Research papers on stem cell research
Advanced Search Abstract The use of human embryos for research on embryonic stem ES cells is currently high on the ethical and political agenda in many research papers on stem cell research. Despite the potential benefit of using human ES cells in the treatment of disease, their use remains controversial because of their derivation from early embryos. There are several reasons for this.
To date, most embryos used for the establishment of hES cell lines have been spare embryos from IVF, but the creation of embryos specifically for deriving hES cells is also under discussion. The UK has been the first to pass a law governing the use of human embryos for stem cell research.
The European Science Foundation has established a committee to make an inventory of the positions taken by governments of countries within Europe on this issue European Science Foundation, In order to discuss the moral aspects of the isolation and use of hES cells, which is the aim of the present article, it is first essential to understand exactly what these cells are, where they come from, their intended applications and to define the ethical questions to be addressed.
What are embryonic stem cells? Broadly speaking, two types of stem cell can be distinguished: In humans, hEG cells cwll first established in culture inshortly after the first hES cells, from tissue derived from an aborted fetus Shamblott et al. In the adult individual, a variety of tissues have also been found to harbour stem cell populations. Examples include the brain, skeletal muscle, bone research papers on stem cell research and umbilical cord blood, although the heart, by contrast, contains no stem cells after birth reviewed in McKay ; Fuchs and Segre, ; Watt and Hogan, ; Weissman et al.
These adult stem cells have generally been regarded as having the capacity to form only the cell types of the organ in which they are found, but recently they have been shown to exhibit an unexpected versatility Ferrari et al. Evidence is strongest in animal experiments, but is increasing in humans, that adult stem cells originating in one germ layer can form a variety of other derivatives of the same germ layer e.
To what extent transdifferentiated cells are immortal or acquire appropriate function in host reearch remains largely to be established but advances in this area are rapid, particularly for multipotent adult progenitor cells MAPCs of bone marrow Reyes and Verfaillie, Answers to these questions with respect to MAPCs, in particular whether they represent biological equivalents to hES and can likewise be expanded indefinitely whilst retaining their differentiation potential, are currently being addressed Jiang et al.
For other adult stem cell types, such as those from brain, skin or intestine Fuchs and Segre,this may remain unclear for the immediate future. Examples in fundamental research on early human development are the causes of early pregnancy loss, aspects of embryonic ageing and the failure of pregnancy in older women where genetic defects in the oocyte appear to be important. A second category might be toxicology, more specifically research on possible toxic effects of new drugs on early embryonic cells which are often more sensitive than adult cells drug screening.
The most important papdrs use of hES cells is, however, clinically in transplantation medicine, where they could be used to develop cell replacement therapies. It is unfortunate that sensational treatment in the media, which implied the generation of whole organs from hES cells, initially left this impression so that the more realistic view emerging is already a disappointment to some patient groups. There are, syem least in theory, various sources of hES cells.
In most cases to date, these have been spare IVF embryos, although IVF embryos have been specifically created for the purpose of stem cell isolation Lanzendorf et al.
Active debates are underway to adapt regulatory frameworks to address the specific challenges of developing, standardizing, and distributing cell-based therapies, while advances in basic research continue to provide a fuller understanding of how stem cells can research papers on stem cell research safely and effectively used. The field holds the potential to revolutionize the way human diseases are treated, and many nations have therefore invested heavily in stem cell research and its applications. NSCs are able to respond to extracellular signals in the brain, amplifying the pool of progenitor Hermann Stefan Liebau Clair Weidgang Thomas Research papers on stem cell research Alexander Kleger Lukas Perkhofer A better molecular understanding of gastrointestinal cancers arising either from the stomach, the pancreas, the intestine, or the liver has led to the identification of a variety of here new molecular Ingber Researcu formation during embryogenesis is controlled through a complex interplay between mechanical and chemical cues. October Shin-ichiro Ito Akishi Onishi Masayo Takahashi Induced pluripotent stem cells iPSCswhich can be differentiated into various tissues and cell types, have been used for clinical research and disease modeling. Username I forgot my password Track accepted paper Once production of your article has started, you can track the status of your oon via Track Your Accepted Article. Mummery Regeneration of the myocardium by transplantation of cardiomyocytes is an emerging therapeutic strategy. Recognized retinal progenitors are a heterogeneous population of cells that lack surface markers for the isolation of live cells
This option is purported to be the optimal medical use of hES technology since the nuclear DNA of the cells is derived from a somatic cell of a patient to receive the transplant, reducing the chances of tissue rejection see Barrientos et al. It is of note that the oocyte in this case is not fertilized, but receives maternal and paternal genomes from the donor cell nucleus.
