Assessment of disease activity in muscular dystrophies by noninvasive imaging

Abstract

Muscular dystrophies are a class of disorders that cause progressive muscle wasting. A major hurdle for discovering treatments for the muscular dystrophies is a lack of reliable assays to monitor disease progression in animal models. We have developed a novel mouse model to assess disease activity noninvasively in mice with muscular dystrophies. These mice express an inducible luciferase reporter gene in muscle stem cells. In dystrophic mice, muscle stem cells activate and proliferate in response to muscle degeneration, resulting in an increase in the level of luciferase expression, which can be monitored by noninvasive, bioluminescence imaging. We applied this noninvasive imaging to assess disease activity in a mouse model of the human disease limb girdle muscular dystrophy 2B (LGMD2B), caused by a mutation in the dysferlin gene. We monitored the natural history and disease progression in these dysferlin-deficient mice up to 18 months of age and were able to detect disease activity prior to the appearance of any overt disease manifestation by histopathological analyses. Disease activity was reflected by changes in luciferase activity over time, and disease burden was reflected by cumulative luciferase activity, which paralleled disease progression as determined by histopathological analysis. The ability to monitor disease activity noninvasively in mouse models of muscular dystrophy will be invaluable for the assessment of disease progression and the effectiveness of therapeutic interventions.

Illuminating regeneration: noninvasive imaging of disease progression in muscular dystrophy

“…They found luciferase activity mainly in the proximal limb muscles as early as 3 months of age, with some involvement in the distal muscles starting at 6 months, and increasing luciferase activity in both proximal and distal muscle groups up to 18 months of age. Further examination of these mice showed a correlation between intensity of luciferase signal (as determined by bioluminescent imaging), number of luciferase positive fibers (as determined by immunohistochemistry), and extent of histopathology, including centrally nucleated fibers and fibers that express embryonic myosin heavy chain, a marker for newly regenerated myofibers (5). This validates luciferase imaging as an alternative to conventional measures of disease progression in muscular dystrophy.…”

“…They first injured the TA muscles with cardiotoxin and compared the luciferase signal between the injured and uninjured limbs. Luciferase activity increased following injury, and immunohistochemical studies confirmed that luciferase-expressing cells were present in the injured TA as nascent myofibers and myotubes (5). This suggests that the noninvasive measurement of luciferase activity in the Pax7Cre ER /LuSEAP strain is an accurate measure of the proliferative activity of satellite cells and therefore has potential to be used to measure muscle regeneration in muscular dystrophy models as well.…”

“…There are two angiotensin II receptors, and it is the angiotensin II receptor type 1 (AT1 R ) subtype that increases blood pressure and fluid volume through vasoconstriction and stimulation of aldosterone secretion from the adrenal gland and salt retention by the kidneys. Coffman and colleagues transplanted the kidneys of AT1 R -deficient mice into control animals and vice versa (5). Subsequent infusion of these mice for two weeks with a high dose of angiotensin II revealed that the mice with AT1 R expression in the kidney, but a complete lack of this receptor elsewhere in the body, developed hypertension and cardiac hypertrophy.…”

zebraflash transgenic lines for in vivo bioluminescence imaging of stem cells and regeneration in adult zebrafish

“…Luciferase-based imaging has been widely used in mice for monitoring gene expression, cell proliferation and migration, and bacterial and viral infections (Contag and Bachmann, 2002;Luker and Luker, 2008;Liu et al, 2011;Tinkum et al, 2011;Martínez-Corral et al, 2012;Maguire et al, 2013). Detection of bioluminescent signals generated from the luciferase-luciferin reaction is sensitive, virtually free of background noise, and can reveal biological information even from deep tissues.…”

Seeing Stem Cells at Work In Vivo

“…Maguire and colleagues monitored luciferase activity in mice expressing an inducible luciferase reporter gene in muscle stem cells. These stem cells proliferated in response to muscle degeneration, thus increasing the level of luciferase expression in dystrophic muscle [131]. …”