Expression of pluripotent stem cell markers in the human fetal ovary

BACKGROUND: Human primordial germ cells (PGCs) can give rise to pluripotentstem cells such as embryonal carcinoma cells (ECCs) and embryonicgerm cells (EGCs). METHODS: In order to determine whether PGCs express markers associatedwith pluripotency in EGCs and ECCs, the following study crossexamines the expression patterns of multiple pluripotent markersin the human fetal ovary, 5.5–15 weeks post-fertilizaton(pF) and relates this expression with the ability to derivepluripotent EGCs in vitro. RESULTS: Specific subpopulations were identified which included OCT4⁺/Nanog⁺/cKIT⁺/VASA⁺PGCs and oogonia. Interestingly, these cells also expressedSSEA1 and alkaline phosphatase (AP) and SSEA4 expression occurredthroughout the entire gonad. Isolation of SSEA1⁺ cells fromthe gonad resulted in AP⁺ EGC colony formation. The number ofOCT4⁺ or Nanog⁺ expressing cells peaked by week 8 and then diminishedafter week 9 pF, as oogonia enter meiosis. In addition, theefficiency of EGC derivation was associated with the numberof OCT4⁺ cells. TRA-1-60 and TRA-1-81 were only detected inthe lining of the mesonephric ducts and occasionally in thegonad. CONCLUSIONS: These results demonstrate that PGCs, a unipotent cell, expressmost, but not all, of the markers associated with pluripotentcells in the human fetal ovary.