THERAPEUTIC VS. REPRODUCTIVE CLONING SCIENTIFIC REALITIES, PUBLIC CONTROVERSY

CLONING

INTRODUCTION Cloning may be the most talked about & most misunderstood issue in Biomedical Research today! Cloning has become a controversial issue with scientists, lawmakers, religious leaders and the general public. In 1997 the controversy grew when they cloned the first mammal…Dolly the sheep. Probably because it drew attention to the possibility of cloning humans.

CONT’D Very few scientists believe that human cloning should be allowed. Surveys show that most people disapprove of cloning a human being…known as reproductive cloning. On the other hand, many scientists are in favor of research into therapeutic cloning, which is the procedure used to produce embryonic stem cells that may be used to treat a number of diseases.

EMBRYONIC STEM CELLS The starter cells that can turn into any sort of body tissue, from brain, to blood, to bone. These unspecialized cells also have the ability to divide for indefinite periods in tissue cultures (in vitro). They are found in embryos during the early stage of development.

WHAT IS A CLONE? Clone = a precise genetic copy. A copy of a biological entity. As simple as DNA or as complex as a plant or animal cell or whole organism. Cloning became confusing because many people use the word to mean lab techniques that created the sheep Dolly. That procedure is actually called somatic cell nuclear transfer (SCNT).

SCNT PROCEDURE Step #1: An unfertilized egg (an oocyte) from a female animal has its nucleus removed (enucleated oocyte). The nucleus is the part that has the DNA. Enucleating is done under microscope & illuminating it with ultraviolet light, which causes the genetic material to glow brightly. The egg is held in place while the scientist extracts the genetic material.

Step #2:The nucleus of a single somatic cell ( any nonreproductive cell in the body) is then inserted into the enucleated oocyte. Dolly was created from a cultured mammary cell & skin cells. Step#3 The remaining reproductive machinery in the oocyte reprograms the genetic material of the somatic cell…producing a reconstituted embryo.

Step #4: For reproductive cloning, the reconstituted embryo is placed into the uterus of a surrogate female. For humans a female would donate her eggs to be enucleated. The nuclei of her cells would be removed & the person being cloned would donate somatic cells for the nuclear transfer. A surrogate mom would then accept the fertilized egg in hope of carrying to term.

Step #5): Therapeutic cloning, the embryo is allowed to undergo cell division for several days until it reaches the blastocyst stage. A blastocyst has 2 layers. The outer one becomes the placenta and inner mass that forms virtually all the tissues of the body. To obtain embryonic stem cells the blastocyst is opened and the inner mass is placed in tissue culture. Here they divide & make exact replicas of themselves…forming clones.

OBSTACLES TO REPRODUCTIVE CLONING USING ANIMALS For every 100 cloned embryos… 3 live births occur. Majority of the problems develop during fetal development, few problems show up after birth, months or years later in animals. One birth is the large offspring syndrome…Cloned newborns are 20-30% larger than usual making it hard to deliver such large babies!

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EMBRYONIC & ADULT STEM CELLS These are the 2 different types of stem cells at this point. Adult stem cells probably exist in very small numbers throughout the body, but the most accessible ones are the blood stem cells that reside in bone marrow. As the fetus develops the embryonic stem cells undergo further specialization into adult stem cells. They are called multipotent because they are committed to give rise to more limited types of cells that have particular functions (ex. skin or blood cells).

BLOOD STEM CELLS Along with residing in bone marrow of every child & adult, a small number of these cells can be found in the circulating blood and the blood that remains in a newborns umbilical chord after the baby is born. Now parent’s have the choice to bank their baby’s umbilical chord blood incase the child needs stem cells later in life. These cells seem to work the best as they less “mature”. People’s whose blood stem cells have been destroyed during chemotherapy, radiation or immune deficiency diseases…a treatment option is a bone marrow transplant(transfusion of adult stem cells). Some cancer patient’s have their bone marrow frozen before treatments then given back after treatment. Patients with immune deficiency receive bone marrow from a well matched donor relative or volunteer.

REVIEW Reproductive Cloning: Using SCNT is to create a new organism (human or animal). Therapeutic Cloning: Using SCNT is not to produce a human but to create embryonic stem cells that are genetically compatible with the recipient.

HUMAN STEM CELL RESEARCH Heated debate because it involves the use of human embryonic tissue. 9/2001 President George Bush declared no federal funding for use of stem cells from newly destroyed embryos or the creation of human embryos for research or the cloning of humans. This decision did not effect research funded by private companies or state governments. 3/2009 President Obama revoked Bush’s decision. States Federal government can support & conduct responsible, scientifically worthy human stem cell research, including human embryonic stem cell research, to the extent permitted by law.

DOWNFALLS Stem cells have not been isolated for all tissues in the body ( ex. cardiac and pancreas ). Adult stem cells are minute and hard to isolate & purify. Some diseases there isn’t time to grow them in time for use. Genetic diseases…The genetics would be in their own stem cells. Adult stem cells might not be able to reproduce in culture like the younger cells. In adult stem cells, studies of the early stages of cell specialization might not be possible with them.

DEBATE SCNT has the potential to become a living thing, if transplanted into a female’s uterus. Is life destroyed if you remove the stem cells from blastocyst 4 days later?

THE FUTURE Individuals with a disease could have stem cells produced that match their own cells, and these cells wouldn’t be seen as foreign. Able to repair damaged tissues…will be a breakthrough for Parkinson’s Disease. Placing stem cells into that area of the brain they can differentiate & produce Dopamine. Early animal experiments found that this has happened in animals.

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