Physical therapy assessment tools to evaluate disease progression and phenotype variability in Golden Retriever muscular dystrophy

Appendicular skeletal muscle mass assessment in dogs: a scoping literature review

BACKGROUND

Monitoring changes in appendicular skeletal muscle mass is frequently used as a surrogate marker for limb function. The primary objective of this study was to review scientific information related to the assessment of appendicular skeletal muscle mass in dogs. The secondary objective was to develop practical recommendations for serial evaluation of muscle mass.

METHODS

A scoping review was conducted with a systematic search of PubMed, Web of Science, CAB abstract, and Cochrane from inception to June 2021. The following modalities were included in the search: limb circumference, diagnostic ultrasound, computed tomography, magnetic resonance imaging, and dual-energy x-ray absorptiometry.

RESULTS

A total of 62 articles that measured appendicular skeletal muscle mass in dogs were identified. Limb circumference (55 articles) was the most commonly used modality. Its reliability was investigated in five studies. Several factors, including measuring tape type, body position, joint angles, and the presence of hair coat, were reported as variables that can affect measurements. Diagnostic ultrasound (five articles) was validated in three articles, but there is scarce information about observer reliability and variables affecting the measurement. Computed tomography (four articles) and magnetic resonance imaging (one article) have been used to validate other modalities at a single time point rather than as a clinical tool for serial muscle mass monitoring. Dual-energy x-ray absorptiometry (two articles) has been used to quantify specific skeletal muscle mass but was mainly used to evaluate body composition in dogs.

CONCLUSION

Limb circumference and ultrasound are likely the main modalities that will continue to be used for serial muscle mass measurement in the clinical setting unless a new technology is developed. The reliability of limb circumference is questionable. Several key factors, including measuring tape type, body position, joint angles, and coat clipping, need to be controlled to improve the reliability of limb circumference measurements. Ultrasound may provide a reasonable alternative, but further studies are required to evaluate the reliability of this modality and identify factors that influence ultrasound measurements.

Use of the six-minute walk test to characterize golden retriever muscular dystrophy

Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder in which loss of the dystrophin protein causes progressive skeletal/cardiac muscle degeneration and death within the third decade. For clinical trials and supportive animal studies, DMD disease progression and response to treatment must be established using outcome parameters (biomarkers). The 6-minute walk test (6MWT), defined as the distance an individual can walk in 6 minutes, is commonly used in DMD clinical trials and has been employed in dogs to characterize cardiac and respiratory disease severity. Building on methods established in DMD and canine clinical studies, we assessed the 6MWT in dogs with the DMD genetic homolog, golden retriever muscular dystrophy (GRMD). Twenty-one cross-bred golden retrievers were categorized as affected (DMD mutation and GRMD phenotype), carrier (female heterozygous for DMD mutation and no phenotype), and normal (wild type DMD gene and normal phenotype). When compared to grouped normal/carrier dogs, GRMD dogs walked shorter height-adjusted distances at 6 and 12 months of age and their distances walked declined with age. Percent change in creatine kinase after 6MWT was greater in GRMD versus normal/carrier dogs at 6 months, providing another potential biomarker. While these data generally support use of the 6MWT as a biomarker for preclinical GRMD treatment trials, there were certain limitations. Results of the 6MWT did not correlate with other outcome parameters for GRMD dogs when considered alone and an 80% increase in mean distance walked would be necessary to achieve satisfactory power.

Night Activity Reduction is a Signature Physiological Biomarker for Duchenne Muscular Dystrophy Dogs

BACKGROUND

Duchenne muscular dystrophy (DMD) is an X-linked lethal muscle disease. Dystrophic dogs are excellent models to test novel therapies for DMD. However, the use of the dog model has been hindered by the lack of an effective method to evaluate whole-body mobility. We recently showed that night activity is a good indicator of dog mobility. However, our published method relies on frame-by-frame manual processing of a 12-hour video for each dog. This labor-intensive and time-consuming approach makes it unrealistic to use this assay as a routine outcome measurement.

OBJECTIVE

To solve this problem, we developed an automatic video-capturing/imaging processing system. The new system reduces the data analysis time over 1,000 fold and also provides a more detailed activity profile of the dog.

