A comprehensive study of dura mater biomineralization: morphological, crystallographic, and immunohistochemical aspects

Abstract

Biomineralization is a process of formation of biominerals widespread among living organisms. This phenomenon occurs in the central nervous system in normal and pathological conditions. Typically, this can manifest age-related changes, and the prevalence of biominerals increases with age. At the same time, it can be a sign of pathology-tumour growth, dystrophy, metabolic disorders, etc. This work aims to study the morphological features of the dura mater with signs of biomineralization. In this work, we examined 30 samples of the dura mater with signs of biomineralization (group I) and 30 samples without these signs (group II) obtained during autopsies in the pathology department of the Sumy Regional Clinical Hospital. For the morphological charact erist ics of the dura mat er, we used hi stologi cal, hi stochemi cal and immunohistochemical methods, as well as scanning electron microscopy. Statistical processing of the results of the immunohistochemical study was carried out in the GraphPad Prism 8.0 statistical package using parametric and non-parametric research methods. To divide the samples into groups, we relied on the histological method-staining with hematoxylin-eosin. Histochemical methods (alizarin red staining, von Koss method) confirmed the presence of calcium compounds in the studied group. Van Gieson staining visualized the collagen fibres of the dura mater, and the PAS reaction di d not reveal the presence of gl ycosaminogl ycans in the mineral deposit s. Immunohistochemical examination of the dura mater with antibodies against osteopontin revealed a significant difference between the study and control groups (p<0.001), confirming the critical role of osteopontin in the biomineralization process in this tissue. With the help of scanning electron microscopy, it was found that biominerals in the dura mater are represented by tens to hundreds of formations of various shapes (rounded, oval and irregular), varying from tens of nanometers to 50 micrometres. Their composition was analyzed using maps and spectra of energy-dispersive X-ray spectroscopy and most probably corresponded to calcium hydroxyapatite. So, the dura mater is characterized by biomineralization, manifested by the formation of microscopic calcium hydroxyapatite composites.