Figure 1. Murine pluripotent stem cells can be derived from different developmental stages.
At Day 3.5 of embryonic development (Day 3.5 post coitum, p.c.), embryonic stem cells can be isolated from the inner cell mass of the blastocyst. At the epiblast stage on Day 5.5, epiblast stem cells (EpiSCs) or primordial germ cells (PGCs) can be isolated from the embryo and propagated in different culture conditions. For derivation of embryonic germ cell lines (EGCs), primordial germ cells (PGCs) are isolated from the base of the allantois of Day-8.5 embryos or from the genital ridges of Day-10.5 embryos (not shown). Very small embryonic like cells (VSELs) are present in all adult tissues, including bone marrow, liver, heart, kidney, brain, and lung. VSELs are also present in the fetal liver (not shown).