METHODS

Using the new system, we analyzed more than 120 twelve-hour recordings from 12 normal and 22 affected dogs.

RESULTS

We observed similar activity profiles during repeated recording of the same dog. Throughout the night, normal dogs were in motion 10.4 ± 0.9% of the time while affected dogs were in motion 4.6 ± 0.2% of the time (p < 0.0001). Further, normal dogs made significantly more movements (p < 0.0001) while affected dogs rested significantly longer (p < 0.0001) during the period of recording (from 6 pm to 6 am next day). Importantly, statistical significance persisted irrespective of the coat color, gender and mutation type.

CONCLUSIONS

Our results suggest that night activity reduction is a robust, quantitative physiological biomarker for dystrophic dogs. The new system may be applicable to study mobility in other species.

Profiles of Steroid Hormones in Canine X-Linked Muscular Dystrophy via Stable Isotope Dilution LC-MS/MS

Golden retriever muscular dystrophy (GRMD) provides the best animal model for characterizing the disease progress of the human disorder, Duchenne muscular dystrophy (DMD). The purpose of this study was to determine steroid hormone concentration profiles in healthy golden retriever dogs (control group - CtGR) versus GRMD-gene carrier (CaGR) and affected female dogs (AfCR). Therefore, a sensitive and specific analytical method was developed and validated to determine the estradiol, progesterone, cortisol, and testosterone levels in the canine serum by isotope dilution liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). To more accurately understand the dynamic nature of the serum steroid profile, the fluctuating levels of these four steroid hormones over the estrous cycle were compared across the three experimental groups using a multivariate statistical analysis. The concentration profiles of estradiol, cortisol, progesterone, and testosterone revealed a characteristic pattern for each studied group at each specific estrous phase. Additionally, several important changes in the serum concentrations of cortisol and estradiol in the CaGR and AfCR groups seem to be correlated with the status and progression of the muscular dystrophy. A comprehensive and quantitative monitoring of steroid profiles throughout the estrous cycle of normal and GRMD dogs were achieved. Significant differences in these profiles were observed between GRMD and healthy animals, most notably for estradiol. These findings contribute to a better understanding of both dog reproduction and the muscular dystrophy pathology. Our data open new venues for hormonal behavior studies in dystrophinopathies and that may affect the quality of life of DMD patients.

Motor physical therapy affects muscle collagen type I and decreases gait speed in dystrophin-deficient dogs

Golden Retriever Muscular Dystrophy (GRMD) is a dystrophin-deficient canine model genetically homologous to Duchenne Muscular Dystrophy (DMD) in humans. Muscular fibrosis secondary to cycles of degeneration/regeneration of dystrophic muscle tissue and muscular weakness leads to biomechanical adaptation that impairs the quality of gait. Physical therapy (PT) is one of the supportive therapies available for DMD, however, motor PT approaches have controversial recommendations and there is no consensus regarding the type and intensity of physical therapy. In this study we investigated the effect of physical therapy on gait biomechanics and muscular collagen deposition types I and III in dystrophin-deficient dogs. Two dystrophic dogs (treated dogs-TD) underwent a PT protocol of active walking exercise, 3×/week, 40 minutes/day, 12 weeks. Two dystrophic control dogs (CD) maintained their routine of activities of daily living. At t0 (pre) and t1 (post-physical therapy), collagen type I and III were assessed by immunohistochemistry and gait biomechanics were analyzed. Angular displacement of shoulder, elbow, carpal, hip, stifle and tarsal joint and vertical (Fy), mediolateral (Fz) and craniocaudal (Fx) ground reaction forces (GRF) were assessed. Wilcoxon test was used to verify the difference of biomechanical variables between t0 and t1, considering p<.05. Type I collagen of endomysium suffered the influence of PT, as well as gait speed that had decreased from t0 to t1 (p<.000). The PT protocol employed accelerates morphological alterations on dystrophic muscle and promotes a slower velocity of gait. Control dogs which maintained their routine of activities of daily living seem to have found a better balance between movement and preservation of motor function.

