Induced pluripotent stem cells (iPS cells or iPSCs) are a type of pluripotent stem cell that can be generated from adult somatic cells such as skin fibrobalsts or peripheral blood mononuclear cells (PBMCs) by genetic reprograming or the 'forced' introduction of reprogramming genes (Oct4, Sox2, Klf4 and c-Myc).
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 It has been reported that reprogramming of human keratinocyte cells withdrawn from skin biopsies to pluripotency proceed at much higher frequency and faster speed than fibroblasts. Recently, non-integrating methods of reprogramming have become popular including RNA sendai virus and RNA based reprogramming methods.
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 isogenic control cell lines using CRISPR/Cas9 gene editing that are genetically tailored to model a disease phenotype.
The retroviruses used in the generation of iPSCs 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 fairly low (<0.02%) in certain non-dividing cell types such as PBMCs or elderly skin fibroblasts.
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 stem cell surface markers and genes that characterize ES cells such as Oct4, Sox2, TRA-1-60, TRA-1-81, SSEA-3, SSEA-4 and Nanog.
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.
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. Another significant benefit of iPS cell technology would permit for creation of isogenic control cell lines using CRISPR/Cas9 gene editing that are genetically tailored to a patient or disease phenotype.
The European Bank of Induced Pluripotent Stem Cells (EBiSC) is a collection of high quality human iPS cells available for researchers for use in disease modelling and other forms of stem cell research. The initial collection has been generated from a wide range of donors representing specific disease backgrounds and healthy controls. EBiSC depositors have established many routine procedures for collecting, expanding and characterizing human iPS cell lines. The stem cell bank includes iPSC cell lines derived from neurodegenerative diseases (Alzheimer’s Disease, Parkinson’s Disease, Dementia, Motor Neuron Disease (ALS) - and Huntington’s Disease), eye and heart diseases, and lines from healthy control donors for age and sex matching.
The ability to expand human iPSCs in vitro and subject them to cell-type specific differentiation protocols is critical for generating patient derived “disease-in-a-dish” cellular models for basic stem cell research and drug-discovery applications. Standardized iPSC protocols on how to thaw, culture and cryopreserve human induced pluripotent stem cells (iPSCs) have been established by the European Bank of induced pluripotent Stem Cells (EBiSC). Human induced pluripotent stem cell (iPSC) lines are different to any other established cell line. If you are not familiar with culturing iPSCs make sure you read the following instructions carefully. Recently, 3D cell culture organoid models have utilized iPS cells to more accurately model many organ systems in vitro.
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