Stem cell research is the laboratory and clinical study of cells that can copy themselves and develop into specialized cell types, used to understand development, model disease, test drugs and develop therapies.
It sits inside the broader field covered in what is regenerative medicine, and this guide maps how the science is organized, what tools it has produced and how to judge claims about it.
How stem cell research is organized
Stem cells are defined by two properties. According to the International Society for Stem Cell Research (ISSCR), stem cells are defined by their ability to self-renew (make copies of themselves) and differentiate (develop into more specialized cells). Everything else in the field, from basic biology to drug screening, builds on those two abilities.
Research moves through a sequence that ISSCR calls clinical translation. On its overview page, the society describes a well-established process that consists of basic research, preclinical research, and clinical research. Each stage asks a different question and answers it with a different kind of evidence.
Basic research aims to increase understanding without necessarily having an immediate practical application. A team might study how a blood-forming cell decides to become a red cell instead of a white cell, with no treatment in mind.
Preclinical research builds on that foundation. ISSCR notes that it involves further laboratory research on cells, tissues, and/or animals to test for safety, toxicity, and efficacy in model systems prior to clinical research in humans. Results here help decide whether a study in people is justified at all.
Clinical research is the stage that studies people. Because it is the point where a claim about a treatment either holds up or does not, later sections of this guide spend extra time on how it works.
The cell types researchers work with
Researchers sort stem cells by how many cell types they can produce. ISSCR describes two broad groups: pluripotent stem cells and tissue-specific (adult) stem cells. In its explainer on stem cell types, ISSCR states that pluripotent stem cells are stem cells that can become any cell in the body.
Pluripotent cells come in two forms. Embryonic stem cells exist only at the earliest stages of development, while induced pluripotent stem cells are made in the laboratory from ordinary cells such as skin cells. The same ISSCR page explains that, because of their flexibility, pluripotent stem cells can be grown in the laboratory in unlimited numbers and can be used to model development and disease, test the efficacy of new drugs, and develop cellular therapies for treatment.
Tissue-specific stem cells are more limited. They live in organs such as bone marrow, skin and the lining of the gut, and under normal conditions they replace the cells of their own tissue. A blood-forming stem cell, for example, regenerates blood cells and does not spontaneously make brain cells. This difference in scope shapes what each cell type is used for in the laboratory.
Other sources of cells also appear in the literature, including cord blood and the connective-tissue cells often grouped as mesenchymal cells. They are described in more detail in separate guides, and the key point for a research overview is that each source has its own properties, its own risks and its own evidence base. Evidence about one cell type cannot be transferred to another.
Reprogramming and the discovery that changed the field
For decades, biologists assumed that once a cell specialized, there was no going back. The Nobel Assembly at Karolinska Institutet announced in its press release that the Nobel Prize in Physiology or Medicine was awarded jointly to John Gurdon and Shinya Yamanaka. It reports that John B. Gurdon discovered in 1962 that the specialisation of cells is reversible.
The second half of the story came later. The same announcement says 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. Those reprogrammed cells are the induced pluripotent stem cells now used in laboratories worldwide.
The practical consequence is that researchers no longer depend on embryos as the only source of pluripotent cells. A sample of skin or blood from a person with a particular genetic condition can be reprogrammed, and the resulting cells can then be coaxed into the cell type affected by that condition. The Nobel announcement adds that by reprogramming human cells, scientists have created new opportunities to study diseases and develop methods for diagnosis and therapy.
The path of the whole field, including embryonic cell derivation, the first reprogramming experiments and the debates they triggered, is told in the history of stem cell research. Reading it alongside this overview helps explain why certain ethical questions and regulatory rules look the way they do today.
Tools built from stem cells and from related technologies
Much of stem cell research today is not about treating anyone. It is about building better models of human biology. ISSCR lists several active areas on its emerging research page, including chimeras, embryo models, mitochondrial replacement and organoids, and it explains that organoids are self-organized three-dimensional structures that are typically derived from stem cells and mimic aspects of the key functional, structural, and biological complexity of an organ.
Organoids are a good example of how basic tools reach the bench. ISSCR reports that to date, organoids have been created to form a number of tissues including kidney, lung, liver and brain. They are not complete organs, but they give scientists a human-derived system that animal models cannot supply. The guide on what are organoids covers how they are grown and what they are used for.
Embryo models are a related development. ISSCR describes them as organized three-dimensional structures created by stem cells that resemble some aspects of early embryo development, which lets researchers study reproductive health, genetic disease and organ formation in ways that were not possible before. Because they raise their own ethical questions, they are an active topic in the oversight discussions described later in this guide.
Stem cells are also linked with two neighbouring technologies. Genome editing lets researchers change specific genes in cells, and crispr gene editing is the best-known method. Engineered immune cells are a third line of work, explained in car t cell therapy. These technologies often overlap with stem cell science, but they are distinct, and the way they are regulated and tested differs.
Whether a therapy modifies cells outside the body or changes genes directly inside it affects how it is classified and studied. The comparison in gene therapy vs cell therapy sets out where those categories meet and where they separate.
What is approved, what is investigational and what is unproven
Newcomers often assume that anything labelled a stem cell therapy has been tested and approved. It has not. ISSCR states plainly that at this time there are very few conditions for which stem cell-based therapies are proven and widely accepted by the global medical community, and that these are primarily limited to blood stem cell transplantation to treat diseases of the blood, such as leukemia and sickle cell anemia.
The United States Food and Drug Administration (FDA) draws the line in similar terms for products on the American market. Its patient and consumer information page, last updated in 2024, states that currently, the only stem cell products that are FDA-approved for use in the United States consist of blood-forming stem cells (also known as hematopoietic progenitor cells) that are derived from umbilical cord blood. Those products are approved for disorders of the blood-forming system and not for other uses. 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.
