Name: Stem Cells
Rating: 4.4 (216 reviews)
Author: Jonathan Slack

What’s in it for me? Everything you always wanted to know about the science of stem cells.

We’ll all grow old and die one day. It’s inevitable. But along the way, wouldn’t it be ideal to avoid as many of the disabilities and diseases associated with old age as possible?

Medical conditions like Alzheimer’s disease or a stroke can be life-changing, and it’s only natural to hope for a “miracle cure” if you or a loved one are affected. But many claim that this miracle might already be here, in the form of stem cell therapy. As a result, a great deal of research – and a large sum of money – is now focused on this very area. But is it worth all the hype?

In this Blink to Jonathan Slack’s Stem Cells, we’ve kept medical jargon and technical aspects to a minimum. Instead, we focus on what stem cells are, the limitations of current stem cell treatments, and the potential for treatments in the future – all in an effort to get to the bottom of this complex science.

In this Blink, you’ll also discover

why embryonic stem cells only exist in tissue cultures;
what “the quickening” refers to; and
the difference between pluripotent and tissue-specific stem cells.

Stem cells

Before we dive into what exactly stem cells are, let’s start with some basics. Cells – measuring no more than .02 mm in diameter – are the building blocks of any plant or animal. Human bodies have around 200 visually different types of cells. Most of these are known as differentiated cells. This means that they have specific functions and can be clearly identified from their appearance under a microscope. Typical examples include our liver cells, brain cells, and heart muscle cells.

Then there are the undifferentiated cells. These have a more generic appearance. But appearances can be deceptive – some of these cells may also be specialized to perform specific functions. For instance, undifferentiated cells can also be found in embryos and develop into differentiated cells as the embryo grows. Unfortunately, they’re also found in some cancers, where their unrestricted growth capacity can spell bad news.

Some, but not all, undifferentiated cells are what we know as stem cells.

The defining characteristic of stem cells is that they’re able to reproduce themselves and generate offspring that become differentiated cells. They usually exist in an organism for the entirety of its life, inhabiting places like the skin, blood, and lining of the intestines.

To examine these cells, let’s take a closer look at skin. The top layer of your skin, the epidermis, is made up of cells called keratinocytes. During the course of the day, these wear away. So, to maintain your skin, new cells are created by stem cells found in your skin’s basal layer. Some of these cells become new stem cells; others mature and develop into new keratinocytes to replenish the old, injured, or dead cells. The epidermis is what’s called a renewal tissue because it’s continually being renewed. Without these tissue-specific stem cells, that wouldn’t be possible.

The most famous stem cells are now embryonic stem cells, or ES cells. It’s this type of stem cell that’s usually the cause of controversy – and what most people think of when stem cell research is mentioned. But, in reality, ES cells don’t actually exist in nature. They’ve been created by scientists and only exist as tissue cultures kept in laboratories.

ES cells are produced from cells found in early embryos and are capable of producing differentiated cells that can divide without limit – making them pluripotent. They're versatile: they can either divide to create more stem cells or transform into any other type of cell in the body. But not all cells in an embryo are stem cells. Once an embryo has matured, its cells are no longer considered stem cells because they develop into other cell types within just a few days.

OK, that was a lot. To wrap up this first chapter, let’s quickly review the differences between embryonic stem cells and tissue-specific stem cells. Embryonic stem cells are pluripotent, which means they can form any cell type found in the body. Tissue-specific stem cells, on the other hand, aren’t pluripotent – they’re only able to produce cells of the tissue type from which they originate.

In the next few chapters, we’re going to dive deeper into these stem cell types and their possible applications.

Embryonic stem cells

As we’ve already mentioned, embryonic stem cells typically cause the most ethical and political debates – especially human ES cells.

Opponents of stem cell research often argue that preimplantation embryos should have full human rights and that using them to make ES cells is tantamount to murder. Usually, the reasoning is based on religious grounds. Modern-day Catholics, for instance, believe that human life begins at fertilization. Interestingly, this wasn't always the case. In the Middle Ages, the Catholic Church proclaimed that the soul entered the fetus during quickening. This was when a mother first felt the fetus move – around 18 to 24 weeks. Buddhists share the modern Catholic view, while Jewish and Islamic teachings acknowledge the embryo only after 40 days have passed. For Hindus, life starts depending on when reincarnation occurs – somewhere between conception and seven months.

Pluripotent stem cells and potential therapies.

It’s 1997 and Ian Wilmut is working at the Roslin Institute near Edinburgh, Scotland. He takes the nucleus from a sheep tissue culture cell and transplants it into the enucleated oocyte of a female sheep. He then transfers the resulting embryo into the uterus of another sheep, which acts as a surrogate mother. Some 22 weeks later, a newborn lamb becomes the first-ever cloned mammal: Dolly.

Actually, successful cloning had been around long before Dolly. By the late nineteenth century, scientists had managed to clone frogs and sea urchins.

Realistic future expectations

We can all be thankful for the advances in medicine in the twentieth and twenty-first centuries. Yet future generations may look back on us with disbelief: we live in a time where spinal injuries can lead to full paralysis, where lost limbs can't be regenerated, and where heart failure and cancer can end in death.

The hype surrounding the promise of cures in the 2000s was partly a result of the controversies over human embryonic stem cells. Many politicians also believed stem cell therapy would be “the next big thing” that might rescue them from failing economies. But scientists are less optimistic about therapies; they see more value in research on embryonic development and in drug screening.

Kernaussagen in Stem Cells

Worum geht es in Stem Cells?

Stem Cells (2021) provides an introduction to stem cells – how they’re used by scientists, the therapies that exist today, and what the near future holds. It focuses on the medical and scientific consideration of stem cells and only briefly considers ethical, political, and legal aspects. This “very short introduction” is part of a series of over 650 short introductions covering myriad subjects in every discipline.