Embryonic stem cells

Embryonic stem cells are cells in the human body that develop during the blastula phase of human embryo development. The blastula phase occurs when the embryo is a few days old. Embryonic stem cells only exist for about five days during embryonic development. After this period, the cells divide and differentiate, or form, into hundreds of cell types.

Embryonic stem cells can develop into any type of human cell. These cells can repair and replenish other cells. Scientists believe embryonic stem cells can be reproduced and manipulated to treat injuries and diseases and have attempted to harness their regenerative potential. During the stem cell extraction process, isolated embryos are usually destroyed, which has raised ethical issues concerning the value of embryonic stem cell research over an embryo's life potential.

Overview

Embryonic stem cells differ from adult stem cells because they are pluripotent, which means they can differentiate into more than two hundred different types of human cells. Adult stem cells are multipotent, which means they can only form into mature cells. Another distinct trait of embryonic stem cells is that they can replicate forever. This characteristic is important for researchers who study the medical benefits of embryonic stem cell therapy. Scientists can grow endless amounts of embryonic stem cells and use them to conduct experimental medical treatments.

Embryonic stem cell research became public in the 1980s. Scientists first discovered ways to extract the cells from mouse embryos in 1981. Continued research led to the discovery in 1998 of a way to isolate human embryonic stem cells and grow them in a controlled environment. Scientists derived these stem cells through in vitro fertilization, a technique that combines donated female eggs and male sperm in a laboratory setting. Once the embryo forms, scientists derive its stem cells and replicate them for research. This process usually destroys the embryo, however.

Embryonic stem cells have the ability to self-renew and replenish other cells around them. By studying embryonic stem cells, scientists learned how to harness the differentiation process of the cells so they could program them to form into any specific type of cell. These cells could then be used in medical research. The scientists found that embryonic stem cell therapy could potentially treat ailments such as blood and immune system diseases, cancer, and diabetes. Research also suggested using these cells to potentially reverse blindness and spinal cord injuries.

Ethics, Laws, and Trials

Many ethical concerns surround embryonic stem cell research. Embryos—cultured or not—have the potential to grow into human beings. Many argue that embryos should be treated with the same respect as humans. They contend that destroying embryos for science is akin to destroying a human life.

The practice of cloning embryos for research purposes also created controversy, particularly among the religious community. Members argued that a person's soul enters its body the moment an egg and sperm unite; therefore, they believe the reproduction of embryos for scientific use is morally offensive. Those on the other side of the debate argued that since heartbeat does not develop until after the blastula phase, the early-stage embryos used in research could not yet be considered a human life. Conservatives further countered this argument by insisting that all embryos have the potential for life at any stage, and the decision to terminate this potential should not be made by scientists.

The argument concerning an embryo's life potential was often cited when politicians sought to limit embryonic stem cell research. In the United States, several state and federal laws limited and prohibited the use of human embryonic stem cells for research. In 2001, President George W. Bush placed restrictions on federal funding for stem cell research, including a provision prohibiting the National Institutes of Health (NIH) from funding embryonic stem cell research beyond the embryos already being studied at the time. Despite this measure, lawmakers supported expansion of funding on several occasions. In 2005, the House of Representatives voted on a bill that would ease restrictions on embryonic stem cell research. President Bush vetoed this bill, saying he believed the bill would support the taking of innocent human lives for scientific benefit.

When Barack Obama became president in 2009, he overturned Bush's NIH ban and lifted some restrictions on federal science programs involving embryonic stem cell research. Obama said he did not believe research efforts should be hampered by the science versus morality argument. He believed the potential to end human suffering was the greater matter at hand. The president, however, implemented strict parameters to ban human cloning.

Early embryonic stem cell studies conducted using cells from mice yielded varying results. The first clinical trial using human embryonic stem cells was approved in January of 2009. The study involved using the cells to treat spinal cord injury. After preliminary trials involving animals, the first human patient was enrolled in 2010. The patient reported experiencing improvement after a year of treatment. In 2014, scientists used human embryonic stem cells to successfully restore normal movement in rats with Parkinson's disease. Scientists hoped to eventually be able to use this treatment on humans.

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