Stem Cell Research: The Impact on Public Health
What Are Stem Cells?
The Issue of stem cell research burst on to the scientific scene in November of 1998 when researchers first reported that they had successfully isolated human embryonic stem cells[1]. Unique properties of stem cells include that they are unspecialized, or they have the potential to make many different types of cells, are capable of dividing and renewing themselves for long periods of time, and they can also turn into specialized cells[2]. Unspecialized cells transform into specialized cells such as neurons, muscle cells, or red blood cells through a process known as differentiation. Stem cells are either harvested from adults or embryos, and growing these cells outside the body requires the right mix of nutrients, hormones, growth factors, and blood serums. Undifferentiated cells are considered pluripotent when they have the potential to become any type of cell provided when the right conditions. Once researchers isolate stem cells and allow for them to proliferate in a culture for six or more months without differentiating, a stem cell line has been created[3].
Adult stem cells are undifferentiated cells found among differentiated tissue or organs, and they have the potential to renew itself or differentiate into major specialized cell types[4].The role of adult stem cells in the body is to maintain and repair the tissues in which they are found. Adult stem cells are thought to reside in a specific area of each tissue where they remain quiesecent, or no-dividing, for years until they are activated by either disease or tissue injury[5]. Tissues that house stem cells include brain, bone marrow, peripheral blood, blood vessels, muscles, skin and liver[6]. Adult stem cells are generally tissue specific, for instance, hematopoietic stem cells are blood-forming cells that are found in bone marrow. While adult stem cells have the potential to differentiate into mature tissue when isolated from the body, they are extremely difficult to multiply in the lab[7]. In the past, scientists believed that adult stem cells from one type of tissue can only yield that same type of tissue when cultured in a laboratory, but recent experiments have raised the possibility that stem cells from one tissue may be able to create cell types of completely different tissue types, also known as plasticity[8]. While adult stem cells are free of ethical concerns, they are surrounded with numerous scientific challenges[9].
Human embryonic stem cells have the potential to develop into essentially any type of cell in the human body (they are pluripotent). In theory, scientists believe that embryonic stem cells have the potential to theoretically divide without limit to replenish or create other cells. Embryonic stem cells also have the potential to either remain a stem cell or to develop into a specialized cell such as a red blood cell or a muscle cell[10]. Embryonic stem cells are primarily obtained from frozen embryos that are donated through In Vitro Fertilization (IVF) programs from extra embryos that were created for infertile couples to use during fertility treatments[11]. A surplus of embryos are usually created and kept frozen for future use by the couple. When couples no longer need their frozen embryos for reproductive purposes, depending on the laws of that particular country, the embryos are used for stem cell research. Cell lines are grown by isolating human embryonic stem cells from the inner cell mass of a human blastocyst, or a 5-day embryo. With the help of fibroblast feeder layers, embryonic stem cells can be cultured indefinitely[12].
Human embryonic stem cells (HESC) can also be obtained by a method referred to as somatic cell nuclear transfer (SCNT), or therapeutic cloning. During SCNT, a nucleus is removed; removing the nuclear genome of an oocyte, and it is replaced with the nucleus of an adult cell[13]. The egg is then activated to form a blastocyst, containing fewer than 100 cells, which contains genetic material identical to the adult donor cell[14]. Scientist can either remove stem cells from the blastocyst or place the blastocyst into a uterus where it would have the potential to develop into a fetus[15]. By using SCNT, researchers are able to control the genotype of HESCs which eliminates the probability of tissue rejection[16]. While a cloned animal is abnormal, cloned stem cells are perfectly normal. If a gene is active in a fertilized stem cell, it is also active in a cloned stem cell at the same activity level[17]. Research shows that there is no significant molecular difference between cloned and non-cloned stem cells[18].
While embryonic stem cells and adult stem cells are both sources of undifferentiated cells, they both have several differences. Because embryonic stem cells are pluripotent, they have the ability to become all types of cells whereas adult tem cells are limited to developing into cell types of the tissue or organ that they originated from[19]. Another difference between the two cells is the ease of growth in a culture. It is relatively easy for researchers to grow a large number of embryonic stem cells in culture compared to adult stem cells which are relatively rare and have no methods for greatly expanding the number in cultures[20]. Finally, if a patient’s own cells are used to create adult stem cells, there is little risk that they would be rejected by the individual’s immune system, but because HESC clinical trials have not been conducted, scientist are unsure of the risk of rejection in the use of embryonic stem cells[21].
