Isolation of rat embryonic stem-like cells: a tool for stem cell research and drug discovery

Thyroid Hormone Signaling in Embryonic Stem Cells: Crosstalk with the Retinoic Acid Pathway

While the role of thyroid hormones (THs) during fetal and postnatal life is well-established, their role at preimplantation and during blastocyst development remains unclear. In this study, we used an embryonic stem cell line isolated from rat (RESC) to study the effects of THs and retinoic acid (RA) on early embryonic development during the pre-implantation stage. The results showed that THs play an important role in the differentiation/maturation processes of cells obtained from embryoid bodies (EB), with thyroid hormone nuclear receptors (TR) (TRα and TRβ), metabolic enzymes (deiodinases 1, 2, 3) and membrane transporters (Monocarboxylate transporters -MCT- 8 and 10) being expressed throughout in vitro differentiation until the Embryoid body (EB) stage. Moreover, thyroid hormone receptor antagonist TR (1-850) impaired RA-induced neuroectodermal lineage specification. This effect was significantly higher when cells were treated with retinoic acid (RA) to induce neuroectodermal lineage, studied through the gene and protein expression of nestin, an undifferentiated progenitor marker from the neuroectoderm lineage, as established by nestin mRNA and protein regulation. These results demonstrate the contribution of the two nuclear receptors, TR and RA, to the process of neuroectoderm maturation of the in vitro model embryonic stem cells obtained from rat.

Growth and Neurotrophic Factors in Embryonic Stem Cells

In this chapter we illustrate protocols to investigate growth and neurotrophic factors in human and rodent (rat and mouse)-derived embryonic stem cells. The conventional two-dimensional cell monolayer system to grow embryonic stem cells is presented, focusing on the coating strategies also using extracellular matrix components. Then, different approaches for three-dimensional stem cell culture are presented, using hydrogels and scaffolds. Quantitative polymerase chain reaction, immunocytochemistry, immunoenzymatic ELISA assay, and multiparametric assays to quantify growth and neurotrophic factor production are presented.

Inducing goat pluripotent stem cells with four transcription factor mRNAs that activate endogenous promoters

BACKGROUND

Traditional approaches for generating goat pluripotent stem cells (iPSCs) suffer from complexity and low preparation efficiency. Therefore, we tried to derive goat iPSCs with a new method by transfecting exogenous Oct4, Sox2, Klf4 and c-Myc mRNAs into goat embryonic fibroblasts (GEFs), and explore the mechanisms regarding the transcription regulation of the reprogramming factors in goat iPSCs induction.

RESULTS

mRNAs of the four reprogramming factors were transfected into GEFs, and were localized in nucleus with approximately 90% transfection efficiency. After five consecutive transfections, GEFs tended to aggregate by day 10. Clones appeared on day 15-18, and typical embryonic stem cell -like clones formed on day 20. One thousand AKP staining positive clones were achieved in 10⁴ GEFs, with approximately 1.0% induction efficiency. Immunofluorescence staining and qRT-PCR detection of the ESCs markers confirmed the properties of the goat iPSCs. The achieved goat iPSCs could be cultured to 22nd passage, which showed normal karyotype. The goat iPSCs were able to differentiate into embryoid bodies with three germ layers. qRT-PCR and western blot showed activated endogenous pluripotent factors expression in the later phase of mRNA-induced goat iPSCs induction. Epigenetic analysis of the endogenous pluripotent gene Nanog revealed its demethylation status in derived goat iPSCs. Core promoter regions of the four reprogramming factors were determined. Transcription factor binding sites, including Elf-1, AP-2, SP1, C/EBP and MZF1, were identified to be functional in the core promoter regions of these reprogramming genes. Demethylation and deacetylation of the promoters enhanced their transcription activities.

CONCLUSIONS

We successfully generated goat iPSCs by transfection of Oct4, Sox2, Klf4 and c-Myc mRNAs into GEFs, which initiated the endogenous reprogramming network and altered the methylation status of pluripotent genes. Core promoter regions and functional transcription binding sites of the four reprogramming genes were identified. Epigenetic regulation was revealed to participate in mRNA induced iPSCs formation. Our study provides a safe and efficient approach for goat. iPSCs generation.

Immortalized tumor derived rat fibroblasts as feeder cells facilitate the cultivation of male embryonic stem cells from the rat strain WKY/Ztm

Feeder cells are essential for the establishment and culture of pluripotent rat embryonic stem cells (ESC) in vitro. Therefore, we tested several fibroblast and epithelial cell lines derived from the female genital tract as feeder cells to further improve ESC culture conditions. The immortalized tumor derived rat fibroblast TRF-O3 cells isolated from a Dnd1-deficient teratoma were identified as optimal feeder cells supporting stemness and proliferation of rat ESC. The TRF-O3 cells were characterized as myofibroblasts by expression of fibroblast specific genes alpha-2 type I collagen, collagen prolyl 4-hydroxylase alpha (II), vimentin, S100A4, and smooth muscle α-actin. Culture of inner cell masses (ICM) derived from WKY/Ztm rat blastocysts in 2i-LIF medium on TRF-O3 feeder cells lacking LIF, SCF and FGF2 expression resulted in pluripotent and germ-line competent rat ESC lines. Therein, genotyping confirmed up to 26% male ESC lines. On the other hand the TRF-O3 specific BMP4 expression was correlated with transcriptional activity of the mesodermal marker T-brachyury and the ectoderm specific nestin in the ESC line ES21 demonstrating mesodermal or ectodermal cell lineage differentiation processes within the ESC population. Substitution of 2i-LIF by serum-containing YPAC medium supplemented with TGF-β and rho kinase inhibitors or by 4i medium in combination with TRF-O3 feeder cells led to enhanced differentiation of ES21 cells and freshly isolated ICMs. These results suggest that the ESC culture conditions using TRF-O3 feeder cells and 2i-LIF medium supported the establishment of male ESC lines from WKY/Ztm rats, which represent a favored, permissive genetic background for rat ESC culture.

Influence of biological matrix and artificial electrospun scaffolds on proliferation, differentiation and trophic factor synthesis of rat embryonic stem cells

Two-dimensional vs three-dimensional culture conditions, such as the presence of extracellular matrix components, could deeply influence the cell fate and properties. In this paper we investigated proliferation, differentiation, survival, apoptosis, growth and neurotrophic factor synthesis of rat embryonic stem cells (RESCs) cultured in 2D and 3D conditions generated using Cultrex® Basement Membrane Extract (BME) and in poly-(L-lactic acid) (PLLA) electrospun sub-micrometric fibres. It is demonstrated that, in the absence of other instructive stimuli, growth, differentiation and paracrine activity of RESCs are directly affected by the different microenvironment provided by the scaffold. In particular, RESCs grown on an electrospun PLLA scaffolds coated or not with BME have a higher proliferation rate, higher production of bioactive nerve growth factor (NGF) and vascular endothelial growth factor (VEGF) compared to standard 2D conditions, lasting for at least 2 weeks. Due to the high mechanical flexibility of PLLA electrospun scaffolds, the PLLA/stem cell culture system offers an interesting potential for implantable neural repair devices.