Saturday, March 8, 2008

The Holy Grail of Blood Stem Cells

"The placenta is believed by some communities to have power over the lives of the baby or its parents." Wikipedia

In the light of recent research, this belief is not far from the truth. UCLA stem cell researchers have been working to discover exactly where blood stem cells originate from, in the hopes of being able to mimic this environment and someday help to treat dieseases such as aplastic anemia and leukemia.

Dr. Hanna Mikkola headed up the research team who discovered that it is within the placenta that blood stem cells are generated. Previously, Mikkola and collaborators from Havard and France had seen that there was a large pool of blood stem cells within the placenta, but could not be sure if this was where they had in fact originated, or if they had simply been moved by blood flow from their place of generation. Mikkola's team was able to use a mouse embryo without a heartbeat, and therefore, without blood flow to find that the blood stem cells did infact generate in the placenta. The research was published March 6, 2008 in the journal Cell Stem Cell.

Mikkola's team discovered that blood stem cells are generated in the large arteries of the embryo and placenta. They then move to a niche where they multiply in number and mature. The placenta’s vascular labyrinth (where nutriants and oxygen are tranferred from the mother to the fetus) is the site for this niche.

Red blood cells and a white blood cell

Now that it is known where blood stem cells generate and differentiate into the different types of blood cells (red and white blood cells and platelets)researchers are now closely studying these environments so that they might be able to more naturally coax blood stem cells into differentiating and self-renewing within the lab.

Flow chart of stem cell to differentiated cells

Currently, only by manipulating the cell's nuclear regulatory machinery with genes through the use of retroviruses can blood stem cells be differentiated in the lab. However, as yet, they have been unsuccessful in creating blood stem cells that self-new or do not differentiate prematurely after being transplanted. If researchers are able to study in detail the enviroment in which blood stem cells 'grow up' then they will hopefully be able to have more success in growing blood stem cells in the lab so that in the future, they can be used to treat leukemia and other blood related dieases.

Of late, there have been much success in using human skin cells to create induced pluripotent stem cells (iPS). Coupling this tenquince with the data collected from studying the environments in which blood stem cells mature, could potentially create healthy blood cells for a patient, which are completely immue-compatible with their own bodies. Thus, there would be no cases of graft vs. host disease.

Related Links:

# Blood Stem Cells Originate And Are Nurtured In The Placenta

# Researchers Identify Genes Involved With Blood Stem Cell Development

# Regulating Embryonic Stem Cell Self-renewal

# Researchers Identify Genes Involved With Blood Stem Cell Development

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