So what exactly are stem cells?

As much as stem cells have been in the news, I don't think I've ever seen them defined in those reports. So, before we get into the details of how induced pluripotent stem cells are made, it's best to go over the basics.

Our bodies are made up of cells. Each of these cells, with some exceptions (red blood cells, B- and T-cells, and the gametes) contain the entirety of an organism's genome. If every cell carries the same genes, then why is a heart cell not a retina cell or a bladder cell or a skin cell? The different cell types arise during a process called differentiation. During differentiation, some genes are turned on while others are turned off. The expression pattern of the genes changes at every step of differentiation and the actions of these genes determine the fate of the cell.

Stem cells are defined by two main qualities: self-renewal and potency. Self-renewal means that they can divide many times to make more stem cells while staying undifferentiated. Potency means that, with the right signals, they can differentiate to become many different types of cells. Both of these features are of great interest to biomedical researchers. Self-renewal means they can keep stem cells in culture for a long time and continue making more as they need them. Potency means they can turn the cells into the type of specific tissue or organ they're interested in, either to study how it works or what causes a disease, or to transplant into a person to replace diseased cells.

There are different levels of potency. The most potent cell is the zygote, the first cell that's formed when an egg is fertilized by a sperm and a new organism comes into being (and the morula, which is formed by the first few cell divisions). The zygote/morula is totipotent because it can become every type of cell necessary for the organism to develop into an adult member of the species. In humans, this includes not only the 200 cell types that make up the body, but also the extra-embryonic structures (placenta, part of the amniotic sac, etc.).

A blastocyst getting ready to implant.

The morula quickly develops into a blastocyst, which consists of a hollow sphere (trophoblast, purple) with a mass of cells on the inside (the creatively named inner cell mass, green). The outer sphere becomes the placenta while the inner cell mass will go on to form the tissues of the body. At this point, the inner cell mass cells, also known as embryonic stem cells, are pluripotent, meaning the can become any type of cell in the body, but no longer become the extra-embryonic cell types.

Hematopoiesis (click here for bigger version)

The inner cell mass eventually becomes all 200 types of human cells, first by differentiating into the three germ layers, and then into more and more specific lineages. There are stem cells within these lineages that are called "adult stem cells." The word "adult" does not imply that they are only found in adult organisms, but it refers to the maturity of the cell. Adult stem cells are multipotent, meaning the can only become a subset of cell types. One example is the blood stem cell (hematopoietic stem cell), which goes through multiple steps to become different blood components: red blood cells, white blood cells, and platelets.

Now, for a very important note. I mention that adult stem cells are not only found in adult organisms because not all sources of adult stem cells are ethical. In particular, I am always wary at the mention of neuronal stem cells. As far as I am aware, the only source of human neuronal stem cells is from an aborted baby. It is possible that they might be harvested from the body of a spontaneously miscarried baby, but I have never seen confirmation of this being done.

Recently, I heard a favorite podcaster praising work using neuronal stem cells. With a sick feeling in my stomach, I looked up the article he referenced, which turned out to be from a pro-life site. They'd gotten their information from The Telegraph, which didn't mention the source of the cells, but a quick google search brought me to the same report on CNN.com, which did:

The company was looking for 12 recently paralyzed patients for a study of its product: purified human neural stems cells derived from donated fetal brain tissue.

Notice they said "from donated fetal brain tissue." Wanting to know the circumstances under which this tissue was donated, I went to the website of the company behind this stem cell line, StemCells, Inc., but the information was not posted and no amount of internet searching turned up an answer.

As I said, it's possible that the fetal tissue was from a spontaneous miscarriage...but it's unlikely. It's much easier to schedule in the harvesting of tissues during an abortion...and the tissues are much fresher.

This is why Catholics and other pro-lifers must be Pro-life 3.0. We need to be able to know the warning signs and dig deeper behind the reports. Otherwise, we risk getting duped into supporting unethical research and medical treatments.

So, back to the science. The final products of all this differentiation are the mature cells of the organs and tissues of the body, the terminally differentiated cells. And terminal they are, because they live and die as the same type of cell. It was believed there was no going back...or is there? In my next post, I'll talk about what induced pluripotent stem cells are and how they're made.

The Case for Being Pro-Life 3.0

Induced pluripotent stem cells. It's quite a mouthful just to say it. The basic science behind them isn't complicated, as I'll hopefully show in the coming posts in this series, but why is it important that non-biologist Catholics understand the science?

