Stem cells come in a variety of forms and have a range of functions. Pluripotent stem cells can differentiate into any type of cell, but have to specialize after their initial division. For example, a pluripotent stem cell can become a blood cell, a heart cell, a neuron, or a skin cell, however, once it becomes a skin cell, it no longer possesses the ability to differentiate into another type of cell. An entire organism cannot be developed using pluripotent stem cells. Totipotent stem cells can produce all types of differentiated cells and can develop into an entire organism. The most useful totipotent stem cells are embryonic stem cells. The ability to reprogram cells into a totipotent state and utilize their abilities to advance medicine and science is the ultimate goal of researchers. Unfortunately, pluripotent stem cells are difficult to make. They require an adult stem cell or a differentiated cell (capable of reproducing) to be reprogrammed into an induced-pluripotent state allowing it, once again, to differentiate into another type of specialized cell. The same process cannot induce a totipotent state as it can a pluripotent state.
Researchers have discovered an effective method of inducing cells to this stem-like pluripotent state by regulating gene expression in cells with four factors. These factors are known as the Yamanaka factors. More recently, a group of researchers from RIKEN in Japan have identified a pair of histone proteins, in combination with the Yamanaka cocktail, that dramatically enhance the production of iPS cells and may be the key to generating induced totipotent stem cells. The 2014 article states, “The study demonstrates that, when added to the Yamanaka cocktail to reprogram mouse fibroblasts, the duo TH2A/TH2B increases the efficiency of iPSC cell generation about twentyfold and the speed of the process two- to threefold. And TH2A and TH2B function as substitutes for two of the Yamanaka factors (Sox2 and c-Myc).” The researchers believe the two histone proteins are utilizing a different pathways which allow for better efficiency and stability. Another method has recently been discovered for inducing pluripotent stem cells from adult stem cells by subjecting them to sublethal pressures and low pH. This causes extreme stress to the cells and essentially forces them to reset. From this state, they can be reprogrammed into a variety of other cells. Both methods have revolutionized the production of pluripotent stem cells and may help to discover a way to program lasting totipotent stem cells.
These new methods benefit researchers in the ethical debate over stem cells. As mentioned before, manipulating and utilizing totipotent stem cells is the ultimate goal of researchers, but obtaining these cells from human embryos presents a significant moral and ethical problem (especially when previous methods have produced some not-so-savory results). Creating viable totipotent stem cells from stable pluripotent stem cells using these new methods could put an end to the ethical dilemma by completely avoiding the use of embryonic stem cells.
posted by Maxwell Liner (2)