Derivation of Putative Porcine Embryonic Germ Cells and Analysis of Their Multi-Lineage Differentiation Potential

Embryonic germ (EG) cells are cultured pluripotent stem cells derived from the primordial germ cells (PGCs) that migrate from the dorsal mesentery of the hindgut to the developing genital ridge. In this study, the morphology of the porcine genital ridge was assessed in embryos harvested on days 22-30 of pregnancy. PGCs from embryos at these stages were cultured to obtain porcine EG cell lines, and EG-like cells were derived from PGCs from embryos harvested on days 24-28 of pregnancy. The EG-like cells expressed Oct4, Sox2, Nanog, SSEA-3, SSEA-4 and alkaline phosphatase (AP). These cells were able to form embryoid bodies (EBs) in suspension culture and differentiate into cells representative of the three germ layers as verified by a-fetoprotein (AFP), alpha-smooth muscle actin (alpha-SMA), and Nestin expression. Spontaneous differentiation from the porcine EG-like cells of delayed passage in vitro showed that they could differentiate into epithelial-like cells, mesenchymal-like cells and neuron-like cells. In vitro directed differentiation generated osteocytes, adipocytes and a variety of neural lineage cells, as demonstrated by alizarin red staining, oil red O staining, and immunofluorescence for neuronal class III beta-tubulin (Tuj1), glial fibrillary protein (GFAP) and galactosylceramidase (GALC), respectively. These results indicate that porcine EG-like cells have the potential for multi-lineage differentiation and are useful for basic porcine stem cell research.