Stem Cell Cloning

[ November 18, 2014 ]

Last year, scientists succeeded in cloning human embryonic stem cells (hESC) that may aid in developing replacement tissue to treat serious and fatal diseases and even create cloned babies in the future.

Stem cells are biological cells that have the ability to develop into many different types of specialized cells during early life and growth. In addition, they serve as an internal repair system in certain tissues, infinitely dividing as long as the organism is still alive. When a stem cell divides, each new cell has the potential to either remain a stem cell or become another type of cell with a more specialized function, such as a neuron, a red blood cell, or a brain cell. In some organs, such as the gut and bone marrow, stem cells regularly divide to repair and replace worn out or damaged tissues. However, in other organs, such as the pancreas and the heart, stem cells only divide under special conditions.

Until recently, scientists primarily worked with two kinds of stem cells from both animals and humans: embryonic stem cells and adult stem cells. Embryonic stem cells are derived from embryos that develop from eggs that have been fertilized in vitro (in a dish) and then donated for research purposes with informed consent of the donors. Scientists discovered ways to derive embryonic stem cells from early mouse embryos nearly 30 years ago, in 1981. The detailed study of the biology of mouse stem cells led to the discovery of a method to derive stem cells from human embryos and grow the cells in the laboratory in 1998.

An adult stem cell, on the other hand, is an undifferentiated cell, found among differentiated cells in a tissue or organ that can renew itself and can differentiate to yield some or all of the major specialized cell types of the tissue or organ. The primary roles of adult stem cells in a living organism are to maintain and repair the tissue in which they are found.

The scientists at Oregon Health and Science University were able to clone the hESCs by taking skin cells from a baby with a genetic disease and fusing them with donated human eggs to create a human embryo that was genetically identical to the 8-month-old.

Following this experiment, researchers in two separate studies in Seoul and New York were also able to create stem cells from cloned embryos this year. The study in Seoul was able to use the skin cells from two men, aged 35 and 75, while scientists in New York used skin cells from a 32-year-old woman with Type 1 diabetes to generate stem cells that matched their cells.

To produce the cloned embryos, all three groups used an optimized version of the laboratory technique called somatic-cell nuclear transfer (SCNT), where the nucleus from a patient’s cell is placed into an unfertilized human egg which has been stripped of its own nucleus, reprograming the cell into an embryonic state. SCNT was the technique used to create the first mammal cloned from an adult cell, Dolly the sheep, in 1996.

Despite these advances, many bioethical dilemmas surround this issue as embryonic stem cells (which can develop into a human) are destroyed in the development of medical treatments. A drawback of therapeutic cloning is that there might not be enough human eggs available to treat all patients, should the therapy ever work. The technique is also very expensive and technically difficult. It creates an embryo only for the purpose of harvesting its cells. Obtaining human eggs also requires regulatory clearance to perform an invasive procedure on healthy young women, who are paid for their time and discomfort. Additionally, these egg donors can suffer serious side effects from the powerful hormones needed to generate multiple eggs. Stem cell cloning could become a real possibility in our future, possibly with some very damaging consequences.

By Prateek Sahni

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