Regenerative mechanisms that regulate intramuscular motor innervation. including configuration of the neuromuscular connections are thought to reside in the spatiotemporal expression of axon-guidance molecules. Our previous studies proposed a heretofore unexplored role of satellite cells as a key source of a secreted neural chemorepellent semaphorin 3A (Sema3A) expression. In order to verify this concept, there is still a critical need to provide direct evidence to show the up-regulation of Sema3A protein in satellite cells in vivo upon muscle injury. The present study employed a Sema3A/MyoD double-immunohistochemical staining for cryo-sections prepared from cardiotoxin injected gastrocnemius muscle of adult mouse lower hind-limb. Results clearly demonstrated that Sema3A expression was up-regulated in myogenic differentiation-positive satellite cells at 4-12 days post-injury period, the time that corresponds to the cell differentiation phase characterized by increasing myogenin messenger RNA expression. This direct proof encourages a possible implication of satellite cells in the spatiotemporal regulation of extracellular Sema3A concentrations, which potentially ensures coordinating a delay in neurite sprouting and re-attachment of motoneuron terminals onto damaged muscle fibers early in muscle regeneration in synchrony with recovery of muscle-fiber integrity.
All Science Journal Classification (ASJC) codes
- General Agricultural and Biological Sciences