Due to the controversy surrounding the use embryonic stem cells, scientists have been constantly searching for other sources of stem cell that would not pose ethical issues. While research has been conducted into obtaining existing stem cells from sources such as cord blood and amniotic fluid, increasingly active approaches have be taken by scientists through the creation stem cells from specialised cells. “Induced pluripotent” stem cells (iPS cells) are created by reprogramming specialised cells such as skin cells into stem cells. This was initially achieved through genetic manipulation of the specialised cell. Retroviruses are used to insert genes into the chromosomes of the specialised cell, reprogramming it into iPS cell. These genetically-manipulated iPS cells, however, are too risky for human transplantation as they are prone to cancer and tumour formation.
<-- Induced pluripotent stem cells (iPS cells)To solve this problem, researchers led by Sheng Ding of the Scripps Research Institue in La Jolia, California, have turned their attention to proteins, which carries out the reprogramming. Instead of inserting genes that encode for proteins, the researchers inferred that adding reprogrammed protein itself could achieve the same effect.
By bathing fibroblast cells from mouse foetuses in four proteins tagged with polyarginine for 12 hours, remove the proteins for 36 hours, then repeating the cycle another four times, colonies of iPS cells were able to be extracted after two weeks. Attaching proteins to the positively-charged polyarginine (made up of 11 arginine amino acide) enables them to pass through the hydrophilic part of the cell membranes. iPS cells produced this way are less likely to develop into cancerous cells as no genetic material are left behind and the protein quickly breaks down after cell reprogramming.
Although the prospect of protein-reprogrammed iPS cells is promising, problems such as efficiency still needs to be solved for this newly developed technology. With conduction of further studies, production of iPS cells using proteins has a vast potential of becoming the primary method of producing safe iPS cells.
Reference
Aldhous, P., (2009), Reprogramming offers hope of safer stem cells, New Scientist, viewed 10 May 2009, <http://www.newscientist.com/article/dn17008-reprogramming-offers-hope-of-safer-stem-cells.html>
Moreno, J., (2007), Stem Celebration – Next steps for regenerative medicine, Science Progress, viewed 10 11 May 2009, <
