Table 1.
Source of VSELs | Characteristics |
---|---|
Murine VSELsa | Enriched in population of cells that are slightly smaller than red blood cells. |
Primitive morphology, large nuclei contain euchromatin, high nuclear/cytoplasmic ratio. | |
Quiescent cells due to epigenetic changes in expression of some genes regulated by paternal imprinting (eg, Igf2-H19, RasGrf1, IGF2R, and p57Kip2). It also explains that they neither form teratomas nor complement blastocyst development. | |
Purified VSELs are enriched for cells that express some markers characteristic for pluripotent stem cells (Oct-4, Nanog, SSEA-1, and presence of bivalent domains), epiblast and germ line cell markers. | |
Number of VSELs decreases with the age and correlates with life span in experimental animals. | |
In appropriate experimental models murine VSELs differentiate into cells from all three germ layers, including germ line. | |
Highly resistant to stress, irradiation and cytostatics. | |
Human VSELsb | Enriched in a population of cells that are slightly smaller than red blood cells. |
Primitive morphology, large nuclei contain euchromatin, high nuclear/cytoplasmic ratio. | |
Purified human UCB-VSELs are enriched for cells that express some markers characteristic for pluripotent stem cells (eg, Oct-4, Nanog, and SSEA-4) and some epiblast and primordial germ cell markers. | |
Do not form teratomas in experimental animals | |
Quiescent cells due to epigenetic changes in expression of some genes regulated by paternal imprinting (eg, Igf2-H19). | |
In appropriate experimental models, human VSELs differentiate into hematopoietic cells, mesenchymal stem cells, and neural cells. Moreover, VSELs isolated from human gonads also differentiate into germ line cells. |
The best characterized so far at molecular level are murine VSELs purified from BM. More work is needed to compare VSELs isolated from other tissues with BM-purified ones.
Recent data reported on VSELs-like cells isolated from human ovaries indicate their molecular similarity to murine BM-purified VSELs [14,15,18,68,117,118].
VSEL, very small embryonic-like stem cells; UCB, umbilical cord blood; BM, bone marrow.