Scientist believe that stem cell research is important to the future of medicine because with adequate research, stem cells have the potential to treat disease by transplanting human stem cells into patients suffering from degenerative diseases such as Parkinson’s disease, diabetes, traumatic spinal cord injury, Purkinje cell degeneration, Duchenne’s muscular dystrophy, heart disease, and hearing and vision loss[22]. With gene therapy, a genetic defect would be corrected by giving a healthy version of the gene to a patient[23]. A physician would isolate stem cells from the patient and introduce a harmless viruses into the stem cells that express the correct version of the mutated gene and readminister the stem cells back to the patient[24]. SCNT could potentially be used to generate disease-specific stem cell lines to treat specific disorders[25]. By using SCNT, scientists may also be able to revert diseased cells to their primordial form and then monitor them to determine how and why abnormalities develop[26]. Once scientists have an understanding of diseased cells, the will be more successful creating treatment options.
While the untapped possibilities leave many members of the medical research community excited, there are numerous obstacles that may impede human stem cell research. Issues such as morality, funding, and national regulation impede scientists across the world from pursuing research possibilities related to gene therapy and stem cell research. While stem cell research is a vivacious field of science, it is an ethical, political, social and legal war zone, and in this paper I hope to address ethical and moral issues surrounding stem cell research, current National and International Laws and Policies, and the progress of current research.
Ethical and Moral Issues
Surround Stem Cell Research
With increasing press coverage on stem cell research there have been two distinctive groups: those who are opponents of human embryonic stem cell research and those who are proponents of human embryonic stem cell research. Many difficult questions engulf the morality of destroying embryos or using remnants of aborted fetuses to improve the medical wellbeing of other human beings[27]. Opponents of embryonic stem cell research argue that human life begins when an egg is fertilized; therefore, a human embryo is equivalent to a human being[28]. Proponents of embryonic stem cell research argue that during the natural reproductive process human eggs often fertilize, but fail to implant in the uterus. While a fertilized egg has the potential to form a human life, it is not equal to a human being until it has at least successfully implanted in a woman’s uterus[29]. In Vitro fertilization (IVF) clinics often create more embryos than needed over the course of fertility treatments and the excess frozen embryos are discarded[30]. Opponents state that research on these embryos still condones the destruction of embryos, while proponents believe that it is morally permissive to use these embryos for potentially life saving biomedical research[31].
Another hot topic surrounding stem cell research is the morality of cloning humans to improve the efficacy of techniques used to create stem cell lines[32]. Different methods of creating human embryonic stem cells without “destroying” embryos, such as removing cells from blastocysts or altered nuclear transfer, involves implanting DNA from a donor’s cell into a human egg that has had it’s nucleus removed and then the egg is stimulated to divide[33]. This method of cloning embryos is also called SCNT and was described in detail in the previous section. In a study, Understanding Australians’ Perceptions of Controversial Scientific Research, the results indicated that a majority of Australians polled were comfortable with research using adult cells, but they were not comfortable with scientist using cells created through cloning[34].
Other crucial ethical concerns involving issues related to stem cell donors still need to be answered. Because the U.S. FDA wants as much information as possible about the health of a stem cell donor, especially issues related to possible pathogens and diseases with genetic or family links, anonymity of stem cell donors can not be guaranteed[35]. Another hot ethical issue is how new stem cell lines are derived[36]. Finally there are issues of property related to stem cell research discoveries. How would intellectual and personal property be divided once scientists have discovered new techniques related to stem cell therapies is an issue that has not been completely tackled[37].
Current National and International
Laws and Policies
Initially, stem cell research was ineligible for public funding due to a ban placed on NIH-funded human research by Congress. In 1995 U.S. Congress attached a ban to the bill appropriating funding for the National Institute of Health (NIH)[38]. In December of 1999, NIH released draft guidelines allowing federally funded research on embryonic stem cells derived in the public sector. Under these guidelines only embryos leftover from fertility clinics that were donated with the consent of the pogenitors and resulted in no profit to the fertility clinics for the donated embryos are acceptable[39].
