The Ethics of Stem Cell Research: A Nursing Perspective
The Ethics of Stem Cell Research: A Nursing Perspective
When the world-famous cloned sheep, Dolly, was euthanized at the relatively young age of 6-1/2 years she was suffering from advanced aging and lung disease (Meek, 2003). In human years, Dolly was only about 40-years old and had been suffering from arthritis for many years. This outcome is consistent with the claims of some scientists that current cloning technology does not accurately replicate natural sexual reproduction and disproportionately generates debilitating and sometimes lethal genetic defects. Dolly was the product of somatic cell nuclear transfer (SCNT), which involved removing the DNA from a sheep somatic (adult) cell, inserting it into an egg, and then transferring the egg to a receptive womb. This technology is very similar to what is currently being developed by stem cell researchers, especially the induced pluripotent stem cells (iPSCs) derived from adult human tissue. What Dolly's demise reveals, however, is that this technology is far from perfected.
On the other hand, adult stem cells have been successfully harvested and used clinically for decades (O'Meara et al., 2014). Bone marrow transplants are the obvious example, but the clinical use of stem cell technology continues to expand in many directions. Sarah Hancox, age 27 and a senior nurse at the Queen's Medical Centre and City Hospital in Nottingham, plans to donate the umbilical cord blood (UCB) harvested during the birth of her child. Two recently opened cord blood banks at the hospital where she works makes this a convenient process and she is excited about the opportunity to help relieve the suffering of very ill patients she encounters as a nurse. The stem cells isolated from her cord blood could be used to reconstitute bone marrow in a leukemia patient, for example, after the patient has undergone chemotherapy or radiation treatment to destroy the endogenous hematopoietic stem cells (O'Meara et al., 2014). This technique has become so successful that the number of procedures conducted at the Basel University Hospital in Switzerland, over the past four decades, has increased from 109 during the first decade to 939 during the past decade. In addition, the mortality rate from allogeneic hematopoietic stem cell transplantation has declined from 43 to 22% over the same period, while the risk of treatment failure has been cut in half. These improvements have occurred despite the eventual inclusion of older patients, patients with more advanced disease, and the increasing use of mismatched donor/host transplantations.
The above two examples highlight the sometimes vast divide between what is occurring in stem cell research laboratories and in medical clinics, but the magnitude of this difference will shrink over time as science advances. Scientists, however, cannot and should not provide answers to the often contentious ethical issues raised by stem cell technology. The ethical issue of human cloning was catapulted into the world's imagination by the birth of Dolly and subsequent unsubstantiated claims of successful human cloning (e.g., Borger, 2002), but a more immediate concern, for example, is the use of discarded in vitro fertilization embryos as a source of pluripotent stem cells for research and medicine. Nurse Hancox is excited about donating her cord blood to help cancer patients and therefore has no ethical problems with this technology, but would she be just as excited about donating eggs for stem cell research or would she have strong ethical reservations? In the past, both cord blood and excess in vitro fertilized embryos were discarded, so what is the difference ethically between these two sources of stem cells?
This research paper will attempt to provide guidance for nursing professionals who are facing or will face the ethical issues created by stem cell research and the many potential clinical applications. In order to accomplish this task, the history of stem cells in science and medicine, the different types and sources of stem cells that have been discovered, and the many ethical issues this technology has created, will be reviewed and discussed. The overall goal is to provide enough information for nursing professionals so that they can make up their own minds what stem cell technologies and research goals are ethically acceptable.
History of Stem Cell Research
The interest in pluripotent cells has been around for quite some time, but in 1954 this interest transformed into experimentation (Solter, 2006). During that year researchers were able to isolate teratocarcinomas from the 129 mouse strain. Culturing these cells in vitro produced a wide variety of differentiated cell types within the same culture dish, such as nervous tissue, organs, skin, hair, and heart. The term teratocarcinoma was derived from the Greek word 'teratos,' which means monster. What is significant about this type of tumor is that a single cell derived from the tumor was shown to be capable of generating multiple cellular phenotypes normally arising from the three germ layers: mesoderm, endoderm, and ectoderm. This ability is called 'pluripotency', which is one of the criteria used to define stem cells. The pluripotent capacity of these cells suggests that they represent a very early developmental stage of embryogenesis.
Further experimentation revealed that not all cells derived from a teratoma are as pluripotent as others (Solter, 2006). This finding was viewed by some researchers as evidence of the existence of tumor stem cells, not only by functional assays, but also by appearance. These tumor stem cells eventually became known as 'embryonal carcinoma cells' and appeared as small, tight colonies in vitro with prominent nucleoli and a thin dark cytoplasm. Injecting these cells into a mouse host would trigger the development of tumors with a wide variety of phenotypes, thereby validating the existence of tumor stem cells. Further experimentation with teratomas resulted in the identification and development of antibodies capable of specific recognition of embryonal carcinoma cells in tumor biopsies from both mice and humans. The stage-specific embryonic antigen 1 (SSEA1) could identify mouse embryonal carcinoma cells, while SSEA3 and SSEA4 could identify human counterparts.
Unfortunately, embryonal carcinoma cells are difficult to control and more than a few contributed to tumor formation after transfer into mouse blastocysts; however, many of the same molecular tools used to identify and isolate embryonal carcinoma cells proved to be valuable when isolating normal stem cells from mice and humans (Solter, 2006). Once this transition had been made, scientific interest in teratomas faded. The crucial discoveries that ushered in the modern era of stem cell research were (1) the discovery of stem cells resident in normal tissues, (2) the ability to maintain viability of these stem cells in vitro with a feeder layer, such as a single layer of mouse fibroblast cells adhered to the bottom of the culture dish, and (3) the prevention of differentiation using leukemia-inhibiting factor (LIF) and the subsequent in vitro expansion of a stem cell line.
The current definition of a stem cell depends on the number of different cellular phenotypes it can generate (Solter, 2006). A totipotent stem cell can generate all the cellular phenotypes that will ever appear in an organism, while a pluripotent stem cell is capable of generating multiple cellular phenotypes from all three germ layers. Multipotent stem cells, however, are much more limited and the cellular phenotypes it can generate are generally restricted to a subset of phenotypes associated with one or two germ layers. For example, researchers were able to show that totipotent stem cells from mice were capable of contributing to the formation of germ cells, in addition to most if not all somatic cells in a mouse body, and could thus be passed on from generation to generation; however, researchers have been unable to prove the existence of totipotent human stems cells.
In the absence of totipotent human embryonic stem (ES) cells many researchers turned toward investigating the possibility that somatic cells could be reverted to pluripotency (Easley, Latov, Simerly, & Schatten, 2014). This considerable body of research has produced human induced pluripotent stem cells (hiPSCs), which can give rise to a limited number of different phenotypes. These cells cannot generate phenotypes from all three germ layers and are therefore not a true pluripotent stem cell, but researchers have revealed that these cells are multipotent and capable of generating multiple cellular phenotypes closely related to the tissue of origin. Current efforts are directed towards isolating, reverting, and controlling the differentiation pathways, thereby creating a possible therapeutic strategy to repair damaged or diseased tissue. The development of pluripotent progenitors from somatic cells also avoids the many moral and ethical objections concerning the harvesting of stem cells from fertilized human embryos. The other advantage of generating hiPSCs is that the patient can be both donor and recipient, which essentially eliminates the risk of graft vs. host disease (GvHD).
Types of Stem Cells
There are two general classes of human-derived stem cells: embryonic and adult (Ding, Shyu, & Lin, 2011). Of these two general classes, only stem cells derived from fetal tissue have raised significant ethical and legal…