Induced pluripotent stem cells, or iPS cells, are cells made in the laboratory by reprogramming ordinary tissue cells, such as skin cells, back to a pluripotent state. They can give rise to every cell type in the adult body and are used mainly in research.
The technology sits within the broader field described in what is regenerative medicine. This page explains how iPS cells are made, how they differ from embryonic cells, what they are used for today and what stands between them and routine medical use.
How iPS cells are made
Reprogramming turns a specialized cell back into an immature one. The International Society for Stem Cell Research describes induced pluripotent stem cells as cells that have been made in the lab by converting tissue-specific cells, such as skin cells, into cells with the same properties as embryonic stem cells. Like embryonic cells, they can give rise to every cell type in the adult body.
The method was first shown in mice. A mouse study described introducing four factors, Oct3/4, Sox2, c-Myc, and Klf4, into embryonic or adult fibroblasts, and found that pluripotent cells could be generated directly from fibroblast cultures with only a few defined factors. The authors named the resulting cells iPS cells.
A follow-up study applied the same idea to people. Its authors reported the generation of iPS cells from adult human dermal fibroblasts with the same four factors. In that study, human iPS cells were similar to human embryonic stem cells in morphology, proliferation, surface antigens, gene expression, epigenetic status of pluripotent cell-specific genes, and telomerase activity, and they could differentiate into cell types of the three germ layers in vitro and in teratomas.
The idea had earlier roots. The Nobel Prize committee notes in its 2012 press release that John Gurdon discovered in 1962 that the specialisation of cells is reversible, and that Shinya Yamanaka discovered more than 40 years later, in 2006, how intact mature cells in mice could be reprogrammed to become immature stem cells.
How iPS cells compare with embryonic and tissue-specific cells
All pluripotent cells share the ability to become any cell type, but their sources differ. The International Society for Stem Cell Research notes that embryonic stem cells only exist at the earliest stages of embryonic development and are derived from cells in the blastocyst, while iPS cells are made from tissue-specific cells. The contrast, including the ethical questions that attach to embryo-derived cells, is covered in the comparison of embryonic vs adult stem cells.
Tissue-specific stem cells are a different category again. According to the same society, they are multipotent, meaning more limited than pluripotent cells. Blood-forming stem cells in bone marrow, for example, can give rise to red and white blood cells and platelets, but cannot generate liver, lung, or brain cells. iPS cells are not limited in that way, which is one reason researchers value them as a starting material.
Pluripotent cells also have a practical advantage in the laboratory. The society explains that pluripotent stem cells are valuable because they can be grown in the laboratory in unlimited numbers.
What iPS cells are used for
Today, most uses are in research and drug development. A review of the technology’s first decade states that human iPSCs have been widely used for disease modelling, drug discovery and cell therapy development. The International Society for Stem Cell Research gives a similar list: scientists use iPS cells to learn about how tissues develop, model diseases in the laboratory, and develop or test new treatments.
One attraction is that cells can be taken from a particular person and reprogrammed. A review of heart research notes that iPS cells can be obtained from patients to allow autologous therapy, and that banks of human leukocyte antigen diverse iPS cells are possible for allogeneic therapy. Those are research proposals under study, not established treatments.
The same heart review explains why the cells attract interest as a manufacturing source: iPS cells can proliferate indefinitely in culture and can differentiate into cardiac lineages, including cardiomyocytes, smooth muscle cells, endothelial cells, and cardiac progenitors. As a result, large quantities of desired cell products can be generated without being limited by cellular senescence. The point concerns production capacity. It says nothing about whether the products help patients, which is what trials are designed to find out.
The decade review also reports that new drugs originating from iPSC screens are in the pipeline and that the first clinical trial using human iPSC-derived products has been initiated. Early-stage trial activity of that kind tests safety and feasibility; it does not show that a treatment works.
Safety questions that remain open
The same cells that can become any tissue also raise safety questions. One pharmaceutical-science study states that one of the most obvious safety issues is the presence of residual undifferentiated cells that have tumorigenic potential. It says that assessing and controlling tumorigenicity of iPS-derived products is essential to prevent tumor development by residual pluripotent stem cells after implantation, and it describes assays able to detect very small numbers of leftover undifferentiated cells.
The heart-research review lists other points that need ongoing study before first-in-human trials, including the risk of tumor formation, immune rejection, induction of arrhythmias, and formation of stable cardiac grafts. It also says preclinical animal studies have shown evidence of cardiac repair, which is an animal finding rather than a result in people.
These points explain why iPS-derived products are being tested carefully in trials rather than offered as routine care. Methods for producing clinical-grade products exist, according to that review, but safety work continues.
Regulatory status
iPS-derived products are not among the approved stem cell products described by the FDA. In a 2020 consumer alert, the FDA said that the only stem cell products that were FDA-approved for use in the United States consisted of blood-forming stem cells derived from umbilical cord blood, for disorders that affect the production of blood. On December 18, 2024, the FDA approved Ryoncil, a donor bone marrow-derived mesenchymal stromal cell therapy, for steroid-refractory acute graft-versus-host disease in children; the FDA’s list of approved cellular and gene therapy products is the current reference. Neither is iPS-derived. The established use of blood-forming cells, from marrow, blood or cord blood, is explained in the guide to hematopoietic stem cell transplant.
The alert is dated July 22, 2020, so readers should treat later approvals as outside what it describes. Anyone weighing a treatment that advertises iPS cells should ask what stage of testing it has reached and who regulates it, and decisions about any treatment belong with a licensed physician who knows the reader’s own situation.
Frequently asked questions
What does “induced” mean in induced pluripotent stem cells?
Show answer
It means the pluripotent state was brought about in the laboratory. Scientists convert tissue-specific cells, such as skin cells, into cells with the same properties as embryonic stem cells.
Who discovered iPS cells?
Show answer
Shinya Yamanaka discovered in 2006 how intact mature mouse cells could be reprogrammed to become pluripotent stem cells, and shared the 2012 Nobel Prize in Physiology or Medicine with John Gurdon.
Do iPS cells come from embryos?
Show answer
No. They are made from tissue-specific cells such as skin cells, while embryonic stem cells are derived from the blastocyst, a very early stage of embryonic development.
What is the main safety concern with iPS-derived products?
Show answer
Residual undifferentiated cells that have tumorigenic potential. Researchers study assays that detect such cells before any product is used.
