Basic research for development of diagnosis of jaw bone quality

本研究对老年性骨质疏松症小鼠（SAMP 6）下颌骨进行了组织学和生化分析。与对照组（SAMR 1）相比，SAMP 6组小鼠下颌骨的骨组织形态计量学分析显示骨量减少，透射电镜分析显示骨基质中胶原纤维变细。骨生化分析显示，两种小鼠的主要细胞外基质均为I型胶原。与SAMR 1相比，SAMP 6的下颌骨显示骨基质中胶原的含量较低，但通过胶原的翻译后修饰产生的羟赖氨酸的程度较高。由于已报道较高的赖氨酸羟基化导致较细的胶原原纤维形成，因此高水平的赖氨酸羟基化可能诱导胶原原纤维变细。同样，在SAMP6和骨质疏松患者的股骨中报告了更高程度的赖氨酸羟基化。提示胶原蛋白的翻译后修饰赖氨酸羟基化影响胶原蛋白的质量，导致骨质疏松症时骨质量降低，提示老年骨质疏松症小鼠下颌骨在数量和质量上具有骨质疏松的性质。因此，可以推测，骨质疏松症患者的颌骨表现出较低的质量以及较低的数量。进一步的研究可能揭示和确认颌骨骨质疏松症患者的骨性质，然后未来的基因组研究可能使颌骨质量的诊断技术的确认和相应的牙科治疗技术的发展。

We investigated the mandibular bones of senile osteoporotic mice (SAMP6) by histological and biochemical analyses. With Comparison of their control mice (SAMR1), the, mandibular bones of SAMP6 exhibited lower bone quantity by histomorphometric analysis and thinner collagen fibrils in the bone matrix by transmission electron microscope analysis. The bone biochemical analysis showed the major extracellular matrix was type I collagen both in the two mice. Compared with SAMR1, the mandibular bones of SAMP6 showed lower content of collagen in the bone matrix but higher extent of hydroxylysine which was produced through a collagen posttransiation modification. Since it has been reported that higher lysine hydroxylation leads to thinner collagen fibril formation, the high level of lysine hydroxylation likely induces collagen fibrils thinner. As well, higher extent of lysine hydroxylation has been reported in the femoral bones of SAMP6 and osteoporotic patients. It is suggested that a collagen posttranslational modification, lysine hydroxylation, affects the quality of collagen, leading to low bone quality in osteoporosis.This study indicates an osteoporotic bone nature in quantity and quality of the mandibular bones in senile osteoporotic mice. Accordingly, the jaw bones of osteoporotic patients may be speculated to exhibit lower quality as well as lower quantity. The further study may reveal and confirm bone nature of the jaw of osteoporotic patients and then the future genome study may enable confirmation of diagnostic technique of jaw bone quality and development of the according dental treatment technique.