There are many claims that stem cells possess anti-ageing properties and other secrets to youth and regeneration. However, there has not been much scientific proof demonstrating these touted abilities.

Dr Paul Lucas, an assistant professor of orthopaedics and pathology from the New York Medical College in the United States, notes that the words “stem cells” are thrown around far too casually, and that many people assume that they are a single type of cell.

“The definition of ‘stem cell’ is an operational definition.

“That is, it describes what the cell can do, and not any particular protein or other marker it can make,” he says.

According to him, a stem cell is a cell that can:

• Differentiate into at least one phenotype (cell type), and

• Has the ability to divide, with at least one daughter cell remaining a stem cell.

What are your views on stem cells being used commercially for anti-ageing purposes? For example, there are many pills and creams made up of stem cells that are said to “reverse the ageing process”. Do you think that these are legitimate?

Lots of hype, very little biology. I have written several answers on the website Quora that address this.

Pills and creams are not legit.

The skin has a barrier called the stratum corneum that prevents bacteria from getting inside the body.

The stratum corneum will also block stem cells, which are much, much larger than bacteria, in the form of a cream.

Any stem cell will not survive in a pill with no water. And of course, any cell will not survive the hydrochloric acid in the stomach.

So there is no way “stem cells” in either a pill or a cream can get inside the body.

Even if a stem cell could get inside the body, there is very little data that any stem cell will be anti-ageing – it’s a way to separate people from their money.

There are several reasons stem cells do not counter ageing.

Stem cells are not magic. They are not magic pixie dust you can sprinkle on everything and make it be perfect.

Ageing has many causes. One of them is DNA and cellular damage.

It is thought that the various adult stem cells are the cells of origin of cancer. The data is very solid for at least hepatomas and leukaemias.

That means that stem cells can suffer mutations that alter cellular function – degrading it in some cases, and causing it to go haywire and be cancer in others.

Also, how are stem cells to be “injected”? Into each tissue? Every muscle, organ, tendon, ligament, etc?

Or are the stem cells to be injected into a vein and travel to all parts of the body?

There are two technical problems with this:

• Injecting into a vein means that most of the cells are going to be trapped in the lungs before they go out to the rest of the body, as our veins all lead first to our heart, then our lungs.

• Blood vessels are sealed tubes. Think pipes.

Just how are the stem cells supposed to exit the pipes?

This is especially true for reversing ageing in the most important organ – the brain.

The neural tissue in the brain is separated from the blood vessels by another layer of tissue called the blood-brain barrier.

Even if stem cells got out of the blood vessels in the brain, they are not going to get to the neural tissue, which is the tissue that needs to rejuvenate.

There is no way any injected stem cells are just going to magically replace all the aged cells in the body.

Stem cells are a class of undifferentiated cells that are able to differentiate into specialised cell types. Photo: 123rf.com

I read that when products use stem cells from plants, they are only using growth factors. Can you explain what this means?

Plants are very different from us. No cell from a plant is going to be able to incorporate into our tissues and act like a stem cell.

Many mammalian stem cells – particularly mesenchymal stem cells– synthesise and secrete several proteins.

Some of these proteins are “growth factors” in that they cause other cells to divide.

The claim seems to be that plant growth factors will have the same effect on human cells as they do on plant cells.

That is false.

Even some of the skincare people admit this. The following quote is from the website of a US-based skincare company that uses both human and plant stem cells: “That said, unlike human stem cells, the growth factors, cytokines and other proteins, which are the products of plant stem cells, do not have the ability to act in the same way in humans, as in plants.

“Plant stem cells communicate in a different biochemical ‘language’ that human cells do not recognise.”

What is the biggest difference between placental stem cells (PSCs) and embryonic stem cells (ESCs)?

First is the source.

ESCs are the inner cell mass of a five to seven-day-old blastocyst, which is formed after the sperm successfully fertilises the egg.

PSCs come either from the tissue of the placenta itself or from the Wharton’s jelly of the umbilical cord.

Secondly, ESCs are pluripotent, meaning they are able to differentiate into every tissue of the body. They can also form tumours in our body.

PSCs are essentially adult stem cells that have limited proliferation potential, i.e. the cell has a fixed number of times it can divide before it dies. They are multipotent, meaning that they have the ability to form more than one cell type, and do not form tumours.

Finally, stem cell injections for sports injuries (such as knee tendonitis) are common, but expensive, in Malaysia. Do you advocate this treatment over surgery and do you think this type of treatment will be less costly in the future?

Probably less costly, but no more effective.

The treatment uses mesenchymal stem cells (MSCs).

The discoverer of MSCs – Prof Dr Arnold Caplan – says they should be called “mesenchymal secreting cells”. Notice that he does not consider them stem cells!

MSCs secrete a large number of cytokines that reduce inflammation. It is inflammation that causes pain.

Aspirin, ibuprofen, and naproxen also reduce inflammation.

A “stem cell” injection with MSCs is essentially putting little aspirin factories at the site of injury.

They reduce the pain, but do little or nothing to regenerate the tissue.

For young athletes, reducing inflammation will allow the body’s healing process to work better, and thus, improve outcome.

For older patients? There is less capacity for healing.