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Bench to bedside and beyond > 18. Stem Cells and Tissue Regeneration > Flashcards

18. Stem Cells and Tissue Regeneration Flashcards

1
Q

What is a stem cell?

A

A cell that can self renew to make more stem cells and can differentiate to make new specialised cells.

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2
Q

What are the 2 types of stem cells?

A
  1. Embryonic stem cells that can generate all cells including adult stem cells.
  2. Adult or tissue resident stem cells that reside in tissues and mainly are for repair
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3
Q

Where are embryonic stem cells taken from?

A

The blastocyst usually from left over IVF embryos

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4
Q

When is the only time we have totipotent stem cells?

A
  1. in the first few days of development from the zygote.
  2. They can form all tissue needed in the embryo and related tissues like the placenta.
  3. once the 1st differentiation occurs the cells are then pluripotent.
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5
Q

What does totipotent mean?

A

the ability to form all lineages of organism.
In mammals this is only the zygote and the first cleavage blastomeres.

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6
Q

what does pluripotent mean?

A

The ability to form all lineages of the body.

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7
Q

what does multipotent mean?

A

The ability of adult stem cells to form multiple cells type of 1 lineage. For example haematopoietic stem cells

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8
Q

what does unipotent mean?

A

Stem cells that form only 1 cell type. For example spermatogonial stem cells. These are very committed.

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9
Q

Characteristics of embryonic stem cells

A
  1. Pluripotent
  2. They are responsible for developing the entire body
  3. They are sourced from unused IVF embryos as it is illegal in the UK to make an embryo just for stem cell use
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10
Q

Characteristics of adult stem cells

A
  1. Multipotent
  2. They replace cells in the body which die due to wear or disease. Replenish the tissues.
  3. Sourced from mature adult tissues but can be hard to identify due to lack of a specific phenotype.
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11
Q

Advantages of embryonic stem cells

A
  1. Strong ability to self renew in the lab so you have a constant supply from 1 sample.
  2. Pluripotency means they can produce any cell type in the body
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12
Q

Disadvantages of embryonic stem cells

A
  1. Different to the cells of potential patients = immune rejection.
  2. Ethical issue about obtaining and using them
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13
Q

Advantages of adult stem cells

A
  1. If taken from the patient’s own body there is no risk of rejection.
  2. Less ethical issues about obtaining and using them
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14
Q

Disadvantages of adult stem cells

A
  1. Only produce a limited number of cell types.
  2. condition for lab self renewal are tricky
  3. they are found only in small numbers
  4. They are hard to isolate.
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15
Q

Why are adult stem cells hard to find?

A
  1. They mingle with the progeny.
  2. They don’t have a distinctive phenotype or other markers
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16
Q

What are some examples of adult stem cells?

A
  1. haematopoietic stem cells that make all blood cells.
  2. bone marrow mesenchymal stem cells that make all bone tissue, adipose tissue and connective tissue
  3. Follicular stem cells that make hair follicles and epidermal cells
17
Q

What are induced pluripotent stem cells?

A
  1. A way of producing pluripotent stem cells from adult stem cells.
  2. Can be generated from our own cells.
  3. discovered in 2006.
  4. They are very powerful and have lots of research potential.
18
Q

How are induced pluripotent stem cells made?

A
  1. Activation of transcription factors present in the inner cell mass of the embryo causes dedifferentiation.
  2. Done by introducing these transcription factors to fibroblasts using viral vectors.
  3. C-MYC is one of these transcription factors
19
Q

How does a Stem cells “choose” its fate?

A
  1. Based on chemical or physical stimuli
  2. Can be from inside the cell or from the environment or other cells
20
Q

What are the 2 fates of stem cells?

A
  1. Cell division and change gene expression to proliferate
  2. differentiate and change gene expression to become a different cell type
21
Q

What makes stem cells so valuable?

A
  1. Cell therapy to repair tissues
  2. Research to develop new treatments and ideas.
  3. New drugs for stem cell disorders or cancers
22
Q

What are some of the differences between cells produced from stem cells?

A
  1. some differentiated cells can be derived easily in 1 step.
  2. Some cells are more committed undergoing multiple steps to get to the end cell.
  3. These stem cells are harder to work with and develop therapies for.
23
Q

Why are some tissues harder to treat with stem cells?

A

They don’t have tissue specific stem cells within them or are not surrounded by them. This means they have a limited ability to replenish.

24
Q

What is tissue engineering?

A

A multidisciplinary field that applies the principles of biology and engineering to develop tissue substitutes to restore, maintain or improve the function of diseased or damaged human tissues.

25
Q

What is the main goal of tissue engineering?

A

to develop methods to construct organs in the laboratory that can subsequently be used in medical applications.

26
Q

Why is tissue engineering necessary?

A
  1. Most tissues cannot regenerate when injured or diseased.
  2. Even tissues that can regenerate spontaneously like skin and bone may not completely do so in large defects.
  3. Replacement of tissues with permanent implants is greatly limited as donor tissues are in short supply. Tissue engineering could speed up this process.
  4. We want to minimise immune system response by using our own stem cells or novel ways to protect transplant and prevent rejection.
27
Q

What kind of tissues can currently be engineered?

A
  1. Simple tissues like skin or cartilage as these only have 1 cell type.
  2. Some blood vessels that are only 2 cell types.
  3. Multilcellular tissues get very complicated.
28
Q

How might tissue engineering work?

A
  1. tissues of 1 cell type
  2. prepare the cell
  3. plug the cells into a scaffold
  4. Feed cells
  5. They start to produce ECM
  6. This can then be implanted
29
Q

Tissue engineering vs regenerative medicine

A

Tissue engineering = regeneration in vitro. by seeding cells into a biomaterial matrix and then implant into the body.

Regenerative medicine = regeneration in vivo. Implant biomaterial matrix with or without cells to facilitate regeneration of the cells in the body.

30
Q

What is needed for tissue engineering?

A
  1. Cells
  2. A biomaterial scaffold
  3. Stimuli to promote growth of the cells like cytokines and growth factors
31
Q

What was the first clinical application of tissue engineering?

A
  1. A trachea was donated from an incompatible donor
  2. Needed to remove the DNA and make the cells compatible
  3. Created a new bronchus coated with the patient’s stem cells and a cell lining
  4. Had normal life for 5 years before developing suboptimal function.
  5. had to be supplemented with a stent.
32
Q

Why is some tissue engineering controversial?

A
  1. The main guy started to work with the Russians.
  2. This was not well regulated and used synthetic materials that shouldn’t be put in the body.
  3. This caused the death of patients for no scientific advancement.

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