Embryonic Stem Cells

Objectiveswhat are stem cells and why are they important?

explain the difference between totipotent, pluripotent, and multipotent using examples of each

what is the potential stem cells have to change modern medicine?

understand the ethical issues surrounding stem cells

Cell Differentiation

we know that somatic cells contain all of our DNA (with a few exceptions)

some of that DNA is expressed, and some of it is not (gene regulation) this is determined through transcription factors

once a cell knows what DNA to use it can specialize (perform its needed duties within the cell)

process of cells changing is called differentiation, once a cell knows what its ‘job’ is it is considered specialized

https://www.youtube.com/watch?v=t3g26p9Mh_k

Stem Cells

undifferentiated cells - they do not have a specific job or function but they have the potential to differentiate

can replace worn out cells when the cells die - our bodies do this already

can be used to create new cells, tissues, and organs through regenerative medicine

https://www.youtube.com/watch?v=evH0I7Coc54

Stem Cell Researchfirst used in a 1950’s in a bone marrow transplant to treat leukemia

initially identified and proven to exist in 1961 by two Canadian scientists, Dr. Jim Till and Dr. Ernest McCulloch.

stem cells are flexible cells in terms of what they will become in the developing organism

ability to reproduce themselves continually, while still keeping the ability create more specialized types of cells

Vocabularytotipotent - cells that can forma all cell types in a body including extra embryonic or placental cells (embryonic cells within the first couple of divisions after fertilization)

pluripotent - give rise to all of the cell types that make up the body (embryonic stem cells) except the cells needed to develop a fetus

multipotent - can develop into more than one cell type but are more limited (adult stem cells and cord blood stem cells)

Types of Stem Cellstissue-specific stem cells (adult stem cells, somatic stem cells)

found in small numbers in tissues that make up organs

replace worn out or dead cells in our organs (small intestine, blood/bone marrow, liver, etc)

partially differentiated as the name suggests so they can only make a small number of different cell types

considered to be multipotent

Types of Stem Cellsembryonic stem cells

created from embryos

willingly donated by individuals from fertility clinics

pluripotent or totipotent depending on when they are ‘harvested’

come from the inner cell mass of a blastocyst

can make all different types of cells in the body

Types of Stem Cellscord blood stem cells

located in the umbilical cord and placenta of a newborn child

can be easily collected and frozen for later use

contains hematopoietic stem cells (blood stem cells) which can produce all blood cells including immune system cells

leaves fewer immune system incompatibilities (less rejection)

multipotent stem cells

Types of Stem Cells

induced pluripotent stem cells

somatic stem cells that have been manipulated by scientists to act like embryonic stem cells

arise from skin, fat, or liver cells

can become any cell in the body

Limitations of Medicinemuch of medicine is non-individualized meaning that few medical treatments are specific to an individual’s genetics or history.

damage to the body from injuries or illness can be permanent and untreatable

some of the damage from a heart attack or stroke is usually permanent, and the patient does not usually obtain a 100% recovery in many serious injuries or illnesses, a complete recovery may not be possible

the need for tissue or organ transplant is far greater than the supply

Even when a matching donor is found, a transplant may be rejected by the patient’s body.

The Promise of Stem Cells

Stem cells may be able to replace damaged cells in the body

lymphoma, leukemia, replacing damaged cornea and cardiac cells

in the future: Parkinson’s, Alzheimer’s, diabetes, etc

Promising animal studies have been completed in sheep, rats, mice, horses

https://www.youtube.com/watch?v=cEB8656TCIE

Sources of Embryonic Stem Cells

embryonic stem cell lines (cultures of cells from cell mass)

excess embryos from in-vetro fertilization clinics

embryos created for research by in-vetro fertilization

therapeutic cloning

https://www.youtube.com/watch?v=K7D6iA7bZG0

Stem Cells vs Embryosstem cells and embryos are not the same thing

stem cells are diploid cells (46 chromosomes) that are isolated from an embryo or from a child/adult

embryos are the result of fertilization of egg and sperm cell

embryo is the stage between a zygote and a fetus being formed

Cloningpurpose of therapeutic cloning is to harvest embryonic stem cells for treatment as a blastocyst is destroyed

purpose of reproductive cloning is to make new person as a blastocyst is implanted in uterus

embryos can be artificially implanted into uterus

CRISPR

technology that allowed for genetic modifications to happen cheaply and easily

stands for clustered regularly interspaced short palindromic repeats

programmable system that can be copied and placed within a living cell and works on every type of cell

has the potential to change humanity forever through its potential to end dies, create designer babies, and halt or reverse the aging process

https://www.youtube.com/watch?v=jAhjPd4uNFY

Ethicsscientific use of embryos by researchers who do not intend to let the embryo develop into a fetus is controversial

harvesting embryonic stem cells destroys the blastocyst

“This is murder”

embryonic stem cell research requires human cells

has the potential to create a commercial market for human cells

“This devalues life”

“If excess IVF embryos are being discarded anyway, they should be put to good use”

“Therapeutic cloning is a slippery slope – it will lead to reproductive cloning”

The Great Debate

http://www.youtube.com/watch?v=6xriJtQ2Tow

https://www.youtube.com/watch?v=y7LXwGfvxwo

https://www.youtube.com/watch?v=hsFEcBwO8O4

Discussion1. What are the advantages? 2. What are the disadvantages?

3. Are stem cells ever good/useful?

4. How far is too far? 5. Other thoughts and comments?

Additional Resources

New York Times Report: https://www.nytimes.com/2007/08/10/us/10stemcell.html?

Promise of Stem Cell Research. From National Institutes of Health:

stemcells.nih.gov/