Porcine induced pluripotent stem (piPS) cell lines have been generated recently by using a cocktail of defined transcription factors, however, the features of authentic piPS cells have not been agreed upon and most of published iPS clones did not meet the stringent requirements of pluripotency. Here, we report the generation of piPS cells from fibroblasts using retrovirus carrying four mouse transcription factors (mOct4, mSox2, mKlf4 and mc-Myc, 4F). Multiple LIF-dependent piPS cell lines were generated and these cells showed the morphology similar to mouse embryonic stem cells and other pluripotent stem cells. In addition to the routine characterization, piPS cells were injected into porcine pre-compacted embryos to generate chimera embryos and nuclear transfer (NT) embryos. The results showed that piPS cells retain the ability to integrate into inner and outer layers of the blastocysts, and support the NT embryos development to blastocysts. The generations of chimera embryos and NT embryos derived from piPS clones are a practical means to determine the quality of iPS cells ex vivo.

The aim of this study was to isolate and characterize porcine amniotic fluid-derived multipotent stem cells (pAF-MSC). The porcine amniotic fluid (AF) from the amniotic cavity of pregnant gilts in the early stages of gestation (at E35) was collected and centrifuged for 5–10 min at 400 g to pellet cells. The primary culture of AF showed the multiple cell types, including the epithelial-like cells and fibroblast-like cells. By culturing in AMM medium for 6 to 8 days, the epithelial-like cells disappeared and the remaining cells presented the fibroblastoid morphology. The doubling time of pAF-MSCs was about 34.6 h, and the cells had been continually cultured over 60 passages in vitro. The flow cytometry results showed that pAF-MSCs were positive for CD44, CD117 and CD166, but negative for CD34, CD45 and CD54. Meanwhile, pAF-MSCs expressed ES cell markers, such as Oct4, Nanog, SSEA4, Tra-1-60 and Tra-1-81. The ratio of CD117⁺ CD44⁺ cells accounted for 98% of pAF-MSCs population. Three germ layer markers, including FGF5 (ectodermal marker), AFP (endodermal marker) and Bra (mesodermal marker), were detected in embryoid bodies derived from pAF-MSCs. Under the different induction conditions, the pAF-MSCs were capable of differentiating into neurocytes, adipocytes and beating cardiomyocytes. Furthermore, the pAF-MSCs didn't form teratoma when injected into immunodeficiency mice. These optimal features of pAF-MSCs provide an excellent alternative stem cell resource for potential cell therapy in regenerative medicine and transgenic animals.

Summary: The objective of this study was to determine if insulin–transferrin–selenium (ITS) promoted a nuclear and cytoplasmic maturation of porcine oocytes that better supports subsequent embryonic development. The rate of oocyte in vitro maturation (IVM) in an experimental group treated with hormones for 42 h was significantly increased compared with that in a control group without hormone treatment (47.8% vs. 11.7%, respectively, p < 0.05). Following reduction of the hormone treatment period from 42 h to 21 h, which included both the first 21 h period of hormones treatment (45.4%) and the second 21 h period of hormone treatment (44.8%), the rate of oocyte IVM was still higher than that of the control group (p < 0.05). To improve porcine oocyte nuclear maturation, 1% ITS was added to medium supplemented with hormones. The rate of nuclear maturation in the ITS-treated group was significantly higher than in the ITS-untreated group (78.6% vs. 54.4%, respectively, p < 0.05). ITS treatment also significantly reduced the per cent of oocytes with type I and type III cortical granule (CG) distribution, respectively, and significantly increased the per cent of oocytes with type II CG distribution (85.3%). These observations indicated that the synchronization rates of nuclear and ooplasmic maturation reached 67.04% (78.56 × 85.33%). In conclusion, the combination of modified Tissue Culture Medium-199 (mM199) + 10 ng/ml epidermal growth factor (EGF) + 10 IU/ml pregnant mare serum gonadotrophin (PMSG) + 10 IU/ml human chorion gonadotrophin (hCG) + 2.5 IU/ml follicle stimulating hormone (FSH) + 1% ITS is suitable for culturing porcine oocytes in vitro, and effectively enhances porcine oocyte nuclear and cytoplasmic maturation.