Derivation of Human Embryonic Germ Cells: An Alternative Source of Pluripotent Stem Cells

Abstract

Based on evidence suggesting similarities to human embryonic stem cells, human embryonic germ (hEG) cells have been advocated as an alternative pluripotent stem cell resource but have so far received limited attention. To redress this imbalance, human fetal gonads were collected for the isolation and culture of primordial germ cells at 7-9 weeks postconception. We provide evidence for the derivation, culture, and differentiation of hEG cells in vitro. This evidence includes the expression of markers characteristic of pluripotent cells, the retention of normal XX or XY karyotypes, and the demonstration of pluripotency, as suggested by the expression of markers indicative of differentiation along the three germ lineages (ectoderm, mesoderm, and endoderm) and an associated loss of pluripotent markers. In assessing this differentiation, however, we also demonstrate a hitherto unacknowledged overlap in gene expression profiles between undifferentiated and differentiated cell types, highlighting the difficulty in ascribing cell lineage by gene expression analyses. Furthermore, we draw attention to the problems inherent in the management of these cells in prolonged culture, chiefly the difficulty in preventing spontaneous differentiation, which hinders the isolation of pure, undifferentiated clonal lines. While these data advocate the pursuit of pluripotent hEG cell studies with relevance to early human embryonic development, culture limitations carry implications for their potential applicability to ambitious cell replacement therapies.

Very small embryonic-like stem cells in adult tissues—Potential implications for aging

“…However, on the other hand, when PGC are cultured over murine embryonic fibroblasts and exposed ex vivo to following growth factors: kit ligand (KL), leukemia inhibitory factor (LIF) and basic fibroblast growth factor (FGF-2), they continue proliferation and form large colonies of embryonic germ cells (EG) which similarly to embryonic stem cells (ESC) can be expanded indefinitely (Matsui et al, 1992;Shamblott et al, 1998;Turnpenny et al, 2003). Such EG have been derived from pre-and post-migratory, as well as from migratory PGC in both mice and humans and were described as cells preserving pluripotency (Matsui et al, 1992;Shamblott et al, 1998).…”

Bone marrow‐derived very small embryonic‐like stem cells: Their developmental origin and biological significance

“…However, when PGC are cultured over murine embryonic fibroblasts and exposed ex vivo to three growth factors (kit ligand, leukemia inhibitory factor, and basic fibroblast growth factor), they continue to proliferate and form large colonies of EG, which similarly as ESC can be expanded indefinitely (Matsui et al, 1992;Shamblott et al, 1998;Turnpenny et al, 2003). EG had been derived from pre-and postmigratory as well as from migratory PGC in both mice and humans and are pluripotent (Matsui et al, 1992;Shamblott et al, 1998).…”

Stem cell factor affects fate determination of human gonocytes in vitro

“…As shown in Fig. 3, the gonocyte colonies were stained positive for Oct-4, SSEA-4, and c-Kit, suggesting that these colonies share similar pluripotent markers as well as embryonic germ cells (EGCs) that were cultured from PGCs (Shamblott et al 1998, Turnpenny et al 2003, Liu et al 2004, Park et al 2004, Pan et al 2005. The result also showed that the cultured gonocyte colonies were only dotted stained with c-Kit, suggesting that the c-Kit might be down-regulated in the present culture system.…”