Apoptosis in Cavitation of Middle Ear Space

Daniel Stewart Roberts and Sue Ann Miller
Department of Biology, Hamilton College, Clinton, New York


Anatomical Record 251(3):286-289 (1998)

Background: 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. Cell death has not been considered important in cavitation of chick middle ear (Jaskoll and Maderson, 1978), but an uncharacterized form of cell death has been reported to play a major role in cavitation of mouse middle ear (Jaskoll, 1977). We investigated whether this uncharacterized cell death is the non-random form known as apoptosis.

Methods: We examined the middle ear cavitation process using the ApopTAG® in situ immunodetection for apoptosis with DAB as the marker. CBy•RF mice during prenatal days 15-20 and postnatal days 1-3 and chick embryos representing HH stages 33 to 38 were investigated.

Results: Apoptotic cells were marked in mouse postnatal day 1. 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.

Conclusions: Previously observed cell death in murine middle ear is the non-random form of cell death known as apoptosis. 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.

Grant sponsor: Sigma Xi; Grant sponsor: The Casstevens Family Fund; Grant sponsor: The Hamilton College Academic Fund for Seniors.

Additional funding that allowed Dan Roberts to travel and present his work at FASEB's Experimental Biology 97 in New Orleans, LA was provided by the Williams-Watrous-Couper Fund.

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