Stem cells are cells that can renew themselves and can develop into more specialized cell types.[1] Stem cell therapy, as the International Society for Stem Cell Research (ISSCR) defines it, uses stem cells, or the specialized cells made from them, to replace or repair a patient’s damaged or missing cells or tissues.[2] Very few such treatments have been proven safe and effective. The best-established is blood-forming (hematopoietic) stem cell transplantation for certain blood and immune disorders and to rebuild the blood system after some cancer treatments; some bone, skin and corneal injuries are also treated with tissue grafts. The ISSCR advises that all other uses be considered highly experimental.[2] This page explains what stem cells are, where they come from, which treatments are established and how to judge a clinic’s claims. Current research is reviewed on our page on stem cell research.
What are Stem Cells?
Scientists group stem cells into two main categories. Pluripotent stem cells, which include embryonic stem cells and induced pluripotent stem cells made in the laboratory, can give rise to all of the cell types of the adult body. Adult stem cells, also called somatic stem cells, live in a particular tissue or organ and make the specialized cell types of that tissue.[1] Despite the name, they are not limited to adults: umbilical cord blood collected at birth is a source of blood-forming stem cells.[3]
When a stem cell divides, its two daughter cells may both remain stem cells, one may remain a stem cell while the other becomes more specialized, or both may become more specialized. A cell usually passes through several stages on the way to its final type, becoming more specialized at each step, in response to signals from other cells and its surroundings.[1] These intermediate stages are described on our pages on progenitor cells and differentiation.
Two Defining Properties of Stem Cells
- Self-renewal. Unlike most muscle, blood or nerve cells, which do not normally divide, stem cells can divide many times while keeping a stock of stem cells in the tissue. In adult tissues they may stay quiet for long periods until they are needed to maintain or repair the tissue.[1]
- Potency. Potency is the range of cell types a stem cell can make. A totipotent cell, such as the fertilized egg, can form an entire organism, including the membranes and tissues outside the embryo.[4] A pluripotent cell can give rise to cells of all three germ layers: ectoderm and endoderm and mesoderm.[5] A multipotent cell is committed to several cell types of one tissue or family;[6] the blood-forming stem cell, which grows into white blood cells, red blood cells and platelets, is an example.[7] Cells limited to a few closely related types, such as the myeloid and lymphoid progenitors of the blood, are called oligopotent.
Definitions of these and many related words are collected in our stem cell glossary.
A Short History of Stem Cell Research
The idea of a stem cell is older than the experiments that proved such cells exist. The main steps are set out below.
| Year | Step |
|---|---|
| 1868 and 1877 | The German zoologist Ernst Haeckel used the word Stammzelle (stem cell), first for single-celled organisms he believed were the ancestors of all multicellular life, and later for the fertilized egg as the cell from which all other cells of the body stem.[8] |
| 1909 | The hematologist Alexander Maximow proposed that one common stem cell gives rise to all types of blood cells, in embryos and after birth.[8] |
| 1957 | E. Donnall Thomas and colleagues reported intravenous infusions of bone marrow into patients receiving radiation and chemotherapy.[9] |
| 1959 | Georges MathΓ© and colleagues reported transfusions and grafts of donor bone marrow in people accidentally exposed to high doses of radiation.[10] |
| Early 1960s | James Till and Ernest McCulloch showed in irradiated mice that injected marrow cells form colonies in the spleen, each derived from one blood-forming stem cell.[11][8] Their spleen colony assay was the first quantitative test for blood stem cells.[8] |
| 1989 | Doctors reported restoring blood formation in a patient with Fanconi anemia using umbilical cord blood from a tissue-matched sibling.[12] |
| 1998 | The first human embryonic stem cell lines were grown from blastocysts; after months in culture they could still form tissues of all three germ layers.[13] |
| 2006 and 2007 | Shinya Yamanaka’s group reprogrammed mouse and then adult human skin cells into induced pluripotent stem cells by adding four genes (Oct3/4, Sox2, Klf4 and c-Myc).[14][15] |
Global Stem Cell Therapies (Since 2004)
This local snapshot shows worldwide relative search interest for the stem cell therapy topic from 2004 through August 9, 2026.
What is Stem Cell Therapy?
