Presentation on theme: "Definition: A stem cell is a "generic" cell that can make exact copies of itself indefinitely. In addition, a stem cell has the ability to produce specialized."— Presentation transcript:
Definition: A stem cell is a "generic" cell that can make exact copies of itself indefinitely. In addition, a stem cell has the ability to produce specialized cells for various tissues in the body -- such as heart muscle, brain tissue, and liver tissue.
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 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.
Embryonic stem cells- these are obtained from either aborted fetuses or fertilized eggs that are left over from in vitro fertilization (IVF). They are useful for medical and research purposes because they can produce cells for almost every tissue in the body. Adult stem cells - these are not as versatile for research purposes because they are specific to certain cell types, such as blood, intestines, skin, and muscle. Both children and adults have them.
Adult stem cells are found in the human body and in umbilical cord blood. The most well known source of adult stem cells in the body is bone marrow but they are also found in many organs and tissues; even in the blood. Adult stem cells are more specialized since they are assigned to a specific cell family such as blood cells, nerve cells, etc.
Embryonic stem cells come from a five to six-day-old embryo. They have the ability to form virtually any type of cell found in the human body. Embryonic germ cells are derived from the part of a human embryo or fetus that will ultimately produce gametes (eggs or sperm). Adult stem cells are undifferentiated cells found among specialized (differentiated) cells in a tissue or organ after birth. Based on current research, adult stem cells appear to have a more restricted ability to produce different cell types and to self-renew than embryonic stem cells. Umbilical cord blood stem cells are used to treat a range of blood disorders and immune system conditions.immune system
Human embryonic germ cells (EG cells) normally develop into eggs and sperm. They are derived from a specific part of the embryo called the gonad ridge, and are isolated from fetuses older than 8 weeks of development.germ cellsgonad ridge One advantage of embryonic germ cells cells is that they do not appear to generate tumors when transferred into the body, as embryonic stem cells do. One of the greatest issues facing researchers is that the derivation of EG cells results from the destruction of a foetus. EG cells are isolated from terminated pregnancies and no embryos or foetuses are created for research purposes.
Cells found early (less than 2 wks.) in the development of an embryo Embryonic stem cells are the most versatile because they can become any cell in the body including fetal stem cells and adult stem cells.
Cloning has brought a revolution in the world of medical science. This process of creating embryos to produce stem cells holds great promise for treating life-threatening diseases like diabetes, Parkinson’s, and many types of cancers.
Step 1 - The scientists first isolate the nucleus from an egg cell, which is unfertilized. Step 2 - The scientists gently push the needle through the hard shell around the egg cell. This shell is known as zona pellucida and it safeguards the egg while it moves down the fallopian tube and enters the uterus.
Step 3 - After removing the nucleus of the egg cell, it is discarded. Step 4 - After removing the nucleus of the egg cell, it is discarded. After several years, this donor cell can be a skin cell taken from an ill patient whom doctors wish to treat by making use of the patient’s own cells that are grown in culture. Once again, the scientists ease the needle tip through the zona pellucida and penetrate deep into the cell without the nucleus. Here, they inject the donor nucleus.
Step 5 - After completion of the nuclear transfer process, scientists “stimulate” the unfertilized egg cell with the help of electrical or chemical treatment, which activates cellular division. Step 6 -Eighty-four hours after the commencement of division, the multiplying cells generate a mass of cells known as blastocyst, which is similar to the size of egg cell
Step 7- When the blastocyst is placed onto a dish that promotes tissue culture, various types of cells get a favorable condition to grow the following: embryonic stem cell colonies from the internal cell mass, cells that are membrane-like, and placental cells. Out of these, the stem cells are the only one to have the capacity of continuing growth under these conditions. In due course of time, they are going to multiply to such an extent that scientists can expand their culture to several dishes. This process is called “passaging.” Step 8- The human as well as the mouse embryonic stem cells produce dense colonies having hundreds of individual cells, which look amazingly similar and are difficult to distinguish even by a trained eye. There are “feeder cells” too, which are actually connective-tissue cells of mouse. The cloning is done. Scientists use these clones to study the growth of specific tissues and cells. These specialized tissues and cells developed from embryonic stem cells through nuclear transfer hold a tremendous potential to treat big diseases, hence, this process is also referred to as “therapeutic cloning.”
