The stem cell toolbox: The promise and problems of stem cell research

man with red tie lectures
Research Unplugged

Kent Vrana

They are debated in political campaigns and over dinner tables. They are the subject of countless newspaper editorials and television documentaries. They are, essentially, what makes you you and me me: embryonic stem cells, the precursors of every cell in our bodies.

Last Wednesday, Research Unplugged kicked off its spring season with a discussion about the use of stem cells in disease research, one of today's most emotionally-charged and fiercely-contested bioethical issues.

The controversial topic drew a crowd of community members to the Penn State Downtown Theatre, with attendees anxious to hear Kent Vrana, professor of pharmacology at the Penn State College of Medicine. Vrana's presentation, "The stem cell toolbox: The promise and problems of stem cell research," aimed to dispel common myths associated with groundbreaking research in this field.

Vrana led a lively discussion about the science of stem cells and also shared his personal beliefs on the topic. "I'm not one of those scientists who say falsely that I can cure all diseases with stem cells," he admitted at the outset. But Vrana also stated his conviction that the potential to cure some diseases is real and should be thoroughly explored.

He described the five potential sources of stem cells for research: adult stem cells, embryonic stem cells, stem cells from in vitro fertilization, amniotic/placental stem cells, and somatic cell nuclear transfer-derived embryonic stem cells (also known as therapeutic cloning). Of these, embryonic stem cells are both the most promising and the most controversial.

Vrana explained that embryonic stem cells are unique in that, unlike other cells in the body, they have not yet decided what they want to be—"just like my 14 year-old daughter," he joked. It is their totipotency—their ability to develop into any type of cell in an organism—that makes these stem cells so promising, Vrana said. "They can potentially be harvested and transformed into any tissue in the body."

The reason use of these cells is controversial, he noted, is that harvesting them requires destruction of the embryo. However, in the case of in vitro fertilization, he argued, excess embryos are routinely destroyed rather than being implanted in the womb.

"If an embryo is not put into a womb, then it can't become a baby," he added. By using cells from embryos in test tubes, scientists aren't ending a pregnancy, but rather "choosing not to begin it," he suggested. "I don't have all of the right answers," he acknowledged, "but it is very important to base our opinions on the facts."

Another hot topic in the discussion was cloning. "Therapeutic cloning is much different than reproductive cloning," said Vrana. During reproductive cloning, animals or humans are wholly cloned to make a genetically identical copy.

Dolly the sheep, cloned by Scottish embryologist Ian Wilmut in 1996, is the most well-known example of reproductive cloning. Dolly proved wrong the idea that "when your cells decide what they want to be, they decide for life," Vrana noted, explaining that the famous ewe was cloned from the breast cell of a donor sheep. That Dolly was the product of 238 attempts, he added, is one measure of the difficulty of reproductive cloning.

"There is no scientific reason for reproductive cloning; it's dangerous and should be illegal," Vrana said, sparking discussion. "And it distracts from the benefits of therapeutic cloning."

By therapeutic cloning, he explained, scientists could theoretically create replacement tissue which when transplanted might cure diabetes, Parkinson's disease, and Alzheimer's disease. It is therapeutic cloning that Vrana's and many of his colleagues' research focuses on.

Another technology currently being explored—one that would bypass the controversial use of fertilized human embryos—is parthenogenesis, a process that activates eggs without sperm. These embryos are non-viable if implanted into the womb and so, for some, are exempt from the ethical dilemma.

Vrana stumbled upon this promising advance after an accidental discovery in the laboratory. He and his team were working to clone an alcoholic monkey to determine whether a clone of that monkey would be automatically destined for alcoholism. He recounted the exciting—and unexplainable—discovery they made when cloned monkey heart cells began beating in a Petri dish.

Adult stem cells present yet another therapeutic option. They have been used for 40 years, in bone marrow transplants, Vrana noted. Though they have interesting potential, he added, they are inferior to embryonic stem cells in several important ways. "They are gathered via invasive surgeries. They're found in low numbers in important organs like the heart and brain. They're not immortal. And they've already decided what they want to be," he explained.

"They're one of the tools in our toolbox, and we need to understand them," he noted. "But should we really put all of the other tools in the toolbox aside until we figure out whether or not adult stem cells work?"

Vrana, self-proclaimed "advocate of open discussion," hopes that stem cells remain a topic of debate and the science of these would-be wonder cells continues to advance. It is this "potential excitement for the next generation," he said, that motivates his work.

Kent Vrana, Ph.D., is Elliot S. Vessel professor and chair of pharmacology in the College of Medicine; kvrana@psu.edu.

Last Updated March 26, 2007