Tongue Muscle for the Analysis of Head Muscle Regeneration Dynamics

Abstract

Tongue muscle damage impairs speaking and eating, thereby degrading overall health and quality of life. Skeletal muscles of the body are diverse in embryonic origin, anatomic location, and gene expression profiles. Responses to disease, atrophy, aging, or drugs vary among different muscles. Currently, most muscle studies are focused on limb muscles and the tongue is neglected. The regenerative ability of tongue muscle remains unknown, and thus there is need for tongue muscle research models. Here, we present a comprehensive characterization of the spatiotemporal dynamics in a mouse model of tongue muscle regeneration and establish a method for the isolation of primary tongue-derived satellite cells. We compare and contrast our observations with the tibialis anterior (TA) limb muscle. Acute injury was induced by intramuscular injection of cardiotoxin, a cytolytic agent, and examined at multiple timepoints. Initially, necrotic myofibers with fragmented sarcoplasm became infiltrated with inflammatory cells. Concomitantly, satellite cells expanded rapidly. Seven days postinjury, regenerated myofibers with centralized nuclei appeared. Full regeneration, as well as an absence of fibrosis, was evident 21 d postinjury. Primary tongue-derived satellite cells were isolated by enzymatic separation of tongue epithelium from mesenchyme followed by magnetic-activated cell sorting. We observed that tongue displays an efficient regenerative response similar to TA but with slightly faster kinetics. In vitro, tongue-derived satellite cells differentiated robustly into mature myotubes with spontaneous contractile behavior and myogenic marker expression. Comparison of gene expression signatures between tongue and TA-derived satellite cells revealed differences in the expression of positional-identity genes, including the HOX family. In conclusion, we have established a model for tongue regeneration useful for investigations of orofacial muscle biology. Furthermore, we showed that tongue is a viable source of satellite cells with unique properties and inherited positional memory.