Until
2001, public funding was never provided for human embryonic stem cell research
in the
Scientist
have raised concerns about the cells
approved for federal funding under the Bush administration based on the
following five questions: 1) Whether
cell lines are robust stem cell colonies 2)
whether procedures used to create the cells are consistent with high ethical standards 3) whether the different
cell lines have sufficient genetic
diversity 4) whether the cells produced
from cell lines are safe for human implantation and 5) whether the owners of the cell lines will make them
available to researchers in a timely fashion and at a reasonable cost[46]. The safety of existing stem cell lines are of
concern because most were grown in cultures with the help of mouse stem cells which introduces the possibility
of animal viruses that are potentially dangerous to humans[47]. Transplantation with existing cells would be
classified as “xenotransplants” or transplants of animal tissue[48]. Existing lines have been shown to accumulate
genetic mutations that make the lines questionable for future therapeutic use[49]. Additional lines need to be created in order to ensure a broad diversity
that would better match patients with cells and to gain a comprehensive
understanding of diseases as it affects
people with different genetic backgrounds[50]. Scientists in the
The National Academy of Sciences is creating a privately funded committee to regulate human embryonic stem cell research. The committee was established to update guidelines on research and provide guidance to local groups on related issues. NIH usually handles all oversights on biomedical research , but Bush’s stance on human embryonic stem cells has left the agency unable to define “ethically acceptable” methods of stem cell research. This group will also make sure that the private sector doesn’t “call all of the shots”[52]. Researchers involved with stem cell research are barred from serving on the National Academy of Sciences panel[53].
Bush signed a bill (HR2520) on December 20, 2005 which authorized $79 million in federal funding for collection and storage of umbilical cord blood. Umbilical cord blood contains hematopoeitic progenitor cells which are stem cells found in adult bone marrow and could potentially be used to treat leukemia, lymphoma, sickle cell anemia, and other diseases[54]. The bill establishes and authorizes funding for a cord blood bank network for the purpose of stem cell research and the treatment of diseases[55].
Many
policies on stem cell research vary from state-to-state. In
In
Countries
like the
In
In
Australian
laws, like the
With
such a great variation in international and even national policies, it can be
confusing as to what scientific practices are allowed within in any given
geographical boundary. The Hixton Group
comprised of 60 bioethicists and stem cell researchers from 14 countries are
advocating for consistent policies between nations[80]. The group believes that it is vital to
address restrictions placed on stem cell research and fears that these
restrictions are hampering the progress of science and complicating the ability
for scientists to conduct stem cell research across national boundaries. For instance, a German stem cell researcher
working in the
Current Research
One
of the most exciting breakthroughs in stem cell research is that scientists at
WiCell Research Institute, a private lab affiliated with the
Other
research that is leading scientists closer to understanding stem cells has
occurred at the
At the University of Rochester Medical Center, a study was launched on January 26, 2006 to investigate whether transplanted stem cells can be safely used to treat damaged heart muscle after a patient’s first heart attack. Researchers are optimistic that cellular cardiomyopatsty, the use of stem cells to replace lost heart muscle cells, will prevent the loss of heart muscles after a heart attack. The treatment is measuring the efficacy of 3 IV doses of adult human stem cells versus placebo in decreasing the damage to heart muscle within 10 days of a first heart attack and has been approved for a new study. The study seeks to ensure that stem cell therapy is safe in treating heart failure. The new study is a randomized, double-blind, placebo-controlled Phase I clinical trial with patients randomized to receive injections of either .5 million, 1.6 million, or 5.0 million cultured adult mesenchymal stem cells per kilogram of body weight or the placebo. The trial is being conducted according to US FDA guidelines to evaluate the safety of treatment of stem cells obtained from healthy, unrelated adult donors. Experts think that mesenchymal stem cells or MSCs have the potential to be a powerful new treatment in cardiology. MSCs, like Blood Type O, are universally compatible and are transplanted without the risk of rejection. Generating MSCs can be expensive, time-consuming, and produce a limited number of cells in culture, however, MSCs can be donated by other humans leaving the possibility for storage of stem cell supplies that would be ready for use as heart attack patients arrive at hospitals. At this time MSCs are already used in the treatment of some cancers. While MSCs do offer some hope to heart attack victims, there are still several complications that may keep them from being a standard treatment offered in hospital emergency rooms. The MSCs hone in on damage for only a short period of time following the injury, so treatment must be administered as soon as possible after a heart attack. Also, implanted stem cells are shown to only partly differentiate and the end result lacks some characteristics of mature heart muscle cells. Finally, most implanted MSCs either re-enter the circulatory system or die rather than engraft to the heart muscle wall[87].
