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Human Embryonic Stem Cells

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On the other hand, the use of Hess ells is highly controversial because they are derived from human overexploitation embryos. To date, most embryos used for the establishment Of Hess cell lines have been spare embryos from IV, but the creation Of embryos specifically for deriving Hess cells is also under discussion. The most controversial variant of this is the transfer of a somatic cell-nucleus from a patient to an enucleated octet (unfertile egg) in order to produce Hess cells genetically identical to that patient for ‘tautology’s’ transplantation (so-called ‘therapeutic’ cloning); this may prevent tissue rejection.

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The question ‘Can these cells be isolated and used and, if so, under what conditions and restrictions’ is presently high on the political and ethical agenda, with policies and legislation being formulated in many countries to regulate their derivation. 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, 2001 In order to discuss the moral aspects of the isolation and use of Hess 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.

Previous Connections Section What are (embryonic) stem cells? Stem cells’ are primitive cells with the capacity to divide and give rise to more identical stem cells or to specialize and form specific cells of somatic tissues. Broadly speaking, two types of stem cell can be distinguished: embryonic Stem (SE) cells which can only be derived from pre-implantation embryos and eave a proven ability to form cells of all tissues of the adult organism (termed ‘plenteous’), and ‘adult stem cells, which are found in a variety of tissues in the fetus and after birth and are, under normal conditions, more specialized (nilpotent’) with an important function in tissue replacement and repair. SE cells are derived from the so-called ‘inner cell mass’ of blastoffs stage embryos that develop in culture within 5 days of fertilization of the octet (Thomson et al. , 1 998; Rebuffing et al. , 2000). Although Hess cells can form all somatic tissues, they cannot form all of the other ‘extraordinary’ tissues accessory for complete development, such as the placenta and membranes, so that they cannot give rise to a complete new individual. They are therefore distinct from the ‘tiptoeing’ fertilized octet and blaster cells deriving from the first cleavage divisions. SE cells are also immortal, expressing high levels of a gene called telemeters, the protein product of which ensures that the telemeter ends of the chromosomes are retained at each cell division and the cells do not undergo senescence. The only other cells with proven plenipotentiary similar to that of SE cells are embryonic germ (EGG) cells, which as heir name implies, have been derived from ‘primordial germ cells’ that would ultimately form the gametes if the fetus had not been aborted.

To what extent transcendentalist cells are immortal or acquire appropriate function in host tissue remains largely to be established but advances in this area are paid, particularly for multivalent adult progenitor cells (Maps) of bone marrow (Rexes and Verifiable, 2001). Answers to these questions with respect to Maps, in particular whether they represent biological equivalents to Hess and can likewise be expanded indefinitely whilst retaining their differentiation potential, are currently being addressed Aging et al. 2002; Schwartz et al. 2002; verifiable, 2002; Chaos et al. , 2002). For other adult stem cell types, such as those from brain, skin or intestine (Fuchs and Serge, 2000), this may remain unclear for the immediate future. Although the discussion here encores Hess cells and the use of embryos, the scientific state-of-the-art on other types of stem cell is important in the context of the ‘subsidiaries principle’ (see below). Potential applications of Hess cells and state-of-the-art In theory, Hess cells could be used for many different purposes (Keller and Snodgrass, 1999).

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 octet appear to be important). A second category might be toxicology, ore 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 potential use of Hess cells is, however, clinically in transplantation medicine, where they could be used to develop cell replacement therapies.

This, according to most researchers in the field represents the real ‘home run’ and it is the ethics of using embryos in this aspect of medicine that will be discussed here. Examples of diseases caused by the loss, or loss of function, of only one or a limited number of cell types ND which could benefit from Hess cell-based therapies include diabetes, Parkinson disease, stroke, arthritis, multiple sclerosis, heart failure and spinal cord lesions.

Although it is known that Hess cells are capable of generating neural, cardiac, skeletal muscle, pancreas and liver cells in transliterations in vivo in immunodeficiency mice as well as in tissue culture, it would be an illusion to consider that cell-therapies will have widespread application in the short term (I. E. Within a couple of years). It is unfortunate that sensational treatment in the media, which implied the generation of hole organs from Hess cells, initially left this impression so that the more realistic view emerging is already a disappointment to some patient groups.

Nonetheless, a proper scientific evaluation of the therapeutic potential is being carried out in countries that allow the isolation and/or use of existing Hess cells. The ethical questions here then also include whether the establishment of new Hess cell lines can be justified, in the realization that eventual therapies, based on either Hess or adult stem cells are long-term perspectives. There are, at least in theory, various sources of Hess cells. In most cases to date, these have been spare IV embryos, although IV embryos have been specifically created for the purpose of stem cell isolation (Landforms et al. 2001). In one variant of ’embryo creation’, it has even been reported that normally organized balloonists develop from chimeras of two morphologically non-viable embryos (Alkali and Williwaws, 2002). The most revolutionary option would be the creation of embryos specifically for the purpose of isolating stem cells via ‘nuclear transfer’ (therapeutic cloning’). This option is purported to be the optimal medical use of Hess technology nice 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 Baritones et al. 1998; 2000). It is of note that the octet 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 octet by sperm, there is no absolute consensus that nuclear transfer gives rise to an embryo (see below). The establishment of embryonic cell lines is becoming increasingly efficient, tit up to 50% of spare IV embryos that develop into balloonists after thawing at the 8-cell stage reported to yield cell lines.

