Hematopoietic stem cells and progenitor cells: their role in normal blood formation 1

Published on March 5, 2014   28 min
0:00
I'm Malcolm Moore. And I'm a professor of cell biology at Memorial Sloan-Kettering Cancer Center in New York. And I would like to talk to you today about hematopoietic stem cells and progenitor cells and their role in normal blood formation.
0:17
What are stem cells? Well, the simple definition is cells that replicate and self-regenerate. This is called self-renewal. And they can do so extensively, only limited by a progressive shortening of the ends of the chromosomes. This is called telomeric shorting. And when they lose a sufficient amount of DNA at the ends of these chromosomes, they undergo death by a DNA damage response. So this is called the Hayflick limit. The shortening of telomeres can be prevented by telomerase enzyme expression. And many stem cells, there are different types, actually produce telomerase. Embryonic stem cells, those that are identified as capable of generating embryos, undergo symmetric self-renewal. And they give rise to all the specialized tissues of the body. Symmetric self-renewal is basically where the stem cell gives rise to two daughter stem cells. Somatic stem cells, that is to say stem cells of the adult, include hematopoietic stem cells, a rare sub-population of tissue-specific, relatively undifferentiated cells that undergo asymmetric division. They're capable of extensive self-renewal. And they can give rise not only to the different types of blood cell, the red cells, platelets, and white blood cells, but also the cells of the immune system and other sub-populations, such as dendritic cells. This definition was established for a hematopoietic stem cells 45 years ago and is still valid today.
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Hematopoietic stem cells and progenitor cells: their role in normal blood formation 1

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