Stem cell – Adult stem cells | Britannica

Some tissues in the adult body, such as the epidermis of the skin, the lining of the small intestine, and bone marrow, undergo continuous cellular turnover. They contain stem cells, which persist indefinitely, and a much larger number of transit amplifying cells, which arise from the stem cells and divide a finite number of times until they become differentiated. The stem cells exist in niches formed by other cells, which secrete substances that keep the stem cells alive and active. Some types of tissue, such as liver tissue, show minimal cell division or undergo cell division only when injured. In such tissues there is probably no special stem-cell population, and any cell can participate in tissue regeneration when required.

The epidermis of the skin contains layers of cells called keratinocytes. Only the basal layer, next to the dermis, contains cells that divide. A number of these cells are stem cells, but the majority are transit amplifying cells. The keratinocytes slowly move outward through the epidermis as they mature, and they eventually die and are sloughed off at the surface of the skin. The epithelium of the small intestine forms projections called villi, which are interspersed with small pits called crypts. The dividing cells are located in the crypts, with the stem cells lying near the base of each crypt. Cells are continuously produced in the crypts, migrate onto the villi, and are eventually shed into the lumen of the intestine. As they migrate, they differentiate into the cell types characteristic of the intestinal epithelium.

Bone marrow contains cells called hematopoietic stem cells, which generate all the cell types of the blood and the immune system. Hematopoietic stem cells are also found in small numbers in peripheral blood and in larger numbers in umbilical cord blood. In bone marrow, hematopoietic stem cells are anchored to osteoblasts of the trabecular bone and to blood vessels. They generate progeny that can become lymphocytes, granulocytes, red blood cells, and certain other cell types, depending on the balance of growth factors in their immediate environment.

Work with experimental animals has shown that transplants of hematopoietic stem cells can occasionally colonize other tissues, with the transplanted cells becoming neurons, muscle cells, or epithelia. The degree to which transplanted hematopoietic stem cells are able to colonize other tissues is exceedingly small. Despite this, the use of hematopoietic stem cell transplants is being explored for conditions such as heart disease or autoimmune disorders. It is an especially attractive option for those opposed to the use of embryonic stem cells.

Bone marrow transplants (also known as bone marrow grafts) represent a type of stem cell therapy that is in common use. They are used to allow cancer patients to survive otherwise lethal doses of radiation therapy or chemotherapy that destroy the stem cells in bone marrow. For this procedure, the patients own marrow is harvested before the cancer treatment and is then reinfused into the body after treatment. The hematopoietic stem cells of the transplant colonize the damaged marrow and eventually repopulate the blood and the immune system with functional cells. Bone marrow transplants are also often carried out between individuals (allograft). In this case the grafted marrow has some beneficial antitumour effect. Risks associated with bone marrow allografts include rejection of the graft by the patients immune system and reaction of immune cells of the graft against the patients tissues (graft-versus-host disease).

Bone marrow is a source for mesenchymal stem cells (sometimes called marrow stromal cells, or MSCs), which are precursors to non-hematopoietic stem cells that have the potential to differentiate into several different types of cells, including cells that form bone, muscle, and connective tissue. In cell cultures, bone-marrow-derived mesenchymal stem cells demonstrate pluripotency when exposed to substances that influence cell differentiation. Harnessing these pluripotent properties has become highly valuable in the generation of transplantable tissues and organs. In 2008 scientists used mesenchymal stem cells to bioengineer a section of trachea that was transplanted into a woman whose upper airway had been severely damaged by tuberculosis. The stem cells were derived from the womans bone marrow, cultured in a laboratory, and used for tissue engineering. In the engineering process, a donor trachea was stripped of its interior and exterior cell linings, leaving behind a trachea scaffold of connective tissue. The stem cells derived from the recipient were then used to recolonize the interior of the scaffold, and normal epithelial cells, also isolated from the recipient, were used to recolonize the exterior of the trachea. The use of the recipients own cells to populate the trachea scaffold prevented immune rejection and eliminated the need for immunosuppression therapy. The transplant, which was successful, was the first of its kind.

