Amizuka Norio, Hasegawa Tomoka, Yamamoto Tomomaya, Oda Kimimitsu
Department of Developmental Biology of Hard Tissue, Graduate School of Dental Medicine, Hokkaido University, Sapporo, Japan.
Clin Calcium. 2014 Feb;24(2):203-14.
In bone, biomineralization induced by osteoblasts is known to be initiated by small extracellular vesicles referred to as "matrix vesicles". Matrix vesicles possess many enzymes and transporters, which synthesize and incorporate Ca²⁺ and PO4⁻ into the vesicles. Calcification initiates when crystalline calcium phosphates are nucleated inside these matrix vesicles, and calcium phosphates, i.e., hydroxyapatite crystals, grow and eventually break through the membrane to get out of the matrix vesicles. Exposed calcium phosphates featuring "ribbon-like" appearance assemble radially, forming spherical mineralized structure, referred to as "mineralized nodule" or "calcifying globule". This process is called "matrix vesicle mineralization". Thereafter, the mineralized nodules make contacts with surrounding collagen fibrils, extending mineralization along with their longitudinal axis from the contact points of collagen fibrils - collagen mineralization. Matrix vesicle mineralization and subsequent collagen mineralization are classified as primary mineralization associated with osteoblastic bone formation. After primary mineralization, secondary mineralization takes place, gradually increasing mineral density of bone matrix. This review will introduce the microscopic findings on matrix vesicle mineralization and subsequent collagen mineralization.
在骨骼中，已知成骨细胞诱导的生物矿化是由被称为“基质小泡”的细胞外小泡启动的。基质小泡含有许多酶和转运蛋白，它们将Ca²⁺和PO4⁻合成并整合到小泡中。当结晶磷酸钙在这些基质小泡内成核时，钙化开始，磷酸钙，即羟基磷灰石晶体，生长并最终突破膜从基质小泡中出来。呈现“带状”外观的暴露磷酸钙呈放射状组装，形成球形矿化结构，称为“矿化结节”或“钙化球”。这个过程称为“基质小泡矿化”。此后，矿化结节与周围的胶原纤维接触，从胶原纤维的接触点沿其纵轴延伸矿化——胶原矿化。基质小泡矿化和随后的胶原矿化被归类为与成骨细胞骨形成相关的初级矿化。初级矿化后，发生次级矿化，逐渐增加骨基质的矿物质密度。本综述将介绍基质小泡矿化和随后的胶原矿化的微观发现。
