Angiogenic Therapy: Novel Approaches to Enhance Bone Regeneration in Aging

项目摘要 老化是骨折的主要危险因素。65岁以上人口占美国总人口的13% 虽然这是一个非常普遍的群体，但在肌肉骨骼损伤的住院患者中占> 50%。骨折是主要的 老年患者的损伤类型，年龄增加是骨折愈合受损的危险因素。延迟 老年患者的骨折愈合是由于间充质干细胞分化能力较低， 血管生成/血管生成受损。内皮集落形成细胞（ECFC）直接参与 血管生成和血管生成。因此，ECFC的数量和/或功能的减少可能是主要的原因。 用于老年患者骨折修复失败的螺丝刀。为了检测是否挽救受损的血管生成 可以充分促进老年人群的骨愈合，该建议将剖析 血管生成因子，并评估新的骨愈合剂通过刺激 内皮细胞（EC）功能在骨愈合与衰老的小鼠模型。我们在一只老鼠身上发现 在CSD模型中，当胶原支架与年轻的ECFC一起接种时，再生加速 被植入了缺损处我们还表明，主要的巨核细胞生长因子，血小板生成素， (TPO)，可以增加CSD愈合小鼠伴随EC的增加。TPO对大鼠CSD也有治疗作用 还有猪我们最近的数据表明，Sirtuin-1（Sirt 1），一种NAD+ III类组蛋白去乙酰化酶， 具有抗衰老作用的CD 45-CD 31 + ECs中的CD 45-CD 31 + CD 45-CD 31 + ECs显著高于老年ECs。 Sirt 1 mRNA在幼鼠骨折愈合过程中表达明显高于对照组。 老老鼠此外，新的初步数据显示，SRT 1720（sirt 1激活剂）治疗可改善骨 治愈基于这些观察结果，我们假设骨愈合可以在衰老中增强， 通过直接植入ECFC或通过TPO刺激EC来改善血管生成， SRT 1720。在目标1中，我们将评估使用年轻或老年ECFC作为骨再生治疗。在目标2中， 我们将评估TPO或SRT 1720对骨愈合的治疗效果，并分析EC的贡献。 老年小鼠的这种反应的信号。这些目标的成功实现将决定 在衰老过程中，内皮细胞的退化是导致骨愈合能力下降的原因， 过程此外，使用两种不同的骨愈合剂已知的目标EC，我们将确定年龄特异性 EC刺激的差异以及这些差异如何影响骨折修复过程。

PROJECT SUMMARY Aging is the dominant risk factor for fracture. Persons over 65 years of age account for 13% of the total US population, but represent > 50% of hospital admissions with a musculoskeletal injury. Fractures are the primary injury type among older patients, and increased age is a risk factor for impaired fracture healing. Delayed fracture healing in elderly patients results from a lower capacity for mesenchymal stem cell differentiation and impaired angiogenesis/vasculogenesis. Endothelial colony forming cells (ECFCs) are directly involved in angiogenesis and vasculogenesis. Thus, the decrease in number and/or function of ECFCs may be a major driver for failed fracture repair in elderly patients. In order to examine whether rescue of impaired angiogenesis may sufficiently enhance bone healing in the aged population, this proposal will dissect the contribution of angiogenesis factors, and evaluate the extent to which novel bone healing agents operate via stimulating endothelial cell (EC) function in a mouse model of bone healing with aging. We have shown in a rat critical sized defect (CSD) model, regeneration was accelerated when collagen scaffolds seeded with young ECFCs were implanted within the defect. We also show that the main megakaryocyte growth factor, thrombopoietin (TPO), can augment CSD healing in mice with concomitant increase in ECs. TPO can also heal CSDs in rats and pigs. Our recent data show that mRNA levels of Sirtuin-1 (Sirt1), an NAD+ class III histone deacetylase with anti-aging effects, were significantly higher in young CD45-CD31+ ECs as compared to old ECs. Additionally, Sirt1 mRNA significantly increased in the fracture regenerate of young mice compared to that of old mice. Further, new preliminary data showed that treatment with SRT1720 (sirt1 activator) improved bone healing. Based on these observations, we hypothesize that bone healing can be enhanced in aging by improvement of angiogenesis via direct implantation of ECFCs or through stimulation of ECs by TPO or SRT1720. In Aim 1, we will assess the use of young or old ECFCs as a bone regeneration therapy. In Aim 2, we will assess the therapeutic efficacy of TPO or SRT1720 on bone healing, and dissect the contribution of EC signaling to this response in aged mice. Successful accomplishment of these Aims will determine the degree to which the degeneration of ECs during aging is responsible for the age-related decline in the bone healing process. Additionally, using two distinct bone healing agents known to target ECs, we will identify age-specific differences in EC stimulation and how these differences influence the fracture repair process.