Introduction The myotendinous junction (MTJ) has a unique transcriptional activity and is highly susceptible to strain injury. Eccentric exercise reduces this risk of injury, but the mechanism is unknown. The aim of this study was to investigate the effect of a single bout of eccentric exercise on the expression levels of some of the genes known to be active at the MTJ.
Materials and Methods 30 subjects were randomized to a single bout of eccentric exercise 1 week prior to tissue sampling or no exercise (control). Samples were collected from the semitendinosus muscle and were divided into fractions containing muscle, MTJ and tendon, respectively. The concentrations of macrophages and satellite cells were counted, and the expression of genes previously demonstrated to be active at the human MTJ were analysed by RT-qPCR.
Results The expressions of nestin and osteocrin mRNA were significantly increased in the MTJ and tendon fractions in the exercise group. In the exercise group a higher concentration of macrophages, but not satellite cells, was seen in the muscle tissue near the MTJ.
Conclusion Eccentric exercise leads to increased expression of nestin and osteocrin in human semitendinosus MTJ and to macrophage infiltration but does not induce proliferation of satellite cells near the MTJ. The increase in nestin and osteocrin indicates that these proteins could be of interest for the understanding of how the MTJ adapts to eccentric exercise and how eccentric exercise protects against strain injury.
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