What are Stem Cells?
Stem cells are immature and unspecific cells that are important for life. In fact, they have unique properties that can be used in cellular therapy. Stem cells are identified by 2 specific characteristics:
- Self renewal: they can produce countless cells like itself with exactly the same feature.
- Differentiation ability: the capacity to differentiate into specialized cell type.
In addition, stem cells obtain easily and they are abundant, safe and effective.
These cells are found in different tissue such as: bone marrow, adipose tissue, lung, liver, dental pulp, peripheral blood and umbolical cord.
Stem cells are 3 types based on their source: embryonic stem cells, adult stem cells and induced pluripotent stem cells.
These cells are used to repair various tissues of the body following injury. They can replace damaged cells and repair tissues by transplanting to damaged tissues.
Cord Blood Stem Cells
Stem cells are often called ‘master cells’ because they are unspecialized cells that give rise to specialized cells in the body’s tissues and organs. Their potential to treat disease is exciting because they can thus replace diseased and dysfunctional cells with new and healthy ones. Scientists are constantly attempting to identify new sources of stem cells in hopes of better harnessing stem cell power for treating disease. One such source of stem cells is cord blood. Stem cells found in cord blood are actually important precursors to a person’s fully functioning immune system. They also differentiate into:
White blood cells: Vital for fighting infections and safeguarding the body
Red blood cells: Important for transporting oxygen to cells
Platelets: Crucial for clotting
What exactly is cord blood?
Cord blood is also known as placental blood; following birth it is the remaining blood in the umbilical cord and placenta after the cord is cut. As a matter of routine, cord blood is usually disposed of following the baby’s birth. The cord blood is, however, a valuable and promising source of stem cells.
How do cord blood stem cells differ from other stem cells?
Cord blood cells hold advantages over other types of stem cells. Umbilical cord blood stem cells are considered the ‘freshest’ and ‘youngest’ stem cells available. They also avoid the ethical debate surrounding embryonic stem cells because cord blood cells do not involve the destruction of an embryo. In addition, cord blood stem cells hold an advantage over adult stem cells because they do not have the DNA mutations that the ‘older’ adult stem cells may have developed over time.
Another benefit of cord blood stem cells relates to a condition called graft versus host disease (GVHD). This is actually a fairly common complication that arises following a transplant that is allogeneic. Allogeneic refers to a transplant involving cells from cord blood or perhaps another family member or an unrelated donor. The consequences of GVHD can be mild or fatal. Research has shown some positive findings, however, in that following a cord blood transplant, fewer patients suffer from GVHD than those who receive other transplants
such as bone marrow. Those who do suffer from GVHD after receiving a cord blood transplant tend to have milder symptoms.
What conditions can cord blood stem cells treat?
Due to the ability of cord blood stem cells to differentiate into specialized cells, they hold the dramatic potential to treat an array of diseases. Some of the serious conditions that cord blood cells could treat include: Osteoarthritis Male infertility Wrinkles Their potential for treating Alzheimer’s and Parkinson’s diseases is particularly promising. Cord blood stem cells can be coaxed to differentiate into neural cells, which are specialized cells that are destroyed in both diseases. Also, the ability of cord blood stem cells to proliferate and differentiate to form blood vessel cells may one day allow for successful treatment of heart disease. Cord blood stem cells can also be used for cancer therapies, where they replenish the patient’s immune system and blood after cancer treatments such as chemotherapy. Because chemotherapy and radiation aren’t just destructive to cancer cells, but stem cells as well, the cord blood stem cells are transplanted following the cancer therapies. Stem cells then proliferate in the patient’s bone marrow and effectively supply what is essentially a new blood and immune system.
Cord blood stem cells are not always an ideal choice
Currently, there are several reasons why cord blood stem cells may not be the primary choice for transplantation therapy. One challenge is that there may be a scarcity of cells in a cord blood unit relative to the patient’s size. Cord blood stem cells also tend to take longer to grow, thereby delaying the completion of a new immune system and blood cells for the patient. The research is also just not as advanced for cord blood stem cells as for bone marrow transplantation therapy, so the potential risks may be much higher. Doctors are trying different ways to increase the number of cells in a cord blood unit so they can use cord blood for larger patients. One method being studied is to give a patient two cord blood units. Another method being studied is to grow the required number of cells in a cord blood unit in a laboratory before giving it to the patient. Cord blood stem cells clearly have their merits but are not always appropriate for every transplantation procedure. Continued research will hopefully yield more information to extend the benefits of cord blood stem cells to other diseases.