Bortezomib (PS-341) treatment decreases inflammation and partially rescues the expression of the dystrophin-glycoprotein complex in GRMD dogs

Golden retriever muscular dystrophy (GRMD) is a genetic myopathy corresponding to Duchenne muscular dystrophy (DMD) in humans. Muscle atrophy is known to be associated with degradation of the dystrophin-glycoprotein complex (DGC) via the ubiquitin-proteasome pathway. In the present study, we investigated the effect of bortezomib treatment on the muscle fibers of GRMD dogs. Five GRMD dogs were examined; two were treated (TD- Treated dogs) with the proteasome inhibitor bortezomib, and three were control dogs (CD). Dogs were treated with bortezomib using the same treatment regimen used for multiple myeloma. Pharmacodynamics were evaluated by measuring the inhibition of 20S proteasome activity in whole blood after treatment and comparing it to that in CD. We performed immunohistochemical studies on muscle biopsy specimens to evaluate the rescue of dystrophin and dystrophin-associated proteins in the muscles of GRMD dogs treated with bortezomib. Skeletal tissue from TD had lower levels of connective tissue deposition and inflammatory cell infiltration than CD as determined by histology, collagen morphometry and ultrastructural analysis. The CD showed higher expression of phospho-NFκB and TGF-β1, suggesting a more pronounced activation of anti-apoptotic factors and inflammatory molecules and greater connective tissue deposition, respectively. Immunohistochemical analysis demonstrated that dystrophin was not present in the sarcoplasmic membrane of either group. However, bortezomib-TD showed higher expression of α- and β-dystroglycan, indicating an improved disease histopathology phenotype. Significant inhibition of 20S proteasome activity was observed 1 hour after bortezomib administration in the last cycle when the dose was higher. Proteasome inhibitors may thus improve the appearance of GRMD muscle fibers, lessen connective tissue deposition and reduce the infiltration of inflammatory cells. In addition, proteasome inhibitors may rescue some dystrophin-associated proteins in the muscle fiber membrane.

Quantitative phenotyping of Duchenne muscular dystrophy dogs by comprehensive gait analysis and overnight activity monitoring

The dystrophin-deficient dog is excellent large animal model for testing novel therapeutic modalities for Duchenne muscular dystrophy (DMD). Despite well-documented descriptions of dystrophic symptoms in these dogs, very few quantitative studies have been performed. Here, we developed a comprehensive set of non-invasive assays to quantify dog gait (stride length and speed), joint angle and limb mobility (for both forelimb and hind limb), and spontaneous activity at night. To validate these assays, we examined three 8-m-old mix-breed dystrophic dogs. We also included three age-matched siblings as the normal control. High-resolution video recorders were used to digitize dog walking and spontaneous movement at night. Stride speed and length were significantly decreased in affected dogs. The mobility of the limb segments (forearm, front foot, lower thigh, rear foot) and the carpus and hock joints was significantly reduced in dystrophic dogs. There was also a significant reduction of the movement in affected dogs during overnight monitoring. In summary, we have established a comprehensive set of outcome measures for clinical phenotyping of DMD dogs. These non-invasive end points would be valuable in monitoring disease progression and therapeutic efficacy in translational studies in the DMD dog model.

Goniometria dos membros torácicos e pélvicos de ovinos em duas faixas etárias

O trabalho teve por objetivo comparar os valores goniométricos das articulações dos membros torácicos e pélvicos em ovinos da raça Santa Inês em duas faixas etárias (jovens e adultos). Foram utilizados 30 ovinos hígidos, fêmeas, divididos em dois grupos: Grupo 1 com 15 animais jovens (idade entre 6 e 12 meses), Grupo 2 com 15 animais adultos (entre 3 e 6 anos). Foram aferidas a máxima flexão, a máxima extensão e calculou-se a amplitude de movimento das articulações, direita e esquerda, dos membros torácicos (ombro, cotovelo e carpo) e pélvicos (coxofemoral, joelho e tarso), com o emprego de um goniômetro universal de plástico. Cada articulação foi aferida em triplicata por dois avaliadores com o animal em estação. Não foram detectadas diferenças estatísticas entre as médias em ambos os lados, entre os avaliadores ou entre os grupos. Foi possível assim concluir que, em ovinos hígidos, os valores goniométricos não foram influenciados pela idade.