Current Obstacles
The potential to treat degenerative disease using stem cell technologies seems to be very promising, which may leave many people to question why the scientific community isn’t pouring more time and resources into stem cell research. In addition to ethical and moral issues and current legislative restrictions as mentioned previously in this chapter, there are other issues that leave the scientific industry hesitant to dedicate more time to stem cell research. The issue of intellectual property within stem cell research has been an issue that has not been addressed[88]. One of the most frustrating aspects of stem cell research is the recent and expected explosion of patents in the stem cell field which may block scientists from developing new treatments. Restrictions resulting from new patents discourage researchers from pursuing particular line of inquire and slows the pace of stem cell research[89]. It has been suggested that institutions such as the California Institute for Regenerative Medicine (CIRM) require all grant recipients to agree to donate exclusive license to any “insights, materials and technologies” that they discover through their research and patent them to a common open source patent pool that would be administered by a new non-profit organization[90]. The patent pool would then serve as a one-stop shop for investigators to obtain no-cost or low-cost licenses for new research. These open source patent pools would stimulate innovative stem cell research[91].
Currently there has been little discussion of the regulation that will govern the results of research as the medical field attempts to move stem cell therapies from the laboratory to physician’s offices. Any future regulation must reassure the end-users, both patients and health care providers that the stem cell products reliably satisfy a medical need without creating unnecessary cost or moral concerns[92]. End-users will also need to be reassured that treatments are not detrimental to their health and that the treatments do not carry any infectious diseases. It is also important that new regulations reassure those who supply raw materials and labor for stem cell research that this industry is beneficial for them to participate in while encouraging responsible manufacturing[93].
Once
stem cell therapies have been created, additional hurdles will remain. Before any new medical treatments can be used
in the
Scientists are also concerned that existing stem cell lines have been shown to accumulate genetic mutations with time. With these genetic mutations, it is very questionable that stem lines currently available would be eligible for therapeutic use[96]. Additional concern is the social impact that stem cell technologies may have around the world. Minority and ethnic groups are unlikely to benefit equally from stem cells as stem cell banks do not include less common tissue haplotypes[97]. More stem cell lines need to be created in order to ensure a broad diversity that will better match patients appropriate stem cells, and for scientists to gain a more comprehensive understanding of human disease as it affects people with different genetic backgrounds[98].
Potential Impact on Public
Health
Scientists think that stem cell research is important to the future of medicine because with adequate research, stem cells have the potential to treat degenerative conditions by transplanting human stem cells into patients. Presently, many of these chronic conditions have no cure and are managed by treating the symptoms. While the initial cost of receiving stem cell therapy may be high, it has the potential to outweigh the life long costs encured through daily medications and hospitalizations. By making disease management easier, the quality of life for those diagnosed with this diseases and their family members would be greatly included. With sufficient development of stem cell medicine, chronic diseases such as diabetes, heart disease, and Parkinson’s disease will be effectively managed.
Diabetes is a chronic disease with severe complications including increased risk for limb amputations and vision loss ,and currently there is no cure. The world-wide estimate of individuals with diabetes in 200 was 177 million people, and that number is expected to reach 300 million by 2025. Deaths attributed to diabetes is reported to be over 800,000 but many experts argue that this figure is grossly underestimated and should be closer to 4 million deaths per year which is nearly 9% of the world population[99]. Managing the disease often involves drastic changes in lifestyle in additions to daily medication and medical monitoring. It was estimated that the total annual economic cost of diabetes in 2002 was approximately US$132 billion or approximately 1 out of 10 health care dollars spent in the U.S.[100]. With more research, future treatments may include transplanting insulin-producing pancreatic beta cells, eliminating the need for daily medications and reducing the risk of diabetes related complications.
Nearly
1 in a million people in the
More
than ½ million Americans suffer have their first heart attack every year,
resulting in injury to the heart and scarring that contributes to the gradual
loss of the heart’s pumping strength[102]. Of the 1.5 million heart attacks per year in
the
Conclusion
While the benefits of stem cell research may seem to be out of reach for the immediate future, with continued research , stem cell therapies are predicted to one day be a common treatment for degenerative diseases. In order for this field to be successful, researchers must collaborate and share limited resources. With increases in funding and continued interest from private investors, stem cell research is expected to evolve rapidly in the next decade.
