The Role of Skeletal Muscle in External Ear Development: A Mouse Model Histomorphometric Study

BACKGROUND Mechanical stimuli imparted by skeletal muscles play an important role during embryonic development in vertebrates. Little is known whether skeletal muscles are required for normal external ear development. METHODS We used Myf5-/-:MyoD-/- (double-mutant) mouse embryos that completely lack skeletal musculature and analyzed the development of the external ear. We concentrated on the external ear because several studies have suggested a muscular cause to various congenital auricular deformities, and middle and inner ear development was previously reported using the same mouse model. Wild-type mouse embryos were used as controls to compare the histomorphometric outcomes. RESULTS Our findings demonstrated an absence of the external auditory meatus, along with an abnormal auricular appearance, in the double-mutant mouse embryos. Specifically, the auricle did not protrude laterally as noted in the wild-type mouse ears. However, histomorphometric measurements were not significantly different between the wild-type and double-mutant mouse ears. CONCLUSION Overall, our study showed that the development of the mouse external ear is dependent on the presence of skeletal muscles.