The Other Side of CD47: a Way to Spawn Induced Pluripotent Stem Cells

CD47 is a cell surface marker that tells immune cells to leave a cell alone. Researchers are presently using CD47 as a target for next-generation cancer therapies - and quite effectively. The marker seems to be present to a greater level that usual in all cancers examined to date, and blocking it frees the immune system to attack the cancer cells.

I noticed another research item today in which a group found that removing CD47 triggers the set of genes known to cause normal adult cells to become induced pluripotent stem (iPS) cells. This is a very interesting result given the cancer connection, and given that this manipulation doesn't seem to make cells prone to generating cancer:

In 2008 [researchers] were using agents that block a membrane protein called CD47 to explore their effects on blood vessels. When cells from the lining of the lungs, called endothelium, had been treated with a CD47 blocker, they stayed healthy and maintained their growth and function for months. [The] team continued to experiment with CD47 blockade, focusing on defining the underlying molecular mechanisms that control cell growth.

They found that endothelial cells obtained from mice lacking CD47 multiplied readily and thrived in a culture dish, unlike those from control mice. [The researchers] discovered that this resulted from increased expression of four genes that are regarded to be essential for formation of iPS cells. When placed into a defined growth medium, cells lacking CD47 spontaneously formed clusters characteristic of iPS cells. By then introducing various growth factors into the culture medium, these cells could be directed to become cells of other tissue types. Despite their vigorous growth, they didn't form tumors when injected into mice, a major disadvantage when using existing iPS cells.

"Stem cells prepared by this new procedure should be much safer to use in patients. Also, the technique opens up opportunities to treat various illnesses by injecting a drug that stimulates patients to make more of their own stem cells. These experiments indicate that we can take a primary human or other mammalian cell, even a mature adult cell, and by targeting CD47 turn on its pluripotent capability. We can get brain cells, liver cells, muscle cells and more. In the short term, they could be a boon for a variety of research questions in the lab."



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