What are the characteristics of adult stem cells?
An adult stem cell is thought to be an undifferentiated cell, found among differentiated cells in a tissue or organ that can renew itself and can differentiate to yield some or all of the major specialized cell types of the tissue or organ. The primary roles of adult stem cells in a living organism are to maintain and repair the tissue in which they are found. Scientists also use the term somatic stem cell instead of adult stem cell, where somatic refers to cells of the body (not the germ cells, sperm or eggs). Unlike embryonic stem cells, which are defined by their origin (cells from the preimplantation-stage embryo), the origin of adult stem cells in some mature tissues is still under investigation. Research on adult stem cells has generated a great deal of excitement. Scientists have found adult stem cells in many more tissues than they once thought possible. This finding has led researchers and clinicians to ask whether adult stem cells could be used for transplants. In fact, adult hematopoietic, or blood-forming, stem cells from bone marrow have been used in transplants for 40 years. Scientists now have evidence that stem cells exist in the brain and the heart. If the differentiation of adult stem cells can be controlled in the laboratory, these cells may become the basis of transplantation-based therapies. The history of research on adult stem cells began about 50 years ago. In the 1950s, researchers discovered that the bone marrow contains at least two kinds of stem cells. One population, called hematopoietic stem cells, forms all the types of blood cells in the body. A second population, called bone marrow stromal stem cells (also called mesenchymal stem cells, or skeletal stem cells by some), were discovered a few years later. These non-hematopoietic stem cells make up a small proportion of the stromal cell population in the bone marrow, and can generate bone, cartilage, fat, cells that support the formation of blood, and fibrous connective tissue. In the 1960s, scientists who were studying rats discovered two regions of the brain that contained dividing cells that ultimately become nerve cells. Despite these reports, most scientists believed that the adult brain could not generate new nerve cells. It was not until the 1990s that scientists agreed that the adult brain does contain stem cells that are able to
generate the brain’s three major cell types—astrocytes and oligodendrocytes, which are non-neuronal cells, and neurons, or nerve cells.
Where are adult stem cells found, and what do they normally do?
Adult stem cells have been identified in many organs and tissues, including brain, bone marrow, peripheral blood, blood vessels, skeletal muscle, skin, teeth, heart, gut, liver, ovarian epithelium, and testis. They are thought to reside in a specific area of each tissue (called a “stem cell niche”). In many tissues, current evidence suggests that some types of stem cells are pericytes, cells that compose the outermost layer of small blood vessels. Stem cells may remain quiescent (non-dividing) for long periods of time until they are activated by a normal need for more cells to maintain tissues, or by disease or tissue injury. Typically, there is a very small number of stem cells in each tissue, and once removed from the body, their capacity to divide is limited, making generation of large quantities of stem cells difficult. Scientists in many laboratories are trying to find better ways to grow large quantities of adult stem cells in cell culture and to manipulate them to generate specific cell types so they can be used to treat injury or disease. Some examples of potential treatments include regenerating bone using cells derived from bone marrow stroma, developing insulin-producing cells for type 1 diabetes, and repairing damaged heart muscle following a heart attack with cardiac muscle cells.
What tests are used for identifying adult stem cells?
Scientists often use one or more of the following methods to identify adult stem cells: (1) label the cells in a living tissue with molecular markers and then determine the specialized cell types they generate; (2) remove the cells from a living animal, label them in cell culture, and transplant them back into another animal to determine whether the cells replace (or “repopulate”) their tissue of origin. Importantly, it must be demonstrated that a single adult stem cell can generate a line of genetically identical cells that then gives rise to all the appropriate differentiated cell types of the tissue. To confirm experimentally that a putative adult stem cell is indeed a stem cell, scientists tend to show either that the cell can give rise to these genetically identical cells in culture, and/or that a purified population of these candidate stem cells can repopulate or reform the tissue after transplant into an animal.
