls the cholesterol metabolism process, was found to stimulate macrophages by promoting the production of multiple inflammatory cytokines upon HTNV infection. NEAT1-2 could potentiate SREBP2 activity by upregulating Srebf1 expression and interacting with SREBP2, thus stimulating inflammatory macrophages and limiting HTNV propagation. More importantly, we demonstrated that the NEAT1-2 expression level in patient monocytes was negatively correlated with viral load and HFRS disease progression. Our results identified a function and mechanism of action for the lncRNA NEAT1 in heightening SREBP2-mediated macrophage activation to restrain hantaviral propagation and revealed the association of NEAT1 with HFRS severity.

HPS-1 is a genetic type of Hermansky-Pudlak syndrome (HPS) with highly penetrant pulmonary fibrosis (HPSPF), a restrictive lung disease that is similar to idiopathic pulmonary fibrosis (IPF). Hps1ep/ep (pale ear) is a naturally occurring HPS-1 mouse model that exhibits high sensitivity to bleomycin-induced pulmonary fibrosis (PF). Traditional methods of administering bleomycin as an intratracheal (IT) route to induce PF in this model often lead to severe acute lung injury and high mortality rates, complicating studies focusing on pathobiological mechanisms or exploration of therapeutic options for HPSPF.To develop a murine model of HPSPF that closely mimics the progression of human pulmonary fibrosis, we investigated the pulmonary effects of systemic delivery of bleomycin in Hps1ep/ep mice using a subcutaneous minipump and compared results to oropharyngeal delivery of bleomycin.Our study revealed that systemic delivery of bleomycin induced limited, acute inflammation that resolved. The distinct inflammatory phase preceded a slow, gradually progressive fibrogenesis that was shown to be both time-dependent and dose-dependent. The fibrosis phase exhibited characteristics that better resembles human disease with focal regions of fibrosis that were predominantly found in peribronchovascular areas and in subpleural regions; central lung areas contained relatively less fibrosis.This model provides a preclinical tool that will allow researchers to study the mechanism of pulmonary fibrosis in HPS and provide a platform for the development of therapeutics to treat HPSPF. This method can be applied on studies of IPF or other monogenic disorders that lead to pulmonary fibrosis.