Mechanism of Bone Destruction Due to Middle Ear Cholesteatoma : Experimental Study

点击翻译按钮获取中文摘要

Details of the mechanism of bone destruction due to middle ear cholesteatoma still remain obscure. In this study, we used laser-Raman spectroscopy to study tissue at the molecular level and based on our results, proposed a hypothesis to explain the process of bone destruction occurring in chronic otitis media associated with cholesteatoma. In this destruction, remineralization may take place in combination with demineralization, and hydroxyapatite [Ca_<10>(PO_4)_6(OH)_2 : HOAP] or its analogues may be deposited on the destroyed bone surface under mildly acidic conditions [Otologia (Fukuoka) 1983, Am J Otolaryngol 1988].To obtain basic data to verify this hypothesis, model simulation in vivo and in vitro were performed. In order to simplify the model system, we paid attention to HOAP,which largely consists of inorganic constituents of mature bone and regarded HOAP as typical specimen of the mineral component of the bone. As the experimental specimen, synthetic auditory ossicle (Apaceram … More ^<<encircledR>>) made from HOAP was employed. In this study, we present model experiment for the de- and remineralization processes at molecular level using a laser-Raman spectrometer.In vivo experiment, the Apaceram discs were implanted subcutaneously into the interscapular region of rats. Untreated Apaceram was observed as a control. In vitro experiment, we carried out consecutive measurement of the ions released in saline solution in which cylinders of Apaceram had been immersed. Results are as follows : 1. Apaceram surface : not only PO_4^<3-> of HOAP but also very small amounts of phosphate were considered to be present. (2) dissolution of ions from Apaceram surface had been increased with time in vitro experiment and demineralization of Apaceram surface had been progressed at 6 months after implantation and in contrast, precipitation of phosphate other than HOAP had occurred at 10 months after implantation. 2. Tissue in contact with Apaceram surface : the more immatured substances like bone at 3 months and osseou substances at 6 or 10 months were observed on the subcutaneous tissue. These data mean that deposition of HOAP progressed with time after implantation.As a result of model simulation in rats de- and remineralization were demonstrated on the Apaceram surface by laser-Raman spectrometry.In conclusion, our proporsed hypothesis on the bone destruction mechanism due to chronic otitis media associated with cholesteatoma will be supported by the experimental data analyzed at molecular level, considering HOAP which is the main inorganic constituent of mature bone. Less