The elite and stochastic model for iPS cell generation: multilineage-differentiating stress enduring (Muse) cells are readily reprogrammable into iPS cells

Induced pluripotent stem (iPS) cells have attracted a great deal of attention, although the mechanism by which they are generated is still not fully understood. Currently, two theories, the stochastic and elite models, have been proposed. Some reports provide theoretical support for the stochastic model. Other reports, however, support the elite model. For example, some human fibroblasts, such as Multilineage-differentiating stress enduring (Muse) cells, are reported to be pluripotent and a primary source of iPS cells. Thus, the mechanism of iPS cell generation continues to be debated. In this review, we discuss the properties of the original cell source, such as the components of the original populations and the potential of each population to become iPS cells, and further discuss the implications of the two theories for iPS cell research.