Hincke Maxwell T, Chien Yung-Ching, Gerstenfeld Louis C, McKee Marc D
Faculty of Dentistry, 3640 University Street, Montreal, Quebec, Canada H3A 2B2.
J Histochem Cytochem. 2008 May;56(5):467-76. doi: 10.1369/jhc.2008.950576. Epub 2008 Feb 5.
During mineralization of the avian eggshell, there is a sequential and orderly deposition of both matrix and mineral phases. Therefore, the eggshell is an excellent model for studying matrix-mineral relationships and the regulation of mineralization. Osteopontin, as an inhibitor of crystal growth, potently influences the formation of calcium phosphate and calcium carbonate biominerals. The purpose of this study was to characterize matrix-mineral relationships, specifically for osteopontin, in the avian eggshell using high-resolution transmission (TEM) and scanning (SEM) electron microscopy to gain insight into how calcite crystal growth is structured and compartmentalized during eggshell mineralization. Osteopontin was localized at the ultrastructural level by colloidal-gold immunocytochemistry. In EDTA-decalcified eggshell, an extensive matrix network was observed by TEM and SEM throughout all regions and included interconnected fibrous sheets, irregularly shaped aggregates, vesicular structures, protein films, and isolated protein fibers. Osteopontin was associated with protein sheets in the highly mineralized palisades region; some of these features defined boundaries that compartmentalized different eggshell structural units. In fractured and undecalcified eggshell, osteopontin was immunolocalized on the {104} crystallographic faces of calcite-its natural cleavage plane. The specific occlusion of osteopontin into calcite during mineralization may influence eggshell structure to modify its fracture resistance.
在禽蛋壳矿化过程中，基质相和矿质相存在着有序的依次沉积。因此，蛋壳是研究基质-矿物质关系及矿化调控的理想模型。骨桥蛋白作为晶体生长的抑制剂，对磷酸钙和碳酸钙生物矿物的形成有显著影响。本研究旨在利用高分辨率透射电子显微镜（TEM）和扫描电子显微镜（SEM）对禽蛋壳中的基质-矿物质关系，特别是骨桥蛋白进行表征，以深入了解在蛋壳矿化过程中方解石晶体生长是如何构建和分区的。通过胶体金免疫细胞化学在超微结构水平上定位骨桥蛋白。在经乙二胺四乙酸（EDTA）脱钙的蛋壳中，通过TEM和SEM在所有区域均观察到广泛的基质网络，其包括相互连接的纤维片、不规则形状的聚集体、囊泡结构、蛋白膜和孤立的蛋白纤维。骨桥蛋白与高度矿化的栅栏层区域中的蛋白片相关联；其中一些特征界定了不同蛋壳结构单元的边界。在破裂且未脱钙的蛋壳中，骨桥蛋白通过免疫定位在方解石的{104}晶面上，这是其天然解理面。矿化过程中骨桥蛋白对方解石的特异性封闭可能会影响蛋壳结构，从而改变其抗断裂性。
