![]() ![]() We carried out this study to investigate the changes in osteocyte characteristics and matrix mineralization in the human auditory ossicles, specifically acknowledging that they are subject to unique vibrational patterns and do not experience high-strain biomechanical loading. In the ossicles, increased numbers of dead osteocytes as a sign of impaired bone remodelling have been reported 11, 12, however the degree of mineralization of the ossicles’ bone matrix along with the distribution of viable and apoptotic osteocytes have not been shown. Hypermineralized osteocyte lacunae accumulate in aged 6, osteoporotic 9 and osteoarthritic 10 bone. The latter describes the in vivo formation of intra-lacunar calcification 8, which is believed to follow apoptosis of some osteocytes 7. In general, the absence of bone remodelling as seen with aging would be associated with hypermineralization of the bone matrix itself, but also with the accumulation of hypermineralized (micropetrotic) osteocyte lacunae 6, 7. The superior part gives origin to the base of the stapes, whereas the inferior part forms the limbs (anterior and posterior crus) and the head of the stapes 4.Īs sound transmission is the major function of the auditory ossicles and biomechanical loads are minor 5, adaptive bone remodelling might be unnecessary here. ![]() In fact, the cranial end of the second pharyngeal arch forms an independent anlage, which develops into a superior and an inferior part. While malleus and incus develop from the first pharyngeal arch, the stapes which is the smallest bone in the human body has two embryologically distinct parts. Damage or deformation of the ossicular chain lead to conductive hearing loss 3. The ossicles are located in the air-filled middle ear and serve for transmission of sound-induced mechanical vibrations from the eardrum to the oval window of the fluid-filled cochlea 2. The human auditory ossicles malleus, incus and stapes present with their final morphology at birth, while in later life decades only minor morphological changes occur 1. With osteocyte apoptosis potentially being a consequence of low mechanical stimuli, the early loss of osteocytes without initiation of bone remodelling indicates an adaptive response conserving the architecture of the auditory ossicles and ensuring stable sound transmission throughout life. The majority of these changes took place in the first months and years of life, while afterwards only minor reorganization was present. ![]() ![]() We detected characteristics of early bone tissue aging, such as decrease in osteocytes, lower total lacunar density and lacunar area, as well as high matrix mineralization accompanied by distinct accumulation of micropetrotic lacunae and decreased indentation depths. No signs of bone remodelling were observed above the age of 1 year. Mineralization of the bone matrix was determined using backscattered electron imaging. Here we analysed the frequency, size and composition of osteocyte lacunae in the auditory ossicles of 22 individuals from early postnatal period to old age. In human auditory ossicles, the early decrease in osteocyte numbers but maintained integrity remains an unexplained phenomenon that might serve for sound transmission from air to the labyrinth. A preserved osteocyte population is a crucial determinant of bone quality. Within the mineralized bone, osteocytes form a multifunctional mechanosensitive network orchestrating bone remodelling. ![]()
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