Learn basics of stem cells, their microenvironment and properties !!

1. Presented by
Dhwani Jhala
Graduate student
School of Life Sciences
Central University of Gujarat

2. What is a Stem Cell?
Two identical daughters Differentiate
Somatic Cell
Self-renewal
Stem Cell
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3. 1 stem cell
Self renewal - maintains
the stem cell pool
4 specialized cells
Differentiation - replaces dead or damaged
cells throughout your life
Why self-renew and differentiate?
1 stem cell
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4. Potency
The range of commitment options available to a cell
• Totipotent
• Pluripotent
• Multipotent
• Oligopotent
• Unipotent
Potency
Pluripotent Multipotent
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5. Terms and their evolving definitions
• Stem Cells
• Self-renew : The fertilized egg and the cells of the inner cell mass of a
blastocyst do not meet the criteria. Both will be exhausted as they give
rise to derivatives that are unlike themselves.
• Potency : A pluripotent mesenchymal stem cell has been described
recently that can contribute to most somatic tissue types when injected
into an early blastocyst, and can maintain its stem cell characteristics in
vitro and in vivo.
• Progenitor Cells
• A progenitor cell is a biological cell that, like a stem cell, has a tendency to
differentiate into a specific type of cell, but is already more specific than a
stem cell and is pushed to differentiate into its "target" cell.
• Precursor Cells
• Precursor cell is a stem cell has the capacity to differentiate into only one
cell types. Sometimes used as an alternative term for unipotent stem
cells.
• Transit amplifying Cells
• They are highly proliferative cells that frequently divide and multiply via
mitosis, thus "amplifying" the pool of available precursor cells.
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6. Role of Telomerase
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7. Human Embryogenesis
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Embryonic stem cells

8. The Blastocyst
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10. Culturing Embryonic Stem Cells
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11. neurons
Embryonic stem (ES) cells:
Challenges
embryonic stem cells
skin
blood
liver
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12. Extra embryonic Stem Cells
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13. Adult Stem Cells

14. Adult Stem Cell Plasticity
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15. Induced pluripotent stem cells
(iPS cells)
cell from the body
‘genetic reprogramming’
= express certain genes to the cell
induced pluripotent stem (iPS) cell
behaves like an embryonic stem cell
Advantage: no need for embryos!
all possible types of
specialized cells
culture iPS cells in the lab
differentiation
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16. Pros and Cons to iPS cell technology
• Pros:
– Cells would be genetically identical to patient or
donor of skin cells (no immune rejection!)
– Do not need to use an embryo
• Cons:
– Cells would still have genetic defects
– One of the pluripotency genes is a cancer gene
– Viruses might insert genes in places we don’t
want them (causing mutations)
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 Trans-differentiation
differentiation
Trans-differentiation
Differentiated cells
Another type of Differentiated cells
Stem cells
Differentiated C. of different lineage
Trans-differentiation

18. Trans-differentiation
Graf T. Cell Stem Cell 9:504-516, 2011
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19. Shinya Yamanaka John Gurdon
2012 Nobel Prize in Physiology or Medicine
“For the discovery that mature
cells can be reprogrammed to
grow new cells."

20. Stem Cell Niche
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Schofield R: The relationship between the spleen colony forming cell and the haemopoietic
stem cell. Blood Cells 1978, 4:7-25.
Xie T, Spradling AC: A niche maintaining germ line stem cells in the Drosophila ovary.
Science 2000, 290:328-330.
• The first niche to be defined at the cellular and functional level was described in the
Drosophila ovary

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22. Some interesting aspects
• A true stem cell niche constitutes a stable aspect of tissue
anatomy whether or not stem cells are present. The ability of
‘empty’ niches to re-acquire and maintain introduced stem cells.
• Replacement of lost stem cells is done by rare symmetric
divisions of an adjacent stem cell maintaining stem cell number
in vivo.
• Niches must ensure that daughter cells differentiate
appropriately as they leave the niche.
• Construct new niches to maintain an adequate stem cell supply.
E.g. During bone remodelling.
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Drosophila testis
• Stem cells for germ cells and somatic
cyst cells lie in contact
• Stem cell–stem cell communication
Hair follicle
• During most of the hair cycle and in the
absence of wounding, transient epithelial stem
cells and melanoblasts support ongoing skin
and hair production.
•Reserve stem cells located in the bulge do not
divide during this period and hence can retain
labeled DNA, a trait often associated with stem
cells.

24. Model for regulation of cystoblast differentiation in the
Drosophila GSC niche.
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25. Suggested Readings
• Stem Cells Handbook by Stewart Sell
• Essentials of Stem Cell Biology by Robert Lanza
• The Cell Biology of Stem Cells by Eran Meshorer and Kathrin
Plath
• Stem Cell Regulators by Gerald Litwack
• Stem Cells Scientific Facts and Fiction by C. Mummery et. al.
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