Stem cells, exosomes, and PRP: what actually does what.

People arrive having read a great deal and having been told very little. The words are used interchangeably in advertising, the claims are frequently extraordinary, and the honest answer — that these are three quite different things at three different stages of evidence — is harder to fit on a banner.

So here is the taxonomy, without the enthusiasm.

PRP and PRF: your own blood, concentrated

Platelet-rich plasma is the simplest and the best established. Blood is drawn, spun in a centrifuge, and the platelet-dense fraction separated and re-injected into the area being treated.

Platelets are not merely clotting cells. When activated they release growth factors that recruit repair machinery to a site. Concentrating them and placing them where you want that response is the whole idea.

PRF — platelet-rich fibrin — is a variant spun differently and without anticoagulant, producing a fibrin scaffold that releases its growth factors more gradually. It is the same principle with different release kinetics.

The evidence base is the largest of the three, and it is genuinely mixed by application. It is strongest in knee osteoarthritis and in certain tendinopathies. It is used widely in hair restoration for androgenetic alopecia with supportive but less definitive data. In aesthetics it is a well-established adjunct to microneedling.

An important caveat runs through all of it: preparation methods vary enormously between clinics, and so does the resulting product. Platelet concentration, whether leukocytes are included, whether it is activated — these differ, and studies using different protocols are not directly comparable. When you read that "the evidence for PRP is inconsistent," part of what you are reading is that the treatments were not the same treatment.

PRP is not one therapy. It is a family of preparations with different compositions, which is a large part of why the literature disagrees with itself.

Exosomes: the message without the messenger

Cells communicate partly by releasing extracellular vesicles — tiny membrane-bound packages carrying proteins, lipids and genetic material such as microRNA. Exosomes are a subclass of these.

The insight driving the field is that much of what mesenchymal stem cells appear to do may be accomplished not by the cells themselves but by what they secrete. If the signal is the active ingredient, you may not need the cell.

The appeal is obvious. A vesicle preparation is not a living cell, which simplifies handling and storage and avoids some of the concerns that attach to cell therapy.

The honest position on evidence: the preclinical work is substantial and interesting. Human clinical data is early, and this is an area where marketing has run ahead of what has been demonstrated. Regulatory status matters too — in the United States, exosome products are not FDA-approved for treating disease, and the agency has issued public warnings about clinics marketing unapproved exosome therapies.

I discuss exosomes with patients as an area of genuine scientific promise where the human evidence is still being built. Anyone presenting them as established for a broad list of conditions is telling you something the literature does not currently support.

Mesenchymal stem cells: the most claimed, the most complicated

Mesenchymal stromal cells can be obtained from bone marrow, adipose tissue, or perinatal sources such as umbilical cord tissue.

The original hope was that they would engraft and become new tissue. The current understanding is largely different: they appear to act mainly by modulating immune activity and secreting signalling factors — the paracrine effect that also underlies the interest in exosomes. Most transplanted cells do not persist long.

This is the therapy that most needs plain speaking, on two fronts.

The first is evidence. Thousands of trials have been registered. Results across indications have been inconsistent, and the strength of evidence varies enormously depending on the condition, the cell source, and the preparation. Some applications are genuinely promising. Many claims made commercially are far beyond what has been shown.

The second is regulation, and it is not a technicality. In the United States, the FDA regulates most cell products for these uses as drugs requiring approval, and very few such products are approved. Minimal manipulation and homologous use are the terms that determine which category a product falls into. The agency has taken enforcement action against clinics offering unapproved stem cell treatments, and it has documented serious adverse events including infections and, in some cases, vision loss.

So the questions worth asking any clinic — including this one — are specific. What exactly is the product. Where does it come from. What is its regulatory status. What evidence exists for my particular condition, not for the category. What is the realistic expected benefit, and what is the plan if it does not work.

A clinic that cannot answer those clearly is not one to hand money to.

How we actually think about them

We use these therapies as part of a plan, not as the plan.

PRP and PRF are the most established of the three and we use them most, particularly in joint, hair and skin applications. Where regenerative approaches are appropriate, we still expect to have addressed the things that determine whether tissue can repair at all — metabolic health, inflammation, iron and vitamin D status, sleep, load management. Injecting growth factors into a system that is inflamed and under-recovered is asking a great deal of the injection.

And we are direct about what is established versus what is emerging. That distinction is the most useful thing a clinician can offer in this field, and it is the first thing marketing removes.

This article is educational and is not medical advice, diagnosis, or treatment. Laboratory results and therapies require interpretation in the context of your history, symptoms, medications, and examination, and what is appropriate differs from person to person. Nothing here should be used to start, stop, or change any treatment. Please speak with a qualified clinician who knows your case.