【作者】 刘洪；

【导师】 苗登顺；

【作者基本信息】 南京医科大学 ， 口腔基础医学， 2008， 硕士

【摘要】 为了明确内源性1,25-二羟基维生素D₃（1,25（OH）₂D₃）在小鼠下颌骨（包括牙齿和牙槽骨）和长骨骨小梁的形成和矿化过程中是否发挥不同的作用,我们使用6周龄1-α羟化酶基因敲除(1α（OH）ase^-/-)小鼠,通过影像学、组织学、组织化学,免疫组织化学和RT-PCR、Western-Blot等方法检测了1,25（OH）₂D₃的缺失对牙齿和牙槽骨的形成和矿化的影响,并且比较分析了成骨细胞骨形成在下颌牙槽骨与长骨的差别。结果显示:与同窝的野生型（WT）小鼠相比,1α（OH）ase^-/-小鼠的牙齿和下颌骨的骨密度明显降低,未矿化的前期牙本质和未矿化的牙槽骨骨基质明显增加;1α（OH）ase^-/-小鼠的牙量、修复性牙本质的面积、Ⅰ型胶原和骨钙素（OCN）的阳性面积及mRNA表达水平、牙本质唾液酸蛋白（DSP）的阳性面积均明显减少;皮质骨厚度、牙槽骨体积和成骨细胞数量也均明显的减少,而长骨中骨小梁的容量、成骨细胞的数量和活性均明显增加;1α（OH）ase^-/-小鼠下颌牙槽骨的甲状旁腺素受体（PTHR）和胰岛素样生长因子-1（IGF-1）蛋白表达水平轻度减少,而长骨骨小梁中PTHR和IGF-1蛋白表达水平明显增加。上述结果表明:在小鼠下颌骨（包括牙齿和牙槽骨）和长骨骨小梁的骨形成中,内源性1,25（OH）₂D₃起着不同的作用;经IGF-1介导,PTH通过与PTHR结合对下颌骨（包括牙齿和牙槽骨）和长骨骨小梁骨形成起着不同的作用。本实验通过体内实验证明:与PTH相比,1,25（OH）₂D₃在牙本质的形成和牙槽骨的骨形成中发挥主导作用。更多还原

【Abstract】 Elevated PTH in the secondary hyperparathyroidism of vitamin D deficiency is believed to be anabolic for long bones.We previously compared mice with targeted disruption of the gene encoding parathyroid hormone（PTH）(PTH^-/-mice)or the gene encoding 25 hydroxyvitamin D 1α-hydroxylase[1α（OH）ase][1α（OH）ase^-/-mice]with compound mutant PTH^-/-1α（OH）ase^-/-mice.We found that PTH plays a predominant role in appositional bone growth,whereas 1,25（OH）₂D₃ acts predominantly on endochondral bone formation in long bones.It is unknown,however, whether 1,25（OH）₂D₃ or PTH plays a role in dentin and dental alveolar bone formation in the mandibles as it does in long bones.To determine whether 1,25（OH）₂D plays a distinctive role in flat bones such as mandibles,we examined the effect of 1,25（OH）₂D₃ deficiency on dentin and dental alveolar bone formation and mineralization in the mandibles, and compared osteoblastic bone formation in the mandibles and tibiae in 1α（OH）ase^-/-mice.Compared to wild-type（WT）mice,the mineral density was decreased in the teeth and mandibles,and unmineralized dentin（predentin and biglycan immunopositive dentin）and unmineralized bone matrix in the dental alveolar bone were increased in 1α（OH）ase^-/-mice.The dental volume,reparative dentin volume and dentin sialoprotein immunopositive areas were reduced in 1α（OH）ase^-/- mice.The cortical thickness,dental alveolar bone volume and osteoblast numbers were all decreased significantly in the mandibles;in contrast,the osteoblast number and surface were increased in the trabecular bone of the tibiae in 1α（OH）ase^-/-mice consistent with their secondary hyperparathryoidism.The expression of parathyroid hormone receptor （PTHR）and insulin-like growth factor-1（IGF-1）was reduced slightly in mandibles,but enhanced in the long bones in the 1α（OH）ase^-/-mice. These results indicate that 1α,25（OH）₂D₃ plays distinct roles in dentin and dental alveolar bone formation in the mandibles relative to trabecular bone formation in long bones,and suggests that 1,25（OH）₂D₃ plays a more prominent anabolic role than does PTH in dentin and dental alveolar bone formation in mandibles.更多还原