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.