Feeding role of mouse embryonic fibroblast cells is influenced by genetic background, cell passage and day of isolation

Mouse embryonic fibroblast (MEF) cells are commonly used as feeder cells to maintain the pluripotent state of stem cells. MEFs produce growth factors and provide adhesion molecules and extracellular matrix (ECM) compounds for cellular binding. In the present study, we compared the expression levels of Fgf2, Bmp4, ActivinA, Lif and Tgfb1 genes at the mRNA level and the level of Fgf2 protein secretion and Lif cytokine secretion at passages one, three and five of MEFs isolated from 13.5-day-old and 15.5-day-old embryos of NMRI and C57BL/6 mice using real-time PCR and enzyme-linked immunosorbent assay. We observed differences in the expression levels of the studied genes and secretion of the two growth factors in the three passages of MEFs isolated from 13.5-day-old and 15.5-day-old embryos, respectively. These differences were also observed between the NMRI and C57BL/6 strains. The results of this study suggested that researchers should use mice embryos that have different genetic backgrounds and ages, in addition to different MEF passages, when producing MEFs based on the application and type of their study.

FACS-based Glucose Uptake Assay of Mouse Embryonic Fibroblasts and Breast Cancer Cells Using 2-NBDG Probe

This is a flow cytometry-based protocol to measure glucose uptake of mouse embryonic fibroblasts (MEFs) and breast cancer cells in vitro. The method is a slightly modified and updated version as previously described ( Dong et al., 2017 ). Briefly, the target cells are incubated with the fluorescently tagged 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose (2-NBDG) for 2 h or 30 min, and the efficiency of glucose uptake is examined using a flow cytometer. This method can be adapted to measure a variety of adipocytes, immune cells, MEFs and cancer cells.

Choice of Feeders Is Important When First Establishing iPSCs Derived From Primarily Cultured Human Deciduous Tooth Dental Pulp Cells

Feeder cells are generally required to maintain embryonic stem cells (ESCs)/induced pluripotent stem cells (iPSCs). Mouse embryonic fibroblasts (MEFs) isolated from fetuses and STO mouse stromal cell line are the most widely used feeder cells. The aim of this study was to determine which cells are suitable for establishing iPSCs from human deciduous tooth dental pulp cells (HDDPCs). Primary cultures of HDDPCs were cotransfected with three plasmids containing human OCT3/4, SOX2/KLF4, or LMYC/LIN28 and pmaxGFP by using a novel electroporation method, and then cultured in an ESC qualified medium for 15 days. Emerging colonies were reseeded onto mitomycin C-treated MEFs or STO cells. The colonies were serially passaged for up to 26 passages. During this period, colony morphology was assessed to determine whether cells exhibited ESC-like morphology and alkaline phosphatase activity to evaluate the state of cellular reprogramming. HDDPCs maintained on MEFs were successfully reprogrammed into iPSCs, whereas those maintained on STO cells were not. Once established, the iPSCs were maintained on STO cells without loss of pluripotency. Our results indicate that MEFs are better feeder cells than STO cells for establishing iPSCs. Feeder choice is a key factor enabling efficient generation of iPSCs.

Gene targeting and site-specific recombination in mouse ES cells

This is a protocol that describes the generation of targeted embryonic stem (ES) cell clones. The targeted cells can be used for generating a mouse either by injection into blastocysts or by morula aggregation. Alternatively, the ES cells can be used for targeting the second allele and thus creating an in-vitro knockout model. In the latter case, the phenotype of the mutation can be analyzed either in the undifferentiated state or after differentiation of the cells into the three germ layers (endoderm, mesoderm, and ectoderm). This protocol describes only a part of the pipeline for generating a conditional knockout mouse. The whole procedure includes (1) design and generation of the targeting construct, (2) generation of targeted ES clones, and (3) generation of the knockout mouse. Detailed protocols for preparing DNA, culturing ES cells, and screening the transfected ES clones for correct targeted events by long-range PCR or Southern blotting can be found elsewhere (see Isolation of Genomic DNA from Mammalian Cells and Analysis of DNA by Southern Blotting). Here, we describe only the protocol used for transfecting the targeting construct into ES cells and for removing antibiotic selection cassettes or other DNA fragments flanked by site-specific recombination target sites using transient transfection of recombinase expression vectors. In addition, we describe a short protocol for screening the clones that underwent complete recombination. A protocol to prepare DNA from 96-, 48-, and 24-well plates is also described.