The history of stem cell research had a benign, embryonic beginning in the mid 1800's with the discovery that some cells could generate other cells. The history of stem cell research includes work with both animal and human stem cells.
A prominent application of stem cell research has been bone marrow transplants using adult stem cells. The early 1900's physicians administered bone marrow by mouth to patients with anemia and leukemia. Although such therapy was unsuccessful, laboratory experiments eventually demonstrated that mice with defective marrow could be restored to health with infusions into the blood stream of marrow taken from other mice. This caused physicians to speculate whether it was feasible to transplant bone marrow from one human to another (allogeneic transplant). Among early attempts to do this were several transplants carried out in France following a radiation accident in the late 1950's.
Marrow transplants in humans was not attempted on a larger scale until in 1958 Jean Dausset, a French medical researcher, identified the first of many human histocompatibility antigens. These proteins, found on the surface of most cells in the body, are called human leukocyte antigens, or HLA antigens. These HLA antigens give the body's immune system the ability to determine what belongs in the body and what does not belong. A bone marrow transplant between identical twins guarantees complete HLA compatibility between donor and recipient. These were the first kinds of transplants in humans.
It was not until the 1960's that physicians knew enough about HLA compatibility to perform transplants between siblings who were not identical twins. 1973 a team of physicians performed the first unrelated bone marrow transplant. It required 7 transplants to be successful. In 1984 Congress passed the National Organ Transplant Act, which among other things, included language to evaluate unrelated marrow transplantation and the feasibility of establishing a national donor registry. This led ultimately to National Marrow Donor Program (NDWP) that took over the administration of the database needed for donors in 1990.
In 1998, James Thompson (University of Wisconsin - Madison) isolated cells from the inner cell mass of early embryos, and developed the first embryonic stem cell lines. In the same year, John Gearhart (Johns Hopkins University) derived germ cells from cells in fetal gonadal tissue (primordial germ cells). Pluripotent stem cell "lines" were developed from both sources. The blastocysts used for human stem cell research typically come from in vitro fertilization (IVF) procedures.
In 1973 a moratorium was placed on government funding for human embryo research. In 1988 a NIH panel voted 19 to 2 in favor of government funding. In 1990, Congress voted to override the moratorium on government funding of embryonic stem cell research,, which was vetoed by President George Bush. President Clinton lifted the ban, but changed his mind the following year after public outcry. Congress banned federal funding in 1995.
In 1998 DHHS Secretary Sullivan extended the moratorium. In 2000, President Bill Clinton allowed funding of research on cells derived from aborted human fetuses, but not from embryonic cells. On August 9, 2001, President George W. Bush announced his decision to allow Federal funding of research only on existing human embryonic stem cell lines created prior to his announcement. In the November 2004 election, California had a Stem Cell Research Funding authorization initiative on the ballot that won by a 60% to 40% margin. It established the "California Institute for Regenerative Medicine" to regulate stem cell research and research facilities..
Replacing damaged tissue cells - Human stem cells could be used in the generation of cells and tissues for cell-based therapies. This involves treating patients by transplanting specialised cells that have been grown from stem cells in the laboratory.
Due to their ability to replace damaged cells in the body, stem cells could be used to treat a range of conditions including heart failure, spinal injuries, diabetes and Parkinson disease. Scientists hope that transplantation and growth of appropriate stem cells in damaged tissue will regenerate the various cell types of that tissue. For example, haematopoietic stem cells (stem cells found in bone marrow) could be transplanted into patients with leukaemia to generate new blood cells. Or, neural stem cells may be able to regenerate nerve tissue damaged by spinal injury.
Studying human development - Stem cells could be used to study early events in human development and find out more about how cells differentiate and function. This may help researchers find out why some cells become cancerous and how some genetic diseases develop. This knowledge may lead to clues about how these diseases may be prevented.
Testing new drugs - Stem cells grown in the laboratory may be useful for testing drugs and chemicals before they are trialled in people. The cells could be directed to differentiate into the cell types that are important for screening that drug. These cells may be more likely to mimic the response of human tissue to the drug being tested than animal models do. This may make drug testing safer, cheaper and more ethically acceptable to those who oppose the use of animals in pharmaceutical testing.
