Ethics of Human Embryonic Stem Cell Research Explained

Introduction: The Stem Cell Debate

Since their discovery in the early 1990s, stem cells have brought with them the promise of significant scientific and medical opportunities — possibilities that could radically improve treatments for diseases such as Alzheimer's, Parkinson's, various cancers, and other conditions that currently leave patients and scientists with few options. Stem cells have been at the center of the scientific research paradigm in terms of developing innovative treatments that could revolutionize the current course of medical care (Bellomo, 2006).

With the advent of medical and scientific research comes the inevitable emergence of controversy — a pattern that has accompanied every major scientific and medical advancement. The use of stem cells is no different. Those who seek to curtail the use of certain stem cell lines revert to an argument that has defined many medically centered debates over the preceding decades: the destruction of human life in order to create life. This is the central philosophical point that all anti-stem cell advocates attempt to make. These individuals equate the use of stem cells with murder, the same vantage point that anti-abortion interest groups use to persuade others that the process constitutes the taking of innocent human life (Bevington, 2002).

Conversely, those who support the use of stem cells often find themselves aligned with scientific evidence demonstrating how potent stem cells are in treating previously untreatable diseases. Humans, for the most part, seek to minimize pain and maximize pleasure — a dichotomy that can be expressed in medical terms as well. Individuals are willing to undergo various treatments that can prolong their lives or reverse their conditions, and to this end, public opinion generally comes down in favor of stem cell research.

For all of the in-depth scientific arguments and studies indicating how effective stem cells are at improving patient well-being, the entire debate over the correct use of stem cells in scientific research ultimately comes down to a moral, philosophical, and religious question that has perplexed theologians and philosophers since the dawn of time: "When does life begin?" The answer to this question will ultimately define this debate and provide the resolution both sides have been searching for. However, this answer has yet to be determined from either a purely religious or a purely scientific perspective. Until it is answered to the greatest extent possible, the debate over the proper use of stem cells is destined to continue with undiminished intensity.

The purpose of this discussion is to analyze the various aspects of the ethical debate concerning the use of stem cells in medical research. This issue is not as simple as right versus wrong; rather, there are complexities involving human suffering balanced against the taking of a human life in the form of an embryo. Implicit in this debate is a range of philosophical, ethical, scientific, and religious frameworks that together make the stem cell debate one of the most contentious in modern society.

Scientific Premise of Stem Cells

This discussion introduces the debate by outlining the science underlying stem cells. The various types of stem cells are discussed, and the general concepts of biochemistry and cell biology are examined to provide a working framework for understanding the nature of stem cells and their effectiveness. In addition to this scientific discourse, the philosophical dimensions of the debate are analyzed within the framework of several relevant philosophical traditions. The discussion concludes with an overall review of the ethical, moral, and religious aspects of the debate, without rendering judgment on any particular approach.

Stem cells function as "blank slates" in terms of their genetic development. They possess two unique qualities that separate them from other cells in the human body (Carrier, 2004). First, stem cells are undifferentiated at their outset, meaning that a stem cell has the ability to develop into any cell type in the body. A stem cell produced in the red bone marrow can, for example, be placed into a petri dish with cardiac cells (Cohen, 2007). Eventually, the stem cell will adopt the properties of the surrounding cardiac cells and develop into a cardiac cell, taking on all the qualities and characteristics of the cells it is introduced to.

This differentiation principle allows stem cells to repair damaged tissues and organ systems (Wobus, 2008). Numerous studies have demonstrated that the infusion of stem cells into damaged muscle tissue following trauma can increase the likelihood of a positive recovery, minimizing damage to internal organs or tissues. This principle is highly valuable to scientists seeking to harness differentiation in order to direct stem cells toward curing certain diseases (Wobus, 2008).

There are two primary types of stem cells that researchers have used: embryonic and adult. The more potent stem cell lines used in medical research are derived from frozen human embryos. These human embryonic stem cells (hESCs) possess the greatest capacity to develop and offer immense possibilities for dealing with disease. They are derived from embryos that have been frozen while awaiting fertilization. In some instances, these embryos are not fertilized and are therefore set to be discarded. Rather than having them destroyed, they are used for scientific research — to harvest their DNA and use it in clinical treatments or academic research investigating the impact of proposed treatments.

In recent years, scientists have been able to identify conditions that allow a cell to be "reprogrammed" and revert to its stem cell state, exhibiting the core properties of differentiation and tissue repair. These cells are referred to as Induced Pluripotent Stem Cells (iPSCs) (Wobus, 2008). All three categories — embryonic, adult, and iPSC — possess the potential to radically alter the course of modern medicine and unlock the full impact of cell-based regenerative therapies for diseases such as diabetes, myocardial infarction, Alzheimer's, and Parkinson's. Despite their similarities, there are important differences between these cell lines.

The first difference lies in differentiation capacity. Human embryonic stem cells (hESCs) possess the highest level of differentiation ability and can be programmed to form any type of cell in the human body. Adult stem cells exhibit a more limited capacity, being restricted to differentiating into additional cells from their tissue of origin. For example, an adult stem cell from a calf muscle cannot be used to regenerate damaged nerve tissue in the spinal column. A second critical difference involves ease of generation: embryonic stem cells are more readily produced in culture, while adult stem cells are rarely found in mature tissue, making isolation increasingly difficult.

A related distinction concerns the likelihood of tissue rejection following transplantation. Currently, there is limited data involving tissues derived from hESCs, as the Food and Drug Administration has only recently granted approval for Phase 1 clinical trials involving hESC-derived tissue transplants. By contrast, there is substantial data suggesting that tissues created from adult stem cells are less likely to be rejected, since the patient's own cells are used to create the new tissue, reducing the probability of the patient's T-cells and B-cells mounting a histological reaction against "self."

