The Science and History of Adult Stem Cells
Dr. Max Gomez
Medical Correspondent, WCBS News
Member of the Board of Directors, The Stem for Life Foundation
Many scientists and medical professionals around the globe are working tirelessly to raise awareness of the potential for stem cell therapies to end the suffering of millions. But for those of you who are new to the subject, let me explain where we are today in the field of adult stem cell research, and share some of the milestones and achievements along the way.
The term “adult stem cells” is a scientifically imprecise, possibly even misleading, term since these cells are actually found in infants as well as adults. We use “adult stem cells” as a kind of shorthand to reference a variety of cells, in fact almost any stem cell that is not a true embryonic stem cell. Adult stem cells are found in virtually every tissue and organ of the body, from bone marrow and brain, to fat, teeth, heart, gut and liver. What makes these cells exciting is that they have the remarkable capacity to transform or become any number of different cell types, with some limitations.
The term “stem cell” first appeared in scientific literature in 1868 in a paper by German biologist, Ernst Haeckel. Over the next few decades, the concept of a stem cell evolved to mean early stage cells that can divide and self-renew indefinitely to produce more stem cells.
Moving into the modern history of stem cells, in 1957, human bone marrow transplants were pioneered by Dr. E. D. Thomas. At the time, Dr. Thomas didn’t realize that it was actually stem cells in bone marrow that made the transplants successful. In 1961, Drs. James Till and Ernest McCulloch proved the existence of stem cells and later showed that blood cells come from what came to be known as hematopoietic, or blood forming, stem cells. In 1986, Drs. Andrew Lassar and Harold Weintraub converted rodent fibroblasts (connective tissue cells) directly into myoblasts (muscle cells) demonstrating that one type of adult cell could be converted into another type of adult cell. Scientific development continued until 2007 when Wake Forest and Harvard scientists announced that stem cells from amniotic fluid resemble embryonic stem cells in their potential to become various different tissues. The researchers turned these stem cells into brain, liver and bone cells.
The same year Drs. Shinya Yamanaka and James Thomson independently reported reprogramming adult skin cells into embryonic-like cells using viruses to insert specific genes into the skin cells. These induced pluripotent stem cells (IPS) cells have been coaxed into becoming beating heart cells and nerve cells. In subsequent years, scientists developed other more efficient and possibly safer ways to create IPS cells, as well as transform them into other cell types.
The pace of discovery has accelerated in recent years as stem cells have moved into clinical practice. In 2008, a team of doctors transplanted a trachea grown by seeding a donor windpipe with the patient’s own bone marrow stem cells, thereby preventing rejection. Three years later, a fully synthetic trachea was transplanted, made by covering a biodegradable scaffold with the patient’s own stem cells, showing the potential that donor tracheas may be unnecessary one day. In recent years, stem cells have been used to grow bladders, blood vessels, heart valves and functional mini livers raising the possibility of made-to-order replacement body parts.
The past five years have seen dozens of other potential clinical uses for adult stem cells. In the heart, adult stem cells have been shown to improve cardiac function in patients with congestive heart failure and ischemic heart disease. Adult stem cells are being used to heal heart muscle scarring, treat unstable angina and prevent worsening of heart function after heart attacks. Stem cells from bone marrow and placentas have treated peripheral artery disease and limb ischemia, preventing amputations. In the nervous system, adult stem cells have been used to stop the progression of multiple sclerosis and lupus through a procedure that resets the immune systems into tolerance. Umbilical cord, bone marrow and olfactory stem cells have helped cerebral palsy and spinal cord injuries. And early work looks promising in the areas of Alzheimer’s disease and other neurodegenerative diseases.
In orthopedics, adult stem cells have healed shattered bones, prevented hip replacements and grown new bones for dental applications. In a surprising development, blood stem cells succeeded in curing an HIV positive patient by replacing his T-cells with stem cells that are naturally genetically immune to the virus. Researchers have been using adult stem cells to successfully treat type 1 diabetes, a major public health problem.
But out of all of this successful scientific investigation, the real reason we care about stem cells is because of what they can and will be able to do for real people, and the countless patients struggling with difficult diseases. The revolution is just beginning.