Differentiation and Proliferation of Human Osteoblasts

临床上重要的骨质流失是I型骨质疏松症、II型骨质疏松症及其继发原因的总和。在妇女中，骨量在35岁之前达到最大值，而骨小梁骨质流失的证据在40岁，即绝经前就已经很明显了。在绝经后时期，骨质流失的速度增加（I型）大约5-10年，在此之后，由于II型骨质疏松症，骨质流失的速度继续下降。在男性中，骨质流失的速度不像女性那么快，它是持续的，仅仅是由于II型骨质疏松症以及继发原因。椎体骨质流失的纵向研究显示骨质疏松症的发生率相对较快，接近于女性。不同类型的骨质疏松症之间的差异是明确的，但相对重要性不太清楚。如果估计是正确的，那么每3个女性中就有1个在90岁时髋部骨折，而男性为1 / 6。75岁以上男性与髋部骨折相关的死亡率为30%，是女性的三倍。因此，II型骨质疏松症是一个非常重要的公共卫生问题，不仅对男性的健康有影响，而且对女性也有附加作用。在这种骨质流失的情况下，破骨细胞活性正常到轻微下降，同时骨形成能力大大下降。这种形式的骨质疏松症被认为是由成骨细胞活性/功能下降引起的，并归因于各种因素，如这些细胞在所需部位的募集、增殖和分化的缺陷，以及其他年龄相关过程导致的环境变化。研究表明，编码骨钙素转录因子（一种仅在成骨细胞中表达的基因）OSF2/Cbfal失活的小鼠不会形成骨。我们在此提出验证一种假设，即细胞衰老导致成骨细胞分化功能缺陷和/或增殖能力下降，并导致与年龄相关的骨质疏松症。我们将通过检测OSF2/Cbfal的表达、年轻和年老供体骨组织中衰老相关基因的表达、增殖潜力以及这些基因在骨源性成骨细胞中的表达来验证这一点。我们还将确定成骨细胞能否在体内的移植模型系统中形成组织。结果将提供初步的数据和证据，我们可以为R01提案执行这些技术。

Clinically important bone loss is a sum of Type I osteoporosis, Type II osteoporosis and the secondary causes. In women, maximum bone mass is attained before age 35 and evidence of trabecular bone loss is already apparent at age 40, before the onset of menopause. During the post- menopausal period, the rate of bone loss is increased (Type I) for approximately 5-10 years, and after this period, bone loss continues at a decreased rate due to Type II osteoporosis. In men, the rate of bone loss is not as rapid as that of women, it is persistent and due solely to Type II osteoporosis as well as secondary causes. Longitudinal studies of vertebral bone loss reveal relatively rapid rates of osteoporosis, approaching that seen in women. The differences between the types of osteoporosis is clear but the relative importance is less clear. If estimates are correct then 1 in every 3 women will have had a hip fracture by age ninety compared to 1 in 6 men. The mortality associated with hip fracture in men aged greater than 75 years is 30%, triple that reported for women. Therefore Type II osteoporosis is a very important public health issue, not only for the impact on the healthspan of men, but also for the additive role it plays in women as well. In this condition of bone loss there is normal to slightly decreased osteoclastic activity in conjunction with greatly decreased bone forming ability. This form of osteoporosis is thought to be caused by decreased osteoblast activity/function and has been attributed to various factors such as deficits in recruitment, proliferation and differentiation of these cells at needed sites, as well as changes in the milieu as a result of other age- related processes. It has been shown that there is no bone formation in mice in which the gene encoding the transcription factor for osteocalcin (a gene expressed only in osteoblasts) OSF2/Cbfal has been inactivated. We here propose to test the hypothesis that deficits in differentiated function and/or decreased proliferative ability due to cell senescence occurs with aging in osteoblast cells and contributes to age related osteoporosis. We will test this by determining OSF2/Cbfal expression, and expression of senescence related genes in bone tissue from young and old donors and proliferation potential as well as expression of these genes in osteoblasts derived from the bone. We will also determine whether osteoblasts can form tissue in a transplatation model system in vivo. The results will provide the preliminary data and evidence that we can perform these techniques for an R01 proposal.