S

Stem Cells

Definition

The capacity of cells to divide and differentiate along different pathways is necessary in embryonic development. It also makes stem cells suitable for therapeutic uses.

Egg and Sperm

A new animal life

2 gametes = 1 zygote

1 cell divided into 2 = embryo

Further division

But cells have not differintiated

Stem Cell Properties

Can divide repeatedly

Produce copious quantities of new cells.

Useful for the growth of tissues or the replacement of cells that have been lost or damaged.

Not fully differentiated

They can differentiate in different ways, to produce different cell types.

Embryonic Stem Cells – Therapeutic

Potentially very useful to:

Regenerate tissue

Means of healing disease

Grow whole replacement organs

Embryonic Stem Cells – Non-therapeutic

Produce large quantities of striated muscle fiberes (meat)

In the future – might not need to slaughter cattle

Differentiation

During embryo development cells commit to a pattern.

Eventually each cell becomes committed to develop into one specific cell types.

They are no longer stem cells.

Some remain

A few remain as stem cells

Present in tissue: bone marrow, skin and liver

Powers of regeneration & repair

S

Therapeutic Uses

Stargardt’s disease

Stargardt’s Macular Dystrophy Genetic disease Appears in children ages 6-12 Recessive mutation of gene

ABCA4 Membrane protein used for

active transport in retina cells malfunctions

Photoreceptive cells in the retina degenerate

These cells detect light so vision worsens

May cause blindness

Stargardt’s Disease

Researchers have developed methods for making embryonic stem cells develop into retina cells.

Originally done in mice Injected cells not

rejected Did not form tumours Cells moved to the

retina, attached and remained

Caused vision improvement

Video

November 2010 - FDA approved stem cell research

Research in England

Trial

Woman in her 50’s

50,000 retina cells derived from embryonic stem cells injected into her eyes

Cells attached to retina

Improvement in vision with no side effects

S

Another use in disease:Leukemia

Leukemia

Cancer – mutation of genes

Begins to make abnormally large numbers of white blood cells

No tumour forms

Normal range = 4,000 – 11,000 per mm3 of blood

With leukemia = 30,000 or above

Cure Leukemia

Must kill cells in bone marro

Chemotherapy

Destroys stem cells in the bone marrow

Blood Stem Cell

Stem cells & Leukemia

A large needle inserted into a large bone (pelvis) – fluid removed

Stem cells extracted from the fluid & frozen (adult stem cells therefore can only make blood cells)

High dose of chemotherapy drugs – bone marrow loses its ability to produce blood cells

Stem cells are returned to the patient’s body and re-establish themselves

Stem Cell Ethics

Stem cell research is controversial

Old research would be considered unethical today Patients without their

consent

People do not understand the sources of stem cells

Sources of Stem Cells

Embryos can be deliberately created by fertilizing egg cells (4 – 16 cells)

Blood can be extracted from the umbilical cord of newborns (frozen)

Stem cells can come from some adult tissues (bone marrow)

Embryonic stem cells

Almost unlimited growth potential.

Can differentiate into any type in body.

More risk of becoming tumour cells than adult stem cells

Less chance of genetic damage due to the accumulation of mutations than with adult stem cells

Likely to be genetically different from an adult patient

Kills the embryo

Cord Blood Stem Cells

Easily obtained and stored. Commercial collection &

storage services already available.

Fully compatible with the tissues of the adult that grow – no rejection problems occur.

Limited capacity to differentiate into different cell types – only naturally develop into blood

Limited quantities of stem cells from one baby’s cord.

The umbilical cord is discarded whether or not stem cells are taken from it.

Adult Stem Cells

Difficult to obtain because there are few and buried deep. Less growth potential than embryonic stem cells. Less chance of malignant tumours developing than from embryonic stem cells. Limited capacity t differentiate into different cell types. Fully compatible with the adult’s tissues; rejection not a problem. Removal of stem cells does not kill the adult from which the cells are taken.

Final Thoughts

When does human life begin?

in vitro fertilization required hormone treatment to women

Should women be paid for supplying eggs