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Stems cells are essential to the advancement of regenerative medicine because they are an alternate and renewable source of specialized cells that cannot be replaced naturally (by the body) if they are seriously damaged or diseased.

What are stem cells?

Stem cells are the progenitors of all cells in the human body and, therefore, of all tissue. Stem cells are “undifferentiated” cells, which means they have the ability to become many different cell/tissue types with specialized functions, such as skin, blood, muscle, bone, brain tissue or organ. They also have unlimited proliferation ability, which means they can divide or self-replicate for indefinite periods.

Put another way, while most cells of the body are specialized and carry out a specific function, a stem cell is “uncommitted’ and will remain this way until it receives a signal to become a specialized cell. This ability to self-sustain and reproduce indefinitely and to differentiate into many types of specialized cells makes them unique and is why they are so important to regenerative medicine as sources of cells to treat many diseases.

Stems cells are essential to the advancement of regenerative medicine because they are an alternate and renewable source of specialized cells that cannot be replaced naturally (by the body) if they are seriously damaged or diseased.

Stem cells are found in a variety of sources including adult tissue, umbilical cord blood, placental tissue, and human embryos. The controversy about stems cells is focused on those derived from human embryos.

Stem cells may lead to more effective treatments or even cures of birth defects, diseases and disabilities affecting millions of Americans including cancer, Parkinson’s Disease and Alzheimer’s, spinal cord injury, stroke, heart disease, diabetes and arthritis.

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What is the controversy about stem cell research?

The controversy about stem cell research is focused on one specific source of these cells: human embryonic stem cells. Human embryonic stem cells are derived from the cells that make up the inner cell mass of the blastocyst, a hollow sphere of cells that forms about four days after a sperm has fertilized an egg. Human embryonic stem cell production requires the destruction of the fertilized egg, which is objectionable to those who believe life begins at conception.

Both mouse and human embryonic stem cell lines exist. Mouse embryonic stem cells are capable of generating any and all cells in the body, under the right conditions, and are therefore said to be pluripotent. That is, they have unlimited potential as far as growth and differentiation.

Less is known about human embryonic stem cell lines because they were identified much more recently. There are, however, several research teams working to determine whether or not they possess the same properties as mouse embryonic stem cells.

In the U.S. additional controversy about research using human embryonic stem cells was prompted by a 2001 presidential directive in which President Bush authorized funding for 78 then-existing human embryonic stem cell lines that had previously been derived from excess embryos created for in vitro fertilization. This directive barred expenditure of federal funds for research on any other embryonic stem cell lines. Of the original 78 eligible lines, approximately 20 remain available today and some of these are affected with chromosomal abnormalities, as well as questions about possible contamination/alteration of their capabilities. 

Further controversy is focused on the potential advantages and limitations of embryonic stem cells versus adult stem cells. While human embryonic stem cells appear to have great pluripotency, if their growth is unchecked they can cause tumors to develop. Multipotent adult stem cells display less capacity to produce varying cell types. Furthermore, scientists have not located adult stem cells for all cell and tissue types (including heart and pancreas) and the quantities of adult stem cells present in tissues are usually small, difficult to isolate and purify, and decrease with age. 

For all of these reasons most scientists believe that it is necessary for research to continue in all types of stem cells, including adult and human embryonic, to realize the full promise of stem cell research.