Blood-forming stem cell transplants. A stem cell transplant restores blood-forming stem cells in people whose own cells have been destroyed by the high doses of chemotherapy or radiation used to treat certain cancers, blood disorders and autoimmune disorders. Most of the cells used come from the bloodstream; others come from bone marrow or umbilical cord blood.[7] As of November 2026, the US Food and Drug Administration (FDA) list of approved cellular and gene therapy products, content current as of 30 October 2026, includes nine cord blood products of blood-forming stem cells and omidubicel (OMISIRGE).[16] OMISIRGE is approved to shorten the time to neutrophil recovery and reduce infections in people aged 12 and older with blood cancers who are planned for a cord blood transplant, and for people aged 6 and older with severe aplastic anemia.[17]
Mesenchymal stromal cells. Mesenchymal stromal cells (MSCs) are cells that stick to plastic in culture, carry the surface markers CD105, CD73 and CD90 but not blood-cell markers, and can form bone, fat and cartilage cells in the laboratory.[18] The only MSC product on the FDA list is remestemcel-L (RYONCIL).[16] Japan has approved six MSC products, each for one narrow use, two of them with conditional, time-limited approval.[19] Outside approved products and their stated uses, MSC treatment is investigational. How MSCs act in the body is still being studied, including through the molecules they release, described on our page on the secretome.
Cells made from pluripotent stem cells. The FDA list includes no product made from embryonic or induced pluripotent stem cells.[16] In March 2026, Japan gave conditional, time-limited approval to the first two: AMCHEPRY, aggregates of dopamine-producing nerve precursor cells made from donor induced pluripotent stem cells, for motor symptoms of Parkinson’s disease that respond inadequately to medicines, and RiHEART, sheets of heart muscle cells made from donor induced pluripotent stem cells, for severe heart failure caused by ischemic cardiomyopathy that responds inadequately to standard care.[19] Pluripotent stem cells themselves are not good candidates for direct use as a treatment: they must first be carefully directed to become the specific cell type needed, because if they are not properly directed they can overgrow and form tumors.[2]
Gene therapy, which modifies a patient’s cells with genetic sequences or other means to treat or reverse disease, is a related field.[20] One gene therapy on the FDA list, ROCTAVIAN, is approved for adults with severe hemophilia A, an inherited lack of the clotting protein factor VIII.[16][21] Gene therapy is covered on our page on gene therapies and precision medicine.
Where are Stem Cells Found?
Stem cells used in treatment can come from the patient (autologous) or from a donor (allogeneic); for a donor transplant of blood-forming cells, the donor’s tissue type must match the patient’s as closely as possible.[3] The main collection sources are:
- Bone marrow. Cells are drawn out with a thick needle inserted through the skin into the hip bone (the iliac crest), under anesthesia. Collection takes an hour to 90 minutes, and the area may feel stiff or sore for a few days.[3]
- Peripheral blood. For four to five days beforehand, the donor receives a medicine that increases the number of stem cells in the bloodstream; the blood then passes through a machine that removes the stem cells and returns the rest (apheresis), which takes 4 to 6 hours. The medicine can cause flu-like symptoms and bone and muscle aches.[3]
- Umbilical cord blood. Blood is collected from the umbilical cord and placenta after the baby is born and the cord has been cut, with no risk to mother or baby. Because only a small amount can be collected, these cells are used mostly for children and small adults.[3] Banking is covered on our pages on cord blood stem cells and cell collection and cryopreservation.
