Longitudinal assessment of skeletal muscle functional mechanics in the DE50-MD dog model of Duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD), caused by mutations in the dystrophin (DMD) gene, is associated with fatal muscle degeneration and atrophy. Patients with DMD have progressive reductions in skeletal muscle strength and resistance to eccentric muscle stretch. Using the DE50-MD dog model of DMD, we assessed tibiotarsal joint (TTJ) flexor and extensor force dynamics, and the resistance of dystrophic muscle to eccentric stretch. Male DE50-MD and wild-type (WT) dogs were analysed every 3 months until 18 months of age. There was an age-associated decline in eccentric contraction resistance in DE50-MD TTJ flexors that discriminated, with high statistical power, WT from DE50-MD individuals. For isometric contraction, at the majority of timepoints, DE50-MD dogs had lower maximum absolute and relative TTJ flexor force, reduced TTJ muscle contraction times and prolonged relaxation compared to those in WT dogs. Cranial tibial muscles, the primary TTJ flexor, of 18-month-old DE50-MD dogs had significant numbers of regenerating fibres as expected, but also fewer type I fibres and more hybrid fibres than those in WT dogs. We conclude that these parameters, in particular, the eccentric contraction decrement, could be used as objective outcome measures for pre-clinical assessment in DE50-MD dogs.

Imaging characteristics of thoracolumbar spinal stenosis due to articular process hyperplasia and degenerative joint disease in six large breed dogs.

Previous studies have reported evidence that thoracolumbar articular process hyperplasia and degenerative joint disease may be a cause of stenotic myelopathy in large breed dogs; however, detailed descriptions of imaging characteristics are currently lacking. The aim of this retrospective, multi-center, case series report was to describe imaging findings in six large breed dogs diagnosed with thoracolumbar articular process hyperplasia and degenerative joint disease causing vertebral canal stenosis. All dogs presented with progressive paraparesis, proprioceptive ataxia of the pelvic limbs, and neuroanatomical localization of T3-L3 myelopathy. All dogs underwent magnetic resonance imaging (MRI) of the thoracolumbar spine and had articular process malformations at T13-L1 (three German Shepherd dogs (GSD) and a Boxer dog) or T12-T13 (two mixed-breed dogs). Five cases were managed surgically. Findings provided more detailed imaging descriptions and supported previously published studies indicating that maldevelopment of articular processes and secondary degenerative changes can be a cause of thoracolumbar spinal stenosis and myelopathy in large breed dogs. While uncommon, this condition should be included as a differential diagnosis for large breed dogs presenting with a T3-L3 myelopathy.

The skeletal muscle phenotype of the DE50-MD dog model of Duchenne muscular dystrophy.

Background: Animal models of Duchenne muscular dystrophy (DMD) are essential to study disease progression and assess efficacy of therapeutic intervention, however dystrophic mice fail to display a clinically relevant phenotype, limiting translational utility. Dystrophin-deficient dogs exhibit disease similar to humans, making them increasingly important for late-stage preclinical evaluation of candidate therapeutics. The DE50-MD canine model of DMD carries a mutation within a human 'hotspot' region of the dystrophin gene, amenable to exon-skipping and gene editing strategies. As part of a large natural history study of disease progression, we have characterised the DE50-MD skeletal muscle phenotype to identify parameters that could serve as efficacy biomarkers in future preclinical trials. Methods: Vastus lateralis muscles were biopsied from a large cohort of DE50-MD dogs and healthy male littermates at 3-monthly intervals (3-18 months) for longitudinal analysis, with multiple muscles collected post-mortem to evaluate body-wide changes. Pathology was characterised quantitatively using histology and measurement of gene expression to determine statistical power and sample sizes appropriate for future work. Results: DE50-MD skeletal muscle exhibits widespread degeneration/regeneration, fibrosis, atrophy and inflammation. Degenerative/inflammatory changes peak during the first year of life, while fibrotic remodelling appears more gradual. Pathology is similar in most skeletal muscles, but in the diaphragm, fibrosis is more prominent, associated with fibre splitting and pathological hypertrophy. Picrosirius red and acid phosphatase staining represent useful quantitative histological biomarkers for fibrosis and inflammation respectively, while qPCR can be used to measure regeneration ( MYH3, MYH8), fibrosis ( COL1A1), inflammation ( SPP1), and stability of DE50-MD dp427 transcripts. Conclusion: The DE50-MD dog is a valuable model of DMD, with pathological features similar to young, ambulant human patients. Sample size and power calculations show that our panel of muscle biomarkers are of strong pre-clinical value, able to detect therapeutic improvements of even 25%, using trials with only six animals per group.

