Kelly Chiang Cluster 7 Dr. LeFebvre 07/26/10
Stem Cell Research: “Adult” or “Somatic” Stem Cells
Abstract
Over the past few decades, stem cells have been a controversial topic in the scientific field. Researchers have been studying the unique characteristics of all the different types of stem cells, and they hope to be able to use stem cells for treating a wide variety of diseases and disorders. This paper introduces the many types of stem cells that scientists are learning about. It includes the basic information about the main three types of stem cells and how they are used to treat patients.
According to National Geographic, nine-year old Anthony Pululu was cured of sickle cell anemia by a bone-marrow transplant performed by Paris physician Francoise Bernaudin
(Liposuction Fat). Bone marrow transplant is actually an old stem cell therapy which is one of the more favorable therapies using “adult” or “somatic” stem cells as opposed to therapies using the more controversial embryonic stem cells. Anthony Pululu’s immune and blood systems were wiped out and replaced with healthy bone marrow stem cells, which quickly reproduce and repopulate the body. This medical research breakthrough of stem cells brings much hope to patients similar to Anthony Pululu. Stem cells have so much potential because they are
unspecialized cells found in most multi-cellular organisms which have the capacity to self-renew and to differentiate further into more mature and specialized cells. These cells serve as an
internal repair system in some tissues because they are able to divide unlimitedly and replenish other cells.
There are three main types of stem cells that have succeeded in scientific research; these three types include embryonic, fat, and adult or somatic stem cells. Embryonic stem cells, as
implied from the name, are derived from the inner cell mass of the blastocyst, an early-stage embryo that develops from eggs in a clinic (Stem Cell Basics). This type of stem cell is pluripotent, meaning that the cell has the potential to differentiate into the endoderm (interior stomach lining, the lungs), mesoderm (muscle, bone, blood), or ectoderm (epidermal tissues and nervous system). In addition to pluripotency, embryonic stem cells have the ability to duplicate indefinitely under defined conditions. These characteristics allow embryonic stem cells to be useful tools in further scientific investigation such as studies of embryogenesis.
Like embryonic stem cells, fat stem cells have been very successful in scientific research. Only recently, scientists have discovered that stem cells can also be extracted from human fat tissue. These stem cells have the same abilities as embryonic stem cells except for the ability to differentiate into sperm or ova (Liposuction Fat). One benefit of using fat stem cells instead of embryonic stem cells is that fat stem cells are abundant, and can easily be extracted (Liposuction Fat). In addition, fat stem cells pose no ethical or political controversy unlike embryonic stem cells. According to Scientific American, these fat stem cells have the ability to treat everything from damaged heart tissue to Parkinson’s disease. Also, MSNBC has reported that surgeons have used stem cells from fat to help repair skull damages in a 7-year old girl from Germany (Stem Cells from Fat). Surgeons mixed bits of the child’s bone with stem cells, in hope of the cells forming into bone-building cells that would create additional bone. Like embryonic stem cells, fat stem cells are definitely a promising new technology and may have the ability to save billions of lives in the future.
The last type of stem cells, or adult/somatic stem cells, are undifferentiated cells found among differentiated cells in a tissue or organ. According to the National Institutes of Health, adult stem exist in various organs and tissues including brain, bone marrow, peripheral blood,
blood vessels, skeletal muscle, skin, teeth, heart, gut, liver, ovarian epithelium, and testis (What is a Stem Cell). Scientists often use the term somatic stem cell rather than adult stem cell, because somatic refers to cells of the body, which does not include the germ cells. Adult stem cells have two distinct characteristics, they can make identical copies of themselves for long periods of time, and they can give rise to mature cell types that have morphologies and specialized functions. In addition, studies and research has shown that adult stem cells live in small blood vessels, and they can be extracted from a patient to help repair diseased or damaged tissue. Adult stem cells are a natural solution, meaning that they naturally exist in our bodies, and they provide a natural repair mechanism for many tissues of our bodies. In other words, these stem cells are responsible for repairing and maintaining the tissue of the living organism in which they are found. They serve as a built-in repair system for the human body, replenishing other cells as long as a person is still alive. Their primary functions are to maintain homeostasis and to replace the cells that have died from injury or disease. Scientific interest in these stem cells have centered around their ability to self-renew indefinitely. These versatile adult stem cells are essentially unused or blank cells that have the ability to become another more differentiated cell type in the body such as a skin cell or nerve cell.
Within the last 50 or so years, researchers have discovered that the bone marrow contains at least two kinds of adult stem cells. The first population of stem cells is called hematopoietic stem cells which forms all the types of blood cells in the body. These stem cells have the ability to differentiate to a variety of specialized cells, mobilize out of the bone marrow into the blood stream, and undergo apoptosis (programmed cell death). Hematopoietic stem cells are easier to obtain compared to adult stem cells from other tissues. As reported by the International Society for Stem Cell Research, HSCs can be either aspirated directly from the bone marrow or
stimulated to move into the peripheral blood stream, where they can be easily collected. HSCs have been studied by scientists for many years, and they were the first stem cells to be used successfully in treatments and therapies. According to the International Society, HSCs have been used to treat blood cancers (ex: leukemia) and blood disorders for decades. Also, just recently, HSCs have been tested in the treatment for other diseases and disorders like cancer and coronary artery diseases. However, one negative aspect about HSC is that basic HSC research has been a difficult challenge because HSCs appear and behave exactly like white blood cells (What are Adult Stem Cells). This makes them difficult to identify by morphology, therefore, scientists still rely on cell surface proteins on white blood cells to differentiate between white blood cells and HSCs. Nevertheless, HSCs are rapidly advancing in the biomedical field and they may soon have the potential to save millions of lives. Along with hematopoietic stem cells, mesenchymal stem cells are slowly gaining potential as well.
Mesenchymal stem cells are another population of stem cells that are also found in the bone marrow. However, MSCS can also be isolated from other tissues including cord blood, peripheral blood, fallopian tube, and fetal liver and lung (What are Adult Stem Cells). These multipotent stem cells can differentiate into a variety of stem cells. Cell types that MSCs have been shown to differentiate into in vitro or in vivo include a variety of beta-pancreatic islets cells. In the laboratory, this well-characterized population of stem cells can form a variety of cells such as fat cells, cartilage, bone, tendon, and ligaments, as well as muscle and skin cells (What are Adult Stem Cells). Mesenchymal stem cells can be obtained in quantities appropriate for clinical applications unlike most other human stem cells, therefore making them good candidates for use in tissue repair. Also, research has proved that when MSCs are transplanted systematically, they are able to migrate to sites of injury in animals, making these stem cells
potentially ideal candidates for tissue engineering. As reported by the International Society for Stem Cell Research, another benefit of MSCs is that they can be preserved by freezing them and when thawed, they function normally. An important consideration about MSCs for human applications is that they can be extracted from a small bone marrow sample from a certain patient, expanded in culture, and then given back to the patient. Scientists are still learning about MSCs; however our knowledge about them is increasing every day. These stem cells may have a lot of potential in the future, as well as other stem cells.
Stem cells are being used today to help people suffering from dozens of diseases and conditions. Adult stem cells are being applied to numerous diseases including brain, ovarian, breast, and testicular cancer, type 1 diabetes, Parkinson’s disease, spinal cord injury, stroke damage, and many more (What is a Stem Cell?). Most importantly, adult stem cells have already been successfully used in human therapies for many years. New therapies using adult type stem cells are being developed all the time.
Works Cited
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