Patient engagement in research: lessons learned from CAPTURE ALS, a longitudinal observational ALS study.

Objective: There are compelling ethical and practical reasons for patient engagement in research (PEIR), however, evidence for best practices remains limited. We investigated PEIR as implemented in CAPTURE ALS, a longitudinal observational study, from study inception through the first 2.5 years of operations. Methods: Data were drawn from three engagement initiatives: a community-led letter-writing campaign; consultation with patient and caregiver focus groups; and a study-embedded 'participant partner advisory council' (PPAC). Data were derived retrospectively from study documentation. We used the International Association of Public Participation (IAP2) participation spectrum as a framework for investigation. Results: 2401 letters from community members to the Canadian government affirmed study objectives and advocated for funding. Feedback from focus group consultation influenced study design and supported the study's data-sharing plan. PPAC collaboration shaped all aspects of the study. Contributions included: co-creation of governance documents, input on study protocols and public-facing communication, and development of engagement webinars for study participants and feedback surveys. Effective communication practices fostered collaboration and helped avoid tokenistic engagement. CAPTURE ALS encompassed all IAP2 participation levels. Conclusions: CAPTURE ALS was shaped by meaningful engagement initiatives over the course of the study. Lessons learned included: begin early and embed PEIR within research; build relationships and foster mutual learning; be flexible, open to adaptation, and seek diversity. Primary challenges included funding for early implementation, time needed to maintain relationships, and attrition due to disease progression. All IAP2 participation levels contributed to meaningful PEIR. 'Empowerment' was demonstrated through advocacy.

CAPTURE ALS: the comprehensive analysis platform to understand, remedy and eliminate ALS.

The absence of disease modifying treatments for amyotrophic lateral sclerosis (ALS) is in large part a consequence of its complexity and heterogeneity. Deep clinical and biological phenotyping of people living with ALS would assist in the development of effective treatments and target specific biomarkers to monitor disease progression and inform on treatment efficacy. The objective of this paper is to present the Comprehensive Analysis Platform To Understand Remedy and Eliminate ALS (CAPTURE ALS), an open and translational platform for the scientific community currently in development. CAPTURE ALS is a Canadian-based platform designed to include participants' voices in its development and through execution. Standardized methods will be used to longitudinally characterize ALS patients and healthy controls through deep clinical phenotyping, neuroimaging, neurocognitive and speech assessments, genotyping and multisource biospecimen collection. This effort plugs into complementary Canadian and international initiatives to share common resources. Here, we describe in detail the infrastructure, operating procedures, and long-term vision of CAPTURE ALS to facilitate and accelerate translational ALS research in Canada and beyond.

Delta opioid receptor activation modulates affective pain and modality-specific pain hypersensitivity associated with chronic neuropathic pain.

Delta opioid receptor (DOR) agonists alleviate nociceptive behaviors in various chronic pain models, including neuropathic pain, while having minimal effect on sensory thresholds in the absence of injury. The mechanisms underlying nerve injury-induced enhancement of DOR function are unclear. We used a peripheral nerve injury (PNI) model of neuropathic pain to assess changes in the function and localization of DORs in mice and rats. Intrathecal administration of DOR agonists reversed mechanical allodynia and thermal hyperalgesia. The dose-dependent thermal antinociceptive effects of DOR agonists were shifted to the left in PNI rats. Administration of DOR agonists produced a conditioned place preference in PNI, but not in sham, animals, whereas the DOR antagonist naltrindole produced a place aversion in PNI, but not in sham, mice, suggesting the engagement of endogenous DOR activity in suppressing pain associated with the injury. GTPγS autoradiography revealed an increase in DOR function in the dorsal spinal cord, ipsilateral to PNI. Immunogold electron microscopy and in vivo fluorescent agonist assays were used to assess changes in the ultrastructural localization of DORs in the spinal dorsal horn. In shams, DORs were primarily localized within intracellular compartments. PNI significantly increased the cell surface expression of DORs within lamina IV-V dendritic profiles. Using neonatal capsaicin treatment, we identified that DOR agonist-induced thermal antinociception was mediated via receptors expressed on primary afferent sensory neurons but did not alter mechanical thresholds. These data reveal that the regulation of DORs following PNI and suggest the importance of endogenous activation of DORs in regulating chronic pain states.

Epiregulin and EGFR interactions are involved in pain processing.