Multimodality characteristics of multifocal choroid plexus carcinoma with bilateral calvarial defects in a dog.

An 8-year-old male intact miniature poodle presented for blindness, obtundation, tetraparesis, and vestibular signs. Magnetic resonance imaging, radiography, and ultrasound revealed a left piriform lobe lesion, right cerebellar and left brainstem lesions, and hydrocephalus and bilateral calvarial defects. Histopathology confirmed a choroid plexus carcinoma with meningeal and intraventricular metastases. The calvarial defect did not show evidence of necrosis, osteoclastic resorption, inflammation or neoplastic infiltration, reflecting a quiescent calvarial atrophy or dysplasia. These novel findings supported inclusion of bone atrophy secondary to chronic increased intracranial pressure as a differential diagnosis for large calvarial defects in dogs with choroid plexus carcinoma.

Clinical reasoning in feline vestibular syndrome: which presenting features are the most important?

OBJECTIVES: The aim of this study was to evaluate whether clinical variables from the history, clinical presentation, and physical and neurological examinations of cats with vestibular syndrome were statistically predictive of the underlying diagnosis. METHODS: In total, 174 cats presenting with vestibular syndrome between January 2010 and May 2019 were investigated. Univariate statistical analysis of clinical variables was performed and those statistically associated with a diagnosis were retained for multivariable binary logistic regression modelling. RESULTS: The seven most prevalent diagnoses represented 95% of vestibular presentations, which included: otitis media/interna (n = 48), idiopathic vestibular syndrome (n = 39), intracranial neoplasia (n = 24), middle ear polyp (n = 17), feline infectious peritonitis (n = 13), thiamine deficiency (n = 13) and intracranial empyema (n = 11). Idiopathic vestibular syndrome was commonly associated with non-purebred cats and had 17.8 times the odds of an improving clinical progression (95% confidence interval [CI] 1.3-250.0; P = 0.03). Intracranial neoplasia was associated with older age and chronic onset of clinical signs, and was significantly more likely to have a central vestibular neuroanatomical localisation (95% CI 8.5-344,349,142.0; P = 0.015) with postural deficits on neurological examination. Thiamine deficiency was more common in female cats, with 52.6 times the odds of a waxing and waning clinical progression (95% CI 1.2-1000; P = 0.038) and 6.8 times the odds of presenting with bilateral vestibular signs (95% CI 1.0-45.7; P = 0.047) and wide excursions of the head (95% CI 1.0-45.7; P = 0.047). Middle ear polyps were associated with 8.8 times the odds of presenting with Horner syndrome (95% CI 1.5-50.0; P = 0.015). CONCLUSIONS AND RELEVANCE: Although it may be difficult to identify the underlying diagnosis in cats with vestibular syndrome from the presenting features alone, there are instances in which discrete clinical features may help to guide clinical reasoning when evaluating cats with vestibular presentations.

Determination of qPCR Reference Genes Suitable for Normalizing Gene Expression in a Canine Model of Duchenne Muscular Dystrophy.

