What are the possible stem cell therapy side effects of going to an unproven clinic? This is a common question I get asked. Most often it is asked by patients who reach out.

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Many clinics have said over the years to potential customers that the worst that can happen is that the stem cells wont work.

We know this isnt true and its irresponsible.

Anything that has the potential to help a medical condition also poses some risks of harm. For this reason, its important to discuss potential stem cell therapy side effects. In this case I am focusing on the risks primarily associated with unproven stem cell clinics. Not for established methods like bone marrow transplantation.

Recent publications in journals including one by my colleague Gerhard Bauer and a special report by The Pew Charitable Trust have helped clarify risks. Gerhards paper presents the types of side effects that appear more common after people go to stem cell clinics. After closely following this area for a decade I was familiar with many of the examples of problems. However, some were new to me.

One of the highest profiles examples of bad outcomes was the case where three people lost their vision due to stem cells injected by a clinic.See image below of one set of damaged eyes. More on that case at the end of the post.

Why do stem cells pose risks?

Stem cells are uniquely powerful cells.

By definition they can both make more of themselves and turn into at least one other kind of specialized cells. This latter process is called differentiation. That former ability to make more of themselves is called self-renewal.

The most powerful stem cells are totipotent stem cells that can literally make any kind of differentiated cell. The fertilized human egg is the best example of a cell having totipotency. Next in the power line are pluripotent stem cells including embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs). Adult stem cells are multipotent. The best type of stem cell depends on the condition that is trying to be treated. The best type may not be the most powerful.

In any case, the power of stem cells is a main reason they also pose risks. These cells are not always easy to control and misdirected power can do harm.

Let me explain and start with the side effect that seems scariest to most.

If someone injects a patient with stem cells, its possible that the self-renewal power of stem cells just wont get shut off. In that scenario the stem cells could drive formation of a tumor or even cancer. Note that tumors are not always malignant whereas cancer is always malignant.

Why wouldnt a transplanted stem cell always eventually hit the brakes on self-renewal? It could be that the stem cell has one or more mutations. For any stem cells grown in a lab, within the population of millions of cells in a dish, there are going to be at least a few with mutations that crop up. Thats just the way it goes with growing cells in a lab.

Even stem cells not grown in the lab have the same spectrum of mutations as the person they were isolated from. It may seem weird to think about, but we all have some mutations.

When someone like a clinic person tells us that theres a risk to you thats a one in a million chance it doesnt sound that bad. However, with cells being injected into a person in theory all it takes is one cell out of a million cells in a syringe with a couple really bad mutations to potentially cause disaster. Research suggests it takes more than one cell with cancer-causing potential to make a tumor in experiments in the lab, but in actual people we just dont know. Many cancers may arise from one stem cell gone awry. If a clinic injects 50 or 100 million cells, a one-in-a-million rate of dangerous cells means that 50-100 such cells end up in the patient.

The odds are far lower for cells never grown in a lab to cause a tumor, but its still possible. Oddly, its possible that receiving someone elses stem cells (we call this allogeneic) might pose a lower cancer risk because your immune system is going to see those cells as foreign from the start.

But some stem cells, especially those with mutations, might be able to somewhat fly under the radar of the immune system to some extent even if they are from another person. This could allow them to grow into a tumor. The Pew report does a nice job of summarizing risks and there are several reports of tumors.

The possibility of infections after stem cell injections is another risk that is often discussed. Infections from injections of stem cells or other materials like PRP are probably the most common type of side effect. Bacteria can either sometimes already be in the product that is injected or can be introduced by poor injection or preparation methods by the one doing the procedure.

The distributor Liveyon had a product contaminated with bacteria that sickened at least a dozen people who were hospitalized. Some of them ended up in the ICU. A few may even have permanent issues.

Clinics using excellent procedures and products should have a low risk of infection more similar to getting any kind of invasive procedure even unrelated to stem cells.

Many preparations of stem cells sold at stem cell clinics these days are made from fat tissue or birth-related materials. I put stem cells in quotes because most fat and birth-related preparations only contain a small population of true stem cells.

In the case of adipose biologics, they mostly consist of a mixture of a dozen or so other kinds of cells found in fat.

The injections of fat cells are most often made IV right into the bloodstream. Fat cells just live in fat so they arent supposed to be floating around in your blood. As a result, after IV injection, many fat cells are thought to get killed right away.

Others end up landing in the lungs, where many are also probably meeting their doom. However, during this process of wiping out the fat cells it is possible that clots can start forming. Maybe the fat cells form small clots in the blood before they even get into the lungs. Either way, if the clots grow and are big enough, patients can get pulmonary emboli.

The same kind of risk may apply to IV injections or nebulizer inhalations of other kinds of stem cells.

There are other possible risks to stem cell injections too.

I wrote a post about possible graft versus host disease in stem cell recipients. This would only happen in people receiving someone elses stem cells. Its not clear if GvHD is something that happens to patients after going to clinics.

Beyond outright tumor formation it is also possible that stem cells will turn into an undesired or even dangerous tissue type. The example that comes to mind is the practice mentioned earlier of some clinics injecting fat cells into peoples eyeballs. What seems to have happened in some cases is that the mesenchymal cells (MSCs) that were injected turned into scar tissue, which caused retinal detachment. Unfortunately, what are called MSCs by some clinics can mostly consist of close relatives of fibroblasts or in some cases may even largely consist of fibroblasts. Fibroblasts are good at making scar tissue under some circumstances and that can create pull on surrounding tissues including the retina if inside the body.

Specific kinds of stem cells or routes of administration may pose unique risks as well. For instance, intranasal administration of stem cells is getting popular with unproven clinics and could lead to stem cells ending up in the brain.

Other products in the regenerative sphere that are not stem cells may be risky as well for various reasons. For instance, an exosome product harmed quite a few people in Nebraska.Some problems may relate to product contamination.

There have also been cases of unusual immune reactions to stem cell injections.

Finally, stem cells also pose unknown risks because of their power. We just dont have long-term follow up data to have a clear sense of risks.

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Stem cell therapy side effects & risks: infections, tumors & more