[Human embryo stem cells and gametes: science fiction or near future?]

In mammalian species, gametes are issued from primordial germ cells (PGC). PGC represent a small cell population, appearing during early embryo development. Gametes production is essential for fertilization process and therefore the establishment of the next generation. The gametes are different from somatic cells because they have a haploid number of chromosomes that are normally generated during the cellular division known as meiosis. The embryonic stem cells that appear at the fifth or sixth day within the blastocyst inner cellular mass are pluripotent cells. Therefore, they can differentiate into the three cellular lineages, somatic as well as germinal. It is well established that the mouse embryonic stem cells can be differentiated in vitro into primordial germinal cells. These cells enter into meiosis forming male or female gametes. In vitro production of gametes by induction from embryonic stem cells has become a very important aspect of the actual research constituting an alternative tool for infertility treatment.