BACKGROUND: Dogs with dystrophin-deficient muscular dystrophy are valuable models of the equivalent human disease, Duchenne Muscular Dystrophy (DMD): unlike the mdx mouse, these animals present a disease severity and progression that closely matches that found in human patients. Canine models are however less thoroughly characterised than the established mdx mouse in many aspects, including gene expression. Analysis of expression in muscle plays a key role in the study of DMD, allowing monitoring and assessment of disease progression, evaluation of novel biomarkers and gauging of therapeutic intervention efficacy. Appropriate normalization of expression data via carefully selected reference genes is consequently essential for accurate quantitative assessment. Unlike the expression profile of healthy skeletal muscle, the dystrophic muscle environment is highly dynamic: transcriptional profiles of dystrophic muscle might alter with age, disease progression, disease severity, genetic background and between muscle groups. OBJECTIVES: The aim of this work was to identify reference genes suitable for normalizing gene expression in healthy and dystrophic dogs under various comparative scenarios. METHODS: Using the delta-E50 MD canine model of DMD, we assessed a panel of candidate reference genes for stability of expression across healthy and dystrophic animals, at different ages and in different muscle groups. RESULTS: We show that the genes HPRT1, SDHA and RPL13a appear universally suitable for normalizing gene expression in healthy and dystrophic canine muscle, while other putative reference genes are exceptionally poor, and in the case of B2M, actively disease-correlated. CONCLUSIONS: Our findings suggest consistent cross-sample normalization is possible even throughout the dynamic progression of dystrophic pathology, and furthermore highlight the importance of empirical determination of suitable reference genes for neuromuscular diseases.

IMAGING DIAGNOSIS-IMAGING AND HISTOPATHOLOGIC CHARACTERISTICS OF A VERTEBRAL HAMARTOMA IN A CAT.

A 9-month-old domestic shorthair cat had progressive ambulatory paraparesis, proprioceptive ataxia, and thoracolumbar hyperesthesia. An extradural mass affecting the left pedicle and lamina of the second lumbar vertebra (L2) causing marked spinal cord impingement was identified in magnetic resonance (MR) images. The mass was predominantly calcified in computed tomographic (CT) images. A hemilaminectomy was performed to resect the mass. Clinical signs were greatly improved at 12-month follow-up. The histopathologic diagnosis was vascular hamartoma. To our knowledge, this is the first report describing the MR characteristics of a vascular hamartoma associated with the vertebral column.

Comparison of medical and surgical treatment for acute cervical compressive hydrated nucleus pulposus extrusion in dogs.

Although successful outcomes have been reported after medical and surgical treatment for dogs with cervical hydrated nucleus pulposus extrusion (HNPE), it is unknown which treatment option is preferred. Thirty-four dogs treated medically (n=18) or surgically (n=16) for cervical HNPE were retrospectively identified. Signalment, clinical presentation and imaging findings were compared between medically and surgically treated dogs. Medical management consisted of restricted exercise in combination with physiotherapy. Surgical treatment consisted of a ventral slot procedure. Short-term follow-up information was retrieved from re-examination visits. Long-term outcome was obtained via telephone interviews. More dogs in the surgical group demonstrated cervical hyperaesthesia on initial clinical presentation (P=0.045), otherwise there was no significant difference in signalment, clinical presentation or imaging findings between both groups. Two dogs in the medically managed group underwent surgical decompression due to an unsatisfactory response to medical management. All cases for which long-term information was available (n=30) were neurologically normal at the time of data collection. There were no significant differences for any of the short-term or long-term outcome variables between both treatment groups. This study demonstrated successful outcomes after medical or surgical treatment and suggests that both treatment modalities can be considered for dogs with cervical HNPE.

Presumptive acute non-compressive nucleus pulposus extrusion in 11 cats: clinical features, diagnostic imaging findings, treatment and outcome.

