Stem cells are relatively unspecialized cells that have the
unique potential to develop into specialized cell types in the body
(for example, blood cells, muscle cells or nerve cells). They occur
at all stages of human development, from embryo to adult, and in
many tissues of the body. What are Stem Cells
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General Properties of Stem cell Stem cells differ from other
kinds of cells in the body. All stem cells (regardless of their
source) have three general 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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Characteristics of Stem cells In some organs, such as the gut
and bone marrow, stem cells regularly divide to repair and replace
worn out or damaged tissues. In other organs, however, such as the
pancreas and the heart, stem cells only divide under special
conditions.
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Where Are Stem Cells Found? Stem cells come from several
sources in the body. The names of the cells below indicate the
sources from which they are derived. Embryonic Stem Cells: These
stem cells come from embryos in the early stages of development.
They have the ability to differentiate into any type of cell in the
initial stages of development and become slightly more specialized
as they mature.
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Fetal Stem Cells: These stem cells come from a fetus. At about
nine weeks, a maturing embryo enters into the fetal stage of
development. Fetal stem cells are found in fetal tissues, blood and
bone marrow. They have the potential to develop into almost any
type of cell.
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Umbilical Cord Blood Stem Cells These stem cells are derived
from umbilical cord blood. Umbilical cord stem cells are similar to
those found in mature or adult stem cells. They are specialized
cells that develop into specific types of cells.
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Placental Stem Cells These stem cells are contained within the
placenta. Like cord blood stem cells, these cells are specialized
cells that develop into specific types of cells. Placentas however,
contain several times more stem cells than do umbilical cords.
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Adult Stem Cells These stem cells are present in mature body
tissues in infants, children and adults. They may also be found in
fetal and umbilical cord blood cells. Adult stem cells are specific
to a particular tissue or organ and produce the cells within that
particular tissue or organ. These stem cells help to maintain and
repair organs and tissues throughout a person's life.
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Hematopoietic stem cells: Hematopoietic stem cells (HSCs) are
cells present in blood and bone marrow. They are capable of forming
mature blood cells, such as red blood cells (the cells that carry
oxygen), platelets (the cells that help stop bleeding) and white
blood cells (the cells that fight infections). They give rise to
the myeloid (monocytes and macrophages, neutrophils, basophils,
eosinophils, erythroc ytes,megakaryocytes/platelets, dendritic
cells), and lymphoid lineages (T-cells, B-cells, NK-cells).
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Hematopoietic Stem Cell
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Types of Stem Cell Totipotent Stem Cells These stem cells have
the ability to differentiate into any type of cell in the body.
Totipotent stem cells develop during sexual reproduction when male
and female gametes fuse during fertilization to form a zygote. The
zygote is totipotent because its cells can become any type of cell
and they have limitless replicative abilities. As the zygote
continues to divide and mature, its cells develop into more
specialized cells called pluripotent stem cells.
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Pluripotent Stem Cells These stem cells have the ability to
differentiate into several different types of cells. Specialization
in pluripotent stem cells is minimal and therefore they can develop
into almost any type of cell. Embryonic stem cells and fetal stem
cells are two types of pluripotent cells.
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Multipotent Stem Cells These stem cells have the ability to
differentiate into a limited number of specialized cell types.
Multipotent stem cells typically develop into any cell of a
particular group or type. For example, bone marrow stem cells can
produce any type of blood cell. However, bone marrow cells don't
produce heart cells. Adult stem cells and umbilical cord stem cells
are examples of multipotent cells.
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Mesenchymal stem cells are multipotent cells of bone marrow
that have the ability to differentiate into several types of
specialized cells related to, but not including blood cells. These
stem cells give rise to cells that form specialized connective
tissues, as well as cells that support the formation of blood.
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Oligopotent Stem Cells These stem cells have the ability to
differentiate into just a few types of cells. A lymphoid stem cell
is an example of a oligopotent stem cell. This type of stem cell
can not develop into any type of blood cell as bone marrow stem
cells can. They only give rise to blood cells of the lymphatic
system, such as T cells.
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Unipotent Stem Cells These stem cells have unlimited
reproductive capabilities, but can only differentiate into a single
type of cell or tissue. Unipotent stem cells are derived from
multipotent stem cells and formed in adult tissue. Skin cells are
one of the most prolific examples of unipotent stem cells. These
cells must readily undergo cell division to replace damaged
cells.
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Stem cell and Diseases Stem-cell therapy is an intervention
strategy that introduces new adult stem cells into damaged tissue
in order to treat disease or injury.Stem cell research treats wider
variety of diseases: Cancer, Type 1 diabetes mellitus Parkinson's
disease, Spinal cord injuries, Huntington's disease, Multiple
sclerosis, Muscle damage, Neurological disorders.
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How stem cell treat various Diseases Tissue Repair Regenerate
spinal cord, Heart tissue or any other major tissues in the body.
Heart Disease Adult bone marrow stem cells injected into the heart
arteries are believe to improve cardiac functions in victims of
heart failure or heart attack. Haematopoitic stem cell treatment
HPCs are used in the treatment of many malignant (e.g., leukemia,
lymphoma) and non-malignant (e.g., sickle cell disease) diseases to
replace or rebuild a patient's hematopoietic system. This type of
treatment is called a bone marrow or stem cell transplant.