Focused Ultrasound-Mediated Disruption of the Blood-Brain Barrier for AAV9 Delivery in a Mouse Model of Huntington's Disease.

Huntington's disease (HD) is a monogenic neurodegenerative disorder caused by a cytosine-adenine-guanine (CAG) trinucleotide repeat expansion in the HTT gene. There are no cures for HD, but the genetic basis of this disorder makes gene therapy a viable approach. Adeno-associated virus (AAV)-miRNA-based therapies have been demonstrated to be effective in lowering HTT mRNA; however, the blood-brain barrier (BBB) poses a significant challenge for gene delivery to the brain. Delivery strategies include direct injections into the central nervous system, which are invasive and can result in poor diffusion of viral particles through the brain parenchyma. Focused ultrasound (FUS) is an alternative approach that can be used to non-invasively deliver AAVs by temporarily disrupting the BBB. Here, we investigate FUS-mediated delivery of a single-stranded AAV9 bearing a cDNA for GFP in 2-month-old wild-type mice and the zQ175 HD mouse model at 2-, 6-, and 12-months. FUS treatment improved AAV9 delivery for all mouse groups. The delivery efficacy was similar for all WT and HD groups, with the exception of the zQ175 12-month cohort, where we observed decreased GFP expression. Astrocytosis did not increase after FUS treatment, even within the zQ175 12-month group exhibiting higher baseline levels of GFAP expression. These findings demonstrate that FUS can be used to non-invasively deliver an AAV9-based gene therapy to targeted brain regions in a mouse model of Huntington's disease.

Phenotyping Pain in Patients With Fibrous Dysplasia/McCune-Albright Syndrome.

CONTEXT: Pain is a poorly managed aspect in fibrous dysplasia/McCune-Albright syndrome (FD/MAS) because of uncertainties regarding the clinical, behavioral, and neurobiological underpinnings that contribute to pain in these patients. OBJECTIVE: Identify neuropsychological and neurobiological factors associated with pain severity in FD/MAS. DESIGN: Prospective, single-site study. PATIENTS: Twenty patients with FD/MAS and 16 age-sex matched healthy controls. INTERVENTION: Assessments of pain severity, neuropathic pain, pain catastrophizing (pain rumination, magnification, and helplessness), emotional health, and pain sensitivity with thermal quantitative sensory testing. Central nervous system (CNS) properties were measured with diffusion tensor imaging, structural magnetic resonance imaging, and functional magnetic resonance imaging. MAIN OUTCOME MEASURES: Questionnaire responses, detection thresholds and tolerances to thermal stimuli, and structural and functional CNS properties. RESULTS: Pain severity in patients with FD/MAS was associated with more neuropathic pain quality, higher levels of pain catastrophizing, and depression. Quantitative sensory testing revealed normal detection of nonnoxious stimuli in patients. Individuals with FD/MAS had higher pain tolerances relative to healthy controls. From neuroimaging studies, greater pain severity, neuropathic pain quality, and psychological status of the patient were associated with reduced structural integrity of white matter pathways (superior thalamic radiation and uncinate fasciculus), reduced gray matter thickness (pre-/paracentral gyri), and heightened responses to pain (precentral, temporal, and frontal gyri). Thus, properties of CNS circuits involved in processing sensorimotor and emotional aspects of pain were altered in FD/MAS. CONCLUSION: These results offer insights into pain mechanisms in FD/MAS, while providing a basis for implementation of comprehensive pain management treatment approaches that addresses neuropsychological aspects of pain.

A pilot investigation of muscle integrity in patients with ADSSL1 myopathy using electrical impedance myography.

