‘Fast’ and ‘slow’ muscle fibres in hindlimb muscles of adult rats regenerate from intrinsically different satellite cells

Abstract

Myosin heavy chain (MyHC) expression was examined in regenerating fast extensor digitorum longus (EDL) and slow soleus (SOL) muscles of adult rats. Myotoxic bupivacaine was injected into SOL and EDL and the muscles were either denervated or neuromuscularly blocked by tetrodotoxin (TTX) on the sciatic nerve. Three to 10 or 30 days later, denervated SOL or EDL, or innervated but neuromuscularly blocked EDL received a slow 20 Hz stimulus pattern through electrodes implanted on the muscles or along the fibular nerve to EDL below the TTX block. In addition, denervated SOL and EDL received a fast 100 Hz stimulus pattern. Denervated EDL and SOL stimulated with the same slow stimulus pattern expressed different amounts of type 1 MyHC protein (8% versus 35% at 10 days, 13% versus 87% at 30 days). Stimulated denervated and stimulated innervated (TTX blocked) EDL expressed the same amounts of type 1, 2A, 2X and 2B MyHC proteins. Cross-sections treated for in situ hybridization and immunocytochemistry showed expression of type 1 MyHC in all SOL fibres but only in some scattered single or smaller groups of fibres in EDL. The results suggest that muscle fibres regenerate from intrinsically different satellite cells in EDL and SOL and within EDL. However, induction by different extrinsic factors arising in extracellular matrix or from muscle position and usage in the limb has not been excluded. No evidence for nerve-derived trophic influences was obtained.

Novel murine clonal cell lines either express slow or mixed (fast and slow) muscle markers following differentiation in vitro

“…Many studies have looked at whether satellite cells are predetermined to differentiate into fast or slow muscle fibers, using satellite cells isolated from a variety of sources (i.e., see review by Schiaffino and Reggiani, 1996). Our results are in agreement with those obtained from primary cultures of isolated mouse slow muscle fibers (Rosenblatt et al, 1996;Kalhovde et al, 2005), which found that myotubes formed by these satellite cells expressed slow MHC1.…”

“…It is likely that both heterodimers (␣␤) and homodimers (␤␤) of muscle-specific enolase isoforms are expressed, as previously observed during in vivo muscle development (Keller et al, 1995). These myotubes also express embryonic and neonatal MHC isoforms, similarly to in vivo regenerating myofibers (Kalhovde et al, 2005). A previous study suggested that cultures on Matrigel tend to favor a slow myogenic phenotype (Dusterhoft and Pette, 1993), whereas we found that Matrigel did not affect MHC expression in differentiated myotubes.…”

Establishment of the epaxial–hypaxial boundary in the avian myotome

“…These cells serve as an endogenous stem cell pool and repair muscle upon injury (Mauro, 1961;Charge and Rudnicki, 2004;BenYair and Kalcheim, 2005;Gros et al, 2005;Kassar-Duchossoy et al, 2005;Relaix et al, 2005). Recent studies established that satellite cells have a recollection of the type of muscle they accompanied and, thus, are able to reconstitute muscle with the correct combination of fast or slow-twitch fibers (Feldman and Stockdale, 1991;Donoghue et al, 1992;Dolenc et al, 1994;Kalhovde et al, 2005). Our study shows that En1 marks the epaxial subset of muscle precursors originating from the dermomyotome proper, including the prospective satellite cells.…”

Regeneration of Reinnervated Rat Soleus Muscle Is Accompanied by Fiber Transition Toward a Faster Phenotype

“…The latter finding is intriguing, particularly because it is the slow-fiber population that becomes dominant in normal soleus muscle regenerating from notexin-induced necrosis (Whalen et al 1990). It cannot be ruled out that intrinsic muscle characteristics, such as a subpopulation of satellite cells determined to produce mainly slow-type or oxidative fibers (Kalhovde et al 2005), are selectively impaired in reinnervated soleus, which in turn hampers the proper reaction to slow-type innervation, causing a delayed regeneration. This possibility might be tested in additional experiments at later stages of regeneration (i.e., several weeks after notexin treatment) to see whether the difference in the size of slow versus fast fibers would be still apparent.…”