Screening toxins - Stem cells may be useful for screening potential toxins in substances such as pesticides before they are used in the environment Testing gene therapy methods - Stem cells may prove useful during the development of new methods forgene therapy that may help people suffering from genetic illnesses.
Stem cells are derived from the inner mass of the blastocyst, which is the early stage in the development of an embryo. So first, one must obtain a blastocyst, then isolate the inner mass cells, then finally grow the stem cells. Harvesting, which is when the cells are gathered from a location in the body, is also a part of the stem cell process. Another process of retrieving stem cells requires a collection of cells from the umbilical cords from new born babies.
There are three types of stem cells; pluripotent stem cell, huam embryonic stem cell, and adult stem cell. Pluripotent stem cells, are taken from human embryos and fetal tissue. Pluripotent stem cells can form all the body’s cell types.
Researchers are working to design stem cell therapies that are more effective and reduce the risks to patients Today’s stem cell therapies rely mostly on cells donated by another person, causing the risk of rejection by the patient’s immune system. In the future it may be possible for a person to use a sample of his/her own stem cell for regenerate tissue. How?
Collecting healthy adult stem cells from a patient and manipulating them in the laboratory to create new tissue.
Therapeutic cloning might enable the creation of embryonic stem cells that are genetically identical to the patient.
By manipulating the existing stem cells within the body to perform therapeutic tasks
The research has evolved to a standard where the physician-scientists can use regular skin cells ands and a “chemical cocktail” to create a INDUCED PLURIPOTENT STEM CELL (iPS) that can produce genetically perfect copes of every cell in a human’s body. Perfect solution for fast recovery! In reality deriving an iPS cell line takes longer than a year, however the scientists have made progress in the research achieving to use stem cells now as tools, to change the state of cells, to understand disease mechanisms and speed drug discovery.
“Opposition to stem cell research is mainly coming from religious and social conservatives who are also pro-life. Most of them believe that a pre-embryo from which embryonic stem cells are removed is a human person, and that the process of extracting the cells murders that person.” The debate centers on "the value of human life" and people who are against stem cell research generally believe that we are destroying innocent life and harvesting babies for our own benefit. These people are not wrong, to obtain an embryonic stem cell an embryo must be destroyed; however, currently this is prohibited by the federal law. “If these stem cells are going to be destroyed anyways, it is best to use them to possibly help save and improve lives. The benefits for supporting stem cell research far out way the moral ambiguity of the source of stem cells.”-Phil B. (philforhumanity.com)
Are not AS versatile or available as embryonic stem cells No harm done to the human donor Fertilized embryos that aren’t wanted are sometimes used for research More abundant Attained from a blastocyst Egg after it has been fertilized, but before an embryo has formed
Due to different opinions research on human embryonic stem cells has slowed because of philosophical qualms, political opposition and confusion about the science. On March 9, 2009, President Barack Obama issued Executive Order (EO) 13505, entitled Removing Barriers to Responsible Scientific Research Involving Human Stem CellsRemoving Barriers to Responsible Scientific Research Involving Human Stem Cells A federal judge then temporarily blocked the Obama administration form using federal dollars to fund expanded human embryonic stem cell research, since it involves the destruction of embryos.
The court challenge was brought by adult stem cell researches who argued that the new rules would increase competition for limited funds and violate federal law. A nonprofit group of Nightlight Christian Adoptions argued that new guidelines would decrease the number of human embryos available for adoption.
The District Court for the District of Columbia granted a preliminary injunction on the research. US District Judge Royce Lamberth ruled that despite attempts to separate the derivation of human embryonic stem cells from the research process that two cannot be separated because culling those stem cells destroys an embryo. The new NIH guidelines did not authorize the explicit creation or destruction of any embryonic stem cells. At issue were rules for working with cells that initially were created using private money.
The NIH came up with a compromise, saying it deems those old stem cell lines eligible for government research dollars if scientists can prove they met the spirit of the new ethics standards. The District Court previously dismissed the case, saying the plaintiffs did not have legal standing. But after an appeals court upheld the suit, the District Court reversed course and allowed the case to proceed.