The Morphologic Study of Elastic Structures in the Developing Murine Eustachian Tube

Abstract

BACKGROUND AND OBJECTIVES: Detailed information on how an epithelial differentiation and elastic structures occurred in the developing eustachian tube would be helpful in understanding both normal physiology and pathology of the tubotympanum. This study was undertaken to establish elastic structures such as cartilage, elastic fiber, and collagen fiber in the embryonic mouse eustachian tube at a stage when epithelial differentiation is taking place. MATERIALS AND METHOD: Thirty four mice (BALB/c mouse), aged from gestational day 11 to postnatal day 21, were investigated using Verhoeff stain, Masson trichrome stain and alpha-1 antitrypsin immunohistochemistry. RESULTS: The cartilage-like structures were first found after birth, however, matured cartilages appeared at postnatal day 7. The elastic fibers and collagen fibers surrounding cartilage were abundantly found about 5 days after birth. alpha-1 antitrypsin, which is an strong inhibitor of elastase, began to be immunolabelled at gestational day 16. Its expression has been significantly increased after birth. CONCLUSION: Although the epithelial differentiation and maturation in eustachian tube occured at late embryonal stage, the elastic structures have developed and matured after birth. These findings might be a explanation to why young children are highly susceptible to otitis media.