For More Information
These websites and journals are helpful in obtaining more information about stem cell research:
Institute for Stem Cell Research (ISCR)- www.iscr.edu.ac.uk
The Journal Regenerative Medicine www.futuremedicine.com
NIH Stem Cell Information Home Page: www.stemcells.nih.gov
American Association for the Advancement of Science: www.aaas.org
Stem Cell Policy: World-wide Stem Cell map: http://mbbnet.umn.edu/scmap.html
[1] http://www.aaas.org/spp/cstc/briefs/stemcells/index.shtml
[2] Ibid
[3] Ibid
[4] www.stemcells.nih.gov
[5] www.stemcells.nih.gov
[6] Ibid
[7] Powerful Technique For Multiplying Adult Stem Cells May Aid Therapies. January 23, 2006. Retrieved from : www.medicalnewstoday.com
[8] Russo E (2005) Follow the Money- The Politics of Embryonic Stem Cell Research. PLoS Biol 3(7): e234
[9] Powerful Technique For Multiplying Adult Stem Cells May Aid Therapies. January 23, 2006. Retrieved from : www.medicalnewstoday.com
[10] www.stemcell.nih.gov
[11] Russo E (2005) Follow the Money- The Politics of Embryonic Stem Cell Research. PLoS Biol 3(7):e234
[12] Russo E (2005) Follow the Money- The Politics of Embryonic Stem Cell Research. PLoS Biol 3(7):e234
[13] Ibid
[14] Ibid
[15] Cloned Stem Cells and Fertilized Stem Cells Identical. January 17, 2006. Retrieved from: www.medicalnewstoday.com
[16] Russo E (2005) Follow the Money- The Politics of Embryonic Stem Cell Research. PLoS Biol 3(7):e234
[17] Cloned Stem Cells and Fertilized Stem Cells Identical. January 17, 2006. Retrieved from: www.medicalnewstoday.com
[18] Ibid
[20] Ibid
[21] Ibid
[22] Ibid
[23] Powerful Technique For Multiplying Adult Stem Cells May Aid Therapies. January 23, 2006. Retrieved from : www.medicalnewstoday.com
[24] Ibid
[25] Cloned Stem Cells and Fertilized Stem Cells Identical. January 17, 2006. Retrieved from: www.medicalnewstoday.com
[26] Cloned Stem Cells and Fertilized Stem Cells Identical. January 17, 2006. Retrieved from: www.medicalnewstoday.com
[27]
Liddell, Kathleen and Susan Wallace.
Emerging Regulatory Issues for Human Stem Cell Medicine.” Genomics, society and Policy 1.1. (2005) :
54-73.
[28] http://www.aaas.org/spp/cstc/briefs/stemcells/index.shtml
[29] http://www.aaas.org/spp/cstc/briefs/stemcells/index.shtml
[30] Ibid
[31] Ibid
[32]
Liddell, Kathleen and Susan Wallace.
Emerging Regulatory Issues for Human Stem Cell Medicine.” Genomics, society and Policy 1.1. (2005) :
54-73.
[33] Group Releases Ethical Guidelines on Stem Cell Research to Clarify Conflicting International Policies. March 2, 2006. Retrieved from: www.medicalnewstoday.com
[34]
Critchley, Christine and Lyn Turney.
“Understanding Australians’ Perceptions of Controversial Scientific
Research.” Australian Journal of Emerging Technologies and Society 2.2
(2004) ; 79-140.
