Isolation and characterization of trophoblast-derived stem-like cells from peri-implantation porcine embryos.

In mammals, the trophoblast lineage of the embryo is specified before attachment/implantation to become the fetal portion of the placenta. Trophoblast-derived cells were isolated and cultured from day 10 and day 13 porcine embryos and were grown in vitro in a defined, serum-free culture medium for over 2 years without showing any signs of senescence. However, trophoblast-derived cells placed into serum-containing medium rapidly senesce and fail to proliferate. Semiquantitative and quantitative gene expression analyses of cells in culture from 0 to 30 days confirmed the presence (and relative abundance) of mRNA transcripts from genes involved in trophoblast function (CDX2, TEAD4, CYP17A1, HSD17B1, FGFR2, PLET, HAND1) as well as some genes known to mediate pluripotency (POU5F1, KLF4, CMYC). Protein immunolocalization demonstrated expression of both trophoblast and mesenchymal cell markers. DNA methylation patterns in promoters of three critical developmental genes (HAND1, KLF4, TEAD4) did not change appreciably over 4 months of culture in vitro. It was demonstrated that these trophoblast-derived cells are easily stably transfected with an exogenous transgene (eGFP) by a variety of methods, and show the ability to survive and to be passaged repeatedly after transfection. In summary, early embryonic porcine trophoblast-derived cells have demonstrated unique characteristics, which means they could be used as valuable tools for laboratory work. Anticipated applications include the study of trophoblast physiology as well as possible solutions for improving efficiency of transgenesis by somatic cell nuclear transfer and for pluripotency reprogramming of cells.

Targeted DNA methylation analysis by high throughput sequencing in porcine peri-attachment embryos.

The purpose of this experiment was to implement and evaluate the effectiveness of a next-generation sequencing-based method for DNA methylation analysis in porcine embryonic samples. Fourteen discrete genomic regions were amplified by PCR using bisulfite-converted genomic DNA derived from day 14 in vivo-derived (IVV) and parthenogenetic (PA) porcine embryos as template DNA. Resulting PCR products were subjected to high-throughput sequencing using the Illumina Genome Analyzer IIx platform. The average depth of sequencing coverage was 14,611 for IVV and 17,068 for PA. Quantitative analysis of the methylation profiles of both input samples for each genomic locus showed distinct differences in methylation profiles between IVV and PA samples for six of the target loci, and subtle differences in four loci. It was concluded that high throughput sequencing technologies can be effectively applied to provide a powerful, cost-effective approach to targeted DNA methylation analysis of embryonic and other reproductive tissues.