1. Stem Cells The process of cell differentiation A primary goal of research on embryonic stem cells is to learn how undifferentiated stem cells turn into differentiated stem cells that form specific tissues and organs. Researchers are also interested in figuring out how to control this process of differentiation.

2. What is a Stem Cell?
A cell that has the ability to continuously divide and differentiate (develop) into various other kind(s) of cells/tissues
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. 2

3. Stem Cell Applications
Tissue repair
nerve, heart, muscle, organ, skin
Regenerate spinal cord, heart tissue or any other major tissue in the body.
Cancers
Studies show leukemia patients treated with stem cells emerge free of disease
Injections of stem cells have also reduces pancreatic cancers in some patients.
Autoimmune diseases
diabetes, rheumatoid arthritis, MS

4. Kinds of Stem Cells Stem cell type Description Examples Totipotent
Each cell can develop into a new individual
Cells from early (1-3 days) embryos
Pluripotent
Cells can form any (over 200) cell types
Some cells of blastocyst (5 to 14 days)
Multipotent
Cells differentiated, but can form a number of other tissues
Fetal tissue, cord blood, and adult stem cells
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. 4

5. Embryonic Stem cells are obtained from In-Vitro Fertilization embryos that were not used -
Illustration by Matt Bohan, 2007

6. Totipotent Pluripotent Multi- potent
This cell
Can form the
Embryo and placenta
Pluripotent
This cell
Can just form the
embryo
Multi-
potent
Fully mature 6

7. Adult Stem Cells Skin Fat Cells Bone marrow Brain
An undifferentiated cells found among specialized or differentiated cells in a tissue or organ after birth
Skin
Fat Cells
Bone marrow
Brain
Many other organs & tissues
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.

8. STEM CELLS HAVE ALSO BEEN FOUND IN “MATURE” ORGANS
Illustration by Matt Bohan, 2007

9. Differences between embryonic stem cells and adult/somatic stem cells
They have different self-renewal capabilities
Embryonic stem cells: near indefinite self-renewal
Adult stem cells: limited self-renewal
They have different differentiation potentials
.Embryonic stem cells: differentiate into all cell types in an organism
Adult stem cells: differentiate into restricted cells types.
They differ in how they respond to external stimuli
Embryonic stem cells are readily to change upon stimulation
Adult cells emphasize on stability and need to be activated by cues, e.g. injuries.

10. PROS AND CONS OF EACH TYPE
EMBRYONIC
CELL LINES LAST AND LAST AND LAST
Pluripotent and totipotent in an early embryonic stage
EASY TO FIND
ETHICAL ISSUES
ADULT
CELL LINES DO NOT LAST
MULTIPOTENT
HARD TO LOCATE
NO ETHICAL ISSUES

11. Why the Controversy Over Stem cells?
Embryonic Stem cells are derived from extra blastocysts that would otherwise be discarded following IVF( in vitro fertilisation)
Extracting stem cells destroys the developing blastocyst (embryo).
-Questions for Consideration-
Is an embryo a person?
Is it morally acceptable to use embryos for research?

12. Current medical application of human stem cell research
-Grow new cells in a laboratory to replace damaged organs or tissues
-Correct parts of organs that don’t work properly
-Research causes of genetic defects in cells
-Research how diseases occur or why certain cells develop into cancer cells
-Test new drugs for safety and effectiveness
- Bone marrow transplantation

13. Cord blood stem cells and amniotic fluid stem cells
Cord blood stem cells are harvested from the umbilical cord after childbirth. They can be frozen in cell banks for use in the future. These cells have been successfully used to treat children with blood cancers, such as leukemia, and certain genetic blood disorders.

14. Dolly the Sheep. Dolly (July 5, February 14, 2003), a ewe, was the first mammal to have been successfully cloned from an adult cell. She was cloned at theRoslin Institute in Midlothian, Scotland, and lived there until her death when she was six years old