INTRODUCTION/AIMS: ADSSL1 myopathy (OMIM 617030) is a recently discovered, congenital myopathic disease caused by a pathogenic variant in ADSSL1. ADSSL1 is an enzyme involved in the purine nucleotide process and facilitates the conversion of inosine monophosphate to adenosine monophosphate within myocytes. Electrical impedance myography (EIM) is a portable, non-invasive, and cost-effective method for characterizing muscle integrity. Three ADSSL1 patients are presented in whom characterization of muscle integrity using EIM was performed. METHODS: A 15-y-old male, 20-y-old female, and 63-y-old male each with a pathogenic variant in ADSSL1 [c.901G > A] as well as three, age-gender matched healthy controls (HCs) were enrolled. Study participants were phenotyped using a virtual EIM procedure. RESULTS: ADSSL1 myopathy patients presented with variable onset of physical disability, disease progression, and severity of muscle weakness. Across multiple proximal and distal muscles groups and relative to HCs, ADSSL1 myopathy patients demonstrated lower phase and reactance values, while resistance was higher, which together indicated diseased muscle. DISCUSSION: EIM can provide a novel, non-invasive and objective biomarker to evaluate muscle integrity in patients with ADSSL1 myopathy. Combining EIM with musculoskeletal imaging and histologic assessments in follow-up studies may further inform on the pathophysiology of ADSSL1 myopathy.

Synthetic CT Assessment of Lesions in Children With Rare Musculoskeletal Diseases.

Imaging modalities such as computed tomography (CT) are critical for monitoring musculoskeletal abnormalities in children with rare diseases. However, CT exposes patients to radiation, which limits its utility in the clinical setting, particularly during longitudinal evaluation. Synthetic CT is a novel, noncontrast, and rapid MRI method that can provide CT-like images without any radiation exposure and is easily performed in conjunction with traditional MRI, which detects soft-tissue and bone marrow abnormalities. To date, an evaluation of synthetic CT in pediatric patients with rare musculoskeletal diseases has been lacking. In this case series, the capability of synthetic CT to identify musculoskeletal lesions accurately in 2 rare disease patients is revealed. In Case 1, synthetic CT, in agreement with routine CT, identified an intraosseous lesion in the right femoral neck in a 16-year-old female with fibrous dysplasia, whereas standard-of-care MRIs additionally revealed mild surrounding edema-like bone marrow signal. For Case 2, synthetic CT applied to a 12-year-old female with fibrodysplasia ossificans progressiva revealed heterotopic ossification present along the cervical spine that had caused the fusion of multiple vertebrae. Our evaluation of synthetic CT offers important insights into the feasibility and utility of this methodology in children with rare diseases affecting the musculoskeletal system.

Pharmacological Interventions Targeting Pain in Fibrous Dysplasia/McCune-Albright Syndrome.

Fibrous dysplasia (FD) is a rare, non-inherited bone disease occurring following a somatic gain-of-function R201 missense mutation of the guanine-nucleotide binding protein alpha subunit stimulating activity polypeptide 1 (GNAS) gene. The spectrum of the disease ranges from a single FD lesion to a combination with extraskeletal features; an amalgamation with café-au-lait skin hyperpigmentation, precocious puberty, and other endocrinopathies defines McCune-Albright Syndrome (MAS). Pain in FD/MAS represents one of the most prominent aspects of the disease and one of the most challenging to treat-an outcome driven by (i) the heterogeneous nature of FD/MAS, (ii) the variable presentation of pain phenotypes (i.e., craniofacial vs. musculoskeletal pain), (iii) a lack of studies probing pain mechanisms, and (iv) a lack of rigorously validated analgesic strategies in FD/MAS. At present, a range of pharmacotherapies are prescribed to patients with FD/MAS to mitigate skeletal disease activity, as well as pain. We analyze evidence guiding the current use of bisphosphonates, denosumab, and other therapies in FD/MAS, and also discuss the potential underlying pharmacological mechanisms by which pain relief may be achieved. Furthermore, we highlight the range of presentation of pain in individual cases of FD/MAS to further describe the difficulties associated with employing effective pain treatment in FD/MAS. Potential next steps toward identifying and validating effective pain treatments in FD/MAS are discussed, such as employing randomized control trials and probing new pain pathways in this rare bone disease.

