What are stem cells and how can they change medicine?

What are stem cells?

In the human body, the majority of cells are specialised for one job. This means that, even if they can be replicated, they can only make other cells like themselves. This makes them hard to manipulate for medical research.

Stem cells, on the other hand, are ideal for scientific study because they have the potential to become different kinds of cell in the body, even those with dramatically different properties. They can become anything from blood and muscle to brain and skin – and it’s this that makes them ideal for the kind of ground-breaking medical research that addresses the conditions affecting millions of people around the world.

There are a few different kinds of stem cell, but each shares the same basic properties:

1. They are unspecialised cells capable of renewing through cell division

2. They possess the power, under certain conditions, to create a different kind of cell

How can stem cells help fight disease?

Given their flexibility, stem cells offer huge potential for medicine, and it’s something that scientists have been aware of since the cells were first identified in mice. Being able to create brand new specialised cells in humans opens up huge branches of medicine and offers hope for diseases that have thus far proved impossible to treat.

If someone’s tissue is damaged by disease or injury, specialised stem cells could be transplanted to replace the damaged cells. Theoretically, stem cells could replace neurons damaged by Alzheimer’s or Parkinson’s disease, produce insulin for diabetics and even repair the heart following a heart attack.

Beyond transplants, stem cell research can also give us great insights into the workings of the human body. By studying how stem cells develop in the lab, we can observe how drugs and treatments impact human tissue without needing a living subject.

What are the different kinds of stem cells?

Stem cells are defined in a number of ways:

Embryonic stem cells

As the name suggests, embryonic stem cells come from embryos on their way to becoming human beings. How else would an embryo be able to create all the different kinds of tissue required?

As they are not specialised, embryonic stem cells have the huge advantage that they can develop into almost any type of cell in the human body, making them extremely flexible. They are described as pluripotent cells, meaning they can transform into virtually any cell type.

For scientific research, embryonic stem cells are typically fertilised in vitro and donated for research with the consent of the donor. Crucially, they are not taken from eggs fertilised in the woman’s body.

Embryonic stem cell research is considered controversial as it prevents a human being born – a controversy we’ll return to later.

Adult stem cells

Adult stem cells, on the other hand, are thought to be specific to tissue, and are also far harder to access and study. They can create different cells, but only a limited range, and this depends on where they are found. For example, epithelial stem cells continually renew the gut lining, while epidermal stem cells are thought to replace skin as it wears away. They are multipotent cells, meaning they have the power to differentiate into a finite number of cell types.

Another limitation of adult stem cells is that they don’t multiply as readily as embryonic stem cells. This makes them far less practical for stem cell replacement therapies, which require a huge number of cells.

However, one possibility – which has yet to be properly tested – is that adult cells might be at lower risk of being rejected by the host, principally because they would be harvested from the patient being operated upon. This may make them a more reliable option than embryonic stem cells, which are more readily rejected as foreign tissue.

Amniotic stem cells

One way of avoiding the controversy of embryonic stem cell collection, and to sidestep the potential drawbacks associated with the adult stem cells, is to consider amniotic stem cells. These are taken from the amniotic fluid and membrane that surrounds the fetus in a pregnant woman. The cells are removed from the amniotic sac without harming the embryo, bypassing the ethical concerns.

Induced Pluripotent stem cells

In 2006, Japanese scientists led by Shinya Yamanaka discovered a way of reprogramming mature adult stem cells to make them pluripotent – namely, his team managed to engineer adult stem cells to give them the same flexibility as embryonic stem cells, without the ethical concerns.

Yamanaka won the Nobel Prize for this discovery in 2012.

So why is stem cell research considered controversial?

The main issue is with embryonic stem cells, and the ethical question depends on when you consider life to begin.

Embryonic stem cell research involves breaking the blastocyst, meaning a potential human life is being created and then destroyed. There is plenty of debate surrounding the point at which human life begins – some would argue that as soon as the embryo is fertilised it should have full rights, but if it is not transferred to a uterus, it cannot become a child.

Others argue that the cut-off point should be 14 days after fertilisation, which is the point at which it can no longer split to become two or more babies. This is also when it begins to develop a central nervous system.

There are others who suggest that an embryo should have no rights at all. This argument centres around the embryo’s incapability to function independently of its mother, concluding that as it can’t, it’s part of the mother’s body. On the other hand, if an embryo is destroyed before it could develop, then outside influences prevent it from becoming what it was meant to be, keeping the ethical can of worms very much open.

Relativism then comes into play in this huge moral grey area: if embryonic stem cell research can save millions of lives, is the sacrifice morally justified?

Unsurprisingly, given how strongly people feel on both sides of the debate, legislation around the world is mixed, with countries enforcing different laws ranging from extremely liberal attitudes to outright bans. The UK comes somewhere in the middle with limitations in place, but research permitted to push scientific advancement forward.

What diseases can be treated with stem cells today?

Currently, the main use of stem cells in disease treatments are those involving blood stem cells – or haematopoietic stem cells – taken from bone marrow. In Europe, 26,000 patients are treated with blood stem cells each year, and bone marrow has been used with cancer patients suffering from leukaemia and lymphoma for more than 30 years.

On a smaller basis, skin stem cells have been used to grow skin grafts for victims of severe burns on large areas of the body. Historically, it’s been far from a perfect solution though, with skin created this way lacking hair follicles and sweat glands.

In September 2015, surgeons at the Moorfields Eye Hospital in London began a process aimed at curing blindness using human embryonic stem cells. The BBC reported that ten patients with age-related macular degeneration (AMD) would undergo the treatment, which involves “seeding” a small patch with eye cells and implanting it on the back of the retina. The first patient to undergo the treatment is currently recovering, but we won’t know if it has worked until the end of the year.

Where is stem cell research legal?

Due to this controversy and local attitudes, the laws regarding stem cell research vary wildly by country. Europe is split in half over this: while the likes of Britain, Sweden, Denmark, Holland, Belgium and Greece permit research, Germany, Ireland, Italy and Portugal all have laws that make stem cell research illegal. The USA is split between its states, with some banning all research outright.

Elsewhere in the world, large nations like India, China, Brazil and Australia support some forms of stem cell research, but most of Africa and South America blocks it.

What is stem cell tourism?

Seeing as the use of stem cells in medicine is far from universal around the world, an industry has built up around ‘stem cell tourism’. The idea is that people can go and get new and untested treatments for illnesses around the world.

As you might guess from the word ‘untested’, this is considered extremely dangerous, and most reputable doctors would dismiss any miracle treatments offered overseas as unlikely to help, and at worse to make things worse. Either way, stem cell tourism is widely seen as taking advantage of desperate people, but like any industry of that type, there is – sadly – money to be made.

What does the public make of stem cell research?

As you might expect, opinions differ vastly by country, but perhaps more importantly so does how well informed the population is about the benefits of stem cell research. Indeed, a 2008 survey found that while 86% of people in Denmark and Sweden had heard of stem cells, while just 33% of Japanese respondents were informed.

Even in the United States, where the debate on stem cell usage is the most politically sensitive, attitudes have changed immensely over the last, with support for embryonic stem cell research rising from 40% to 65% in just eight years between 2002 and 2010.

In the UK, a Public Attitudes to Science survey conducted last year found that 57% of Brits believe that the benefits of stem cell research outweigh the risks, while just 34% of the population felt well informed on the subject.

Images: Joseph Elsbernd, Paul Baker, and William Murphy used under Creative Commons