Induced pluripotent stem cells (iPSCs) are the most recently developed category. Rather than representing an entirely distinct stem cell line like embryonic or adult stem cells, they are more akin to a subdivision — cells that have been genetically reprogrammed through recombinant DNA and RNA technologies to revert to a stem cell phase. Two types of iPSCs were developed: mouse-derived (2006) and human-derived (2007). Both exhibited key pluripotent properties: they were able to form tumor-necrosing cells, express numerous cell markers, and differentiate into a variety of tissues once injected into mice. Although these stem cells have only existed for a short time, they hold tremendous potential, particularly in transplant medicine, where they may significantly reduce infection rates and organ rejection.

The potential for using stem cells is of vast clinical and medical importance. These cells could allow scientists to learn what occurs at the cellular and molecular levels of human development and identify molecular pathways that contribute to a variety of conditions. Furthermore, stem cells could help scientists discover the genes triggered by certain cellular conditions that cause rapid, unchecked cell growth or irregular cellular patterns. Despite this growing potential, the utilization of these cell lines comes attached with legal, ethical, moral, and philosophical issues — the focus of the remainder of this discussion.

Philosophical Arguments Supporting Embryonic Stem Cell Research

Those who assert that killing human embryos is morally reprehensible typically argue that all individuals were once embryos and are therefore deserving of full human respect. This argument blends ethical, religious, and philosophical elements concerning the commencement of human life. It has two main branches: (1) the embryo is the earliest stage of development in the existence of a human being, and (2) human beings have the same moral standing at all stages of growth and development, including the embryonic stage (DeGette, 2008). These branches are philosophical in nature in that they make distinctions regarding human nature. Yet these maxims appear incompatible with the moral reasons commonly used to justify treating individuals differently based on their nature. If an individual was once an embryo, it logically follows that the individual's nature was radically different at that stage — and therefore it might be permissible to treat that embryo in a manner that would be inappropriate once the individual matured. It appears implausible to assume that radical changes in nature can never affect moral status.

The major counterpoint to the religious anti-stem cell argument is to ask: "Are six-day-old embryos human organisms?" (Fox, 2007). Although modern science has not definitively answered whether a six-day embryo is a human being, there is room for reasonable doubt. Two competing views exist regarding what happens once conception occurs. The first assumes that subsequent cell division is the first step in the lifespan of a single individual whose differentiating characteristics will define their essential self and allow them to develop into a rational adult. The second does not treat the combination of female and male gametes as a human organism (Friedman, 2009).

With respect to the first premise, although it is true that all cells are within a single unit held together by a single cellular membrane, it remains difficult to determine what makes these various cells parts of a single individual. This leads to yet another question: what, exactly, is a human organism? A "first principles" approach to this question suggests that human organisms are entities with human genes composing living organs that function together in harmonious concert; however, such organs in and of themselves do not constitute living organisms (Green, 2001).

The second construct holds that the combination of male and female gametes, and the subsequent cell division, does not constitute a human organism. According to this philosophical premise, when the first cell divides, it ceases to exist, leaving in its place two daughter cells. Likewise, when those cells divide, they cease to exist. There is therefore no single individual that persists throughout the transformation. Only when there is a substantial differentiation in cellular function, position, and structure can the claim be made that an organismic structure is present. Scientifically, this level of distinctive presentation does not appear until roughly two weeks after fertilization, suggesting that this is the point at which human beings can be said to exist.

Those who assert that the earliest levels of embryonic development constitute a valid human life worthy of the highest levels of protection face an objection rooted in the issue of cellular specialization (Herold, 2007). At the stage they claim the embryo represents a human life, does the embryo represent a higher order of life? This question moves from the purely biological to the metaphysical (Holland, 2001). If minimal cellular interaction is to be considered the beginning of human life, then brain death should not serve as the legal, ethical, and biological standard for when a person ceases to live. Brain death is compatible with the basic cellular interaction between neural cells and other tissues (Humber, 2004). Yet modern science and practical consensus define brain death as the state in which individuals have ceased to live — they have lost all essential qualities of selfhood and have become merely an amalgamation of cells and organ systems, sustained in almost all cases by artificial means. Even the most ardent defender of embryonic rights would be hard-pressed to define an individual possessing the same level of cellular interaction as a six-day embryo as a viable, living human being (Juengst, 2000).

The arguments in favor of human embryonic stem cell research incorporate various philosophical and metaphysical principles to establish the position that embryos are not individuals. Although the embryo is a collection of cells working in concert at a level higher than any single cell would exhibit in isolation, their concerted effort does not make the embryo a "higher order of life" — a human being. The logical conclusion, according to this argument, is that if the embryo is not an individual, it is not deserving of the equivalent protections afforded to traditional human beings (Kass, 2002).

The arguments against embryonic stem cell research are deeply rooted in ethical, moral, and religious grounds, forming an overarching framework that the embryo represents the most innocent form of human life and must be afforded maximum protection under the law.

Conclusion

Stem cell research has been at the forefront of biotechnological advances because of the potential curative uses of these cells. Research into how stem cells divide can help provide answers about normal cellular division and, it is hoped, ultimately teach researchers how improper cell division occurs in cancer and birth defects. Once scientists learn the processes involved, they may be able to develop cures. Stem cell research can also lead to improvements in the efficiency of drugs for treating a variety of illnesses. Many researchers believe that stem cell research can help develop cures for diabetes, cardiovascular disease, and other conditions by enabling scientists to create new body organs or repair existing diseased ones.