Morphometric investigation on osteocytes in human auditory ossicles

Abstract

An osteocyte lacunae differential count (1-lacunae with live osteocytes, 2-lacunae with degenerating osteocytes, 3-empty lacunae) was carried out on ear ossicles and clavicles from cadavers as well as on stapes removed by stapedotomy. The distance of the three types of lacunae from the vascular source was also determined by a computer-assisted light microscope. Results showed that the delayed fixation of bone from cadavers does not significantly interfere with osteocyte preservation, at least with the scope of this investigation. The results of osteocyte differential count show that the number of empty lacunae and lacunae with degenerating osteocytes: (a) is significantly higher in ear ossicles than in clavicles, (b) increases with age, (c) is higher in stapes than in incuses and mallei, (d) increases with the distance from the vascular sources in both ear ossicles and clavicles. Additionally it appeared that the process of osteocyte degeneration in ear ossicles is very rapid and widespread, over 40% of the cells being dead within the 2nd year of age. In the light of the recent literature and personal findings, which ascribe to osteocytes the function of mechanical detectors, and considering that bone remodeling occasionally occurs in ear ossicles, it is postulated that osteocyte death in these bones could be a programmed phenomenon (apoptosis?), due to which they lose the ability to react to strains and stresses and achieve the structural stability they need to perform their peculiar stereotyped function.