The EGFR belongs to the well-studied ErbB family of receptor tyrosine kinases. EGFR is activated by numerous endogenous ligands that promote cellular growth, proliferation, and tissue regeneration. In the present study, we have demonstrated a role for EGFR and its natural ligand, epiregulin (EREG), in pain processing. We show that inhibition of EGFR with clinically available compounds strongly reduced nocifensive behavior in mouse models of inflammatory and chronic pain. EREG-mediated activation of EGFR enhanced nociception through a mechanism involving the PI3K/AKT/mTOR pathway and matrix metalloproteinase-9. Moreover, EREG application potentiated capsaicin-induced calcium influx in a subset of sensory neurons. Both the EGFR and EREG genes displayed a genetic association with the development of chronic pain in several clinical cohorts of temporomandibular disorder. Thus, EGFR and EREG may be suitable therapeutic targets for persistent pain conditions.

Sympathetic fibre sprouting in the skin contributes to pain-related behaviour in spared nerve injury and cuff models of neuropathic pain.

BACKGROUND: Cuff and spared nerve injury (SNI) in the sciatic territory are widely used to model neuropathic pain. Because nociceptive information is first detected in skin, it is important to understand how alterations in peripheral innervation contribute to pain in each model. Over 16 weeks in male rats, changes in sensory and autonomic innervation of the skin were described after cuff and SNI using immunohistochemistry to label myelinated (neurofilament 200 positive-NF200+) and peptidergic (calcitonin gene-related peptide positive-CGRP+) primary afferents and sympathetic fibres (dopamine ß-hydroxylase positive-DBH+) RESULTS: Cuff and SNI caused an early loss and later reinnervation of NF200 and CGRP fibres in the plantar hind paw skin. In both models, DBH+ fibres sprouted into the upper dermis of the plantar skin 4 and 6 weeks after injury. Despite these similarities, behavioural pain measures were significantly different in each model. Sympathectomy using guanethidine significantly alleviated mechanical allodynia 6 weeks after cuff, when peak sympathetic sprouting was observed, having no effect at 2 weeks, when fibres were absent. In SNI animals, mechanical allodynia in the lateral paw was significantly improved by guanethidine at 2 and 6 weeks, and the development of cold hyperalgesia, which roughly paralleled the appearance of ectopic sympathetic fibres, was alleviated by guanethidine at 6 weeks. Sympathetic fibres did not sprout into the dorsal root ganglia at 2 or 6 weeks, indicating their unimportance to pain behaviour in these two models. CONCLUSIONS: Alterations in sympathetic innervation in the skin represents an important mechanism that contributes to pain in cuff and SNI models of neuropathic pain.

Behavioral signs of pain and functional impairment in a mouse model of osteogenesis imperfecta.

Osteogenesis imperfecta (OI) is a congenital disorder caused most often by dominant mutations in the COL1A1 or COL1A2 genes that encode the alpha chains of type I collagen. Severe forms of OI are associated with skeletal deformities and frequent fractures. Skeletal pain can occur acutely after fracture, but also arises chronically without preceding fractures. In this study we assessed OI-associated pain in the Col1a1Jrt/+ mouse, a recently developed model of severe dominant OI. Similar to severe OI in humans, this mouse has significant skeletal abnormalities and develops spontaneous fractures, joint dislocations and vertebral deformities. In this model, we investigated behavioral measures of pain and functional impairment. Significant hypersensitivity to mechanical, heat and cold stimuli, assessed by von Frey filaments, radiant heat paw withdrawal and the acetone tests, respectively, were observed in OI compared to control wildtype littermates. OI mice also displayed reduced motor activity in the running wheel and open field assays. Immunocytochemical analysis revealed no changes between OI and WT mice in innervation of the glabrous skin of the hindpaw or in expression of the pain-related neuropeptide calcitonin gene-related protein in sensory neurons. In contrast, increased sensitivity to mechanical and cold stimulation strongly correlated with the extent of skeletal deformities in OI mice. Thus, we demonstrated that the Col1a1Jrt/+ mouse model of severe OI has hypersensitivity to mechanical and thermal stimuli, consistent with a state of chronic pain.

Novel expression pattern of neuropeptide Y immunoreactivity in the peripheral nervous system in a rat model of neuropathic pain.

