What Makes Stem Cells Unique Rejuvenators?
Stem cells differ from every other kind of cell in our body because of the following properties:
• Stem Cells can divide and renew themselves for long periods of time giving rise to large populations of other stem cells like themselves. Other cells in our body cannot do this.
• Stem Cells are unspecialized. Normal cells in our body tend to become specialized, for example, heart cells, blood cells, pancreatic cells, liver cells and so on.
• Stem Cells can give rise to specialized cell types even though they are unspecialized themselves. This is called “differentiation” and involves coordination of internal gene signals with external microenvironmental signals.
These unique abilities confer a type of cellular immortality on stem cells. While differentiated cells – the kinds of cells that do the work in organs – are destined to wear out and die, stem cells are destined to live and rejuvenate organs and tissues.
Where Can Stem Cells Be Found In Our Bodies? What Purpose Do They Serve?
Stem cells are seeded in limited numbers into every developing organ or structure of our body during embryological development and remain in place for our entire lifetime. Therefore, every organ (ie. brain, bone marrow, peripheral blood, blood vessels, skeletal muscle, skin, teeth, heart, gut, liver, ovarian epithelium, and testes, etc) in our body contains stem cells. Stem cells are thought to be maintained in each tissue in a specialized molecular environment called a “stem cell niche”. The niche is thought to maintain resident stem cells in a quiescent or non-divisional state until they are activated to divide in response to appropriate signaling from daily stressors or other cellular assault or injury. In this way, stem cells provide the potential for lifetime organ maintenance and functional rejuvenation through a resident population of stem cells while simultaneously sustaining a population of differentiating cells involved in daily turnover and replacement.
Why Does Our Body Need More Stem Cells?
Stem cells are seeded in limited numbers into the developing organs of our body during embryological development. Every organ in our body contains stem cells. These stem cells form the basis of lifetime organo-function by contributing to daily cellular turnover and rejuvenation. However, stem cells can be overpowered by disrupted and poisoned toxic metal and chemical microenvironments within the organ. Factors such as stress, poor life-style choices, lack of exercise, sleep, smoking, poor nutrition may interfere with biochemical balance and associated molecular signaling necessary to support optimal stem cell function within an organ. When this happens, rejuvenation of the organ may suffer; if not stopped the organ may become disabled and diseased. Organ malfunction creates a domino effect. Organ decline affects the function of other organs.
One of the ways to arrest or reverse this decline is to deliver regenerative stem cells to the organ in numbers capable of overcoming the chemical blockade and re-establishing appropriate signaling – in other words, the poisoned stem cell microenvironment of the diseased organ which paralyzes the regenerative stem cells is reversed and an adequate number of new stem cells travel to the ailing tissue to commence a healing process.
What Are Somatic (Adult) Stem Cells?
Adult stem cells are undifferentiated cells located in organs or tissues including bone marrow. Somatic stem cells not only renew themselves as identical undifferentiated stem cells but they can also differentiate into the specialized cell types making up the tissue or organ where they are located. Therefore, somatic stem cells serve to sustain, maintain and regenerate the organs and tissues in which they are found. This means that somatic stem cells are a source of cellular replacement and rejuvenation. Plasticity of adult stem cells can generate lineages of cells different from their original organ of origin. Thus, these cells can be used for organ regeneration and for cellular repair in humans.The Bone Marrow Niche – A Regenerative Cell Compartment.
The Bone Marrow Niche – A Regenerative Cell Compartment
Bone marrow contains resident stem cells. These stem cells can divide and generate populations of cells that can be released from the marrow space. Once released, these cells travel throughout the body to differentiate, replace, repair and regenerate blood components, organs, and tissues. Highly diverse, they may replace aged red and white blood cells or may differentiate into cells forming blood vessels, bone, cartilage, muscle, pancreas, brain and other tissues and organs as they partake in repair and regeneration.
The three types of stem cells in the bone marrow space:
1. HEMATOPOIETIC STEM CELLS (HSCs) are multipotent stem cells that give rise to the three types of vital blood components: erythrocytes (red blood cells), leukocytes (white blood cells), and thrombocytes (platelets). The microenvironment of the hemopoietic compartment provides soluble biochemical factors which guide some stem cells to further develop as progenitors which will further differentiate into mature blood components. Factors within the same microenvironment also prevent lymphocyte activation in the marrow cavity which could be highly damaging to the blood-forming elements of the bone marrow compartment. Hematopoietic stem cells can cross the bone marrow barrier, and may thus be harvested from blood.
2. MESENCHYMAL STEM CELLS or Marrow Stromal Cells (MSCs) are multipotent stem cells that differentiate into numerous non-hematopoietic derived cell types including osteoblasts, chondrocytes (bone and cartilage-forming cells), myocytes (muscle cells), adipocytes (fat cells), beta-pancreatic islets cells insulin-producing cells, neuronal (nerve) cells and others. MSCs also play an important role in supporting hematopoiesis by providing a microenvironment conducive to blood formation by hematopoietic stem cells. Evidence further suggests that MSCs are a crucial source of progenitor cells with diverse differentiation potential and capability to hone to a wide variety of target tissues to partake in repair and regeneration.
Hematopoietic and mesenchymal stem cells share a vital interdependence. In fact, mesenchymal stem cells are necessary for keeping HSC’s in the bone marrow alive. Mesenchymal stem cells play an important role in stem cell maintenance, movement, and regeneration of the bone marrow. Bone marrow-derived growth factors and cytokines that regulate cellular growth and regeneration via cellular secretion mechanisms are also integral to the bone marrow regenerative compartment.
3. ENDOTHELIAL STEM CELLS are stem cells which promote the repair and regeneration of the lining of target blood vessels. Patent vessels facilitate cell migration into a tissue or alternatively may act as a physical and molecular barrier to inappropriate cellular entry. In the bone marrow, blood vessels inhibit immature blood cells from leaving the space. Only mature blood cells expressing the appropriate membrane proteins to attach to and pass the blood vessel endothelium are released.