[35] Stem Cell Research: Legal and Ethical Questions. March 1, 2006. Retrieved from www.medicalnewstoday.com
[36] Ibid
[37] Ibid
[38] http://www.aaas.org/spp/cstc/briefs/stemcells/index.shtml
[39] Ibid
[40] Ibid
[41] http://www.aaas.org/spp/cstc/briefs/stemcells/index.shtml
[42] Ibid
[43] Ibid
[44] Ibid
[45] Ibid
[46] http://www.aaas.org/spp/cstc/briefs/stemcells/index.shtml
[47] Ibid
[48] Ibid
[49] Wisconsin Scientists Grow Two New Stem Cell Lines in Animal Cell-free Culture. January 2, 2006. Retrieved from: www.medicalnewstoday.com
[50] Ibid
[51] http://www.aaas.org/spp/cstc/briefs/stemcells/index.shtml
[52]
[53] Ibid
[54] President Bush Signs Bill Authorizing Funding for Establishment of Umbilical Cord Blood Network. December 22, 2005. Retrieved from: www.medicalnewstoday.com
[55] Ibid
[56] Russo E (2005) Follow the Money- The Politics of Embryonic Stem Cell Research. PLoS Biol 3(7):e234
[57] Ibid
[58] Ibid
[59] Russo E (2005) Follow the Money- The Politics of Embryonic Stem Cell Research. PLoS Biol 3(7):e234
[60] Ibid
[61] Broad Foundation Donates $25 Million to Create New Stem Cell Institute at USC. February 25, 2006. Retrieved from: www.medicalnews.com
[62] Radical Proposal to Speed Development of Stem Cell Therapies. March 1, 2006. Retrieved from : www.medicalnewstoday.com
[63] Russo E (2005) Follow the Money- The Politics of Embryonic Stem Cell Research. PLoS Biol 3(7):e234
[64] Ibid
[65] Ibid
[66] Liddell, Kathleen and Susan Wallace. Emerging Regulatory Issues for Human Stem Cell Medicine.” Genomics, society and Policy 1.1. (2005) : 54-73.
[67] Ibid
[68] Ibid
[69] Russo E (2005) Follow the Money- The Politics of Embryonic Stem Cell Research. PLoS Biol 3(7):e234
[70] Ibid
[71] Ibid
[72] Ibid
[73] Ibid
[74] Russo E (2005) Follow the Money- The Politics of Embryonic Stem Cell Research. PLoS Biol 3(7):e234
[75] Ibid
[76] Ibid
[77] Ibid
[78] Ibid
[79] Ibid
[80] Group Releases Ethical Guidelines on Stem Cell Research to Clarify Conflicting International Policies. March 2, 2006. Retrieved from: www.medicalnewstoday.com
[81] Group Releases Ethical Guidelines on Stem Cell Research to Clarify Conflicting International Policies. March 2, 2006. Retrieved from: www.medicalnewstoday.com
[82]
[83] Ibid
[84] Wisconsin Scientists Grow Two New Stem Cell Lines in Animal Cell-free Culture. January 2, 2006. Retrieved from: www.medicalnewstoday.com
[85] Ibid
[86]
[87] Stem Cell Study Seeks to Prevent Heart Failure. January 26, 2006. Retrieved from: www.medicalnewstoday.com
[88] Stem Cell Research: Legal and Ethical Questions. March 1, 2006. Retrieved from www.medicalnewstoday.com
[89] Radical Proposal to Speed Development of Stem Cell Therapies. March 1, 2006. Retrieved from : www.medicalnewstoday.com
[90] Ibid
[91] Radical Proposal to Speed Development of Stem Cell Therapies. March 1, 2006. Retrieved from : www.medicalnewstoday.com
[92] Liddell, Kathleen and Susan Wallace. Emerging Regulatory Issues for Human Stem Cell Medicine.” Genomics, society and Policy 1.1. (2005) : 54-73.
[93] Ibid
[94] Radical Proposal to Speed Development of Stem Cell Therapies. March 1, 2006. Retrieved from : www.medicalnewstoday.com
[95] Powerful Technique For Multiplying Adult Stem Cells May Aid Therapies. January 23, 2006. Retrieved from : www.medicalnewstoday.com
[96] Wisconsin Scientists Grow Two New Stem Cell Lines in Animal Cell-free Culture. January 2, 2006. Retrieved from: www.medicalnewstoday.com
[97] Liddell, Kathleen and Susan Wallace. Emerging Regulatory Issues for Human Stem Cell Medicine.” Genomics, society and Policy 1.1. (2005) : 54-73.
[98] Wisconsin Scientists Grow Two New Stem Cell Lines in Animal Cell-free Culture. January 2, 2006. Retrieved from: www.medicalnewstoday.com
[99] www.who.int/mediacentre/factsheets/fs236/en
[100] www.diabetes.org
[101] www.pdf.org
[102] Stem Cell Study Seeks to Prevent Heart Failure. January 26, 2006. Retrieved from: