Stem Cell Types: A Comparison Overview

The International Society for Stem Cell Research splits stem cells into two broad functional groups: pluripotent and tissue-specific [1]. Pluripotent cells can become almost any cell type in the body. Tissue-specific cells, also called adult or somatic stem cells, are restricted to producing the cell types found in the organ they came from. Five cell types account for nearly all clinical and commercial use inside these two groups.

Embryonic stem cells (ESC) are pluripotent cells taken from the blastocyst stage of a human embryo, roughly 5 to 6 days after fertilization [1]. They can generate any of the roughly 200 cell types in the adult body. Clinical use is narrow and mostly experimental. A 2012 Lancet report described the first two patients to receive ESC-derived retinal cells for macular degeneration [7], and later trials tested ESC-derived retinal pigment epithelium patches and encapsulated pancreatic cells (see the diabetes and embryonic stem cell pages). No ESC-derived product holds full FDA or EMA approval as of this writing.

Induced pluripotent stem cells (iPSC) are adult cells, often skin or blood cells, reprogrammed in the lab to a pluripotent state. Shinya Yamanaka and Kazutoshi Takahashi did this first in mice in 2006 and in human cells in 2007, using four transcription factors now called the Yamanaka factors [2][3]. James Thomson's lab published a parallel human reprogramming method the same year. Yamanaka and John Gurdon shared the 2012 Nobel Prize in Physiology or Medicine for showing that mature cells can be pushed back to a pluripotent state [4]. iPSCs avoid the ethical debate tied to destroying embryos and can be made from a patient's own tissue, which matters for immune matching. A Kyoto University trial has already transplanted iPSC-derived dopamine neuron progenitors into people with Parkinson's disease, published in Nature in 2025 [17]. No iPSC-derived therapy has full regulatory approval yet.

Hematopoietic stem cells (HSC) sit in bone marrow and produce every blood cell type: red cells, white cells, and platelets. HSC transplantation is the oldest and most established stem cell therapy in medicine, used for decades to treat leukemia, lymphoma, and inherited blood disorders. It is also the only stem cell category with multiple full FDA licenses in the United States, specifically for cord-blood-derived hematopoietic progenitor cell products such as ALLOCORD, CLEVECORD, Ducord, and HEMACORD [5].

Mesenchymal stem cells (MSC) are multipotent, tissue-specific cells found in bone marrow, fat tissue, and umbilical cord tissue. They cannot become blood or nerve cells the way pluripotent cells can, but they secrete a wide range of signaling molecules, including growth factors, interleukin-10, TGF-beta, and exosomes carrying microRNA, that influence surrounding tissue [8][9]. This paracrine signaling, rather than the cells physically replacing damaged tissue, is the leading explanation for most observed clinical effects (see the MSC deep-dive page). MSCs are by far the most commercially marketed stem cell type in longevity and wellness clinics worldwide, despite holding only two EMA approvals globally: Alofisel for Crohn's-related anal fistulas, withdrawn from the market by its manufacturer in December 2024 [11], and the corneal product Holoclar, which uses limbal stem cells rather than MSCs [10]. No MSC product carries full FDA approval for any indication as of mid-2026.

A useful pattern across these five categories: potency and regulatory approval move in almost opposite directions. HSC transplants, the most restricted and tissue-specific cells on this list, have the deepest approval record because five decades of clinical use built an enormous safety and efficacy record for a narrow set of diseases. ESCs and iPSCs, the most flexible cells, remain mostly in early trials because their flexibility also means a higher theoretical risk of forming tumors or growing into the wrong tissue. MSCs occupy a middle position: enough mechanistic plausibility and safety data to support hundreds of trials, but a thin approval record and, as later pages in this section detail, a real placebo-effect problem in the best-studied indication, knee osteoarthritis [12].

For a comparison of clinical trial evidence quality across specific health conditions, see the evidence tier framework page.