Stem Cell Primer
Stem cell research is the most promising path to healing many severe diseases and disabling medical conditions. It may yield remedies for such conditions as Parkinson’s and Alzheimer’s diseases, juvenile diabetes, spinal cord injury, MS, ALS, and certain forms of cancer and heart disease.
Stem cells are unspecialized cells that can develop into more mature, specialized cells. They are found in embryos during their first few days of development, in fetal tissue, umbilical cords, and more rarely, in some adult tissues. Embryonic stem cells are “pluripotent,” meaning that they have the potential to differentiate into any cell type (brain, liver, heart, pancreas, etc.) of the human body. Scientists work with both embryonic and adult stem cells, but embryonic stem cells have certain advantages. Adult stem cells are problematic for research purposes because they are rare, and often difficult to extract and maintain in culture.
Scientists have recently had some success in "reprogramming" adults cells to gain some of the properties of stem cells. There remains today a broad scientific consensus, however, that this advance does not negate the essential role that embryonic stem cell research will play in the search for effective new therapies. Harvard scientist Doug Melton, one of the pioneers of cell reprogramming research, explains that “We would not be where we are today without having worked with human embryonic stem cells. These unique cells provide a window into human development and disease development that is needed if we are to make further progress in understanding and treating chronic diseases. Embryonic stem cells remain the key to long-term progress in this field.”
Regenerative medicine based on embryonic stem cell research aims to use pluripotent stem cells to heal severe illnesses and injuries. The hope is that we can grow stem cells in laboratories to form specific tissues, such as brain, heart, lung, kidney or pancreatic tissue, which could then help repair damaged and diseased organs or provide alternative to organ transplants. Many of the illnesses that are targets of stem cell therapy have few or no treatment options, so millions of Americans are looking to stem cell research as a promising path to new, effective treatments.
How Does Stem Cell Research Lead to Cures?
Some children are born with organs that do not work right. A child with juvenile diabetes, for example, has a pancreas that does not generate enough insulin – a hormone needed by the body in order to digest sugars.
Adults too sometimes have cells or entire organs that have become damaged so that they no longer function well. In the brain of a person who has Parkinson’s or Alzheimer’s disease, for example, cells no longer work in the normal way. In a spinal cord injury, crushed or damaged cells cause paralysis. In a heart attack, heart muscle is destroyed and replaced by useless scar tissue. In each of these cases, the result is illness, disability, and suffering.
Doctors and scientists have long been looking for a way to replace damaged or worn-out tissue in the human body with new healthy tissue, thereby giving patients – literally – a new lease on life. A very promising path to cures is the regeneration of differentiated tissue from embryonic stem cells. Research using these cells may succeed in developing the cures needed by the nearly 100 million Americans afflicted by conditions ranging from Parkinson’s and Alzheimer’s diseases to juvenile diabetes, MS, ALS, and spinal cord injury.
There are today two main sources of pluripotent stem cells that can be used to advance the search for cures:
1. Scientists can use stem cells from left-over embryos that would otherwise be discarded from fertility clinics. From these cells, healthy new tissue can be formed to replace the tissue that an illness or injury has damaged or destroyed.
2. Scientists can use therapeutic cloning to generate stem cells for research to find cures.
The technical term for therapeutic cloning is “somatic cell nuclear transfer” (SCNT). Scientists remove the nucleus of an unfertilized egg cell and replace it with the genetic material from the nucleus of a "somatic cell" (a skin cell, for example). Then they stimulate this cell to begin dividing. No sperm is involved in this process, and no embryo is created to be implanted in a woman’s womb. The clump of cells resulting from this process is stored in a petri dish and never leaves the lab. The stem cells generated in this way won’t become a human being, but they can potentially develop into specialized cells – brain cells, blood cells, pancreatic cells, etc. — that are useful for treating many devastating medical conditions.
SCNT would produce stem cells that are genetically identical to a patient’s original cells.
Therapeutic cloning produces no cloned individual, but only cell tissue that can be used to heal an individual. Therapeutic cloning research is endorsed by the American Medical Association, the National Academy of Sciences, the Association of American Universities, and many other medical, scientific, and educational associations.
In their statement of support for therapeutic cloning research, forty Nobel Laureates say that SCNT research is needed not only to develop cell-replacement therapies, but also to increase our understanding of how inherited genetic predispositions lead to a wide variety of diseases. A deeper understanding of how diseases arise will help us to cure them.