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The explosion of interest in stem cell research raises a raft of controversial policy questions. When should human embryos be used to create stem cells? Should cloning be outlawed? Should egg and tissue donors be paid? Should we allow scientists to patent stem cells? Is the government entitled to a portion of the revenue from stem cell technology created with public funds? How should the regulators and courts balance the competing goals of access to revolutionary treatments and protection of the public from unknown risks?
Russell Korobkin, with contributions from Stephen R. Munzer, provides the first thorough discussion and analysis of these and other unsettled questions of law, policy, and ethics that surround stem cell science. His clear and concise description of complex problems coupled with logical and well-balanced conclusions makes this volume essential reading for all Americans, general readers and experts alike, interested in the promise of stem cell research and the future of regenerative medicine.
Hans Keirstead is a professor of anatomy and neurology at the University of California at Irvine who has done something incredible with paralyzed rats. Able to walk only with their forelegs, the rats dragged their torsos, hind legs, and tails behind them. Keirstead coaxed stem cells derived from human embryos into becoming oligodendrocytes, cells that help neurons send impulses throughout the body. He then injected the cells into the rats. The result: the rats miraculously could move their hind legs and tails.
In the fall of 2004, Keirstead campaigned for California's stem cell initiative-Proposition 71-by showing "before" and "after" videos of his rats to various groups of potential voters. He and his work have been featured in a segment of the news magazine 60 Minutes and an article in the New Yorker magazine. Keirstead's primary financial backer, the biotechnology firm Geron, hopes that the Food and Drug Administration (FDA) will soon make its oligodendrocyte preparation the first product derived from human embryonic stem cells approved for use in human clinical trials in the United States.
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Hwang Mi Soon spent nineteen years in a wheelchair, paralyzed after falling from a bridge at the age of nineteen while running from a would-be attacker. In October 2004, she received a spinal injection of stem cells collected from umbilical cord blood. The next month, with the help of a walker, she stood up and shuffled several steps. Repeating the description used by Soon herself, newspapers around the globe called the results a miracle. The creator of the therapy announced plans for clinical trials and claimed that it would be widely available by 2006.
Within weeks, though, the apparent benefits had completely dissipated. Just months after her first injection, Soon underwent a second stem cell treatment. This one caused an infection and, according to reports, left her in constant pain and unable to sit for more than a couple of hours at a time. "I was like an animal they used for testing," she said the following year. "I don't want there to be another victim." She blamed her condition on "unscrupulous doctors who were more concerned with making their names and earning money by enabling me to walk than the potential risks."
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Over the past decade, there has been no shortage of scientific experts and political leaders predicting that stem cell research will lead to the most important medical care advances in our lifetimes. Former National Institutes of Health (NIH) director Harold Varmus testified before Congress that "there is almost no realm of medicine that might not be touched by this innovation.... It is not too unrealistic to say that this research has the potential to revolutionize the practice of medicine and improve the quality and length of life." The dean of the Harvard University Faculty of Medicine claimed that stem cell therapies "have the potential to do for chronic diseases what antibiotics did for infectious diseases" and hopes that current research will lead to a "penicillin for Parkinson's."
Senator Orrin Hatch (R-Utah) called stem cell research "the most promising research in healthcare perhaps in [the] history of the world." More than two hundred members of Congress signed a letter to President George W. Bush claiming that "stem cells have the potential to be used to treat and better understand deadly and disabling diseases that affect more than 100 million Americans, such as cancer, heart disease, diabetes, Parkinson's, Alzheimer's, multiple sclerosis, spinal cord injury, and many others."
Whether the potential of stem cell research will be achieved, justifying these prophecies, or whether a path strewn with unfulfilled expectations will cause history to regard the stem cell revolution as more hype than substance depends on the intrinsic power of stem cells and the creativity and brilliance of the research scientists who work on the revolution's front lines. But that is only part of the story. The ability of these scientists to deliver improved treatments and cures for a raft of debilitating diseases depends, in turn, on how our government makes the policy choices, designs the laws, and creates the institutions that surround the stem cell research endeavor. This book is about what the critical choices are, how the law ought to be structured, and how institutions should be designed.
The policy issues raised by stem cell research are wide ranging and varied. As a result, this book has an extremely broad scope. Some of these issues garner a fair bit of attention in the popular press, although the media's superficial coverage rarely does justice to the complexity of the questions involved. Many of the issues receive little attention at all outside of a very small circle of people who study bioethics and scientific research for a living. Dealing with all of the issues in a thoughtful and prudent manner, however, is critical to ensuring that the stem cell revolution leads to the most far-reaching improvements in the treatment of disease that the underlying science is capable of delivering while at the same time not undermining our society's moral fabric.
