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1. BME 101
STEM CELL
Dr M Tarik Arafat
Professor
Department of Biomedical Engineering (BME)
Bangladesh University of Engineering and Technology (BUET)
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2. Stem cell
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 An undifferentiated cell of a multicellular organism which is
capable of giving rise to indefinitely more cells of the same type,
and from which certain other kinds of cell arise by differentiation.
 Stem cells are cells that proliferate and also can differentiate to
produce cells with new phenotypes and functions.

3. Properties of stem cells
■ Stem cell differ from other kinds of cells
■ Regardless of their source, all stem cells have the following
properties:
– They are capable of dividing and renewing themselves for long
periods
– They are unspecialized
– They can give rise to specialized cell types
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4. What defines a Stem cell?
■ Scientists continue to develop methods to identify stem cells but
the two properties that are most closely associated with stem cells
are self-renewal and differentiation.
■ Self-renewal is the process by which stem cells divide to make
more stem cells, perpetuating the stem cell pool throughout
life. Self-renewal is division with maintenance of the
undifferentiated state
■ The second defining property of a stem cell is its ability to
differentiate into a more specialized cell. The number of cell types a
stem cell can differentiate into is determined by its potency.
■ Can a Stem Cell Become Everything It Wants to Be? – depends on
its potency.
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5. Stem cells potential
■ Totipotency: capacity to generate all cell types within the body +
extraembryonic tissue
■ Pluripotency: capacity to generate all cell types within the body
■ Multipotency: capacity to give rise to more than 1 cell type
■ Unipotent stem cell: tissue precursor cells, capacity to give rise to one
cell type only
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6. Embryo development
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The blastocyst is a structure formed in the early development of mammals.
It possesses an inner cell mass (ICM) which subsequently forms the
embryo. The outer layer of the blastocyst consists of cells collectively called
the trophoblast.
Days: 5–9

7. Stem cell potential
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8. Types of stem cell
■ Embryonic stem cells (ESCs)
– Derived from blastocyst of a 5 day old embryo
– Are pluripotent, i.e. they can differentiate into all most any cell type in
the body
– Can renew themselves indifinently
■ Induced pluripotent stem cells (iPSCs)
– Generated from reprogrammed somatic cell
– Similar or equivalent to ESCs i.e. pluripotent and the ability to renew
themselves indefinitely
■ Adult stem cells (e.g. MSCs, NSCs, HSCs)
– Isolated from adult tissues, organs or blood or cord blood etc
– Are multipotent i.e can give rise to a number of related cell types
– Can renew themselves a number of times but not indefinitely
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9. Stem cell
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-> Cultured human mesenchymal stem
cells can be expanded a millionfold
and retain their multipotential
properties. Figure shows that 100
million MSCs after harvest and
gentle centrifugation is about 300
μl volume.

10. Stem cell niche – the house of stem cell
Stem-cell niche refers to a
microenvironment, within the
specific anatomic location
where stem cells are found,
which interacts with stem
cells to regulate cell fate.
The word 'niche' can be in
reference to the in vivo or in
vitro stem cell
microenvironment
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11. Stem cell niche – the house of stem cell
Fig. Composition of stem cell niche including physical, chemical and cellular
components. All the components interact dynamically.
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12. Embryonic stem cells (ESCs)
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- Pluripotent
- No genetic abnormalities
- In vitro culture and expansion
- Ethical issues

13. Embryonic stem cells (ESCs)
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14. Embryonic stem cells (ESCs)
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15. Human Embryonic stem cells (hESCs)
■ hESCs were first isolated in 1998 from the inner cell mass (ICM) of a
pre-implantation human blastocyst in a landmark study by Thompson
et al.
■ In 2001, the decision was made to allow federal funding for hESC
research on the condition that only hESC lines already in existence
could be used.
■ https://stemcells.nih.gov/research/registry.htm
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16. iPSC
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Shinya Yamanaka is a Japanese Nobel Prize-
winning stem cell researcher. He serves as
the director of Center for iPS Cell (induced
Pluripotent Stem Cell) Research and
Application and a professor at the Institute
for Frontier Medical Sciences at Kyoto
University.
who showed in 2006 that the introduction of
four specific genes encoding transcription
factors could convert adult cells into
pluripotent stem cells. He was awarded the
2012 Nobel Prize along with Sir John
Gurdon "for the discovery that mature cells
can be reprogrammed to become pluripotent.

17. iPSC - Application
■ Since iPSCs can be derived directly from adult tissues, they not only bypass the need
for embryos, but can be made in a patient-matched manner, which means that each
individual could have their own pluripotent stem cell line. These unlimited supplies
of autologous cells could be used to generate transplants without the risk of immune
rejection. While the iPSC technology has not yet advanced to a stage where
therapeutic transplants have been deemed safe, iPSCs are readily being used in
personalized drug discovery efforts and understanding the patient-specific basis of
disease
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18. Other adult stem cells (e.g. MSCs, NSCs
etc)
■ Mesenchymal stem cells are multipotent stromal cells that can differentiate
into a variety of cell types, including osteoblasts (bone cells), chondrocytes
(cartilagecells), myocytes (muscle cells) and adipocytes (fat cells which give
rise to marrow adipose tissue).
■ Neural stem cells (NSCs) are self-renewing, multipotent cells that firstly
generate the radial glial progenitor cells that generate the neurons and glia
of the nervous system of all animals during embryonic development.
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