Despite the popular secular myth, the Catholic Church isn't anti-science. To the contrary, the argument can be made that the modern scientific method would not exist without the Catholic world view, which believes the universe to be orderly and rational (Wisdom 11:21), and acknowledges secondary causes. Additionally, the modern university owes its existence to the Church, as it grew out of the old cathedral schools.

Certainly, our two most recent popes have spoken favorably of the relationship between faith and science.

 Science can purify religion from error and superstition. Religion can purify science from idolatry and false absolutes.  -John Paul II

...there is friendship between science and faith, and...scientists can, through their vocation to study nature, follow an authentic and absorbing path of sanctity.  -Benedict XVI

Just as science cannot comment on God -- at least, it cannot comment on the God that Christians believe in, the God Who is not another being but Being Itself, Who created the laws of nature that science attempts to define and therefore exists outside of them -- the Church does not claim jurisdiction over scientific truth. However, the Church does have a lot to say about the ethics of how science is done and how technology is used.

In no field is this more obvious than the life issues. A while ago the author of the Mary Meets Dolly blog wrote about an interview with someone named Scott Rae who coined the term "Pro-life 3.0," which was explained as follows:

• Pro-life 1.0 deals with "the taking of life."  Abortion, assisted suicide, and euthanasia
• Pro-life 2.0 deals with "the making of life."  Artificial insemination, IVF, surrogacy, preimplantation genetic diagnosis, egg and sperm "donation"
• Pro-life 3.0 deals with "the remaking of life."  Genetic engineering, human enhancements, nanotechnology, human cloning, transhumanism

Pro-life 3.0 isn't something we need to worry about in the future; it's happening now. Sometimes, the ethical problems are obvious, like in the case of human-animal hybrids and three-parent children. But other times, it's only after examining the details of an experiment that unethical practices are unearthed. These practices might not be related to the goal of the experiment, but rather (sadly) routine choices, like using tissues from aborted babies.

It's important that pro-lifers be able to both uncover these ethical problems and to be able to distinguish what role they play in the research (i.e. whether the unethical action is intrinsic to the research or simply a bad decision by a particular researcher). A good example is the production of vaccines. Vaccines are not immoral in and of themselves, and their goal is laudable, but many are made in cell lines that are descended from the cells of aborted babies, not because the cell type is necessary to their production (for many, there are alternatives made in ethical cell types), but because the researchers made a decision based on economics, ease of use, etc.

To be frank, pro-lifers also need to understand the science in order to not look stupid, which keeps us from being taken seriously. When it was reported that Pepsi was employing a company that uses human embryonic kidney (HEK) cells to test flavor enhancers (thankfully, they've stopped this, though HEK cells are still widely used in many applications), you could find many raising the alarm that there were fetal cells in the soda we drink. Unfortunately, these people, who were rightly outraged about Pepsi's cooperation with evil, did not take the time to understand the science, making it easier for those who disagree to mock and dismiss them and all pro-lifers.

When Catholics don't take the time to understand the science, but jump to a rejection of a certain technology based on ignorance or a misunderstanding of the facts, it does make us seem anti-science. Instead, we need to make the effort to at least understand the basic science underlying these issues so that when we raise the alarm, we can do so in an informed and nuanced manner, and be taken seriously in our criticisms.

In my next post, I will explain what exactly stem cells are, where researchers get them from, and which ones are ethical. (Hint: not all "adult" stem cells are!)

Introduction

A few years ago, I considered starting a blog about the intersection of faith and science. In particular, I wanted to blog about issues in biology from a Catholic perspective -- but then I discovered someone was already doing that and the whole idea seemed rather redundant.

So, why am I starting this blog now? Mostly, because a couple of friends convinced me it would be a good idea. I've decided to call it "Double-Stranded" because I'm a geneticist by education, but also because I'm strongly interested in the complementarity of faith and reason, of science and theology.

Since my involvement in the conversation about the ethics of induced pluripotent stem cell (iPSC) research (and in particular, my frustration with the scientific inaccuracies that were being spread through the Catholic blogosphere -- based, I believe, on a lack of familiarity with basic biological technique) was what led to the suggestion that I blog, I'll begin with a series explaining what exactly stem cells are, where they come from (both the ethical and unethical sources -- you may be surprised!) how iPSCs are made, and why it's important that Catholics make the effort to understand the details of biological research.

As for what I'll do after that, I guess you'll just have to check back and find out.