Degradation and Recovery of Bone: OVX and Treatment

描述(由申请人提供)：与年龄相关的骨折只能部分解释为随年龄增长而普遍发生的骨量减少。未能预测骨折的部分原因是a)使用投影x射线方法测量骨量时丢失了几何信息，b)忽视了关于骨骼破坏特性的足够详细的信息，以及c)忽视了骨骼上的详细活体载荷(骨折风险与载荷与强度的比率有关，而不仅仅与骨骼强度有关)。准确预测骨折风险的第四个障碍是，X射线方法无法检测到由年龄或疾病相关的骨胶原、非胶原蛋白或水分含量变化引起的骨组织力学性能变化。由于X射线检测的软组织改变是不可见的，与年龄和绝经有关的组织材料特性(骨质量)的变化是看不见的，不被理解的，并且不可预测地增加骨折的风险。 我们的数据支持新的工作假设：1)骨的粘弹性特性影响骨组织的断裂韧性和表观强度，2)去卵巢后羊骨的粘弹性特性退化，导致骨组织的强度和断裂韧性在与跌倒相关的载荷速率下下降。 这项工作的主要目的是确定粘弹性退化的开始时间，以及使用雌激素替代后皮质骨是否可以恢复正常的粘弹性和强度特性。

DESCRIPTION (provided by applicant): Age-related bone fracture is only partially explained by the reduction in bone mass that universally occurs with aging. The failure to predict fracture comes in part from a) the loss of geometrical information when projection x-ray methods are used to measure bone mass, b) ignorance of sufficiently detailed information about the failure properties of bone, and also c) ignorance of detailed in vivo loads on bones (Fracture risk is related to the ratio of load to strength, rather than to bone strength alone). A fourth barrier to accurately predicting fracture risk is that changes in bone tissue mechanical properties caused by age or disease related changes in the collagen, non-collagenous proteins or water content of bone are not detectable to xray methods. As a result of the invisibility of soft tissue changes to x-ray detection, there are age and menopause related changes in tissue material properties (in bone quality) that are invisible, not understood and that unpredictably increase bone fracture risk. Our data support the novel working hypotheses: 1) The viscoelastic properties of bone affect the fracture toughness and apparent strength of bone tissue, 2) The viscoelastic properties of ovine bone degrade after ovariectomy, causing a decrease in the strength and fracture toughness of bone tissue for rates of loading associated with falls. The main goal of the proposed work is to determine the onset time of viscoelastic property degradation and whether cortical bone can recover normal viscoelastic and strength properties with estrogen replacement.