Stem Cells. Definition The capacity of cells to divide and differentiate along different pathways...
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Transcript of Stem Cells. Definition The capacity of cells to divide and differentiate along different pathways...
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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
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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
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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