In November 2007, a significant development occurred when Japanese researcher Shinya Yamanaka announced that his team had developed a new technology to cause mature human cells to resemble pluripotent stem cells similar in many ways to human embryonic stem cells. These reprogrammed cells are referred to as induced pluripotent stem (iPS) cells.
Initially iPS cells were generated using viruses to genetically engineer mature cells to achieve a pluripotent status. The purpose of the virus was to insert reprogramming genes, commonly found in stem cells, into an adult cell such as a skin cell and then culture the cells in the laboratory for 4-5 weeks after which a small number of iPS cells begin to appear. However, technologies for reprogramming cells are moving very quickly and researchers are now investigating the use of new methods that do not remain in the cells causing permanent and potentially harmful changes. These new technologies currently utilise different types of non-integrating viruses and chemicals and small molecules.
Similar to SCNT, this technology allows scientists a new method of creating diseased cells for research by using mature cells from a patient with a genetic disease, such as Huntington’s disease, and turning those cells into iPS cells.
Such disease-specific stem cells may enable disease investigation and drug development offering a unique opportunity to recreate both normal and diseased human tissue formation in the laboratory.
iPS technology also has the potential to produce genetically identical “patient specific” embryonic stem cell-like lines that would be recognised as “self” and not rejected by the patient.
Whilst the discovery of iPS cells is a significant breakthrough in the field of reprogramming, the use of iPS cells in the clinic is many years away - if it occurs at all - as several significant hurdles need to be overcome. It is still unclear how genetically stable or safe iPS cells will be for potential clinical use. More research needs to be done into iPS cells to discover if they will offer the same equivalent research value as embryonic stem cells. Having only recently discovered these cells, scientist are yet to confirm if iPS cells have the ability to divide and remain chromosomally stable like embryonic stem cells over a long period of time.