What are stem cells?

Stem cells are capable of further dividing and thus giving rise to daughter cells with different and definite characteristics, as well as retaining the abilities of renewing themselves. Stem cells are formed shortly after fertilization. They are the building-blocks of the body. There are many types of stem cells. Hence, they are broadly named into groups according to their source and functions: embryonic stem cells and adult stem cells. Embryonic stem cells are pluripotent and are taken from 5 to 7 day-old embryos. These cells are capable of forming tissues of all embryonic germ layers including endoderm, mesoderm and ectoderm. Adult stem cells have been identified in various organs including bone marrows, adipose tissue and skin, etc. Adult stem cells are multipotent and can differentiate into limited numbers of mature cell types depending upon the tissue type they reside.

To know how organisms grow and maintain their integrity throughout life, stem cells research is of great importance. By understanding how damaged cells are being put back again with new cells produced from stem cells, there is a potential that stem cells may serve as a cell therapy to repair complex damaged tissues caused by trauma and disease. Many animal experiments on stem cells are being carried out. To date, most of the clinical studies of stem cell involve the transplantation of autologous stem cells which are taken from the patients themselves.

幹細胞是一類未分化細胞，能夠分裂成不同種類的子細胞。幹細胞具有自我更新和分化能力。受孕之後幹細胞形成，並且增殖分化形成軀體。幹細胞種類很多，大體分為胚胎幹細胞和成體幹細胞。胚胎幹細胞來源於5-7天的胚胎，具有多能分化能力（能夠從各個胚層，內胚層、中胚層和外胚層，形成組織）。成體幹細胞是一種專能祖細胞（僅能分化成部分成熟細胞，這主要是依賴於這些成體幹細胞所在的組織）。多個組織器官內證明存在成體幹細胞，比如骨髓、脂肪組織和小腸組織。

幹細胞研究非常重要，因為通過對他們的研究可以揭示在一生中器官是如何生長和保持完整性。通過理解幹細胞替換損傷細胞的機制，幹細胞是細胞治療修復創傷或疾病導致組織損傷的有效來源。很多幹細胞的研究正在進行。目前，絕大多數的臨床幹細胞治療研究是進行自體幹細胞的移植。

More information:

	http://www.isscr.org/visitor-types/public/stem-cell-faq

	http://www.eurostemcell.org/stem-cell-faq

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