What is known about adult stem cell differentiation?
Hematopoietic and stromal stem cell differentiation. (© 2001 Terese Winslow) As indicated above, scientists have reported that adult stem cells occur in many tissues and that they enter normal differentiation pathways to form the specialized cell types of the tissue in which they reside.
Normal differentiation pathways of adult stem cells
In a living animal, adult stem cells are available to divide, when needed, and can give rise to mature cell types that have characteristic shapes and specialized structures and functions of a particular tissue. The following are examples of differentiation pathways of adult stem cells that have been demonstrated in vitro or in vivo. Hematopoietic stem cells give rise to all the types of blood cells: red blood cells, B lymphocytes, T lymphocytes, natural killer cells, neutrophils, basophils, eosinophils, monocytes, and macrophages.
Mesenchymal stem cells
give rise to a variety of cell types: bone cells (osteocytes), cartilage cells (chondrocytes), fat cells (adipocytes), and other kinds of connective tissue cells such as those in tendons.
Neural stem cells
in the brain give rise to its three major cell types: nerve cells (neurons) and two categories of non-neuronal cells—astrocytes and oligodendrocytes.
Epithelial stem cells
in the lining of the digestive tract occur in deep crypts and give rise to several cell types: absorptive cells, goblet cells, paneth cells, and enteroendocrine cells.
Skin stem cells
occur in the basal layer of the epidermis and at the base of hair follicles. The epidermal stem cells give rise to keratinocytes, which migrate to the surface of the skin and form a protective layer. The follicular stem cells can give rise to both the hair follicle and to the epidermis.
A number of experiments have reported that certain adult stem cell types can differentiate into cell types seen in organs or tissues other than those expected from the cells’ predicted lineage (i.e., brain stem cells that differentiate into blood cells or blood-forming cells that differentiate into cardiac muscle cells, and so forth). This reported phenomenon is called transdifferentiation. Although isolated instances of transdifferentiation have been observed in some vertebrate species, whether this phenomenon actually occurs in humans is under debate by the scientific community. Instead of transdifferentiation, the observed instances may involve fusion of a donor cell with a recipient cell. Another possibility is that transplanted stem cells are secreting factors that encourage the recipient’s own stem cells to begin the repair process. Even when transdifferentiation has been detected, only a very small percentage of cells undergo the process. In a variation of transdifferentiation experiments, scientists have recently demonstrated that certain adult cell types can be “reprogrammed” into other cell types in vivo using a wellcontrolled process of genetic modification. This strategy may offer a way to reprogram available cells into other cell types that have been lost or damaged due to disease. For example, one recent experiment shows how pancreatic beta cells, the insulin-producing cells that are lost or damaged in diabetes, could possibly be created by reprogramming other pancreatic cells. By “re-starting” expression of three critical beta-cell genes in differentiated adult pancreatic exocrine cells, researchers were able to create beta cell-like cells that can secrete insulin. The reprogrammed cells were similar to beta cells in appearance, size, and shape; expressed genes characteristic of beta cells; and were able to partially restore blood sugar regulation in mice whose own beta cells had been chemically destroyed. While not transdifferentiation by definition, this method for reprogramming adult cells may be used as a model for directly reprogramming other adult cell types. In addition to reprogramming cells to become a specific cell type, it is now possible to reprogram adult somatic cells to become like embryonic stem cells (induced pluripotent stem cells, iPSCs) through the introduction of embryonic genes. Thus, a source of cells can be generated that are specific to the donor, thereby avoiding issues of histocompatibility, if such cells were to be used for tissue regeneration. However, like embryonic stem cells, determination of the methods by which iPSCs can be completely and reproducibly committed to appropriate cell lineages is still under investigation.