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Stem cell - Adult stem cells | Britannica

Adult Stem Cells for Regenerative Therapy – PubMed

Cell therapy has been identified as an effective method to regenerate damaged tissue. Adult stem cells, also known as somatic stem cells or resident stem cells, are a rare population of undifferentiated cells, located within a differentiated organ, in a specialized structure, called a niche, which maintains the microenvironments that regulate the growth and development of adult stem cells. The adult stem cells are self-renewing, clonogenic, and multipotent in nature, and their main role is to maintain the tissue homeostasis. They can be activated to proliferate and differentiate into the required type of cells, upon the loss of cells or injury to the tissue. Adult stem cells have been identified in many tissues including blood, intestine, skin, muscle, brain, and heart. Extensive preclinical and clinical studies have demonstrated the structural and functional regeneration capabilities of these adult stem cells, such as bone marrow-derived mononuclear cells, hematopoietic stem cells, mesenchymal stromal/stem cells, resident adult stem cells, induced pluripotent stem cells, and umbilical cord stem cells. In this review, we focus on the human therapies, utilizing adult stem cells for their regenerative capabilities in the treatment of cardiac, brain, pancreatic, and eye disorders.

Keywords: Blood disorders; Cardiospheres; Diabetes mellitus; Myoblasts; Neurogenesis; Regenerative therapy; Stem cells; Stroke.

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Adult Stem Cells for Regenerative Therapy - PubMed

About Adult Stem Cell Therapy – University of Kansas Medical Center

Adult Stem Cell Therapy 101

The initial concept of regenerative medicine dates all the way back to 330 BC, when Aristotle observed that a lizard could grow back the lost tip of its tail.

Slowly over time, humans have grown to understand regenerative medicine, and how it may change the way we treat diseases. It's been only relatively recently that adult (non-embryonic) stem cell therapy, a type of regenerative medicine, has gathered fast momentum.

Adult (non-embryonic) stem cells are unspecialized or undifferentiated cells, which means they have yet to develop into a specific cell type. Found in most adult tissues, adult stem cells have two primary properties:

Simply put, adult stem cells have the potential to grow into any of the body's more than 200 cell types.

Adult stem cells have been found in most parts of the body, including brain, bone marrow, blood vessels, skin, teeth and heart. There are typically a small number of stem cells in each tissue. Due to their small number and rate of division (growth), it is difficult to grow adult stem cells in large numbers.

Scientists at the Midwest Stem Cell Therapy Center are working to understand how to grow large amounts of adult stem cells in cell culture. These scientists are also working with more "primitive" stem cells, isolated from the umbilical cord after normal births.

Stem cell transplants, also referred to as bone marrow transplants, have been done since the late 1960s and are well-established treatments for blood cancers and bone marrow failure conditions. Umbilical cord blood also has stem cells that can be used for transplantation for these diseases.

Stem cell transplants for other diseases that use bone marrow, umbilical cord cells or other sources of stem cells are still experimental and need to viewed as such.

The practice of stem cell therapy is not new: One of the oldest forms of it is the bone marrow transplant, which has been actively practiced since the late 1960s. Since then, scientists haven't slowed down with the advancement of adult stem cell therapy.

Every day, scientists worldwide are researching new ways we can harness stem cells to develop effective new treatments for a host of diseases. In the case of a patient suffering with a blood cancer such as leukemia, a bone marrow transplant will replace their unhealthy blood cells with healthy ones.

This same concept inserting healthy cells so they may multiply and form new tissue or repair diseased tissue can be applied to other forms of stem cell therapy.

Stem cell research continues to advance as scientists learn how an organism develops from a single cell and how healthy cells replace damaged cells.

For example, the Midwest Stem Cell Therapy Center is collaborating to investigate the potential of a select group of umbilical cord stem cells in the treatment of Amyotrophic Lateral Sclerosis (ALS, or Lou Gerhig's disease).

Developing a stem cell treatment that has been shown to be both safe and efficacious is not as simple as removing stem cells from one part of the body and putting it in another.

Working with appropriate regulatory agencies, the Midwest Stem Cell therapy Center is conducting R&D activities that will permit the Center to conduct human clinical trials on a variety of diseases over the next several years.

Similar to the development of a new drug, this process when completed, will assure patients in both clinical trials and eventually patients using the approved product, that the product is safe for use in humans and the stem cells being administered are effective in treating the injury or disease they are being used for.

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About Adult Stem Cell Therapy - University of Kansas Medical Center