Adult stem cells

The main focus of stem cell research over the last few decades has been directed to embryonic stem cells. However, more recently, research upon and an understanding of various populations of adult stem cells has gathered pace. Adult stem cells are undifferentiated cells found amongst differentiated cells in a tissue or organ. These cells can renew themselves and can differentiate to yield the major cell types characteristic of the tissue in which they reside. The main physiological role of adult stem cells, therefore, appears to be to maintain and to repair (to a certain extent at least) the tissue in which they reside.

For many years it was believed that adult stem cell populations were present in a very limited number of tissue types, and that they could only differentiate into cells characteristic of the tissue in which they reside. Recent research challenges both of these assertions. Adult stem cells are being discovered in a growing number of tissues, including bone marrow, peripheral blood and

Human embryonic stem cells

Culture as floating aggregrates (embryoid bodies), forming neuroepithelial cells

Culture to form midbrain dopamine neurons

Commercial culture Culture media with various Culture medium supplemented with FGF-8

media containing FGF-2 supplements & grow in and SHH, added at specific culture timepoints adhesive culture dishes

Figure 14.19 Simplified schematic overview of the directed differentiation of human embryonic stem cells to form differentiated dopamine like neurons. The full pathway details are available in Yan, Y., Yang, D., Zarnowska, E.D., Du, Z., Werbel, B., Valliere, C., et al. 2005. Directed differentiation of dopaminergic neuronal subtypes from human embryonic stem cells. Stem Cells 23, 781-790. FGF: fibroblast growth factor; SHH: sonic hedgehog (a regulatory protein)

blood vessels, the brain and spinal cord, skeletal muscle, skin, liver, pancreas, digestive system, cornea and retina. Identification and study of such cells can be made difficult by the low levels in which they are normally found, the presence of many additional cell types and the difficulties in culturing them. Much basic research is required to answer fundamental questions regarding adult stem cells, including: How many types exist and where are they located? What was their ultimate source? What level of plasticity (see below) do they exhibit? What factors stimulate their relocation and differentiation at a site of tissue damage?

The use of adult, as opposed to embryonic, stem cells in regenerative medicine would have a number of significant advantages. It would overcome moral/ethical difficulties associated with blastocyst destruction. It would also allow for autologous transplantation of cells, i.e. adult stem cells could be harvested from a patient, cultured and differentiated in vitro and then reintroduced back into the patient. This would overcome potential immunological complications and a requirement to use immunosuppressive drugs. Hurdles to this approach not only include the difficulties in isolating and successfully culturing these cells, but also ascertaining the level of plasticity exhibited by adult stem cells. This refers to the range of potential fully differentiated cell types that could be produced from adult stem cell populations, and such investigations represent a very active area of current stem cell research.

10 Ways To Fight Off Cancer

10 Ways To Fight Off Cancer

Learning About 10 Ways Fight Off Cancer Can Have Amazing Benefits For Your Life The Best Tips On How To Keep This Killer At Bay Discovering that you or a loved one has cancer can be utterly terrifying. All the same, once you comprehend the causes of cancer and learn how to reverse those causes, you or your loved one may have more than a fighting chance of beating out cancer.

Get My Free Ebook


Post a comment