- Fat (adipose tissue). Fat removed by liposuction contains a stromal cell population that, like bone marrow MSCs, can form bone, fat, cartilage and muscle-type cells in the laboratory.[22] Fat-derived cell preparations are described on our page on stromal vascular fraction; the FDA lists fat-derived stromal vascular fraction among the products marketed without approval.[23]
- Dental pulp. The pulp of baby teeth that are falling out and of surgically removed wisdom teeth contains mesenchymal stromal cells, but the American Academy of Pediatric Dentistry states that no treatment using harvested dental stem cells is currently available in humans.[24]
A patient’s own cells are not automatically safe. Cells removed from the body can be contaminated by viruses, bacteria or other organisms, processing can interfere with their normal function, including the controls on their growth, and some clinics inject cells into places where they do not belong.[2]
Stem Cell Scams & Warnings
Unproven stem cell treatments are sold in many countries, often marketed directly to patients online with testimonials rather than evidence. They carry real risks, may make a patient ineligible for later clinical trials, and their costs, including travel and accommodation, are usually not covered by insurers or government health programs.[2] The FDA has received reports of blindness, tumor formation and infections after products used without approval, and it states that no regenerative medicine therapy is approved for conditions such as ALS, Alzheimer’s or Parkinson’s disease, stroke, heart disease, emphysema or COPD, osteoarthritis, or back, knee or shoulder pain.[23] Warning signs named by the ISSCR and the FDA include:
- a treatment offered without regulatory approval or outside a registered clinical trial;[2]
- the same cells offered for many unrelated diseases, or cells taken from a part of the body unrelated to the condition;[2]
- claims that injected cells will somehow know where to go and what to repair;[2]
- testimonials in place of published results, and risks that are glossed over or minimized;[2]
- being asked to pay to take part in a study: in a responsible clinical trial, the cost of the new treatment and its monitoring is not charged to the participant;[2]
- a listing on ClinicalTrials.gov or a registration with the FDA presented as approval; neither means a product is legally marketed.[23]
No stem cell treatment works for every disease. Tissue-specific stem cells make only the cell types of their own tissue without careful manipulation in the laboratory, so the same treatment is unlikely to work for diseases of different organs.[2] What a written treatment quote should include is explained on our page on stem cell therapy cost.
How to Read a Stem Cell Claim
Laboratory studies, animal studies and human clinical studies answer different questions, and an approach that looks promising in the laboratory may fail in animals, or work in animals and fail in people.[2] The first induced pluripotent stem cells were made from mouse cells, and the test that showed they were pluripotent was that, injected under the skin of mice, they formed tumors containing tissues of all three germ layers;[14] this is why undifferentiated pluripotent cells are not given to patients.[2] When reading a claim, a news report or an article in a medical journal, these questions help:
- Which cells exactly were used, where did they come from, and how were they prepared and tested?
- Were the people treated similar to you, how many were there, and was there a comparison group that did not receive the cells?
- Have the results been published in full, including any that were negative?
- Is the treatment approved for this condition by a named regulator, or is it being tested in a registered trial with regulatory and ethics oversight?[2][23]
The ISSCR recommends discussing any such information with your own doctor and healthcare team before deciding.[2]
Published Clinical Citations
[1] ^ National Institutes of Health. Stem Cell Basics. NIH Stem Cell Information. https://stemcells.nih.gov/info/basics/stc-basics
[2] ^ International Society for Stem Cell Research. Nine Things to Know About Stem Cell Treatments. About Stem Cells. https://www.aboutstemcells.org/stem-cells-medicine/nine-things-to-know-about-stem-cell-treatments/
[3] ^ National Cancer Institute. Donating Blood Stem Cells for Stem Cell Transplants. https://www.cancer.gov/about-cancer/treatment/types/stem-cell-transplant/donating-blood-stem-cells
