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Cell Culture

Induced Pluripotent Stem Cell FAQs

Glossary – definitions of stem cell terms
Protocols – induced pluripotent stem cell protocols
iPS Products
– extensive list of iPS cell lines for stem cell culture
Need technical help? Ask a Scientist

What are induced pluripotent stem cells (iPSCs)?
Induced pluripotent stem cells (iPSCs or iPS cells) are a type of pluripotent stem cells that can be produced from adult cells by genetic reprograming or 'forced' introduction of genes.1

How are the induced pluripotent stem (iPS) cells produced?
In 2006, Shinya Yamanaka produced the first iPS cells - murine ES (embryonic stem) like cell lines - from mouse embryonic fibroblasts (MEFs) and skin fibroblasts by inserting four transcription factor genes encoding Oct4, Sox2, Klf4, and c-Myc. Another group of researchers identified two other genes, Nanog, and Lin28 as a replacement of Klf4, and c-Myc to reprogram human cells. The source of reprogramming genes could be generated from various origins, including neuronal progenitor cells, keratinocytes, hepatocytes, B cells, and fibroblasts of mouse-tail tips, kidneys, muscles, and adrenal glands. Fusion of two types of cells could convert specialized cell types from one lineage to another. These newly developed cells possess similar morphology and growth characteristics as parent ES cells by expressing ES cell-specific genes. The success of reprogramming iPS cell technology depends on the sources of cell lines. It has been reported that reprogramming of human keratinocyte cells withdrawn from skin biopsies to pluripotency proceed at much higher frequency and faster speed than fibroblasts.2,3

What are the advantages of iPS cells over embryonic stem cells?
The advantage of iPS cells is that they are not derived from human embryos, which is the ethical concern in this field. By removing the bioethical issues, the scientists are more likely to obtain more federal funding and support. Another significant benefit of iPS cell technology would permit for creation of cell lines that are genetically tailored to a patient. This could eliminate the concern of immune rejection, where the body’s immune system identifies implanted cells or tissues as unknown and attacks them.

What are the risks associated with iPS cell use in humans?
The retroviruses used in the generation of iPSc are associated with cancer because they insert DNA anywhere in a cell's genome, which could potentially trigger the expression of cancer-causing genes. Another risk associated with iPS cell technology applied to humans is the fact that c-Myc, which is one of the genes used in reprogramming, is a known oncogene whose overexpression could also cause cancer. In addition, the successful reprogramming rate in human iPS cells from fibroblasts is very low (<0.02%).3

How are iPS cells similar to ES cells?
iPS cells are similar to ES cells in morphology, teratoma formation, proliferation, expression of pluripotency markers, long telomeric zone, generation of embryoid bodies and viable chimeras as well as their ability to differentiate along a given lineage. They also express cell surface markers and genes that characterize ES cells.3

Does iPS cell technology eliminate the need for embryonic stem cell research?
Recent advances do not eliminate the need for ES cell research since it is not yet quite clear whether iPS cells differ extensively from the embryonic stem cells. To bring stem cell research to clinical realization, it is necessary to investigate all the aspects in this field such as the most efficient stem cell for cell replacement therapies.4

What are disease specific iPS cells?
Disease specific iPS cells are iPS cells generated from subjects with a genetic disease. These cells, generated from patients with untreatable diseases, can be used to study the pathophysiology of various diseases in vitro and enable drug development.5,6

Is there an iPS cell bank and where?
The National Institutes of Health’s Center for Regenerative Medicine, The Coriell Institute in Camden (iPSC lines related to Parkinson’s, amyotrophic lateral sclerosis (ALS), and Huntington’s disease), WiCell in University of Wisconsin–Madison, The Harvard Stem Cell Institute, The European Bank for Induced Pluripotent Stem Cells, Human Induced Pluripotent Stem Cells Initiative (HipSci) in UK, and StemBANCC. There, the scientists grow, test, store and distribute iPS cell lines.8,9

Which media should be used for culturing iPS cells?
Sigma-Aldrich has a variety of media products that can be used for pluripotent stem cell culture, especially for differentiated cells. Our products include neural stem cell media, T-cell expansion media, hematopoietic media, keratinocyte media, and mesenchymal stem cell media. Additionally, we offer media for culturing differentiated astrocytes and neurons from stem cells. More information about our stem cell media can be found here.

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