Objectives The aim of the study was to describe the clinical features, diagnostic imaging findings, treatment and outcome in cats diagnosed with presumptive acute non-compressive nucleus pulposus extrusion. Methods Medical records and imaging studies of cats diagnosed with presumptive acute non-compressive nucleus pulposus extrusion were retrospectively reviewed. Information on long-term outcome was acquired from patient records and from either owners or referring veterinary surgeons via a telephone questionnaire. Results Eleven cats met the inclusion criteria. All cats had a peracute onset of clinical signs, with eight cats experiencing witnessed (n = 6) or suspected (n = 2) external trauma based on imaging findings. Neuroanatomical localisation included C1-C5 (n = 1), T3-L3 (n = 7) and L4-S3 (n = 3) spinal cord segments. MRI revealed acute non-compressive nucleus pulposus extrusions located at C3-C4 (n = 1), T12-T13 (n = 1), T13-L1 (n = 1), L1-L2 (n = 1), L3-L4 (n = 3), L4-L5 (n = 1) and L5-L6 intervertebral disc spaces (n = 3). Treatment included supportive care and 10 cats were discharged with a median hospitalisation time of 10 days (range 3-26 days). One cat was euthanased during hospitalisation owing to complications unrelated to neurological disease. All cats that presented as non-ambulatory regained an ambulatory status with the median time to ambulation of 17 days (range 6-21 days). Overall, the outcome for cats diagnosed with acute non-compressive nucleus pulposus extrusion was successful, with almost 90% returning to ambulation with urinary and faecal continence. Conclusions and relevance The majority of cats diagnosed with acute non-compressive nucleus pulposus extrusion had good outcomes. Acute non-compressive nucleus pulposus extrusion should be considered as a differential diagnosis for cats presenting with peracute onset of spinal cord dysfunction, particularly if there is a clinical history or evidence of trauma.

Epidemiology of Cranial Cruciate Ligament Disease Diagnosis in Dogs Attending Primary-Care Veterinary Practices in England.

OBJECTIVE: To estimate the prevalence and risk factors for a diagnosis of cranial cruciate ligament (CCL) disease in dogs and to describe the management of such cases attending primary-care veterinary practices. STUDY DESIGN: Historical cohort with a nested case-control study. SAMPLE POPULATION: Nine hundred and fifty-three dogs diagnosed with CCL disease from 171,522 dogs attending 97 primary-care practices in England. METHODS: Medical records of dogs attending practices participating in the VetCompass project that met selection criteria were assessed. Univariate and multivariate logistic regression methods were used to evaluate association of possible risk factors with diagnosis of CCL disease. RESULTS: The prevalence of CCL disease diagnosis was estimated at 0.56% (95% confidence interval 0.52-0.59). Compared with crossbred dogs, Rottweilers, West Highland White Terriers, Golden Retrievers, Yorkshire Terriers, and Staffordshire Bull Terriers showed increased odds of CCL disease diagnosis while Cocker Spaniels showed reduced odds. Increasing bodyweight within breeds was associated with increased odds of diagnosis. Dogs aged over 3 years had increased odds of diagnosis compared with dogs aged less than 3 years. Neutered females had 2.1 times the odds of diagnosis compared with entire females. Insured dogs had 4 times the odds of diagnosis compared with uninsured dogs. Two-thirds of cases were managed surgically, with insured and heavier dogs more frequently undergoing surgery. Overall, 21% of cases were referred, with referral more frequent in heavier and insured dogs. Referred dogs more frequently had surgery and an osteotomy procedure. CONCLUSION: Breed predispositions and demographic factors associated with diagnosis and case management of CCL disease in dogs identified in this study can be used to help direct future research and management strategies.

Phenotypical and morphological changes in the thymic microenvironment from ageing mice.

The thymus is crucial for T-cell output and the age-associated involution of this organ, is thought to have a major impact in the decline in immunity that is seen in later life. The mechanism that underlines thymic involution is not known, however, we have evidence to suggest that this is may be due to changes in the thymic microenvironment. To further test this hypothesis, we quantified the in situ changes to markers that identify cortical and medullary thymic epithelial cells. This analysis revealed an age-dependent decline in cortical and medullary markers together with an increase in Notch and Delta expression, in older mice, as judged by immunohistochemistry. This was accompanied by alterations of the archetypal staining patterns and three dimensional analysis revealed changes in the morphology of the thymic microenvironment. These studies suggest that there are age-associated alterations in the thymic microenvironment, which may therefore play a role in thymic involution.