Research Symposium

BIO

Kaitlyn Harrison is a second-year student at Florida State University, purising a Bachelor's of Science in Athletic Training, with minors in Chemistry and Physiology and a Certificate in Leadership Studies. She works under Dr. Jacob Brown in the College of Education, Health, and Human Sciences on the impacts of disuse-atrophy on neuromusclar junctions. Outside of the classroom, Kaitlyn is a Resident Assistant for Ragans and Traditions and a Clinical Medical Assistant at Patient's First. Her goal is to attend medical school and become a physician at a research hospital.

Disuse-Atrophy Exacerbates Denervation in Aged Rats

Abstract

Older humans fail to recover skeletal muscle mass and function after muscle loss due to bedrest, which contrasts with young and adult humans, leading to muscle loss and an increase in morbidity and mortality in the aged population. Disorders disrupting the neuromuscular junction, the synapse where motor nerves meet muscles, are associated with age-related muscle atrophy and dysfunction. We hypothesized that periods of disuse-atrophy will exacerbate neuromuscular pathologies in aged rats. 28-month-old rats were hindlimb unloaded, a condition where the rats cannot put weight on their hindlimbs, for 14 days to induce disuse atrophy. 28-month-old weight-bearing rats were used as controls. Muscle wet weights were measured at sacrifice. Via immunofluorescence, we assessed acetyl choline receptor endplate area, acetyl choline receptor endplate fragmentation, and denervation of the neuromuscular junctions. Oxylipins, oxidized lipid signaling molecules, were measured in gastrocnemius muscle. We performed a student’s t-test for statistical analysis. Muscle wet weights were 20-40% lower in rats that were hindlimb-unloaded compared to controls. Acetyl choline receptor area and fragmentation were 20% higher in gastrocnemius from hindlimb-unloaded rats compared to controls. Denervation was 30% higher in the gastrocnemius from hindlimb-unloaded rats compared to controls. The muscle oxylipin profile in aged weight-bearing and adult hindlimb-unloaded rats were significantly altered when compared to adult weight-bearing rats. However, muscle oxylipin profile was not different when comparing aged and aged hindlimb unloaded muscle. These data show that hindlimb-unloading exacerbates neuromuscular pathologies in aged rats. Therapies that protect neuromuscular junctions may help improve recovery following disuse-atrophy in aged subjects.

Keywords: Disuse-Atrophy, Neuromuscular Junction, Muslcular Atrophy