Stem Cell Technology

Editor's Notes

• #6: Stem cells are different from other cells of the body in that they have the ability to differentiate into other cell/tissue types. This ability allows them to replace cells that have died. With this ability, they have been used to replace defective cells/tissues in patients who have certain diseases or defects.
• #7: Common variants, called polymorphisms, occur at greater than 1% frequency I have given some examples of how exposure induced risk is modified in various ways Typically the effects are modest in magnitude. We are interested in how genetics modifies Exposure and exposure-related diseases Because…..
• #9: Stem cells can be classified into three broad categories, based on their ability to differentiate. Totipotent stem cells are found only in early embryos. Each cell can form a complete organism (e.g., identical twins). Pluripotent stem cells exist in the undifferentiated inner cell mass of the blastocyst and can form any of the over 200 different cell types found in the body. Multipotent stem cells are derived from fetal tissue, cord blood and adult stem cells. Although their ability to differentiate is more limited than pluripotent stem cells, they already have a track record of success in cell-based therapies. Here is a current list of the sources of stem cells: Embryonic stem cells - are harvested from the inner cell mass of the blastocyst seven to ten days after fertilization. Fetal stem cells - are taken from the germline tissues that will make up the gonads of aborted fetuses. Umbilical cord stem cells - Umbilical cord blood contains stem cells similar to those found in bone marrow. Placenta derived stem cells - up to ten times as many stem cells can be harvested from a placenta as from cord blood. Adult stem cells - Many adult tissues contain stem cells that can be isolated.
• #15: Every cell contains a complete copy of “the blueprint of life” DNA consists of two strands of nucleotides - 4 bases (A,G,T,C) 23 pairs of chromosomes If unwound and tied together, human DNA in one cell would stretch ~ 5 feet, but would be only 50 trillionths of an inch wide! Genes are specific sequences of DNA, each of which “codes” for a protein with a specific function Genes are copied each time a cell divides, passing on the blueprint
• #17: 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. A. 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. B. 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.
• #30: Adult stem cells are found all over your body. Here are a few examples of places in the body with stem cells. Who here has been told that brain cells never regenerate? (hands) Whoever told you that was misinformed! Relatively recently scientists discovered that in two specific parts of your brain, neural stem cells divide and differentiate to become neurons and glial cells, which support the growth of neurons. Without neural stem cells in the hippocampus, you would probably not be able to learn or remember. The top right picture is a cross-section of the rat hippocampus, and neural stem cells are the blue dots, which divide and differentiate to form mature neurons (green) and astrocytes (red). The bottom right picture is of cultured neural stem cells (just plain blue dots), and derived from those stem cells, neurons (blue dots surrounded by red) and oligodendrocytes (blue dots surrounded by green).