Exosomes · 1 October 2026
Exosomes: are they all the same? What a 2026 review found
No. A review published on 23 September 2026 in the journal Cells brought together 70 studies comparing exosomes produced by different cells. The cells of origin change the content and the effects, but no source turned out to be the best overall, and almost all the evidence still comes from the laboratory and from animal studies.
In brief
What we know
- Exosomes change in content and effects depending on the cells they come from.
- No source turned out to be the best overall: the tissue, the dose and the preparation matter.
- In humans, the first studies showed acceptable safety.
What we do not know yet
- Whether they work in patients: studies with a comparison group are missing.
- Which source is best, and for which condition.
- Long-term safety and consistency from one batch to the next.
To begin
What exosomes are
Exosomes are tiny vesicles that cells release into the tissues: a membrane of fats that carries proteins, fats and nucleic acids from one cell to another. Researchers prefer the term «extracellular vesicles», because «exosome» refers only to those formed in a particular way inside the cell, which is often not demonstrated. In this article we use «exosomes», the better-known word.
The study
How the review was done
Three researchers, Yasaman Zandi Mehran, Michael Weber and Fateme Hoseinzade, searched three scientific databases (PubMed, Europe PMC and OpenAlex) for everything published up to 14 August 2026. They screened 5980 papers and, with a few additional targeted searches, kept 70: those that compare exosomes from different cells or tissues in the same experiment and with the same method.
Mesenchymal stem cells, supporting cells obtained from bone marrow, fat tissue or the umbilical cord, were included in 52 of these 70 studies. The other sources, such as cells of the immune system, the heart or the nervous system, were compared much less often.
The results
The cells of origin matter, but none always wins
In a comparison on wound healing, exosomes from bone marrow, fat tissue and umbilical cord all helped repair, but not in the same way. Those from bone marrow acted more on fibroblasts, the cells of connective tissue. Those from the cord acted more on the movement of skin cells.
No source always wins, though. In a 2021 study on cartilage and bone, exosomes from fat tissue were more active; in a 2026 study on the bones of the face and skull, those from bone marrow. In a 2025 comparison on osteoarthritis, those from bone marrow and cord did better than those from fat tissue in that experimental model. The result changes with the tissue, with the cells that receive the signal, with the dose and with how the exosomes are prepared.
The authors also note that the same property can be useful or harmful. Promoting the growth of new blood vessels or calming the immune system helps a tissue that needs repair, but is not desirable, for example, when a tumour is present.
For patients
How close we are to clinical practice
Not very. Almost all the comparisons were made in the laboratory or in animals. In humans there are early phase I and II studies that mainly checked feasibility and safety. For example, in 2024, umbilical cord exosomes were given to patients with a spinal cord injury: safety was acceptable, but the study had no comparison group. According to the authors, studies like this do not yet show a clinical benefit.
On safety they give an example: in mice, a fraction of umbilical cord exosomes injected into a vein at high doses caused blood clots in the lungs. This applies to that preparation, that dose and that route, not to all exosomes, but it shows why every product has to be assessed on its own.
The limits
What the review cannot say
It is a narrative review, not a meta-analysis: the studies were too different to pool their results. The studies were selected by a single person, and three large subscription databases (Embase, Scopus and Web of Science) were not searched. The categories the authors use to classify the evidence are their own proposal, not validated tools. The authors' conclusion is cautious: more comparisons, made with the same methods, are needed before saying which source works best, and for which condition.
Transparency. The work received no external funding and the authors declare no conflicts of interest. One of the authors, Michael Weber, works at the European Laser Academy in Recklinghausen (Germany); the «European Laser Clinics» logo appears at the bottom of this site's pages.
At the practice
PBM and exosomes
At the practice, exosomes are used together with photobiomodulation, for joints and tendons, skin and hair. The contraindications are the same as for PRP: pregnancy, an ongoing infection, an active tumour and anticoagulant therapy. Indications, protocol and studies are on the dedicated page; whether the treatment is indicated is always decided after the specialist visit.
Scientific sources
- Zandi Mehran Y, Weber M, Hoseinzade F. Not All Extracellular Vesicles Are Equal: A Narrative Comparative Review of Source-Dependent Function and Therapeutic Potential. Cells. 2026;15(19):1731. doi:10.3390/cells15191731
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