One set of issues that we as a society must confront in the early years of the stem cell century is whether, in spite of its potential health benefits, ethical considerations should lead us to prohibit or refuse to fund certain types of stem cell research. A second set concerns the regulation of the relationship between researchers and the donors of the biological matter that is the raw material for stem cell research. Of course, embryonic stem cell research has attracted enormous interest in the United States and internationally, not only because of its scientific and medical potential, but also because of its commercial promise. Forecasts of the market for stem cell technologies range from a fairly modest $100 million to a more optimistic $10 billion by 2010. Such financial projections raise a third set of important policy concerns: how the law should allocate intellectual property rights to the innovations that result from stem cell research. Rules of property and contract law not only serve to allocate the financial proceeds of research, but they also create incentives for research that are likely to have a significant impact on what research is undertaken, how much private funding it will attract, and how successful the research will be in leading to new and more effective medical treatments.
The following nine chapters engage this broad range of legal issues implicated by stem cell research and the potential of that research to revolutionize the treatment of disease. Each issue-specific chapter attempts to achieve three interrelated but distinct goals: (1) identify the most important, interesting, and salient legal issues raised by stem cell research; (2) for each legal issue raised, describe the current state of the law. In some instances, the law is clear and this task is straightforward; in others, it is quite unsettled, and a large amount of interpretation is required; (3) offer a critical assessment of the law and proposals for optimal policy.
Chapters 2 and 3 concern the legal relationship between the scientists on the front lines of stem cell research and the government. Chapter 2 addresses the stem cell research controversy that has gained the strongest foothold in the media and the popular imagination: the morality of human embryonic stem cell (hESC) research, whether the U.S. government ought to fund such research, and the consequences of the current funding embargo. Chapter 3 considers the subject of therapeutic cloning, including both the policy issues and constitutional concerns implicated by proposed legislation to prohibit this area of research, which has tremendous but uncertain medical potential.
Chapters 4 and 5 turn to issues relating to intellectual property rights in the fruits of stem cell research. Chapter 4 considers patents. Should people be able to own innovations in stem cell technology to the extent that they can prohibit others from using that technology without permission? A negative answer might stifle basic research, but a positive one might stifle applied research, in addition to having the unsettling consequence of making what exists in one person's body the property of another. Chapter 5 focuses on controversies over whether and how the public ought to benefit from innovations that owe their development to public funding. What payback, if any, should we expect from innovations that blossom from our tax dollars?
Chapters 6-8 shift from the scientists upon whom society relies to innovate in the field to the donors of human tissues, the raw materials on which scientists will increasingly need to rely. Chapter 6 examines the autonomy principle and "informed consent" rules that underlie the legal regulation of scientific research involving human subjects and considers complicated questions in this area of law raised by stem cell research. Chapter 7 takes on the controversial question of whether the embryos, ova, and other human tissues needed to fuel stem cell research should be subject to market transactions rather than merely altruistic donations. Chapter 8 grapples with how the law does and ought to deal with tissue donations when compensation is not mentioned at all by either researcher or donor.
Chapter 9 looks ahead to an era of clinical regenerative medicine in which stem cells are routinely conceived of as therapeutic treatments. It addresses three distinct questions: In what circumstances is it appropriate to use one person's stem cells for the medical benefit of another? To what extent should the origin of stem cells in the human body subject them to different regulatory treatment than other medical products? In what circumstances should the makers of such a new class of products be legally liable for harm that they inadvertently cause? Finally, Chapter 10 concludes with a summary of the book's findings.
While this book is about public policy and law rather than cell biology or medical research, for nonbiologists a brief description of stem cell science and its potential is nevertheless a necessary prelude to analyzing the social issues that are considered in detail in the chapters that follow. It is at this point that we shall begin.
The Role of Stem Cells in Human Biology
Each human cell contains forty-six chromosomes, half inherited from the mother and half from the father. Together these chromosomes contain the person's entire genome-that is, every one of his or her genes. According to the findings of the Human Genome Project, the genome of each human consists of between twenty thousand and twenty-five thousand genes. Different types of cells have different characteristics and different functions-skin cells, blood cells, bone cells, and brain cells, for example. In order to serve such different functions, different genes are activated, or "expressed," in different types of cells, while the remaining genes in any particular type of cell are inactive. Through gene expression, the cell creates particular proteins that, working together with proteins created by other cells, build and maintain the organism and enable it to function.
