Mesenchyme cells surround early ossicles in the developing middle ear, then are replaced by space that is created by what has been described as an expansion of the pharyngeal pouch. We investigated whether this uncharacterized cell death is the non-random form known as apoptosis. We examined the middle ear cavitation process using an in situ immunomarker for apoptosis. No indication of apoptosis was present in other prenatal and postnatal days of development included in this study, although morphology showed that cavitation proceeds over several perinatal days in the mouse. Apoptosis was not marked in the chick middle ear.
Apoptotic bodies are the dark spots within mesenchyme of the cavitating middle ear space.
Mouse, postnatal day 1. Cell death has not been reported in avian middle ear, and lack of apoptotic marker supports those observations. The limited occurrence of apoptosis in mice and apparent absence of apoptosis in chicks suggest that several mechanisms contribute to cavitation of vertebrate middle ear space. The Hamilton College Academic Fund for Seniors.