Journal of Rehabilitation Research & Development (JRRD)

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Volume 51 Number 5, 2014
   Pages 841 — 854

Abstract — Intrinsic transient tracheal occlusion training and myogenic remodeling of rodent parasternal intercostal fibers

Barbara K. Smith, PhD, PT;1* Sunita Mathur, PhD, PT;1 Fan Ye, MD, PhD;1 A. Daniel Martin, PhD, PT;1 Sara Attia Truelson, BS;2 Krista Vandenborne, PhD, PT;1 Paul W. Davenport, PhD3

1Department of Physical Therapy, College of Public Health and Health Professions, University of Florida, Gainesville, FL; 2Department of Biology, College of Liberal Arts and Sciences, University of Florida, Gainesville, FL; 3Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL

Abstract — It is recognized that diaphragm muscle plasticity occurs with mechanical overloads, yet less is known about synergistic parasternal intercostal muscle fiber remodeling. We conducted overload training with intrinsic transient tracheal occlusion (ITTO) exercises in conscious animals. We hypothesized that ITTO would yield significant fiber hypertrophy and myogenic activation that would parallel diaphragm fiber remodeling. Sprague-Dawley rats underwent placement of a tracheal cuff and were randomly assigned to receive daily 10 min sessions of conscious ITTO or observation (sham) over 2 wk. After training, fiber morphology, myosin heavy chain (MHC) isoform composition, cross-sectional area, proportion of Pax7-positive nuclei, and presence of embryonic MHC (eMHC) were quantified. Type IIx/b fibers were 20% larger after ITTO training than with sham training (ITTO: 4,431 +/– 676 µm2, sham: 3,689 +/– 400 µm2, p < 0.05), and type I fibers were more prevalent after ITTO (p < 0.01). Expression of Pax7 was increased in ITTO parasternals and diaphragm (p < 0.05). In contrast, the proportion of eMHC-positive fibers was increased only in ITTO parasternals (1.2% [3.4%–0.6%], sham: 0% [0.6%–0%], p < 0.05). Although diaphragm and parasternal type II fibers hypertrophy to a similar degree, myogenic remodeling appears to differ between the two muscles.

Key words: diaphragm, exercise training, fiber hypertrophy, muscle plasticity, muscle regeneration, myogenic activation, remodeling, respiratory muscles, tracheal occlusion, ventilation.

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This article and any supplementary material should be cited as follows:
Smith BK, Mathur S, Ye F, Martin AD, Attia Truelson S, Vandenborne K, Davenport PW. Intrinsic transient tracheal occlusion training and myogenic remodeling of rodent parasternal intercostal fibers. J Rehabil Res Dev. 2014;51(5):841–54.

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