Since by some definitions an embryo is the result of fertilization of an oocyte by sperm, there is no absolute consensus that nuclear transfer gives rise to an embryo see below. Growth of the cell lines over extended periods and in some cases under defined conditions Xu et al. In addition, research will be required on how to deliver cells to the appropriate site in the patient to ensure that they survive, integrate in the host tissue and adopt appropriate function.
These are the current scientific challenges that will have to be overcome before cell therapy becomes clinical practice; the problems are common to both hES and adult stem cells.
The efficiency of establishing embryonic stem cell lines from nuclear transfer embryos is currently unknown, but expected to be lower than research papers on stem cell research IVF embryos. Ethical exploration In the following section, the status of hES cells is first considered. Should they be considered equivalent to embryos or not? What, then, is the status of the individual cells from the ICM once isolated, and the embryonic stem cell lines derived from them?
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Commentators who, against this background, regard hES paperss as equivalent to embryos, apparently take recourse to the opinion that any cell from which a human being could in principle be created, even when high technology micromanipulation would be required to achieve this, should be regarded as an embryo. It is therefore unreasonable to regard hES cells as equivalent to embryos.
Between these extremes are various intermediates. Differences of opinion exist on the weight of these arguments how much protection does the embryo deserve? In view of the fact that up to 14 days of development, before the primitive streak develops and three germ layers appear, embryos resarch split and give rise to twins or two embryos may fuse into one, it may reasonably be argued that at these early stages there is in principle no ontological individuality; this limits the moral value of an embryo.
The precise implications of this moral difference for the regulation of the instrumental use of embryos is, however, beyond the scope of the present article. The international debate focuses on defining these conditions. Ethics of using surplus IVF embryos as a source of hES cells Possible objections are connected to rseearch principle of proportionality, the slippery slope argument, and the principle of subsidiarity.
Opinions differ on how this should be interpreted and made operational. Internationally, however, such a limitation is being increasingly regarded as too restrictive De Wert et al. It is difficult to argue that research into hES cells is disproportional. If embryos may be used for research into the causes or treatment of infertility, then it is inconsistent to reject research into the possible treatment of serious invalidating diseases as being not sufficiently important.
The British Nuffield Council on Bioethics Nuffield Council on Bioethics, also saw no reason for making a moral distinction between research into diagnostic methods or reproduction and research into potential cell therapies.
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Even if one argued that there is a difference between the two types of research, research on cell therapy would, if anything, be more defensible than research on reproduction. One in research opinion somewhat dubious argument is to be resezrch in McGee and Caplan ; here the suggestion is made that in using embryos for cell therapy, no embryos are actually sacrificed: A second, more convincing, argument, that the instrumental use of embryos is in principle easier to justify for isolation of hES cells than, for example, research directed towards improving IVF, is that it has potentially far wider clinical implications.
It therefore, unquestionably meets the proportionality requirement. Slippery slope The slippery slope argument can be considered as having two variants, one empirical and the other logical. The empirical version involves a prediction of the future: The logical version concerns the presumed logical implications resulting from the moral justification of X: In this context the problem often lies in the lack of precise definition of X: An example of the logical version is that acceptance of hES cells for the development of stem cell therapy for the treatment of serious disease automatically means there is no argument against acceptance of use, for example, for cosmetic rejuvenation Nuffield Council on Bioethics, One answer to this objection is to consider each case individually rather than reject researcch cases out of hand.
One could use the same objection for example against surgery, which can equally be used for serious as well as trivial treatments. The presumed automatism in the empirical version of the slippery slope argument is disputable. Subsidiarity A further condition for the instrumental use of embryos is that no suitable alternatives exist that may serve the same goals of the research. Critics of the use of hES cells claim that at least three such alternatives exist, which have in common that they do not require the research papers on stem cell research use researc embryos: The question is not whether these possible alternatives require further rrsearch this is, at least for the latter two, largely undisputedbut whether only these alternatives should be the subject of research.
In order to discuss the moral aspects of the isolation and use of hES cells, which is the aim of the present article, it is first essential to understand exactly what these cells are, where they come from, their intended applications and to define the ethical questions to be addressed. Looking at the data, we see continued publications in ES and hES, but do observe that the global volume of iPS publications has surpassed the volume of hES cell publications in see Figure 6. Check the status of your submitted manuscript in EES: Nevertheless, the prospect research papers on stem cell research autologous transplantation of haematopoietic stem cells of bone marrow in the long term makes this an important research area in terms of alternatives to therapeutic cloning see below. The empirical version involves a prediction of the future:
Is a moratorium for research papers on stem cell research hES cells required, or is it preferable to carry out research on the different options, including the use of hES cells, in parallel? The answer to this question depends on how the principle of subsidiarity ought to be applied.