Adult Stem Cells Niche
Stem cells reside in adult bone marrow and fat, as well as other tissues and organs of the body. These cells have a natural ability to repair damaged tissue, however in people with degenerative diseases they are not released quickly enough to fully repair damaged tissue. In the case of fat stem cells they may not be released at all. The process of actively extracting, concentrating and administering these stem cells has been shown in clinical trials to have beneficial effects in degenerative conditions. Few patients have access to clinical trials. We offer patients and their doctors access to these therapies now. Stem cell treatments are not covered by most insurance policies.
Mesenchymal Stem Cells
Adult stem cells can be extracted from many areas of the body, including the bone marrow, fat, and peripheral blood. Once the cells have been harvested, they are sent to the lab where they are purified and assessed for quality before being reintroduced back in the patient. Since the stem cells come from the patient there is no possibility for rejection. Stem Cell Institute advocates the use of autologous (your own) stem cells as they have no ethical or moral issues and pose no possibility for rejection. Stem cells isolated from the bone marrow or fat have the ability to become different cell types (i.e. nerve cells, liver cells, heart cells, and cartilage cells). Studies have also shown that these are capable of homing to and repairing damaged tissue. Animal studies have shown that these stem cells also secrete proteins and peptides that stimulate healing of damaged tissue, including heart muscle and spinal cord.
Fat Derived Stem Cells
Fat stem cells are essentially sequestered and are not available to the rest of the body for repair or immune modulation. Fat derived stem cells have been used for successful treatment of companion animals and horses with bone and joint injuries for the last 5 years with positive results. Experimental studies suggest fat derived stem cells not only can develop into new tissues but also suppress pathological immune responses as seen in autoimmune diseases. In addition to orthopedic conditions, our Stem Cell Institute has experience treating patients with Osteoarthritis, Rheumatoid Arthritis, Multiple Sclerosis, and other autoimmune diseases using fat derived stem cells.
Bone Marrow Stem Cells
The bone marrow stem cell is the most studied of the stem cells, since it was first discovered to in the 1960s. Originally used in bone marrow transplant for leukemias and hematopoietic diseases, numerous studies have now expanded experimental use of these cells for conditions such as peripheral vascular disease, diabetes, heart failure, and other degenerative disorders.
Human Umbilical Cord Blood (HUCB) Stem Cells
Umbilical cord blood stem cells reside in the *umbilical cords of newborn babies. HUCB stem cells, like all post-natal cells, are “adult” stem cells.
HUCB Mesenchymal Stem Cells
Our Stem Cell Institute utilizes both CD34+ and mesenchymal stem cells that are separated from the cord blood and tissue. For certain indications, these cells are expanded into greater numbers under very strict, internationally recognized guidelines. Among many other things, CD34+ stem cells from umbilical cord blood have anti-inflammatory properties. Mesenchymal stem cells from the umbilical cord are known to help modulate the immune system and secrete factors that help the central nervous system to regenerate. Because HUCB stem cells are less mature than other cells, the body’s immune system is unable to recognize them as foreign and therefore they are not rejected. We’ve treated hundreds of patients with HUCB stem cells and there has never been a single instance rejection (graft vs. host disease). HUCB stem cells also proliferate/differentiate more efficiently than “older” cells, such as those found in the bone marrow and therefore, they are considered to be more “potent”. All donated cords are the by-products of normal, healthy births. Each cord is carefully screened for sterility and infectious diseases under International Blood Bank standards.
Search source: http://www.cellmedicine.com/stem-cells/
What are the key questions about adult stem cells?
How many kinds of adult stem cells exist, and in which tissues do they exist? How do adult stem cells evolve during development and how are they maintained in the adult? Are they “leftover” embryonic stem cells, or do they arise in some other way? Why do stem cells remain in an undifferentiated state when all the cells around them have differentiated? What are the characteristics of their “niche” that controls their behavior? Do adult stem cells have the capacity to transdifferentiate, and is it possible to control this process to improve its reliability and efficiency? If the beneficial effect of adult stem cell transplantation is a trophic effect, what are the mechanisms? Is donor cell-recipient cell contact required, secretion of factors by the donor cell, or both? What are the factors that control adult stem cell proliferation and differentiation? What are the factors that stimulate stem cells to relocate to sites of injury or damage, and how can this process be enhanced for better healing?