The FDA also keeps a public list of licensed cellular and gene therapy products. The agency describes it as a list of licensed products from the Office of Therapeutic Products (OTP). That list covers more than stem cell products, since engineered immune cells and gene therapies are on it too, which is one reason the terms should not be used interchangeably.
Between approved and unproven sits a middle category. ISSCR calls a treatment investigational while it is being tested in clinical trials with proper regulatory oversight. The society contrasts this with an unproven stem cell treatment, an experimental treatment that is new, untested, or different from standard medical treatment and has not undergone the proper regulatory process. Calling something experimental does not make it part of a research study.
The research pipeline for approved treatments exists for a reason. The same ISSCR page notes that there are currently active clinical trials using stem cell treatments for a number of conditions including diabetes, among others, which means the work is real and ongoing. Active trials are a sign of research interest and are not evidence that a treatment works.
Why do researchers insist on this level of control? Part of the answer is biological. ISSCR explains that undifferentiated pluripotent stem cells are unsafe to inject into a patient as they could cause tumors to form. Cells have to be guided into the specific type needed and tested carefully before any use in people.
The FDA lists the safety concerns it has seen with unapproved products. It reports that FDA has received reports of blindness, tumor formation, infections, and more linked to unapproved regenerative medicine products. These reports are one reason regulators, and not marketing language, set the terms for what can be offered to the public. How the agency decides which products need review is explained in fda regulation of cell therapy.
The broader question for any reader is what a given claim rests on. A product approved through a formal process, a treatment under study in a registered trial and a service sold with testimonials are three different things, and only the first has passed the full evidence test. Decisions about any treatment belong with a licensed physician who knows the individual circumstances involved.
Reading the evidence: clinical trials and registries
Clinical trials are the mechanism that separates a hopeful idea from a demonstrated one. ISSCR describes how they are built: a clinical trial includes a comparison to determine whether or not the treatment is having an effect. Without a comparison group, improvement after treatment cannot be separated from natural recovery, from the placebo response or from chance.
Blinding is one of the main protections against bias. ISSCR explains that in a double-blind trial, neither the participants nor the investigators know who is in the test or the control group. This design feature reduces bias on the part of those conducting the trial.
Trials are also divided into stages that test different questions, usually safety first and effectiveness later. The stages and what each one can and cannot show are laid out in phases of clinical trials. An early-stage result about safety in a small group is not the same kind of finding as a large comparison showing benefit.
Public registries let anyone see which studies exist. Finding a study and interpreting what its entry means are separate skills, and the guide on stem cell clinical trials explains how to look up and read an entry. One caution comes directly from the FDA: the inclusion of a product in the clinicaltrials.gov database or the fact that a firm has registered with FDA and listed its product does not mean the product is legally marketed.
That caution points to a general principle. A registry entry shows that a study has been listed. It does not show that the study was reviewed, that it has results or that the product has been shown to be safe or effective. Looking at who sponsors the study, whether it has a control group and whether results have been reported gives a far clearer picture than the listing alone.
Oversight, ethics and where the field is heading
Because stem cell science touches embryos, human tissue donation and potential treatments, it has developed its own professional standards. The most widely cited are the ones described in isscr guidelines, which cover how laboratory work should be conducted and how a laboratory finding should be turned into a clinical study responsibly.
Regulation and self-governance work together. Professional standards describe good practice, while regulators decide what can legally be offered to patients. Neither replaces the other, and both exist because the field combines fast scientific progress with patients who are often seriously ill and understandably hopeful.
Looking forward, the research directions that ISSCR highlights include organoids, embryo models, chimeras and mitochondrial replacement. Alongside these, trials continue for conditions where the cell source and the disease mechanism match. ISSCR also describes approved stem cell treatments as those approved by the appropriate regulatory bodies, and each new advance faces that same review as it moves toward use.
The field is also closely tied to the question of what a treatment actually is. The overview in what is stem cell therapy sets out the approved, investigational and unproven categories in more depth, and it is a useful next step after this research overview.
For readers following the science, the most reliable approach is to keep three questions in view. What kind of cell is it, and does it match the tissue involved? What stage of research produced the result, and was there a control group? And has an appropriate regulator reviewed it? ISSCR also strongly encourages patients and families to discuss any treatment they may be considering, including an experimental treatment, with a physician who is familiar with their individual circumstances.
Frequently asked questions
What is the difference between stem cell research and stem cell therapy?
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Research is the work of studying cells, building models and running studies. Therapy is a medical treatment that has been shown, through regulated testing, to be safe and effective for a specific condition. ISSCR notes that very few stem cell therapies are currently proven.
Why are induced pluripotent stem cells important to researchers?
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They are made from ordinary cells such as skin cells, so researchers can obtain pluripotent cells without using embryos and can build cell models of specific diseases. The Nobel announcement for the discovery says it created new opportunities to study diseases and develop methods for diagnosis and therapy.
Does a listing in a trial registry mean a treatment is approved?
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No. The FDA states that a product being included in the clinicaltrials.gov database does not mean the product is legally marketed. A listing only shows that a study has been registered.
Are cells taken from a person’s own body automatically safe to use?
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No. ISSCR points out that collecting, growing and returning cells carries risks, including contamination and interference with normal cell function, even when the cells come from the same person.
Where can a reader learn how research becomes medicine?
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ISSCR publishes a plain-language overview of the path from basic research to preclinical and clinical research at its patient education site, and the FDA publishes consumer pages on regenerative medicine products. A licensed physician can help apply any of that information to an individual situation.
