Short answer
Conditioned media is the liquid collected after stem cells have been cultured in it, with the cells removed. It contains what the cells released: soluble proteins such as growth factors and cytokines, plus extracellular vesicles. Exosomes are a type of extracellular vesicle that can be separated from conditioned media. Put simply, conditioned media is the whole mixture; exosomes are one fraction of it.
Key takeaways
- Mesenchymal stem cells act partly through what they release, known as the secretome.
- Conditioned media is the cell-free liquid containing that secretome; its composition depends on cell source and culture conditions.
- The MISEV2023 guidelines recommend the umbrella term “extracellular vesicles” unless a vesicle’s origin is shown; many “exosome” products are better described as small extracellular vesicles.
- Whichever you consider, ask for source, processing method, batch characterisation and regulatory status in your market.
The secretome in brief
Much of the interest in mesenchymal stem cells comes from paracrine signalling: the cells release proteins, lipids and vesicles that act on neighbouring cells. This collection of released factors is called the secretome, and it has become a focus for cell-free approaches in regenerative medicine[1].
What is conditioned media?
To make conditioned media, stem cells are grown in culture, the growth medium is usually replaced with a fresh (often serum-free) medium, and the cells are left to “condition” it for a set period. The liquid is then collected, the cells and debris are removed, and it may be filtered or concentrated.
Because it captures everything released, its composition varies with the cell source, donor, passage, oxygen level and conditioning time. That variability is why batch characterisation matters.
What are exosomes?
Extracellular vesicles (EVs) are particles released from cells, enclosed by a lipid bilayer, that cannot replicate on their own[2]. “Exosome” strictly refers to EVs that originate from a specific internal cell pathway. Because this origin is hard to prove, the MISEV2023 guidelines recommend the umbrella term “extracellular vesicles”, or size-based terms such as “small EVs”, unless the origin is demonstrated[2].
EVs are separated from conditioned media by methods such as ultracentrifugation, size-exclusion chromatography or tangential flow filtration, then characterised by particle size and concentration, protein markers and imaging.
Side-by-side comparison
| Conditioned media | Exosomes (small EVs) | |
|---|---|---|
| What it is | Cell-free liquid after culture | Vesicles isolated from that liquid |
| Main contents | Growth factors, cytokines, other proteins and EVs | Vesicles carrying proteins, lipids and RNA |
| Processing | Collection, cell removal, filtration or concentration | Additional separation and purification steps |
| Characterisation | Protein content, key growth factors, sterility | Particle size and count, EV markers, purity |
| Main challenge | Batch-to-batch variability | Standardised isolation and accurate labelling |
Questions to ask about any product
- Which cells produced it, and how were donors screened? MSC identity should meet ISCT criteria[4].
- Was conditioning done in serum-free medium?
- How were cells removed, and how were vesicles isolated, if relevant?
- What is measured for each batch: protein content, particle count, sterility, endotoxin?
- What is the product’s registration or notification status in your market?
A note on regulation
Rules differ by market and by product category. In the European Union, for example, cells, tissues or products of human origin are on the list of substances prohibited in cosmetic products[3]. Other markets apply their own rules. In Malaysia, check the product’s status with the National Pharmaceutical Regulatory Agency (NPRA) for its category before use or sale.
Frequently asked questions
Are exosomes better than conditioned media?
They are different rather than better or worse. Conditioned media contains the full secretome; exosome products isolate one fraction. Which suits a purpose depends on the use, the evidence and how well the product is characterised.
Does conditioned media contain living cells?
No. Cells are removed after conditioning. A supplier should be able to show how cells and debris were removed and confirm it in quality control.
What does “exosome” on a label usually mean?
Often it means small extracellular vesicles. Ask for characterisation data such as particle size, particle count and EV markers to understand what the product actually contains.
References
- Vizoso FJ, Eiro N, Cid S, Schneider J, Perez-Fernandez R. Mesenchymal stem cell secretome: toward cell-free therapeutic strategies in regenerative medicine. Int J Mol Sci. 2017;18(9):1852. https://doi.org/10.3390/ijms18091852
- Welsh JA, Goberdhan DCI, O’Driscoll L, et al. Minimal information for studies of extracellular vesicles (MISEV2023): from basic to advanced approaches. J Extracell Vesicles. 2024;13(2):e12404. https://doi.org/10.1002/jev2.12404
- Regulation (EC) No 1223/2009 of the European Parliament and of the Council on cosmetic products, Annex II (list of prohibited substances). https://eur-lex.europa.eu/eli/reg/2009/1223/oj
- 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
Links accessed 2 October 2026.
Responsible for the cell culture process and quality records at every passage.
Reviews clinical usage standards and works directly with physicians at partner hospitals and clinics.
This article is for general information and education and is not medical advice. Decisions about any cell therapy should be made with a registered physician. Meet the team