Current state of the opportunities for derivation of germ-like cells from pluripotent stem cells: are you a man, or a mouse?

The concept of pluripotency as a prerogative of cells of early mammal embryos and cultured embryonic stem cells (ESC) has been invalidated with the advent of induced pluripotent stem cells. Later, it became clear that the ability to generate all cell types of the adult organism is also a questionable aspect of pluripotency, as there are cell types, such as germ cells, which are difficult to produce from pluripotent stem cells. Recently it has been proposed that there are at least two different states of pluripotency; namely, the naïve, or ground state, and the primed state, which may differ radically in terms of timeline of existence, signalling mechanisms, cell properties, capacity for differentiation into different cell types, etc. Germ-like male and female rodent cells have been successfully produced in vitro from ESC and induced pluripotent stem cells. The attempts to derive primate primordial germ cells (PGC) and germ cells in vitro from pluripotent stem cells, however, still have a low success rate, especially with the female germline. The paper reviews the properties of rodent and primate ESC with regard to their capacity for differentiation in vitro to germ-like cells, outlining the possible caveats to derivation of PGC and germ cells from primate and human pluripotent cells.