BIOT 412, Stem Cells, Ch. 12
December, 2012
Stem cells
Stem cells
- Ability to renew themselves
- Differentiate into diverse range of specialized
cell
History
The term "stem cell" was proposed for scientific
use by the Russian histologist Alexander
Maksimov (1874–1928) at Congress of
Hematologic Society in Berlin in 1908. It
postulated existence of haematopoietic stem
cells.
Definitions Related to Stem Cells
Differentiation
Qualitative change in cellular phenotype resulting from the onset of
synthesis of new genetic products. Differentiation is commonly identified
by production of novel protein
Maturation
Qualitative change in the cellular phenotype or the cellular constituent
proteins leading to functional competence
Self Maintenance
The ability to maintain its own number without input from other cell stages is
self maintenance
Self-Renewal
This term applies “to make like new cells” or simple rejuvenation
Self-Replication
-Duplication
-Production of identical cell
Regeneration: “to make something again” that
was already preexisting. It could apply to
tissue or population of cells that contain
ability to self maintain and regulation.
Types of Stem Cells
Three broad categories, based on their ability to differentiate.
Totipotent stem cells
are found only in early embryos. Each cell can form a complete
organism (e.g., identical twins)
Pluripotent stem cells
exist in the undifferentiated inner cell mass of the blastocyst and
can form any > 200 different cell types in body
Multipotent stem cells
are derived from fetal tissue, cord blood and adult stem cells; they
can form a limited number of cell types
Sources of stem cells
Embryonic stem cells - are harvested from the inner cell mass of the
blastocyst seven to ten days after fertilization RELAYES TO TRANSGENICS
Fetal stem cells - are taken from the germline tissues that will make up the
gonads of aborted fetuses
Umbilical cord stem cells - Umbilical cord blood contains stem cells similar to
those found in bone marrow
Placenta derived stem cells - up to ten times as many stem cells can be
harvested from a placenta as from cord blood
Adult stem cells - Many adult tissues contain stem cells that can be isolated
Totipotent
When given
 the right
differentiation
factors
Pluripotent stem cells
Embryonic Stem Cells(ESC)
Martin Evans & Matthew Kaufman,
-First derived ESC from mouse embryo in 1981
-Most human embryonic stem cells come from embryos developed
from eggs fertilized in vitro for research purposes with informed
consent of the donors
-They are not derived from eggs fertilized in a woman's body
-The embryos from which human embryonic stem cells are derived are
typically four or five days old and are a hollow microscopic ball of
cells called the blastocyst
-The blastocyst includes three structures: the trophoblast, which is the
layer of cells that surrounds the blastocoel, a hollow cavity inside
the blastocyst; and the inner cell mass, which is a group of cells at
one end of the blastocoel that develop into the embryo proper.
-Embryonic Stem (ES) cells are pluripotent. This means they are able to
differentiate into more than 220 cell types in the adults.
Adult Stem Cells
- Partially differentiated cells; multipotent
- Found throughout the body after embryonic development;
multiply by cell division to replenish dying cells and
regenerate damaged tissues
- Also known as somatic stem cells; they can be found in
juvenile as well as adult animals and humans
-Scientific interest is their ability to divide or self-renew
indefinitely, and generate all the cell types of the organ
from which they originate
Multipotent stem cells
Hematopoietic stem cells (HSCs)
- They are multipotent stem cells that give rise to all the
blood cell types including myeloid (monocytes and
macrophages, neutrophils, basophils, eosinophils,
erythrocytes, megakaryocytes/platelets, dendritic
cells), and lymphoid lineages (T-cells, B-cells, NK-cells)
- HSCs are found in the bone marrow of adults, which
includes femurs, hip, ribs, sternum, and other bones.
- Cells can be obtained directly by removal from the hip
using a needle and syringe, or from the blood following
pre-treatment
Stem Cell lines
- Stem cell line is a population of cells that can
replicate themselves for long periods of time in
vitro, meaning outside of the body, provided the
environment is like that found in the mammalian
body
-
There different types of stem cell lines
- These cell lines are useful in human
developmental biology, drug discovery, and
transplantation medicine
Embryonic stem cell lines
Are created from embryos.
A living single stem cell from the embryo is placed in a Petri
dish (without agar) and provided with nutrients and growth
factors that simulate those found in the womb. The resulting
cell line will continue to divide provided it receives sufficient
chemical signals signaling it to remain undifferentiated.
- The U.S. National Institutes of Health currently lists only 21
lines, out of sixty, that are available for distribution to
researchers. THEY ARE NOT VERY USEFUL.
Adult Stem Cell Lines
Adult stem cell lines isolated from mature
tissues, as are cells isolated from umbilical cord
blood. However, these cells have a genetic
imprint of the host they were taken from, thus
limiting their therapeutic use in genetic
disorders. Also, adult stem cells are not totipotent
or pluripotent like embryonic stem cells, but rather
more specialized cells that are multipotent
Induced pluripotent stem cells
They are commonly abbreviated as iPS cells or
iPSCs, are a type of pluripotent stem cell
artificially derived from a non-pluripotent cell,
typically an adult somatic cell, by inducing a
"forced" expression of certain genes.
Human Relevance and Role of Stem
Cells
-Treatments offered by stem cell in heart diseases,
diabetes, cancer, and diseases of the nervous system,
such as Parkinson’s disease and Alzheimer’s disease.
-Stem cell therapies:
Bone marrow transplants (BMT) are a well known
clinical application of stem cell transplantation.
The isolation of additional stem and progenitors cells is
now being developed for many other clinical
applications.
• Skin Replacement
• Neural Stem Cells for Brain & Spinal Cord
Repair
• Spinal Cord Injury
• Parkinson’s disease
• Stem Cell Transplant for Cancer and other
Diseases
• Replace dysfunctional bone marrow