When a specialized cell is created, its function is decided and is fixed. In the language of cell biology, such a specialized cell is "fully differentiated" or "terminally differentiated." The genes that are expressed will remain expressed, while the others generally will remain dormant. A stem cell, in contrast, is one that is not fully differentiated. It can divide into two identical copies of itself, but-and here is the important part-it also can divide into one copy of itself and one different, more specialized cell with a different gene expression pattern.
At the earliest stage of development, a sperm cell fertilizes an egg cell and the nuclei of the two gametes fuse, creating a single cell that contains a new genome. This cell, called a zygote after the fertilization process is complete, has the ability to create all the cell types needed to produce a mature version of the organism; from that one cell all of the body's cells will descend. This necessarily means the zygote is completely undifferentiated and possesses maximum potential, earning it the description of being "totipotent."
By the fourth or fifth day after fertilization, a human embryo has matured to a stage at which it is called a blastocyst. At this point, the embryo is made up of approximately 150-200 cells, is approximately 0.1 millimeter across in size, and has yet to implant in the womb. The blastocyst is made up of two types of cells at this point. Some cells have formed an outer wall of the embryo, called the trophectoderm. These cells will develop into the placenta and other membranes necessary to connect the embryo to the uterus and maintain it. An interior group of approximately thirty cells, called the inner cell mass or ICM, will develop into the embryo itself, later to become a fetus.
The ICM contains human embryonic stem cells (hESCs), which are "pluripotent," meaning that they have the ability to create all of the tissues that make up the human body. hESCs usually are not considered totipotent because they do not create the type of cells that form the trophectoderm and are thus unable to create a person on their own. The value of this distinction has been called into some doubt in recent years, however, by research showing that hESCs can be coaxed in vitro into differentiating into trophectoderm cells.
From this time forward, the cells that make up the ICM differentiate in a series of steps. When the embryo reaches the age of about fourteen days, cells begin to cluster in a line, forming what is called the "primitive streak." The embryonic stem cells thus begin a week-long project, called gastrulation, of differentiating into three groups of cells that will make up the ectoderm, mesoderm, and endoderm of the developing organism. Up until this point, the embryo may divide spontaneously in two, creating monozygotic (identical) twins. When gastrulation is complete, the potential of the cells has become somewhat limited. Ectodermal cells, for example, can become nerve or skin cells (among others) but cannot become muscle or bone cells.
By the end of the fourth week of development, the embryo develops what are called primordial germ cells. These are precursors of egg or sperm cells, depending on whether the embryo later develops into a male or female fetus. At their primordial stage, these cells are diploid, meaning that they have twenty-three pairs of chromosomes (forty-six total). Before they can become sperm or egg cells, they will need to go through a process called meiosis, which results in the creation of haploid cells (having only one set of twenty-three chromosomes), suitable for combining with another haploid gamete cell and creating a new genome. Primordial germ cells share the pluripotency of hESCs and are often referred to as human embryonic germ cells (hEGCs).
By the time the human embryo reaches two months of age, its stem cells have differentiated into cells with more particularized functions. At this stage and beyond, cells that have the ability to self-renew and differentiate are usually referred to generally as human adult stem cells (hASCs). This term can be confusing for laypeople because adult stem cells appear long before the organism reaches adulthood and, in fact, even before it is fully gestated.
hASCs have differentiated to the point at which they can produce only one category, or "lineage," of specialized cells. In some cases, hASCs are "unipotent"-that is, they can produce only one type of specialized cell. In other cases, they are "multipotent"-that is, they can produce several types of cells that are usually closely related. For example, one type of stem cell found in the skin produces only keratinocytes (cells that produce keratin). Hematopoietic stem cells, in contrast, can produce nine different types of blood cells. Adult stem cells are thus less flexible in their potential than embryonic stem cells. However, like their embryonic cousins, they have the ability both to reproduce themselves through mitosis-forming additional adult stem cells of the same variety-and to produce specialized cells. Some types of hASCs produce an even more differentiated type of stem cells, called progenitors, as an intermediate step toward producing specialized cells.
Excerpted from Stem Cell Century by RUSSELL KOROBKIN Stephen R. Munzer Copyright © 2007 by Russell Korobkin. Excerpted by permission.
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