Degeneration/Regeneration as a Mechanism Contributing to the Effect of Manual Acupuncture-Induced Injury on Rat Skeletal Muscle

This book chapter is to further improve our understanding of the underlying mechanism of local injury that occurs after manual acupuncture needle manipulation that initiates muscle degeneration/regeneration process, which is essential for muscle maintenance and adaptation. Muscle injury triggers a sequence of events that begins with the host inflammation, secretion of myogenic transcription factor and various growth factors that are important for the activation and proliferation of muscle satellite (stem) cells. Skeletal muscle is maintained by resident stem cells call muscle satellite cells because of their location on the periphery of the myofiber under the surrounding basal lamina (Mauro, 1961). Satellite cells are quiescent mononuclear cells that are present in different types of skeletal muscle and are associated with all muscle fiber types, although the distribution might be unequal. For instance the percentage of satellite cell in adult tibialis anterior muscle is larger than other muscles (Pavlath et al., 1998). Satellite cells are responsible for post natal growth, hypertrophy and repair of skeletal muscle (Grounds, 1999). In normal undisturbed muscle, these cells remain in a quiescent stage (Schultz et al., 1985). After muscle injury, satellite cells become mitotically active, proliferate, differentiate and eventually fuse together to regenerate new muscle fiber, which is well-innervated, fully vascularized, through a process that resembles in some aspects embryonic (Seale et al., 2001). During muscle differentiation, satellite cells exhibit increased expression of the myogenic transcription factor MyoD (Cooper et al., 1999). Analysis of muscle regeneration has previously been studied using experimental models that induce muscle injury by various protocol such as eccentric contraction (Rathbone et al., 2003) or treadmill exercise (Smith et al., 2001). Although exercise induces injury-related satellite cell activation (Smith et al. 2001), its use is limited in patients with restricted exercise capacity during long periods of bed rest. Instead, such injury can be induced during acupuncture needle manipulation, which has been shown to induce muscle injury on acupuncture point (ST-36) in the tibialis anterior (TA) muscle (see Figure 1) and produce muscle regeneration via up-regulation of MyoD (see Figure 2 and Figure 3).