[4] ^ National Library of Medicine. Totipotent Stem Cells (MeSH descriptor D039901). Medical Subject Headings. https://meshb.nlm.nih.gov/record/ui?ui=D039901
[5] ^ National Library of Medicine. Pluripotent Stem Cells (MeSH descriptor D039904). Medical Subject Headings. https://meshb.nlm.nih.gov/record/ui?ui=D039904
[6] ^ National Library of Medicine. Multipotent Stem Cells (MeSH descriptor D039902). Medical Subject Headings. https://meshb.nlm.nih.gov/record/ui?ui=D039902
[7] ^ National Cancer Institute. Stem Cell Transplants in Cancer Treatment. https://www.cancer.gov/about-cancer/treatment/types/stem-cell-transplant
[8] ^ Maehle AH. Ambiguous cells: the emergence of the stem cell concept in the nineteenth and twentieth centuries. Notes and Records of the Royal Society of London. 2011;65(4):359-378. https://doi.org/10.1098/rsnr.2011.0023
[9] ^ Thomas ED, Lochte HL, Lu WC, Ferrebee JW. Intravenous infusion of bone marrow in patients receiving radiation and chemotherapy. New England Journal of Medicine. 1957;257(11):491-496. https://doi.org/10.1056/NEJM195709122571102
[10] ^ MathΓ© G, Jammet H, Pendic B, et al. Transfusions et greffes de moelle osseuse homologue chez des humains irradiΓ©s Γ haute dose accidentellement (Transfusions and grafts of homologous bone marrow in humans after accidental high dosage irradiation). Revue FranΓ§aise d’Γtudes Cliniques et Biologiques. 1959;4(3):226-238. https://pubmed.ncbi.nlm.nih.gov/13646287/
[11] ^ Becker AJ, McCulloch EA, Till JE. Cytological demonstration of the clonal nature of spleen colonies derived from transplanted mouse marrow cells. Nature. 1963;197:452-454. https://doi.org/10.1038/197452a0
[12] ^ Gluckman E, Broxmeyer HA, Auerbach AD, et al. Hematopoietic reconstitution in a patient with Fanconi’s anemia by means of umbilical-cord blood from an HLA-identical sibling. New England Journal of Medicine. 1989;321(17):1174-1178. https://doi.org/10.1056/NEJM198910263211707
[13] ^ Thomson JA, Itskovitz-Eldor J, Shapiro SS, et al. Embryonic stem cell lines derived from human blastocysts. Science. 1998;282(5391):1145-1147. https://doi.org/10.1126/science.282.5391.1145
[14] ^ Takahashi K, Yamanaka S. Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors. Cell. 2006;126(4):663-676. https://doi.org/10.1016/j.cell.2006.07.024
[15] ^ Takahashi K, Tanabe K, Ohnuki M, et al. Induction of pluripotent stem cells from adult human fibroblasts by defined factors. Cell. 2007;131(5):861-872. https://doi.org/10.1016/j.cell.2007.11.019
[16] ^ US Food and Drug Administration. Approved Cellular and Gene Therapy Products. Content current as of 30 October 2026. https://www.fda.gov/vaccines-blood-biologics/cellular-gene-therapy-products/approved-cellular-and-gene-therapy-products
[17] ^ US Food and Drug Administration. OMISIRGE (omidubicel-onlv). Content current as of 12 February 2026. https://www.fda.gov/vaccines-blood-biologics/omisirge
[18] ^ Dominici M, Le Blanc K, Mueller I, et al. Minimal criteria for defining multipotent mesenchymal stromal cells. The International Society for Cellular Therapy position statement. Cytotherapy. 2006;8(4):315-317. https://doi.org/10.1080/14653240600855905
[19] ^ Pharmaceuticals and Medical Devices Agency (Japan). List of Approved Regenerative Medical Products, April 2015 to July 2026. https://www.pmda.go.jp/files/000283257.pdf
[20] ^ National Library of Medicine. Genetic Therapy (MeSH descriptor D015316). Medical Subject Headings. https://meshb.nlm.nih.gov/record/ui?ui=D015316
[21] ^ US Food and Drug Administration. ROCTAVIAN (valoctocogene roxaparvovec-rvox). Content current as of 8 October 2025. https://www.fda.gov/vaccines-blood-biologics/roctavian
[22] ^ Zuk PA, Zhu M, Ashjian P, et al. Human adipose tissue is a source of multipotent stem cells. Molecular Biology of the Cell. 2002;13(12):4279-4295. https://doi.org/10.1091/mbc.e02-02-0105
[23] ^ US Food and Drug Administration. Important Patient and Consumer Information About Regenerative Medicine Therapies. Content current as of 8 April 2024. https://www.fda.gov/vaccines-blood-biologics/consumers-biologics/important-patient-and-consumer-information-about-regenerative-medicine-therapies
[24] ^ American Academy of Pediatric Dentistry. Policy on using harvested dental stem cells. The Reference Manual of Pediatric Dentistry. American Academy of Pediatric Dentistry; 2026:222-223. https://www.aapd.org/globalassets/media/policies_guidelines/p_stemscells26.pdf
[25] ^ Goebel HH, Walther G, Meuth M. Fresh cell therapy followed by fatal coma. Journal of Neurology. 1986;233(4):242-247. https://doi.org/10.1007/BF00314028