A basis for initiating a comparative ethical analysis is set out below: This risk is, at least for the time being, an ethical and safety threshold for clinical trials. To date, however, hEG cells have been difficult to isolate and culture, with only one research group reporting success Shamblott click al. In addition, research in research suggests abnormal reprogramming of these cells in culture: This makes the outcome of eventual clinical application of these cells difficult to predict in terms of health risks for the recipient.
Experiments carried out within the last two years have demonstrated, for example, that bone marrow cells can give rise to nerve cells in mouse brain Mezey et al. Clonal analysis has provided rigorous proof of plasticity: Nonetheless, there are potential hazards to using cells that have been cultured for long periods for transplantation and although MAPCs seem to have normal chromosomes, it is research papers on stem cell research to establish that the pathways governing cell proliferation are unperturbed.
This is also true for hES cells. Bone marrow stem cells have been shown very recently to restore function to some extent in a mouse heart damaged by coronary ligation, an experiment that mimics the conditions of the human heart soon after infarction Orlic et al.
Although clinical restoration of function in a damaged organ is usually sought rather longer after the original injury than in these experiments, which were performed before scar tissue had formed, this approach will certainly be worth pursuing. This is used clinically for transplantation as an alternative to bone marrow in patients for whom no bone marrow match is available.
Cord blood contains precursors of a number of lineages but its pluripotency, or even multipotency, is far from proven. Nevertheless, the prospect of autologous transplantation of haematopoietic stem cells of bone marrow in the long term makes this an important research area in terms of alternatives to therapeutic cloning see below.
Although studies with adult stem cells so far have been research papers on stem cell research, Galliauthor of the first adult neural stem studies and much cited by advocates of the view that adult stem cells have a proven developmental potency equal to that of ES cells, himself disagrees entirely with this viewpoint see Editorial, However the stem cell research community and Verfaillie herself Vastag, have called for more research on both adult and embryonic stem cells.
ES cells that can perform as powerfully as those described by Kim et al. The question remains, however, should a moratorium be imposed on isolating hES cells for research in cell therapy in the light of the indisputably promising results from adult stem cell research?
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The lack of consensus arises largely from disagreement on interpretation of the subsidiarity principle. Against the restrictive viewpoint that research on hES cells may only take place if there is proof that adult stem cells are not optimally useful, there is the more permissive viewpoint that hES cell research may, and indeed should, take place so long it is unclear whether adult stem cells are complete or even partial alternatives.
On the basis of the following arguments, a less restrictive interpretation of the subsidiarity principle is morally justified. Stem Cell Research, To begin with, the most optimistic expectation is that only in the long run will adult stem cells prove to have equal plasticity and developmental potential as hES cells and be as broadly applicable in the clinicand there is a reasonable chance that this will never turn out to be the case.
Secondly, the simultaneous development of different research strategies is preferable, considering that research on hES cells will probably stem to speeding up and optimising clinical applications of adult stem cells. In particular, the stimuli to drive cells in particular directions of differentiation may be common to both cell types, while methods of delivery to damaged tissue are as likely to be common as complementary.
A moratorium on hES cell research would remove the driving force behind adult stem cell research. A final variant on adult stem cell sources concerns the use of embryonal carcinoma EC cells, a stem cell population found in tumours teratocarcinomas of young adult patients. These cells have research papers on stem cell research very similar to hES cells. The patients received neural cells derived from retinoic acid vitamin A treatment of teratocarcinoma stem cells. Although the scientific and ethical consensus is that these trials were premature in terms of potential risk of teratocarcinoma read more at the transplant site, all patients survived with no obvious detrimental effects, no tumour formation and in two cases a small improvement in symptoms.
After two years, the transplanted cells were still detectable by scanning Kondziolka et al. Despite its controversial nature, this trial has nevertheless probably set a precedent for similar trials using neural derivatives of hES, the best controlled differentiation pathway of hES cells at the present time Reubinoff et al. Proponents believe that such trials would be feasible even in the short term McKay, Others have pointed out the disadvantage of this alternative term, namely that it masks the fact that an embryo is created for instrumental use.
Qualifications click to see more for these constructs include: Although the purpose of therapeutic cloning is not the creation of a new individual and it is unlikely that the viability of the constructed product is equivalent to that of an embryo derived from sexual reproduction, it is not correct to say that an embryo has not been created.
The core of the problem is that here human embryos are created solely for instrumental use.