There are reports of efficiencies much lower than 50%, however, the quality of the donated embryos being an important determinant of success. Growth of the cell lines over extended periods and in some cases under defined conditions (Xx et 2001) has also been reported, but the controlled expansion and differentiation to specific cell types is an area where considerable research will be required before cell transplantation becomes clinical practice (for review, see Pastier and Mummery, 2003).

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 Hess 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 from IV embryos. Ethical exploration In the following section, the status of Hess cells is first considered.

The questions Of whether it is acceptable to use pre-implantation embryos as a source of SE cells for research on cell transplantation therapy and if so, whether embryo use should be limited to spare embryos or may also include the creation of embryos via nuclear transfer (therapeutic cloning’), are then addressed. The status of Hess cells What is the ontological status of Hess cells? Should they be considered equivalent to embryos or not? Let us first consider the status of the ‘naked’, isolated inner cell mass (CM; the source for deriving Hess cell lines).

The CM is s it were the ‘essence’ of the pre-implantation embryo, the precursor of the ’embryo proper’. The isolated CM, however, no longer has the potential to develop into a fetus and child, as tropical’s cells, necessary for implantation and nourishment of the embryo, and extra-embryonic endoderm, are absent. It does not necessarily follow, though, that the isolated CM is no longer an embryo-?we suggest that the whole, isolated CM could best be qualified as a disabled, ‘Nan-viable’ embryo (even though it might, at least in theory, be ‘rescued’ by enveloping the CM with sufficient tropical’s cells).

What, then, is the status of the individual cells from the CM once isolated, and the embryonic stem cell lines derived from them? Should we consider these cells/cell lines to be Nan-viable embryos too? We would argue that when the cells of the CM begin to spread and grow in culture, the CM disintegrates and the non-viable embryo perishes. Some might argue that Hess cells are embryos, because, although Hess cells in themselves cannot develop into a human being, they might if they were ‘built into’ a cellular background able to make extra-embryonic tissues necessary for implantation ND nutrition of the embryo.

At present this is only possible by ’embryo reconstruction’ in which the CM of an existing embryo is replaced by SE cells (Nagy et al. , 1993). Commentators who, against this background, regard Hess cells 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 (mispronunciation) would be required to achieve this, should be regarded as an embryo.

An absurd implication of this ‘inclusive’ definition of an embryo is that one should then also regard all somatic cells as equivalent to embryos-?after all, a somatic nucleus may become an embryo after nuclear transplantation in an enucleated octet. It is therefore unreasonable to regard Hess cells as equivalent to embryos. Instrumental use of embryos Research into the development of cell-replacement therapy requires the instrumental use of pre-implantation embryos from which Hess cells are derived since current technology requires lists of the thermoformed and culture of the CM; the embryo disintegrates and is thus destroyed.

As has already been discussed extensively in the embryo-research debate, inconsiderable differences of opinion exist with regard to the ontological and moral status of the pre-implantation embryo (Whorehouse, 1987). On one side of the spectrum are the ‘conventionalist’ view (the embryo is a person’) and the ‘strong’ version of the potentiality-argument (because of the potential of the embryo to develop into a person, it ought to be considered as a person’). On the other side of the spectrum we find the view that the embryo (and even the fetus) as a ‘non-person’ ought not to be attributed any moral status at all.

Between these extremes are various intermediates. Here, there is a kind of overlapping consensus’: the embryo has a real, but relatively low moral value. The most important arguments are the moderate version of the potentiality argument (the embryo deserves some protection because of its potential to become a person’) and the argument concerning the symbolic value Of the embryo (the embryo deserves to be treated with respect because it represents the beginning of human life).

Differences of opinion exist on the weight of these arguments (how much protection does the embryo deserve? ) and their extent (do they apply to pre-implantation embryos? ). In view of the act that up to 14 days of development, before the primitive streak develops and three germ layers appear, embryos can 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. Re-implantation embryos are generally regarded from the ethical point Of view as representing a single class, whereas in fact – 50-60% of these embryos are manipulated and mostly non-viable. For non-viable embryos, the argument of potentiality does not of course apply. Their moral status is thus only based on their symbolic value, which is already low in ‘pre-individualized’ overexploitation embryos. 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 view that research with pre-implantation embryos should be categorically forbidden is based on shaky premises and would be difficult to reconcile with the wide social acceptance of contraceptive intrauterine devices. The dominant view in ethics is that the instrumental use Of overexploitation embryos, in the light of their relative moral value, can be justified under retain conditions. The international debate focuses on defining these conditions. Ethics of using surplus IV embryos as a source of Hess cells Possible objections are connected to the principle of proportionality, the slippery slope argument, and the principle of subsidiaries.

