Ability to self-renew by multiplying in an undifferentiated state, retaining the
same characteristics of the original cell
Ability to differentiate into various cell types that constitute an organism
According to their differentiation potential:
Totipotent
can differentiate into every type of cell: extraembryonic membranes and
tissues, the embryo, and all postembryonic tissues and organs
9. Stem Cells - hESC and iPSC 1
, is the only type of stem cell that can originate an entire organism
they can replicate indefinitely without losing their total potency
the morula is the last structure of totipotent stem cells in humans
Pluripotent
capable of giving rise to most tissues of an organism but cannot originate
an entire organism
the morula (totipotent) gives rise to the blastocyst (pluripotent) composed of:
the inner cell mass and trophectoderm (outer layer - composed by
trophoblast cells)
the inner cell mass can differentiate into almost every type of cell - cells
from the three germ layers: mesoderm, endoderm, and ectoderm
Unlike totipotent cells, pluripotent stem cells fail in its ability to
differentiate into extra embryonic membranes:
trophectoderm, will give rise to the placenta
trophoblast, extra embryonic tissue responsible for negotiating
implantation, developing into the placenta and controlling the exchange
of oxygen and metabolites between the mother and the embryo
Give rise to:
ESC (embryonic stem cells)
derived from a group of cells called the inner cell mass, which is part of the
early embryo (5 days), called the blastocyst.
Embryonic stem cells are an in vitro artifact. In vivo they are only call
inner cell mass.
differentiate into cells from the germ layers: mesoderm, endoderm, and
ectoderm
These cells can divide indefinitely due to a high expression of
telomerase, however, in vitro they have a tendency to accumulate
serious genetic mutations.
EGC (embryonic germ cells)
9. Stem Cells - hESC and iPSC 2
, derived from fetal tissue, isolated from the primordial germ cells of the
gonadal ridge
the gonadal ridge develops into the testes or ovaries and the primordial
germ cells give rise to eggs or sperm
ECC (embryonal carcinoma cells)
isolated from teratocarcinomas, a tumor that occasionally occurs in the
gonads.
unlike the other two, they are usually aneuploid.
Multipotent
can differentiate into only a limited range of cell types
Cardiac, skeletal and smooth Digestive cells (include intestine)
muscle cells
Red blood cells
Kidney
hESC - Human Embryonic Stem Cells
9. Stem Cells - hESC and iPSC 3
, Properties
Clonogenic cells capable of undergoing an unlimited number of symmetrical
divisions without differentiating (long-term self-renewal)
Because they express high levels of telomerase
Pluripotent cells capable of giving rise to cells from all three germ layers of the
embryo (ectoderm, mesoderm, endoderm) in vitro
Develop, always, into teratomas (benign tumors made up of several different types
of tissue) when injected into SCID mice (immunocompromised mice) → hESC are
tumor-genetic
Exhibits stable diploid karyotype
Express specific transcription factors such as Oct-4, Sox2 and Nanog and
surface markers such as Tra-1-60, Tra-1-81, SSEA-3 and SSEA-4, and alkaline
phosphatase (AP)
Sources
Available hESC lines
Excess embryos from IVF (in vitro fertilization) clinics
Embryos created for research by IVF
Therapeutic cloning, or somatic cell nuclear transfer – SCNT – allows us to create
hESC lines with a specific genetic background, useful for organ or tissue
9. Stem Cells - hESC and iPSC 4
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