• competent vs. non-competent;
  • embryonic stem cell;
  • epiblast stem cell;
  • induced pluripotent stem cell;
  • naïve vs. primed;
  • reprogramming;
  • signaling

Embryonic stem cells (ESCs) are now classified into two types of pluripotency: “naïve” and “primed” based upon their differing characteristics. Conventional human ESCs have much more in common with mouse epiblast stem cells and are now deemed to be primed. Naïve human ESCs that resemble mouse ESCs have recently been generated from their primed counterpart by cellular reprogramming. Isolation of naïve hESCs from human embryos has proven to be difficult. Is the inability to capture naïve hESCs the result of suboptimal derivation conditions or because they are so transient they cannot be “captured” in vitro? Prevailing evidence surrounding this issue are inconclusive and require additional human embryo research. However, negative public opinion regarding human embryo research, may make this an uphill battle. The solution may come from cellular reprogramming.