Proportionality It is generally agreed that research involving embryos should be related to an important goal, sometimes formulated as ‘an important health interest’ (the principle of proportionality). Opinions differ on how this should be interpreted and made operational. In a number of countries, research on re-implantation embryos is permitted provided it is related to human reproduction. Internationally, however, such a limitation is being increasingly regarded as too restrictive (De Wert et al. , 2002). The isolation of Hess cells for research into cell-replacement therapies operates as a catalyst for this discussion.

It is difficult to argue that research into Hess 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 Minefield Council on Bioethics (Minefield Council on Bioethics, 2000) also saw no reason for making a moral distinction between research into diagnostic methods or reproduction and research into potential cell therapies.

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 our opinion somewhat dubious) argument is to be found in McGee and Kaplan (1 999); here the suggestion is made that in using embryos for cell therapy, no embryos are actually sacrificed: ‘In the ease of embryos already slated to be discarded after IV, the use of stem cells may actually lend permanence to the embryo.

Our point here is that the sacrifice of an early human embryo, whether it involves a human person or not, is not the same as the sacrifice of an adult because life off 100-cell embryo is contained in its cells nuclear DNA’ In other words, the unique characteristic of an embryo is its DNA’ by transplanting cells containing this DNA to a new individual, the DNA is preserved and the embryo therefore not sacrificed-?a ‘win-?win’ situation for both the embryo and cell transplant recipient.

The implication is thus that the use of embryos for cell transplantation purposes is ethically preferable to disposing of them or using them in other (truly destructive’) types of research. This extreme genetic ‘reductionism’ is highly disputable and not convincing: the fact that embryos are actually sacrificed in research into cell therapy is masked. A second, more convincing, argument, that the instrumental use of embryos is in principle easier to justify for isolation of Hess cells than, for example, research directed towards improving IV, 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: ‘Acceptance of practice X will inevitably lead to acceptance of (undesirable) practice Y. To prevent Y, X must be banned’. The logical version concerns the presumed logical implications resulting from the moral justification of X: ‘Justification of X automatically implies acceptance of (undesirable) practice Y’.

In this context the problem often lies in the lack Of recipes definition of X: The difficulty in making a conceptual distinction between X and Y that is sharp enough to justify X without at the same time justifying Y, is a reason to disallow X. ‘ Both versions of the argument play a role in the debate about the isolation of Hess cells for research into cell replacement therapy.

An example of the logical version is that acceptance of Hess 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 (Minefield Council on Bioethics, 000). The main difficulty is, according to these critics, the ‘grey area’ between these two extremes. One answer to this objection is to consider each case individually rather than reject all 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.

An example of the empirical version of the slippery slope argument is that the use of Hess cells for the development of cell therapy would inevitably lead to applications in germ-line gene therapy and in therapeutic cloning, then ultimately reproductive cloning. This version of the argument is unconvincing too; even if germ line gene therapy and therapeutic cloning would be categorically unacceptable, which is not self-evident, it does not necessarily follow from this that the use of Hess cells for cell-therapy is unacceptable.

The presumed automatism in the empirical version of the slippery slope argument is disputable. Us bestiality A further condition for the instrumental use of embryos is that no suitable alternatives exist that may serve the same goals of the research. This is termed ‘the principle of subsidiaries’. Critics of the use of Hess cells claim that t least three such alternatives exist, which have in common that they do not require the instrumental use of embryos: (I) sensationalistic; (ii) human embryonic germ cells (huge cells), and (iii) adult stem cells.

The question is not whether these possible alternatives require further research (this is, at least for the latter two, largely undisputed), but whether only these alternatives should be the subject of research. Is a moratorium for isolating Hess cells required, or is it preferable to carry out research on the different options, including the use of Hess cells, in parallel? The answer to this question depends on how the principle of subsidiaries ought to be applied.

Although the principle of subsidiaries is meant to express concern for the (albeit limited) moral value of the embryo, it is a sign of ethical one-dimensionality to present every alternative, which does not use embryos, as a priori superior. For the comparative ethical analysis of Hess cells from overexploitation embryos on the one hand, and the possible alternatives mentioned on the other, a number of relevant aspects should be taken into account.

These include: the burdens and/or risks of the different options for the patient and his or her environment; the chance that the alternative options have the same (probably broad) applicability as Hess cells from pre-implantation embryos; and the time-scale in which clinically useful applications are to be expected. A basis for initiating a comparative ethical analysis is set out below: (I) Sensationalistic is viewed at present as carrying a risk, albeit limited, of cross-species infections and an accompanying threat to public health. This risk is, at least for the time being, an ethical and safety threshold for clinical trials.

Apart from that, the question may be raised from a perspective of animal ethics whether it is reasonable to breed and kill animals in order to produce transplants, when at the same time spare human embryos are available which would otherwise be discarded; (lie) In principle, the use of huge cells from primordial germ cells of dead fetus seems from a moral perspective to be more acceptable than the instrumental use of living pre-implantation embryos, provided that the decision to abort was not motivated by the use of fetal material for transplantation purposes.

Cite this Human Embryonic Stem Cells

Human Embryonic Stem Cells. (2018, Mar 16). Retrieved from https://graduateway.com/human-embryonic-stem-cells/

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