Scientific, ethical and moral aspects of human cloning

Until the cloning of Dolly the sheep in 1996, the idea that human cloning might soon become a reality seemed more like science-fiction than anything else. Recent claims of successful human cloning by Clonaid, though as yet unsubstantiated, have served to fuel the ongoing debate on this very controversial subject.

Scientific developments have been proceeding at a rapid pace and nowhere has this been more apparent than in the field of cytogenetics.

Before the advent of in vitro fertilisation (IVF), the earlier stages in human embryology had always occurred in the highly inaccessible uterus of a human female.

Since then the process of fertilisation has become an observable phenomenon amenable to experimental manipulation and the earliest stages of human embryological development have ceased to be shrouded in uterine obscurity.

For a better understanding of human cloning it is worthwhile reviewing briefly the microscopic world of the cell and the process of fertilisation.

The cell is the basic unit of every living organism. Practically all the cells that make up the human body have 46 chromosomes in their nucleus. Gametes (eggs and spermatozoa) have 23 chromosomes.

The major part of the genetic material of the cell - deoxyribonucleic acid (DNA) - is to be found in the genes that make up the chromosomes, although small amounts of DNA are also present in the cytoplasmic organelles.

Fertilisation is not an instantaneous event. It lasts between 22 and 24 hours. It starts with the first contact of the fertilising spermatozoon with the female egg cell and ends with the mingling of the nuclear material of the two gametes to form the unicellular zygote.

The first appearance of the new genotype constitutes a recognisable biological landmark of the beginning of a new human life.

Every authority in human embryology identifies the zygote as the first cell of a new and distinct organism possessing all the genetic material needed to inform and organise its further growth and development.

Cloning technology

Human cloning refers to the production of genetically identical human beings which can be achieved through either "embryo splitting" or the more commonly used "nuclear transfer" techniques.

Embryo splitting involves the separation of the component cells of the early human embryo when each blastomere still has the potential to develop into a blastocyst which, if implanted, can develop into a whole organism.

Somatic cell nuclear transfer (SCNT) consists in the removal of the nuclear material from an oocyte and its replacement from a somatic cell. The resulting cell with an nucleus containing 46 chromosomes all of which derived from the donor is then activated electrically or chemically to start dividing.

Human cloning by SCNT may be carried out for reproductive or therapeutic purposes. The aim of the former is to produce a genetically identical child to an individual who may otherwise remain childless.

The aim of the latter is to produce embryonic stem cells that are genetically identical to a patient. The stem cells could then be differentiated into precursor replacement cells which, hopefully, could be used to treat one of a variety of degenerative diseases from which the patient may be suffering

The blastomeres resulting from the early divisions of the zygote are totipotent. Stem cells from the ICM, on the other hand, are pluripotent because their potential is not total and, if implanted into an uterus, are unable to give rise to the placenta and supporting tissues necessary for intra-uterine fetal development.

One of the reasons why stem cell research is considered important is because it will lead to a better understanding of the complex events that occur during early human development.

This type of research will help in the identification of the factors involved in the cellular decision-making process that results in cell specialisation. Some of the most serious medical conditions, such as cancer and birth defects, are due to abnormal cell specialisation and cell division.

But perhaps the most far-reaching potential application of human stem cells is their use for so-called 'cell-therapies' in chronic heart disease, spinal cord damage, diabetes mellitus, Alzheimer's disease and Parkinson's disease.

Stem cells have two special characteristics: (a) they are able to reproduce themselves over a long period without becoming differentiated, and (b) they are capable of producing progenitor cells from which a variety of lineages of highly differentiated cells, such as, neural cells, muscle cells, and blood cells, can be obtained to be used for therapeutic purposes.

Embryonic stem cells (ESC), as their name implies, are derived from the inner cell mass (ICM) of the blastocyst. ESC have also been obtained from fetal tissue derived from terminated pregnancies. Harvesting stem cells from the ICM kills the human embryo.

As the cloning of Dolly has clearly demonstrated, biological development of cells is not as irreversible as had previously been thought, although the precise mechanism remains unknown.

Adult stem cells (ASC) are undifferentiated cells found among differentiated cells in a tissue or organ. They can renew themselves and can differentiate to yield major specialised cell types of the tissue or organ.

Their primary role in a living organism is to maintain and repair the tissue in which they are found. ASC have been identified in mature tissues and organs but their origin in mature tissues is unknown.

They have been found in brain tissue, bone marrow, peripheral blood, umbilical cord blood, skeletal muscle, skin and liver.

Moral status of human embryo

The nature of the human embryo is of central importance in bioethics. For obvious reasons the arguments for or against human cloning are intimately linked with the controversial issue of the moral status of the early human embryo.

