Division of Stem Cells

As well as being able to differentiate into specialised cells, the other key property of stem cells is their ability to divide. In the context of embryo development, stem cells are the biological basis for the formation of different types of body tissue. In an adult body, they act to maintain tissue and can be found in bone marrow, skin, muscles and the gut. They are important for tissue regeneration both in terms of continual cell renewal and also after injury. Adult stem cells are multipotent and can differentiate into the respective body tissue from which they originate.

Stem cells divide in the surrounding tissue both symmetrically into two stem cells identical to the mother cell (or two differentiated cells) and also asymmetrically into one stem cell and a differentiated cell. Thanks to this facility, stem cells are not only capable of unlimited proliferation but are also able to generate large amounts of new tissue. The division and growth of stem cells is usually regulated by the stem cell niche which provides signals governing growth and differentiation. If the cells leave the niche, they lose their multipotent characteristics and differentiate. For a long time, it was assumed that only asymmetrical division was of significance for these processes. A more recent study has shown however that intestinal tissue can manage solely using symmetrical differentiation processes. In this case, contact to certain other cells, the Paneth granular cells, was revealed to be key to the stem cell differentiation. 

A study on the skin of mouse paws showed that in this case stem cells regulate the production of certain signals themselves. Here too, on the face of it, asymmetrical cell division does not appear to be of vital importance. The stem cells in the skin of the mouse paws sometimes divide symmetrically and sometimes asymmetrically and this does not follow any rigid pattern. The ratio however remains stable.

He, S. / Nakada, D. / Morrison, S. J. (2009): Mechanisms of Stem Cell Self-Renewal. In: Annual Review of Cell and Developmental Biology 25, 377–406. doi: 10.1146/annurev.cellbio.042308.113248 Online Version 

Clevers, H. (2013): The Intestinal Crypt. A Prototype Stem Cell Compartment. In: Cell 154(2), 274–284. doi: 10.1016/j.cell.2013.07.004 Online Version 

Lim, X. / Tan, S. H. / Koh, W. L. C. / Chau, R. M. W. / Yan, K. S. / Kuo, C. J. / van Amerongen, R. / Klein, A. M. / Nusse, R. (2013). Interfollicular epidermal stem cells self-renew via autocrine Wnt signaling. In: Science 342, 1226–1230. doi: 10.1126/science.1239730 Online Version 

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