Diminished muscle integrity in patients with fibrodysplasia ossificans progressiva assessed with at-home electrical impedance myography.

Fibrodysplasia ossificans progressiva (FOP) is an ultra-rare disorder involving skeletal dysplasia and heterotopic ossification (HO) of muscle and connective tissue. We aimed to define a novel biomarker in FOP that enables reliable assessment of musculoskeletal tissue integrity. Considering logistical difficulties that FOP patients often face, our goal was to identify an at-home biomarker technique. Electrical impedance myography (EIM) is a non-invasive, portable method that can inform on muscle health. 15 FOP patients (age 10-52) and 13 healthy controls were assessed. Using EIM, multiple muscle groups were characterized per participant in a 45-min period. The Cumulative Analogue Joint Involvement Scale (CAJIS) was implemented to determine mobility burden severity. We additionally evaluated physical activity levels via a Patient-Reported Outcomes Measurement Information System (PROMIS)-based questionnaire. Relative to controls, FOP patients demonstrated significantly lower regional and whole-body phase values at 50 kHz and 100 kHz, indicating more diseased muscle tissue. Lower whole-body phase and reactance values, and higher resistance values, were associated with greater FOP burden (CAJIS score range: 4-30) and lower physical activity levels at 50 kHz and 100 kHz. This study points to the potential utility of EIM as a clinical biomarker tool capable of characterizing muscle integrity in FOP.

Case Report: The Imperfect Association Between Craniofacial Lesion Burden and Pain in Fibrous Dysplasia.

Patients with fibrous dysplasia (FD) often present with craniofacial lesions that affect the trigeminal nerve system. Debilitating pain, headache, and migraine are frequently experienced by FD patients with poor prognosis, while some individuals with similar bone lesions are asymptomatic. The clinical and biological factors that contribute to the etiopathogenesis of pain in craniofacial FD are largely unknown. We present two adult females with comparable craniofacial FD lesion size and location, as measured by 18F-sodium fluoride positron emission tomography/computed tomography (PET/CT), yet their respective pain phenotypes differed significantly. Over 4 weeks, the average pain reported by Patient A was 0.4/0-10 scale. Patient B reported average pain of 7.8/0-10 scale distributed across the entire skull and left facial region. Patient B did not experience pain relief from analgesics or more aggressive treatments (denosumab). In both patients, evaluation of trigeminal nerve divisions (V1, V2, and V3) with CT and magnetic resonance imaging (MRI) revealed nerve compression and displacement with more involvement of the left trigeminal branches relative to the right. First-time employment of diffusion MRI and tractography suggested reduced apparent fiber density within the cisternal segment of the trigeminal nerve, particularly for Patient B and in the left hemisphere. These cases highlight heterogeneous clinical presentation and neurobiological properties in craniofacial FD and also, the disconnect between peripheral pathology and pain severity. We hypothesize that a detailed phenotypic characterization of patients that incorporates an advanced imaging approach probing the trigeminal system may provide enhanced insights into the variable experiences with pain in craniofacial FD.

Case Report: A Neuro-Ophthalmological Assessment of Vision Loss in a Pediatric Case of McCune-Albright Syndrome.

Patients diagnosed with McCune-Albright Syndrome (MAS) frequently manifest craniofacial fibrous dysplasia (FD). Craniofacial FD can impinge nerve fibers causing visual loss as well as craniofacial pain. Surgical decompression of affected nerves is performed, with variable efficacy, in an attempt to restore function or alleviate symptoms. Here, we present a case of a 12-year-old MAS patient with visual deficits, particularly in the left eye (confirmed by enlarged blind spots on Goldmann visual field testing), and craniofacial pain. Decompression surgery of the left optic nerve mildly improved vision, while persistent visual deficits were noted at a 3-month follow-up assessment. An in-depth, imaging-based evaluation of the visual system, including the retinal nerve fiber layer, optic nerves, and central nervous system (CNS) visual pathways, revealed multiple abnormalities throughout the visual processing stream. In the current FD/MAS patient, a loss of white matter fiber density within the left optic radiation and functional changes involving the left primary visual cortex were observed. Aberrant structural and functional abnormalities embedded within central visual pathways may play a role in facilitating deficits in vision in FD/MAS and contribute to the variable outcome following peripheral nerve decompression surgery.

