Gene and protein expressions of vimentin and desmin during embryonic development of the mylohyoid muscle

Meckel’s cartilage is known to be involved in formation of the prenatal mandible. However, the relationship between Meckel’s cartilage and the embryonic mylohyoid muscle during growth and development has been investigated only rarely. This study examined the expression of intermediate filaments in Meckel’s cartilage and the embryonic mylohyoid muscle in fetal mice during morphological development. Specimens of E12–16 ICR mice sectioned in the frontal direction were subjected to immunohistochemistry for vimentin and desmin. Hematoxylin and eosin sections showed that the immature mylohyoid muscle began to grow along Meckel’s cartilage during fetal development. Weak vimentin expression was detected in the mylohyoid muscle and surrounding tissues at E12. Desmin expression was detected specifically in the mylohyoid, and strong expression was evident after E13, and increased with age. It was inferred that the mylohyoid muscle is one the tissues developing from Meckel’s cartilage, the latter exerting a continuous influence on the growth of the former. In the early stage, the surrounding mesenchymal tissues expressing vimentin formed a scaffold for the developing mylohyoid muscle. Muscle attachment at E13 showed steady desmin expression, which continued until maturity. This study suggested the possibility that Meckel’s cartilage has an influence not only on the mandibular bone, but also on the development of the mylohyoid muscle attached to the mandibular bone. Furthermore, it revealed a stage of the developmental process of the mylohyoid muscle in which the expression of vimentin, which is a common protein in the surrounding tissue such as muscle and bone, induces the morphological formation of the mylohyoid muscle, cooperating with the surrounding structures.