BACKGROUND: The vestibular system undergoes considerable modification during spaceflight [5]. This is paralleled by microgravity-induced muscle atrophy [6]. However, the possibility of vestibulo-autonomic regulatory mechanisms affecting skeletal muscle structure and function have not yet been addressed. OBJECTIVE: We hypothesise that the vestibular system affects anti-gravitational skeletal muscle phenotype composition, size and the transcriptional factor called nuclear factor of activated T cells (NFATc1). METHODS: In a laboratory study, we examined the morphological and histochemical properties including intramyocellular NFATc1 changes in slow-type soleus muscle of chemically labyrinthectomized rats (VLx; n=8) compared to a control group (Sham; n=6) after a period of one month. RESULTS AND CONCLUSION: Neurochemical vestibular deafferentation resulted in smaller myofibre sizes, altered myofibre phenotype composition, high yields of hybrid fibre formation, and reduced myonuclear NFATc1 accumulation as signs of slow-type myofibre atrophy, myofibre type remodelling, and altered nuclear transcriptional activity in the postural soleus muscle of rats. We propose that vestibulo-autonomic modification of skeletal muscles occurs during prolonged microgravity. Our findings are likely to have implications for vestibular rehabilitation in clinical settings.
BACKGROUND: The vestibular system undergoes considerable modification during spaceflight [5]. This is paralleled by microgravity-induced muscle atrophy [6]. However, the possibility of vestibulo-autonomic regulatory mechanisms affecting skeletal muscle structure and function have not yet been addressed. OBJECTIVE: We hypothesise that the vestibular system affects anti-gravitational skeletal muscle phenotype composition, size and the transcriptional factor called nuclear factor of activated T cells (NFATc1). METHODS: In a laboratory study, we examined the morphological and histochemical properties including intramyocellular NFATc1 changes in slow-type soleus muscle of chemically labyrinthectomized rats (VLx; n=8) compared to a control group (Sham; n=6) after a period of one month. RESULTS AND CONCLUSION: Neurochemical vestibular deafferentation resulted in smaller myofibre sizes, altered myofibre phenotype composition, high yields of hybrid fibre formation, and reduced myonuclear NFATc1 accumulation as signs of slow-type myofibre atrophy, myofibre type remodelling, and altered nuclear transcriptional activity in the postural soleus muscle of rats. We propose that vestibulo-autonomic modification of skeletal muscles occurs during prolonged microgravity. Our findings are likely to have implications for vestibular rehabilitation in clinical settings.
Authors: Vanessa Martins-Lopes; Anna Bellmunt; Erin A Greguske; Alberto F Maroto; Pere Boadas-Vaello; Jordi Llorens Journal: J Assoc Res Otolaryngol Date: 2019-07-11