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Short answer. Stem cell differentiation is the process by which an unspecialised cell becomes a specialised one, with some genes switched on and others off. At the bench the harder question is proof: the ISSCR Standards for Human Stem Cell Use in Research say differentiation capacity must be shown by functional, quantitative assays, because marker expression alone does not establish it.
General research information for laboratory readers; not medical advice.
Definition and scope
A stem cell is unspecialised and can give rise to other cell types; differentiation is the step that commits a cell towards a specialised identity such as neuroectoderm, mesoderm or endoderm progenitors. Potency describes how many fates a cell can reach. A pluripotent cell can give rise to all somatic lineages; a multipotent cell is restricted to a narrower family of cell types. The ISSCR describes human pluripotent stem cells (hPSCs) as unique in their undifferentiated developmental state and their potential to give rise to all somatic lineages (ISSCR Standards, Dec 2023 update, Section 2, read 2026-11-08).
This page covers the in vitro, bench-science view. For the cells themselves see embryonic stem cells and induced pluripotent stem cells.
How labs demonstrate differentiation
Functional proof comes before marker panels
The ISSCR is explicit that, for human cells, pluripotency “should be demonstrated experimentally by assays that assess differentiation capacity” (Recommendation 2.1.1). Differentiation should be shown by quantitative measurement of marker combinations representative of ectoderm, endoderm and mesoderm lineages, alongside loss of markers of the undifferentiated state. Because the definitive test (contribution to a developing embryo) is not possible for human cells, surrogate assays are used: teratoma formation or in vitro differentiation. The Standards state that xenograft (teratoma) assays are not required (Recommendation 2.1.2) and that in vitro differentiation can supply equivalent evidence.
What counts as unequivocal evidence
For a pluripotency designation, the Standards call for unequivocal evidence of differentiation into progenitors of definitive endoderm, mesoderm and neuroectoderm, and preferably further differentiation into lineage-specific cell types. Evidence should rest on multiple criteria, which may include morphology, lineage or cell-type specific mRNA or protein expression, cell surface markers and functional properties. The efficiency and extent of differentiation into each germ layer should be reported.
Why markers alone mislead
The Standards note that none of the commonly used markers is uniquely associated with pluripotent differentiation capacity. Nullipotent embryonal carcinoma cells from germ cell tumours have little or no capacity to differentiate yet express markers of undifferentiated cells including OCT4 (POU5F1) and NANOG. For that reason these should be called markers of the undifferentiated state, not “pluripotency markers”. The ISSCR adds that absence of a key marker such as OCT4 can strongly indicate loss of pluripotency but is not definitive.
Evidence checklist: what each result does and does not show
Built from the ISSCR Standards (read 2026-11-08); each row restates a recommendation or statement in that document.
| Evidence in hand | What the ISSCR Standards say it supports |
|---|---|
| Expression of undifferentiated-state markers only (for example OCT4, NANOG) | Undifferentiated status; not proof of differentiation capacity, because nullipotent cells can express them. A line monitored only this way, when others in a set have been functionally tested, is designated a “putative pluripotent line”. |
| Quantitative in vitro differentiation to endoderm, mesoderm and neuroectoderm progenitors, with loss of undifferentiated markers | Demonstration of pluripotency by differentiation capacity (Recommendation 2.1.1). |
| Further differentiation into lineage-specific cell types | Preferred additional evidence; supports a claim of differentiation into specific lineages or cell types. |
| Teratoma (xenograft) assay | Evidence of histogenesis, but not required for a pluripotency claim (Recommendation 2.1.2). |
Reporting a differentiation experiment
Section 5 of the Standards asks that tests of pluripotency and of the undifferentiated status be thoroughly described, and that published reports include the cell line source or derivation details, culture and passaging methods, and passage number (Recommendations 5.1.1 and 5.2.1). The Standards also expect developmental state to be corroborated by appropriate lineage-specific differentiation, including potential lineage biases. When the culture inputs matter, note them: see mouse embryonic fibroblast feeders and coculture systems.
Types and related concepts
- Pluripotent: capacity of a single cell to differentiate into all somatic cell types (ISSCR, Recommendation 2.1.1).
- Undifferentiated state: the developmental state maintained in culture before differentiation is induced; the Standards treat it as something to be monitored, not assumed.
- Nullipotent: stem-like cells that have lost the capacity to differentiate (ISSCR).
- Self-organising 3D outcomes: see organoids.
Common misunderstandings
- “OCT4-positive means pluripotent.” It means the cells express a marker of the undifferentiated state; functional evidence is still needed.
- “A teratoma is mandatory.” The 2023 Standards say it is not, where in vitro assays give equivalent information.
- “Differentiation is one switch.” The ISSCR asks for lineage-by-lineage evidence and reporting of efficiency, which implies outcomes vary by line and condition.
Frequently asked questions
When did my stem cells first start to differentiate?
In an embryo, cells begin to specialise as development proceeds, so there is no single answer that applies to every cell. In a culture the question is an experimental one: the Standards want undifferentiated status monitored by quantitative markers and differentiation shown by assays, so the record of your own markers and protocol is the evidence.
Which type of stem cells can differentiate the most?
Pluripotent stem cells, which can give rise to all somatic lineages, have a wider range than multipotent cells, which are restricted to a narrower set of cell types.
What can stem cells currently fix or cure in 2026?
This page does not list therapies. For research-use context, see the induced pluripotent stem cell guide. Questions about treatment belong with a qualified clinician.
What does Joe Rogan say about stem cell therapy?
This guide does not characterise any individual’s statements; it relies on published standards. For claims about a therapy, check the regulator and the primary literature.
Sources
- International Society for Stem Cell Research (ISSCR). Standards for Human Stem Cell Use in Research, December 2023 update, Sections 2 and 5 and Appendix 4. isscr.org/basic-research-standards. Read 2026-11-08. Cited in the standards: Ludwig et al. 2023, Stem Cell Reports 18(9):1744-1752.
