Stem cells Flashcards
How are embryonic stem cells often described?
- Their potential is ‘total’.
- Have the ability to develop into any cell in the human body including the extra-embryonic tissue including the placenta.
Show the development of the preimplantation blastocyst in humans
Define Pluripotent
Have the potential to differentiate into almost any cell in the body
In humans, how many days after fertilisation do totipotent cells start to specialise from a cluster of cells known as the blastocyst?
4 days
Which group of cells within a blastocyst go on to create most of the cells in the body?
•Within the blastocyst a group of cells known as the inner cell mass (pluripotent stem cells) will go on to create most of the cells in the body
Describe how Embryonic stem cells are derived
- Are derived from embryos
- Are derived from eggs that have been fertilised in vitro as part of IVF procedure.
- Donated for research with informed consent of donors.
- Not derived from eggs fertilised in a woman’s body.
Show the differentiation of human tissues
At the time of implantation, the mammalian embryo is a blastocyst: What does it consist of?
- It consists of the trophoblast - a hollow sphere of cells that will go on to implant in the uterus and develop into extra embryonic tissues, i.e. placenta and umbilical cord.
- inner cell mass (ICM) that will develop into the embryo
Test for pluripotency
Reprogrammed mouse astrocytes retain a “memory” of tissue origin and possess more tendencies for neuronal differentiation than reprogrammed mouse embryonic fibroblasts
Explain the ariticle ‘Reprogrammed mouse astrocytes retain a “memory” of tissue origin and possess more tendencies for neuronal differentiation than reprogrammed mouse embryonic fibroblasts’
Direct reprogramming of a variety of somatic cells with the transcription factors Oct4 (also called Pou5f1), Sox2 with either Klf4 and Myc or Lin28 and Nanog generates the induced pluripotent stem cells (iPSCs) with marker similarity to embryonic stem cells.
However, the difference between iPSCs derived from different origins is unclear. In this study, we hypothesized that reprogrammed cells retain a “memory” of their origins and possess additional potential of related tissue differentiation.
- We reprogrammed primary mouse astrocytes via ectopic retroviral expression of OCT3/4, Sox2, Klf4 and Myc and found the iPSCs from mouse astrocytes expressed stem cell markers and formed teratomas in SCID mice containing derivatives of all three germ layers similar to mouse embryonic stem cells besides semblable morphologies.
- To test our hypothesis, we compared embryonic bodies (EBs) formation and neuronal differentiation between iPSCs from mouse embryonic fibroblasts (MEFsiPSCs) and iPSCs from mouse astrocytes (mAsiPSCs). We found that mAsiPSCs grew slower and possessed more potential for neuronal differentiation compared to MEFsiPSCs.
- Our results suggest that mAsiPSCs retain a “memory” of the central nervous system, which confers additional potential upon neuronal differentiation.
Test for pluripotency in vitro
Potency
Adult stem cells:
What are multipotent stem cells?
- Self-renew for long periods and differentiate into specialised cells with specific functions.
- Limited in its ability to differentiate.
- Committed to produce specific cell types e.g. NSC produce neurons and glia.
- Adult stem cells are considered multipotent.
- Found in most organs.
What are the properties of Adult stem cells/tissue specific stem cells?
- Stem cells found in the postnatal body.
- Typically multipotent, Oligopotent and unipotent
- Responsible for tissue renewal or repair following damage
- Ability to self-renew and differentiate.
- Tissue homeostasis.
Why is self-renewal and differentiation important?
- Sustain the pool of stem cells throughout life
- Generate the progeny that sustain function of tissues.
- Essential to the maintenance of tissues such as:
- Blood
- Skin
Where are somatic stem cells located in the body?
- Teeth
- Blood vessels
- Bone marrow
- Liver
- Gut
- Skeletal muscle
- Skin
- Brain
Show epithelial self-renewal in the small intestine
Show Brain stem cells
Show the Stem cell hierarchy
Explain stem cell Quiescence
- Quiescence is a common feature of diverse tissue stem cells, including hematopoietic and neural stem cells.
- The satellite cell of striated muscle is probably the most illustrative example of a quiescent resident tissue stem cell, waiting to be called into action following injury.
- Quiescence is not a requisite feature of stem cells, as exemplified by the constantly dividing stem cells of the intestinal crypt and the squamous oesophageal epithelium
History: Cloning (Somatic cell nuclear transfer)
- 1928 Hans Spemann- Salamander
- 1952 Briggs and King – Leopard frog
- The Developmental Capacity of Nuclei taken from Intestinal Epithelium Cells of Feeding Tadpoles
- Gurdon 1962
Somatic cell nuclear transfer (SCNT)
Human SCNT
Nuclear transfer embryonic stem cells (NT-ESC)
Nuclear reprogramming to a pluripotent state by three approaches
Reprogramming using transcription factors: A timeline
Induced pluripotent stem cells
Yamanaka factors
Patient derived
Induced pluripotent stem cells
