Abstract
Craniofacial muscles drive critical functions in the head, including speech, feeding and expression. Compared with their counterparts in trunk and limbs, craniofacial muscles are of distinct embryonic origins, which might consequently lead to different growth patterns and regenerative potential. In this study, rat levator veli palatini muscle and masseter muscle were compared with tibialis anterior muscle in their response to exogenous Wnt7a stimulus, which has been proved effective in promoting muscle regeneration in the limbs. Histological, cellular and molecular analyses were performed both under basal condition and after a single dose injection of recombinant human Wnt7a. Under basal condition, levator veli palatini muscle demonstrated considerably more satellite cells than the others. After Wnt7a administration, regeneration-related activities, including satellite cell expansion, myofiber hyperplasia and hypertrophy were generally observed in all three muscles, but with obvious differences in the extent. The composition of fast/slow myofibers underwent substantial alterations, and the pattern varied among the three muscles. Location-specific alterations in the expression level of core components in planar cell polarity pathway, Akt/mTOR pathway and myostatin pathway were also observed. In conclusion, both craniofacial and limb muscles could be effectively expanded by exogenous Wnt7a stimulus, but muscle-to-muscle variations in response patterns existed.
Highlights
Skeletal muscle is highly coordinated and malleable tissue and compromises up to 40% of the total body mass[1]
Regeneration-related activities vary among levator veli palatini (LVP), MAS andTA muscle
Our previous study in rat demonstrated that LVP muscle was of distinct histological features and myofiber composition, compared with tibialis anterior (TA) muscle, and exogenous Wnt7a induced different levels of hyperplasia in LVP muscle and TA muscle[16]
Summary
Skeletal muscle is highly coordinated and malleable tissue and compromises up to 40% of the total body mass[1]. With intrinsic properties to withstand stress and produce force, skeletal muscle supports body posture and drives body movements, ranging from sudden and intensive limb movements like jumping and kicking, to continuous and mild activities like respiration, speech and expressions in the craniofacial region[2]. These critical functions could be impaired when pathological alterations occur to skeletal muscle. The potential regenerative responses of craniofacial LVP muscle and MAS muscle were illustrated in details, using the limb tibialis anterior (TA) muscle as a control
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