Mouse and human cells can both be reprogrammed with one cluster of specific miRNAs

The miRNA302/367 cluster was first found to be a direct target for the stem cell-specific factors Oct4 and Sox2, recently Anokye-Danso et al. showed that by overexpressing this miRNA cluster mouse and human cells can be reprogrammed without the OSKM factors. Moreover, according to the publication in Cell Stem Cell, miRNA-mediated reprogramming is “up to two orders of magnitude” more efficient than OSKM overexpression (but the authors used individual Oct4, Sox2, Klf4, and c-Myc lentiviruses, instead of a polycistronic virus such as Allele’s lenti-iPS-4-in-1).

To reprogram mouse embryonic fibroblasts (MEFs), suppression of chromatin remodeling factor Hdac2 is necessary when using miRNA for iPSC isolation. Surprisingly, the Hdac2 level is low in human fibroblasts, which do not need an Hdac inhibitor such as valproic acid (VPA) for reprogramming. Oct4-GFP positive cells (stem cells) are observed only 7 days post infecting MEFs with the miRNA302/367, and hundreds colonies appear per 10 thousand cells. When using human fibroblasts, iPSCs form at 18 to 26 days, at an efficiency of approximately 10%, which is significantly higher than using individual OSKM viruses.

The high efficiency from using miRNA for reprogramming is likely due to the fact that miRNAs can target hundreds of mRNAs, compared to providing one mRNA at a time. Although this study concluded that the miRNA302/367 expressing lentivirus was eventually silenced post stem cell induction, emphasis must still be placed on finding a non-integrating method to deliver this miRNA cluster.

New Product of the Week: Chemically synthesized miRNAs by your own design, email for details.

Promotion of the week: Promotion of the week: save 10% on AlleleBalanced Luciferase Assay Kits. Email the code Luc10 to to redeem this offer.

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Wednesday, May 25th, 2011 iPSCs and other stem cells No Comments

FAQ About Feeder Cells for Stem Cells –Part One

The cost of preparing feeder cells for induced pluripotent stem cells (iPSCs) or embryonic stem cells (ESCs) is mainly due to 1. serum and media, 2. labor for growing and treating cells, and 3. expenses for freezing media and vials. Ready-to-use feeder cells saves one important labor-intensive step of iPSC generation, it should be an important help for iPSC and stem cell researchers. We know that most of our colleagues are tired of preparing fresh early passages of MEFs and treating them with expensive mitomycin C or finding an irradiator to pre-treat the MEFs. A lot of iPSC researchers lost iPS stem cells due to the lack of patience in handling MEF feeders. The offering of Allele’s feeder cell product line is really an easy solution and convenience to iPSC researchers.

Question 1: There are companies offering drug-resistant feeder cells such as MEF cells expressing neo-, puro-, or hygromycin-resistance genes. Is it important to have such drug-resistance genes when choosing feeder cells?

Adding drug resistant markers to these cells should not be necessary because iPSCs grown on feeder cells are usually not cultured in antibiotics-containing medium. The feeder cells will not be selected by drug resistance nor will they contaminate iPS cells since they can not propagate after irradiation. However, for those who do need to use drug selection for any reason, we will provide drug-resistant feeder cells upon request.

Question 2: There are publications showing the use of cells lines as feeder cells instead of primary fibroblasts, e.g. SL10, MRC-5, STO. Are there any advantages of using these cell lines?

Not really. Handling primary cells requires certain amount of experience and may be tedious; using cell lines, on the other hand, would be easier for preparing feeder cells. We provide feeder cells from immortalized early passage human foreskin fibroblasts at prices often lower than those from cell lines.

Question 3: Should I choose fluorescent protein expressing feeder cells for easy separation from iPSCs?

You do not need to include fluorescent protein in feeder cells, as feeder cells are quite different in morphology from iPS cells or ES cells. In fact, many labs use iPS factors that are co-expressed with fluorescent markers, in which cases feeder cell expressed fluorescent proteins will confuse the readout.

Question 4: What are the main advantages of using bFGF-expressing feeder cells?

Our bFGF-feeder cells not only eliminate the needs for added recombinant bFGF to stem cell cultures, but also form very nice cell lawn to serve iPSC colony formation because of their strictly controlled passage and growth conditions. We have used these cells without coating dishes with gelatin and obtained nice iPSC colonies.

Preview: Next Part of FAQ on Feeder Cells: choosing mouse or human fibroblasts, selecting iPSC colonies…

Announcement: An audience-orientated User Forum will be added to Allele Biotech webpages so that people can freely discuss or review products and technologies. A distilled version of discussions will be presented in a related but separate FAQ section, which will also include all Allele eNewsletters sent to our contacts about every quarter. Look for the links on in coming weeks.

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Wednesday, October 7th, 2009 iPSCs and other stem cells No Comments