It is crucial that we recognise the importance of making correct use of the biological facts in our attempt to determine at what stage during embryological development it may be claimed that a human being is present.

Up to the late 1950s, everyone understood conception to mean the moment when a spermatozoon fertilised the egg and a new human being came into existence.

As contraceptive technology progressed in the early 1960s, its proponents realised that some of their products, like the intra-uterine device (IUD), did not always act as contraceptives by preventing the union of sperm and egg.

Sometimes they acted as abortifacients by preventing the early human embryo from implanting into the lining of the maternal uterus.

The American College of Obstetrics and Gynecology overcame this problem by re-defining "conception" as "the implantation of a fertilised ovum". The fact that the human ebmryo is already two weeks old by the time implantion occurs was totally ignored.

The most highlighted indicators of the moral status of the human embryo are those which occur in the very early stages of embryology.

Common sense acknowledges the distinction between 'what one is' and 'what one does' and thus between 'being a person' and 'functioning as a person'.

Indeed one cannot function as a person without first being a person. The distinction betwen a human being and a human person is artificial rather than real.

After all, we are human by virtue of what we are, and not by virtue of what we can do. It is because of what we are, because of our nature, that we can and do function in certain ways.

It makes a lot of sense, therefore, to postulate that every human being starts his/her existence as a unicellular zygote, the immediate end-product of fertilisation.

It is at this stage that the unique new genotype is formed in the zygote. From then on the zygote grows and develops as a human being producing specifically human proteins and enzymes and follows the genetic programme for building a human body.

Ethical aspects

There seems to be widespread public revulsion about cloning human beings. Such a reaction may indeed be based on false beliefs about genetic influence and the nature of the individuals that would be produced through cloning.

As many scientists have pointed out, a clone would not be an identical "carbon copy" but more like a delayed identical twin.

And just as identical twins are two separate individuals - biologically, psychologically, morally and legally, though not genetically - a clone, too, would be a separate person from his/her own non-contemporaneous twin.

Genes do not determine everything about us. Environmental factors and random events also exert a significant influence on our development.

The possibility of genetic mutation or other biological damage as a result of human cloning constitutes a major ethical concern.

The ethical issues of greatest importance however do not involve possible technological failures but rather the consequences of technological success.

If there is something deeply objectionable about human cloning, it is more likely to be found by examining the implications of the cloning process itself, or the reasons people might have for availing themselves of it.

Many proponents of human cloning see it as part of the technology of IVF in assisted reproduction. That is, another way of overcoming the problem of infertility by providing a couple with a biological child they might otherwise be unable to have.

They argue that cloning should be acceptable for this purpose. On the other hand, many opponents of cloning see it as part of the emerging technologies of genetic engineering, specifically gene transplantation technologies.

Human cloning is ethically objectionable because it violates certain fundamental principles of medically assisted reproduction.

It undermines the dignity of the human person by treating it as a means rather than as an end in itself. It also denies the person the right to genetic uniqueness and the right to be able to programme his/her future life without being conditioned biologically and culturally.

Cloning undermines the structure of the family by making identities and lineages unclear and by creating ambiguities. Is the clone an offspring or a sibling?

Does the clone have one biological parent or two? The moral significance of these ambiguities lies in the fact that in many societies, including our own, lineage identifies responsibilities.

Moral considerations

The Catholic position has always been that human life is to be respected from the first moment of its existence till its natural end. From fertilisation onwards a living human embryo is a human subject with a well-defined identity which determines its own co-ordinated, continuous and gradual development, such that at no later stage can it be considered as a simple "mass of cells".

Foremost among the rights of the human embryo is the inviolable right of every innocent human being to life.

Therefore, any intervention which involves the destruction of a human embryo is an act which violates that right.

Harvesting embryonic stem cells involves the ablation of the ICM of the blastocyst which critically damages the human embryo and interrupts its further development.

The Catholic Church regards this procedure as morally objectionable on the grounds that a good intention does not make right an action which, in itself, is wrong.

It also condemns as immoral any procedure, including cloning, which dissociates the conjugal act from that of human procreation.

This notwithstanding, a cloned human embryo embarking on normal development, would arguably be of equal moral status to a normal human embryo and, therefore, should be accorded the same rights.

Fortunately, not all stem cell research involves the destruction of human embryos or the use of aborted fetuses.

Studies in recent years suggest that stem cells in different adult tissues may have a developmental repertoire close to that of embryonic stem cells.

New technologies have been developed which could stimulate the growth and specialisation of stem cells derived from bone marrow and umbilical cord blood.

In this way the benefits of this promising field of research could be obtained without destroying the human embryo which, so far, constitutes the main ethical and moral objections to therapeutic human cloning.

Lino J. German, MD, M.Phil., FRCOG, is the Ethics Officer of the Medical Association of Malta