REGENERATIVE MEDICINE & REJUVENATION VIA THERAPEUTIC STEM CELL TRANSPLANTS:
Many diseases may be treated by transplanting new “replacement” cells to the source of disease or injury.
TYPES OF ADULT STEM CELLS:
- Mesenchymal (Adipose & Bone Marrow) stem cells
- Hematopoietic (Bone Marrow) stem cells
- Endothelial stem cells
- Intestinal stem cells
- Mammary stem cells
- Neural stem cells
- Olfactory adult stem cells
- Neural crest stem cells
- Testicular cells
WHAT ARE STEM CELLS?
Stem cells are biological cells found in all multicellular organisms, that can divide and differentiate into diverse specialized cell types and can self-renew to produce more stem cells.There are two main classes of stem cells: Adult Stem Cells (ASC) and Embryonic Stem Cells (ES).
ADULT STEM CELLS (ASC):
Undifferentiated cells, found throughout the body after embryonic development, that multiply by cell division to replenish dying cells and regenerate damaged tissues. Also known as somatic stem cells (from Greek Σωματικóς, meaning of the body), they can be found in juvenile as well as adult animals and humans.
Scientific interest in adult stem cells is centered on their ability to divide or self-renew indefinitely, and generate all the cell types of the organ from which they originate, potentially regenerating the entire organ from a few cells. Unlike Embryonic Stem Cells, the use of adult stem cells in research and therapy is not considered to be controversial, as they are derived from adult tissue samples rather than destroyed human embryos.
These cells can be found within the bone marrow, the body's fat, the cornea and retina of the eye, brain tissue, skeletal muscle, dental pulp, liver, skin, pancreas, the lining of the gastrointestinal tract of an organism, and just about everywhere else in the body known or unknown.
Adult stem cells are capable of self-renew with and without differentiation for the lifetime of an organism. They are multipotent, possessing the ability to divide to generate progenitor cells, leading to mature specialized cell types of the tissue from which they came. Clinically, we use these stem cellsfor regenerative medicine and tissue replacement after diagnosis of an injury, condition, or disease
- Mesenchymal stem cells (MSCs) are of stromal origin and may differentiate into a variety of tissues. Found primarily in Adipose Tissue - most likely serving a protective role and regenerative potential when an injury occurs from the environment. Additionally, MSCs have been isolated from placenta, lung, bone marrow and blood, Wharton's jelly from the umbilical cord, and teeth (perivascular niche of dental pulp and periodontal ligament). MSCs are attractive for clinical therapy due to their ability to differentiate, provide trophic support, and modulate innate immune response.
- Hematopoietic stem cells are the majority of stem cells found in the bone marrow and give rise to all the blood cell types. Of the cell types in bone marrow, only 1 of every 10,000 may be mesenchymal, so some institutes try to separate out these mesenchymal cells and growth them (expand) for treatment.
- Mammary stem cells provide the source of cells for growth of the mammary gland during puberty and gestation and play an important role in carcinogenesis of the breast.
- Intestinal stem cells divide continuously throughout life and use a complex genetic program to produce the cells lining the surface of the small and large intestines. Intestinal stem cells reside near the base of the stem cell niche, called the crypts of Lieberkuhn.
- Endothelial Stem Cells are one of the three types of Multipotent stem cells found in the bone marrow. They are a rare and controversial group with the ability to differentiate into endothelial cells, the cells that line blood vessels.
- Neural Stem Cell - The existence of stem cells in the adult brain has been postulated following the discovery that the process of neurogenesis, the birth of new neurons, continues into adulthood. The presence of stem cells in the mature primate brain was first reported in 1967. It has since been shown that new neurons are generated in adult mice, songbirds and primates, including humans. Normally, adult neurogenesis is restricted to two areas of the brain - the subventricular zone, which lines the lateral ventricles, and the dentate gyrus of the hippocampal formation. Although the generation of new neurons in the hippocampus is well established, the presence of true self-renewing stem cells there has been debated. Under certain circumstances, such as following tissue damage in ischemia, neurogenesis can be induced in other brain regions, including the neocortex.
- Olfactory adult stem cells have been successfully harvested from the human olfactory mucosa cells, which are found in the lining of the nose and are involved in the sense of smell. If they are given the right chemical environment these cells have the same ability as embryonic stem cells to develop into many different cell types. Olfactory stem cells hold the potential for therapeutic applications and, in contrast to neural stem cells, can be harvested with ease without harm to the patient. This means they can be easily obtained from all individuals, including older patients who might be most in need of stem cell therapies.
- Neural crest stem cells - Hair follicles contain two types of stem cells, one of which appears to represent a remnant of the stem cells of the embryonic neural crest. Similar cells have been found in the gastrointestinal tract, sciatic nerve, cardiac outflow tract and spinal and sy mpathetic ganglia. These cells can generate neurons, Schwann cells, myofibroblast, chondrocytes and melanocytes.
- Testicular stem cells - Multipotent stem cells with a claimed equivalency to embryonic stem cells have been derived from spermatogonial progenitor cells found in the testicles of laboratory mice by scientists in Germany and the United States, and, a year later, researchers from Germany and the United Kingdom confirmed the same capability using cells from the testicles of humans. The extracted stem cells are known as human adult germline stem cells (GSCs). Multipotent stem cells have also been derived from germ cells found in human testicles.
Derived from the inner cell mass of a pre-implantation embryo called a blastocyst. Embryonic Stem Cells (ES) are distinguished by two distinctive properties:
- their pluripotency, and
- their ability to replicate indefinitely.
ES cells are pluripotent, that is, they are able to differentiate into all derivatives of the three primary germ layers: ectoderm, endoderm, and mesoderm. These include each of the more than 220 cell types in the adult body. Pluripotency distinguishes embryonic stem cells from adult stem cells found in adults; one of the main difference is that embryonic stem cells can generate germ cells (gametes for reproduction).
Because of their plasticity and potentially unlimited capacity for self-renewal, ES cell therapies have been proposed for regenerative medicine and tissue replacement after injury or disease. Besides the ethical concerns of embryonic stem cell therapy, there is a technical problem of graft-versus-host disease associated with allogeneic (coming from someone else) stem cell transplantation. However, these problems associated with histocompatibility may be solved using autologous (self) donor Adult Stem Cells.