A multi-instrumental approach to identify and purify very small embryonic like stem cells (VSELs) from adult tissues.

We employed several complementary cell image analytical methods including ImageStream system (ISS analysis) and molecular approaches to identify and purify from adult murine organs a population of very small embryonic like stem cells (VSELs). These cells are (i) small in size, (ii) possess high cytoplasmic/nuclear ratio, (iii) contain primitive unorganized euchromatin, (iv) in mice are found among Sca-1(+) Lin(-) CD45(-) cells and in humans among CD133(+) CXCR4(+) CD34(+) Lin(-) CD45(-) cells and (v) express embryonic markers such as Oct-4 protein in nuclei and SSEA antigens on the surface. In mice the highest number of these cells resides in brain, kidney, pancreas and bone marrow. Data from our laboratory indicate that VSELs are most likely a population of germ line/epiblast-derived pluripotent stem cells, that is deposited during organogenesis in developing tissues as a source of tissue committed stem cells and that the number of these cells decreases with the age. We believe that VSELs could be harnessed as a source of pluripotent stem cells for regenerative medicine.