Clinics often say "stem cells" as if there were only one kind. In reality, there are several very different types of stem cells, each with its own source, abilities, risks and level of evidence. Knowing the difference is the first step in judging any treatment offer. This guide explains the main types, from mesenchymal stem cells and umbilical cord stem cells to induced pluripotent stem cells (iPSCs) and cells derived from embryonic stem cells, and which of them are approved or still in clinical trials.
What makes a cell a stem cell?
A stem cell has two key abilities: it can renew itself by dividing, and it can develop into other, more specialised cell types. Stem cells are grouped by how many cell types they can become:
Pluripotent: can become almost any cell type in the body. Embryonic stem cells and iPSCs belong here.
Multipotent: can become a limited family of cells. Blood-forming stem cells and mesenchymal stem cells belong here.
In general, the more types of cells a stem cell can become, the more carefully it must be controlled before it is used in people.
1. Hematopoietic (blood-forming) stem cells
These cells live in the bone marrow and produce all blood cells. They can also be collected from blood or from umbilical cord blood. Hematopoietic stem cell transplantation is the most established stem cell therapy in medicine and has been used for decades for leukaemia, lymphoma, multiple myeloma and other blood and immune disorders. Autologous hematopoietic stem cell transplantation is also studied, and used in specialised centres, for highly active multiple sclerosis.
2. Mesenchymal stem cells (MSCs)
Mesenchymal stem cells, also called mesenchymal stromal cells, are the most widely studied cells in regenerative medicine. They can be obtained from:
Bone marrow
Adipose (fat) tissue
Umbilical cord tissue (Wharton's jelly), donated after healthy births
Research shows that MSCs work mainly by releasing signals that calm inflammation and support the body's own cells, rather than by turning into new tissue. They are studied in knee osteoarthritis, autoimmune diseases, lung and heart conditions and more. In December 2024, the US FDA approved the first MSC therapy (Ryoncil) for children with steroid-refractory acute graft-versus-host disease. For most other conditions, MSC treatments are still investigational.
3. Umbilical cord stem cells
The umbilical cord provides two different types of stem cells:
Cord blood stem cells: mainly blood-forming stem cells, used in transplants for certain blood disorders.
Cord tissue MSCs: mesenchymal stem cells from Wharton's jelly. They are young cells, can be expanded in the laboratory and tested before use, and are a common source in clinical research.
Because they come from donated tissue after birth, umbilical cord stem cells do not raise the ethical questions linked to embryos.
4. Induced pluripotent stem cells (iPSCs)
Induced pluripotent stem cells are adult cells, for example skin or blood cells, that have been "reprogrammed" in the laboratory back into a pluripotent state. This discovery earned the 2012 Nobel Prize in Physiology or Medicine. iPSCs can then be turned into specific cell types such as nerve, heart or eye cells.
In March 2026, Japan granted a conditional, time-limited approval to an iPSC-derived dopamine neuron therapy for Parkinson's disease. Most other iPSC-based therapies are in clinical trials. Read more in our guide: What are iPSCs?
5. Embryonic stem cells and embryonic-derived cells
Embryonic stem cells come from the inner cell mass of a blastocyst, an early embryo about five to six days after fertilisation, usually donated from IVF treatment. They are pluripotent and can become almost any cell type.
Undifferentiated embryonic stem cells are not injected into patients, because of the risk of uncontrolled growth. Instead, researchers first turn them into specialised, fully differentiated cells, such as dopamine-producing neurons, retinal pigment cells or insulin-producing cells, and test them carefully. Examples in clinical development include:
Parkinson's disease: embryonic stem cell-derived dopamine neurons, which have moved from early safety studies into a large randomised phase 3 trial.
Eye diseases: retinal cells derived from embryonic stem cells for macular degeneration, in clinical trials.
Type 1 diabetes: stem cell-derived islet cells, with promising results in recent trials.
These therapies are offered only within clinical trials, and their use is regulated differently from country to country. In the European Union, they are classified as Advanced Therapy Medicinal Products (ATMPs). You can also read our article on fetal vs embryonic stem cells.
Comparison: which type is used for what?
Hematopoietic stem cells: approved standard treatment for many blood disorders.
Mesenchymal stem cells: one approved indication in the US; widely studied for inflammatory, joint and autoimmune conditions.
Umbilical cord cells: cord blood is used in transplants; cord tissue MSCs are mainly used in clinical research.
iPSCs: first conditional approval in Japan; most uses in clinical trials.
Embryonic-derived differentiated cells: clinical trials only, including late-stage trials in Parkinson's disease.
Questions to ask about any stem cell treatment
Which exact type of cells will be used, and from which source?
In which laboratory are they prepared, and how are they tested?
Is the treatment approved, or offered within a clinical study? If a study, what is its registration number?
Which published results support this cell type for my condition?
What are the risks, and what can realistically not be promised?
Frequently asked questions
What are the main types of stem cells?
The main types used in medicine are hematopoietic (blood-forming) stem cells, mesenchymal stem cells, umbilical cord stem cells, induced pluripotent stem cells (iPSCs) and cells derived from embryonic stem cells.
Which type of stem cell is best?
There is no single best type. The right choice depends on the condition, the evidence for that specific cell type, safety, and the regulatory framework. A doctor should explain why a particular cell type is suggested for your case.
Are embryonic stem cells used in treatment?
Undifferentiated embryonic stem cells are not used directly. Specialised cells derived from them are being tested in clinical trials, for example in Parkinson's disease and eye diseases.
Are umbilical cord stem cells safe?
In clinical studies, cord tissue MSCs have generally shown a good safety profile, provided they are prepared and tested in a qualified laboratory and given under medical supervision.
What is the difference between MSCs and iPSCs?
MSCs are multipotent adult or cord-derived cells that mainly act by calming inflammation. iPSCs are reprogrammed pluripotent cells that can become almost any cell type and are used to produce specific replacement cells.
Get an honest medical opinion
Regenova BioTech is a regenerative medicine clinic in Sofia, Bulgaria, inside the European Union. Every case starts with a free review of your medical records, and we explain openly what is and is not realistic for your condition. See the conditions we assess, or read our guide to stem cell therapy in Bulgaria.
Send your medical reports for a free, no-obligation review via WhatsApp at +49 176 5689 1000 or through our contact form.
This article is for general information and does not replace individual medical advice. Medically reviewed by Dr. Younis Yaseen, Medical Director, Regenova BioTech.
References
U.S. Food and Drug Administration. Approved Cellular and Gene Therapy Products (Ryoncil, December 2024).
Tabar V, et al. Phase I trial of hES cell-derived dopaminergic neurons for Parkinson's disease. Nature. 2025.
BlueRock Therapeutics. Bemdaneprocel phase 3 exPDite-2 trial announcement, January 2025.
Sumitomo Pharma. Conditional, time-limited approval of AMCHEPRY (raguneprocel) in Japan, March 2026.
Takahashi K, Yamanaka S. Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures. Cell. 2006;126:663-676.
Regulation (EC) No 1394/2007 on advanced therapy medicinal products.
