Abstract
The dermal striated muscle
panniculus carnosus
(PC), prevalent in lower mammals with remnants in humans, is highly regenerative, and whose function is purported to be linked to defence and shivering thermogenesis. Given the heterogeneity of responses of different muscles to disease, we set out to characterize the PC in wild-type and muscular dystrophic
mdx
mice. The mouse PC contained mainly fast-twitch type IIB myofibers showing body wide distribution. The PC exemplified heterogeneity in myofiber sizes and a prevalence of central nucleated fibres (CNFs), hallmarks of regeneration, in wild-type and
mdx
muscles, which increased with age. PC myofibers were hypertrophic in
mdx
compared to wild-type mice. Sexual dimorphism was apparent with a two-fold increase in CNFs in PC from male versus female
mdx
mice. To evaluate myogenic potential, PC muscle progenitors were isolated from 8-week old wild-type and
mdx
mice, grown and differentiated for 7-days. Myogenic profiling of PC-derived myocytes suggested that male
mdx
satellite cells (SCs) were more myogenic than female counterparts, independent of SC density in PC muscles. Muscle regenerative differences in the PC were associated with alterations in expression of calcium handling regulatory proteins. These studies highlight unique aspects of the PC muscle and its potential as a model to study mechanisms of striated muscle regeneration in health and disease.