Pain Phenotypes in Rare Musculoskeletal and Neuromuscular Diseases.

For patients diagnosed with a rare musculoskeletal or neuromuscular disease, pain may transition from acute to chronic; the latter yielding additional challenges for both patients and care providers. We assessed the present understanding of pain across a set of ten rare, noninfectious, noncancerous disorders; Osteogenesis Imperfecta, Ehlers-Danlos Syndrome, Achondroplasia, Fibrodysplasia Ossificans Progressiva, Fibrous Dysplasia/McCune-Albright Syndrome, Complex Regional Pain Syndrome, Duchenne Muscular Dystrophy, Infantile- and Late-Onset Pompe disease, Charcot-Marie-Tooth Disease, and Amyotrophic Lateral Sclerosis. Through the integration of natural history, cross-sectional, retrospective, clinical trials, & case studies we described pathologic and genetic factors, pain sources, phenotypes, and lastly, existing therapeutic approaches. We highlight that while rare diseases possess distinct core pathologic features, there are a number of shared pain phenotypes and mechanisms that may be prospectively examined and therapeutically targeted in a parallel manner. Finally, we describe clinical and research approaches that may facilitate more accurate diagnosis, monitoring, and treatment of pain as well as elucidation of the evolving nature of pain phenotypes in rare musculoskeletal or neuromuscular illnesses.

Pharmacological modulation of brain activity in a preclinical model of osteoarthritis.

The earliest stages of osteoarthritis are characterized by peripheral pathology; however, during disease progression chronic pain emerges-a major symptom of osteoarthritis linked to neuroplasticity. Recent clinical imaging studies involving chronic pain patients, including osteoarthritis patients, have demonstrated that functional properties of the brain are altered, and these functional changes are correlated with subjective behavioral pain measures. Currently, preclinical osteoarthritis studies have not assessed if functional properties of supraspinal pain circuitry are altered, and if these functional properties can be modulated by pharmacological therapy either by direct or indirect action on brain systems. In the current study, functional connectivity was first assessed in order to characterize the functional neuroplasticity occurring in the rodent medial meniscus tear (MMT) model of osteoarthritis-a surgical model of osteoarthritis possessing peripheral joint trauma and a hypersensitive pain state. In addition to knee joint trauma at week 3 post-MMT surgery, we observed that supraspinal networks have increased functional connectivity relative to sham animals. Importantly, we observed that early and sustained treatment with a novel, peripherally acting broad-spectrum matrix metalloproteinase (MMP) inhibitor (MMPi) significantly attenuates knee joint trauma (cartilage degradation) as well as supraspinal functional connectivity increases in MMT animals. At week 5 post-MMT surgery, the acute pharmacodynamic effects of celecoxib (selective cyclooxygenase-2 inhibitor) on brain function were evaluated using pharmacological magnetic resonance imaging (phMRI) and functional connectivity analysis. Celecoxib was chosen as a comparator, given its clinical efficacy for alleviating pain in osteoarthritis patients and its peripheral and central pharmacological action. Relative to the vehicle condition, acute celecoxib treatment in MMT animals yielded decreased phMRI infusion responses and decreased functional connectivity, the latter observation being similar to what was detected following chronic MMPi treatment. These findings demonstrate that an assessment of brain function may provide an objective means by which to further evaluate the pathology of an osteoarthritis state as well as measure the pharmacodynamic effects of therapies with peripheral or peripheral and central pharmacological action.