血管内皮衰老的系统生物学研究与干细胞治疗初探

Aging is the biggest risk factor for many complex diseases, including cardiovascular disease, type 2 diabetes and cancer etc. One compelling evidence comes from the studies on a severe premature aging genetic disorder, i.e. Hutchinson-Gilford progeria syndrome (HGPS), predominantly caused by a Lamin A mutation called Progerin. Patients suffering from HGPS only survive for 12 to 16 years and recapitulate many aging features, such as insulin resistance, decreased body fat, hair loss, stiff joints, osteolysis, dilated cardiomyopathy and atherosclerosis etc. Most of HGPS patients died of cardiovascular diseases. Although the prevalence of HGPS is only about one in 4 million, its clinical resemblance to normal aging makes HGPS an ideal model for the understanding of the molecular and pathological mechanisms underlying normal aging, especially vascular aging...Endothelial dysfunction is one of the characteristics of vascular aging. In human body, all the blood vessels is lined with an endothelial layer in the lumen, which plays critical roles in regulating coagulation, arterial tone, permeability, vessel growth, and inflammation. The functional integrity of endothelium is of particular importance for the maintenance of vascular homeostasis and the prevention of cardiovascular diseases. Increasing evidence suggests that circulating endothelial progenitor cells (EPCs) plays crucial role in vascular repair and regeneration. Upon endothelial damage, EPCs home to sites of injury and contribute to new blood vessel formation. .In HGPS, Progerin primarily targets vascular smooth muscle cells and endothelial cells. Human umbilical vein endothelial cells (HUVEC) expressing ectopic Progerin undergo early senescence with misshapen nuclei and hyperactivation of a proinflammatory/atherogenic pathway. In an HGPS mouse model, the endothelium-dependent vasodilatation is compromised and the number of EPCs is significantly decreased. In addition, we recently found that Lamin A directly interacts with and activates SIRT1, which regulates endothelial function by de-acetylating eNOS, PPARγ and LKB1. In progeria mouse model, the activity of SIRT1 is substantially decreased, leading early depletion of adult stem cells and premature aging. Therefore we hypothesize that accumulation of Progerin jeopardizes the activity of SIRT1, leading to endothelial dysfunction and early decline of EPCs. We will test this hypothesis in endothelial cells derived from HGPS patients and progeria mouse model. Further, we would like to examine whether endothelium-specific expression of Sirt1 or injection of healthy EPCs could ameliorate endothelial dysfunction and progeroid features in progeria mouse model. ..These studies will not only provide mechanistic insights into how endothelial dysfunction contribute to premature aging, but will also suggest additional therapeutic strategy for progeria. It also help to understand the basis of and to develop interventions of cardiovascular diseases.

心脑血管疾病是老年性疾病。理解衰老机理是预防及治疗心脑血管疾病的关键所在。人类衰老进程缓慢，不利于机理与干预研究。早老症是一种快速老化性遗传疾病，多死于老龄化性血管病变，提供了一种独特的研究血管衰老的人类疾病模型。我们初步研究发现，Lamin A蛋白异常（早老症的突变）导致内皮细胞快速老化及分泌功能紊乱，内皮祖细胞，并且影响早老小鼠动脉内皮舒缩功能。本项目以早老症与基因敲除早老小鼠为模型，从细胞、组织、整体三个层次，利用系统生物学与候选基因相结合的方法，探讨血管内皮衰老与功能紊乱的分子基础。反过来，运用转基因与干细胞治疗技术，研究血管内皮衰老、功能紊乱、内皮祖细胞衰老与机体衰老的关联机制。本项目预期成果不仅可以阐明早老症血管内皮早老与功能紊乱的分子网络及关键的分子靶点，从组织水平上解析血管内皮老化及功能紊乱与机体早老的关联机制，还有望提供一个干细胞治疗血管功能紊乱及早老症的新策略。

心血管疾病是老年疾病，理解衰老机理是预治心血管疾病的关键。由Lamin A突变（Progerin）导致的早老症是快速老化性遗传疾病，患者多死于老龄化性血管病变，因此提供了独特的研究血管衰老的人类疾病模型。本项目为了能够更加系统地研究血管特异衰老与整体（系统）衰老的关系，构建了一些列血管衰老研究小鼠模型，包括Zmpste24敲除小鼠（Prelamin A），Progerin全身敲入小鼠，以及血管内皮特异衰老（Tie2-Cre，Progerin敲入）小鼠。（1）借助离体血管张力测定实验、后肢缺血模型与激光多普勒影像技术等方法分析、发现了衰老伴随的血管舒缩功能紊乱与血管新生障碍。（2）建立了人脐静脉内皮细胞（HUVEC）衰老模型，通过多组学动态基因表达网络分析，发现了内皮衰老的驱动网络因素即以DNA损伤修复蛋白激酶ATM为核心的DNA修复机器（DNA repair machinery）。（3）利用全身性与血管内皮特异早老小鼠模型，发现血管内皮衰老很可能决定了整体（系统）衰老速度。本项目的研究成果为理解血管衰老机制以及血管衰老与系统衰老的关系打下了基础。

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