Abstract
Skeletal muscle injury stimulates normally quiescent resident satellite (stem) cells to re-enter the cell cycle and execute the myogenic program to restore muscle structure and function. Previously, we reported that manual acupuncture needling of the tibialis anterior (TA) (ST36 = Zusanli) muscle of young male rats produced focal injury and morphological changes that accompanied the presence of activated satellite cells (SC) 72 hours post-needling. To investigate whether aging TA muscle responds in a similar fashion to acupuncture needling, 17-month-old female rats were subjected to a single insertion and manual manipulation of an acupuncture needle. At 72 hours’ post-needling, hematoxylin staining of the TA revealed increased mononuclear cell infiltration that was indicative of localized injury. Moreover, this was accompanied by a four-fold increase in the expression of proliferating cell nuclear antigen within cells of needled tissues. Heightened immunofluorescence for MyoD was found within SC in the needled muscle, which correlated with a 6- and 10-fold increase in two MyoD isoforms (~38 and 42 kDa, respectively), when analyzed by Western blotting. An additional 56 kDa MyoD immunoreactive species was observed in both needled and control muscle of the aging rats. The present study in pre-senile female rats, in conjunction with our previous study in young male rats, suggests that muscle remodeling and restructuring after injury may constitute the initial cellular and molecular mechanisms that underlie the benefits associated with acupuncture throughout the life-span.
Highlights
Skeletal muscle contains specialized somatic stem cells that are termed satellite cells (SC) because of their location on the periphery of myofibers under the surrounding basal lamina [1] [2]
The purpose of the present study was to assess the effect of manual acupuncture needling on aging tibialis anterior (TA) skeletal muscle by: 1) determining if manual needling produced localized injury to the muscle, and 2) assessing if muscle injury correlated with regeneration processes similar to what was previously observed in young adult rats [19]
Acupuncture Induces a Proliferative Response in TA Muscle Proliferative activity in response to acupuncture needling was analyzed by quantifying proliferating cell nuclear antigen (PCNA) expression in TA muscles
Summary
Skeletal muscle contains specialized somatic stem cells that are termed satellite cells (SC) because of their location on the periphery of myofibers under the surrounding basal lamina [1] [2]. These resident satellite cells are responsible for muscle growth and repair after injury throughout the life span [3]. These cells remain in a quiescent stage [4]. The transcription factor MyoD is essential for promoting gene expression that regulates proliferation, differentiation and the regeneration of new muscle fiber [3]-[6]. The activated phenotype is defined by the presence of MyoD [7]
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