Changes In Soleus Myosin Heavy Chain Expression In Response To Training Following Spinal Cord Injury

Abstract

PURPOSE To study the effect of treadmill vs cycling training on soleus myosin heavy chain (MHC) expression following spinal cord injury (SCI). METHODS: Contusion injuries were produced using a MASCIS impactor and protocol. Sprague Dawley rats were randomly assigned into a treadmill training, cycling training, or untrained control group. Rats in both training groups were trained from 1-week post SCI continuously for 3 months, 5 days a week, 20minutes/trail, 2 trails/day. Soleus MHC isoform expression was determined using immunofluorescence techniques with monoclonal antibodies (BA-D5, SC-71, BF-F3, and BF-35). RESULTS: Following 3 months of contusion injury, soleus MHC isoforms shifted from MHCI towards MHCII, with approx. 77.9% (vs 85.1% in the uninjured animal), 19.9% (vs 15.0% in the uninjured animal), and 4.3% (vs 0% in the uninjured animal) of the total fibers containing MHCI, MHC-IIa and MHC-IIx, respectively. Both treadmill and cycling training reversed this shift. Following 3 months treadmill training, the soleus contained 89.5 ± 2.7% type I fibers and 9.4 ± 1.5% type IIx fibers. No type IIx fibers were observed. Similar results were noted following cycling training. In addition, both training paradigms significantly increased the soleus fiber cross-sectional area (CSA), with an average fiber CSA of 2,452.9 ± 67.7mm2 in the untrained group, 2,804.1 ± 99.0mm2 and 2,779.0 ± 109.5mm2 in the treadmill and cycling group, respectively. CONCLUSION: This study demonstrates that both cycling and treadmill training paradigms can effectively reverse both the fiber type shift and decrease in fiber CSA following SCI. ACKNOWLEDGEMENTS: This study was supported by Christopher Reeve Paralysis Foundation (CRPF) # BA2-0202-2 and RO1HD37645, RO1HD40850.