BACKGROUND: Neuropeptide Y (NPY) has been implicated in the modulation of pain. Under normal conditions, NPY is found in interneurons in the dorsal horn of the spinal cord and in sympathetic postganglionic neurons but is absent from the cell bodies of sensory neurons. Following peripheral nerve injury NPY is dramatically upregulated in the sensory ganglia. How NPY expression is altered in the peripheral nervous system, distal to a site of nerve lesion, remains unknown. To address this question, NPY expression was investigated using immunohistochemistry at the level of the trigeminal ganglion, the mental nerve and in the skin of the lower lip in relation to markers of sensory and sympathetic fibers in a rat model of trigeminal neuropathic pain. RESULTS: At 2 and 6 weeks after chronic constriction injury (CCI) of the mental nerve, de novo expression of NPY was seen in the trigeminal ganglia, in axons in the mental nerve, and in fibers in the upper dermis of the skin. In lesioned animals, NPY immunoreactivity was expressed primarily by large diameter mental nerve sensory neurons retrogradely labelled with Fluorogold. Many axons transported this de novo NPY to the periphery as NPY-immunoreactive (IR) fibers were seen in the mental nerve both proximal and distal to the CCI. Some of these NPY-IR axons co-expressed Neurofilament 200 (NF200), a marker for myelinated sensory fibers, and occasionally colocalization was seen in their terminals in the skin. Peptidergic and non-peptidergic C fibers expressing calcitonin gene-related peptide (CGRP) or binding isolectin B4 (IB4), respectively, never expressed NPY. CCI caused a significant de novo sprouting of sympathetic fibers into the upper dermis of the skin, and most, but not all of these fibers, expressed NPY. CONCLUSIONS: This is the first study to provide a comprehensive description of changes in NPY expression in the periphery after nerve injury. Novel expression of NPY in the skin comes mostly from sprouted sympathetic fibers. This information is fundamental in order to understand where endogenous NPY is expressed, and how it might be acting to modulate pain in the periphery.

Spatial and temporal pattern of changes in the number of GAD65-immunoreactive inhibitory terminals in the rat superficial dorsal horn following peripheral nerve injury.

Inhibitory interneurons are an important component of dorsal horn circuitry where they serve to modulate spinal nociception. There is now considerable evidence indicating that reduced inhibition in the spinal dorsal horn contributes to neuropathic pain. A loss of these inhibitory neurons after nerve injury is one of the mechanisms being proposed to account for reduced inhibition; however, this remains controversial. This is in part because previous studies have focused on global measurements of inhibitory neurons without assessing the number of inhibitory synapses. To address this, we conducted a quantitative analysis of the spatial and temporal changes in the number of inhibitory terminals, as detected by glutamic acid decarboxylase 65 (GAD65) immunoreactivity, in the superficial dorsal horn of the spinal cord following a chronic constriction injury (CCI) to the sciatic nerve in rats. Isolectin B4 (IB4) labelling was used to define the location within the dorsal horn directly affected by the injury to the peripheral nerve. The density of GAD65 inhibitory terminals was reduced in lamina I (LI) and lamina II (LII) of the spinal cord after injury. The loss of GAD65 terminals was greatest in LII with the highest drop occurring around 3-4 weeks and a partial recovery by 56 days. The time course of changes in the number of GAD65 terminals correlated well with both the loss of IB4 labeling and with the altered thresholds to mechanical and thermal stimuli. Our detailed analysis of GAD65+ inhibitory terminals clearly revealed that nerve injury induced a transient loss of GAD65 immunoreactive terminals and suggests a potential involvement for these alterations in the development and amelioration of pain behaviour.

Changes in morphine reward in a model of neuropathic pain.

In addition to sensory disturbances, neuropathic pain is associated with an ongoing and persistent negative affective state. This condition may be reflected as altered sensitivity to rewarding stimuli. We examined this hypothesis by testing whether the rewarding properties of morphine are altered in a rat model of neuropathic pain. Neuropathic pain was induced by chronic constriction of the common sciatic nerve. Drug reward was assessed using an unbiased, three-compartment conditioned place preference (CPP) paradigm. The rats underwent two habituation sessions beginning 6 days after surgery. Over the next 8 days, they were injected with drug or vehicle and were confined to one CPP compartment for 30 min. On the following test day, the rats had access to all three compartments for 30 min. Consistent with the literature, systemic administration of morphine dose-dependently increased the CPP in pain-naive animals. In rats with neuropathic pain, however, the dose-dependent effects of morphine were in a bell-shaped curve, with a low dose of morphine (2 mg/kg) producing a greater CPP than a higher dose of morphine (8 mg/kg). In a separate group of animals, acute administration of morphine reversed mechanical allodynia in animals with neuropathic pain at the same doses that produced a CPP. The increased potency of systemic morphine to produce a CPP in animals with neuropathic pain suggests that the motivation for opioid-induced reward is different in the two states.