Endothelium Aging and Vascular Diseases

Aging is a biological process that causes a progressive deterioration of structure and func‐ tion of all organs over the time [1]. According to the United Nation’s report, the number of people aged 60 and over in the world has increased from 8% (200 million) in 1950 to 11% (760 million) in 2005, and it is estimated that this number will further increase to 22% (2 bil‐ lion) in 2050. It is expected that in the US alone, the aged population of 65 and over will grow rapidly and reach 81 million by 2050 [2,3]. This rapidly increasing aging population will not only cause a decline of productive workforce but also negatively affect the country’s economy. Furthermore, aging is one of the major risk factors for the development of many diseases including cardiovascular diseases [4], stroke [5] and cancer [6]. Moreover, the epi‐ demiological data strongly suggests that more often these diseases are diagnosed in older people compared to younger individuals. In addition to the huge economical impact, these diseases also cause loss of productivity and disability in the elderly population. Therefore, it is extremely important to give high priorities to aging and age-associated disease research in order to develop novel therapies to slow the aging process as well as to prevent and /or treat the age-associated diseases more effectively. It has been found that many factors including genetics [7,8], metabolism [9], diet [10] and stress [11] can in part contribute to the aging process. Similar to other organs, the vascular system, which provides oxygen and nutrients to all the organs in the body, is also affected by the aging process and becomes more vulner‐ able to disease development in the elders [12,13]. For example, vascular diseases such as cor‐ onary artery disease, peripheral arterial disease, stroke and microvascular disease are more often found in the aged population. This is in part due to the structural and functional changes that occur in the vascular system of aged people. In this review, we highlighted (i) the changes that occur in the vascular system, particularly in the endothelium due to aging; (ii) the mechanisms by which the age-associated changes lead to decreased angiogenesis;