Stem Cells & Tissue Engineering

Question 1

When was the first stem cell therapy created and what was it?

Answer 1

1968 - bone marrow transplant

Question 2

What 2 conditions must a cell fulfill to be classed as a stem cell?

Answer 2

Be capable of self-renewal

Give rise to multiple types of cells

Question 3

What are stem cells classified on?

Answer 3

Differentiation potential (potency)
Source

Question 4

What are unipotent stem cells?

Answer 4

Cells that can only give rise to a single type of cell, make up the majority of the bodys cell types

Question 5

What are multipotent stem cells?

Answer 5

Can give rise to multiple types of cells, are unable to generate all cell types of the 3 germ layers

Question 6

What are pluripotent stem cells?

Answer 6

Can generate all cell types of the 3 germ layers (endoderm, mesoderm, ectoderm)

Question 7

What are totipotent stem cells?

Answer 7

Only type of cell capable of producing and supporting the development of a whole organism (fertilised ovum)
4 germ layers (endoder, mesoderm, ectoderm and trophectoderm)

Question 8

What type of stem cell is derived from adult tissue?

Answer 8

Multipotent - can be extracted from neural tissue, bone marrow, adipose tissue and blood etc.

Question 9

Name the 2 different types of adult stem cells

Answer 9

Hematopoietic stem cells - present in bone marrow, produce blood cells and immune cells
Mesenchymal stem cells - found in multiple locations

Question 10

Where are embryonic stem cells derived from?

Answer 10

Inner mass of a developing embryo (blastocyst)

Question 11

What are induced pluripotent stem cells?

Answer 11

Artificially created stem cells

Question 12

How are iPS made?

Answer 12

Unipotent cell from adult id taken, genes associated with the regulation of pluripotency are activated

Question 13

What are the genes associated with pluripotency?

Answer 13

Oct3/4
Sox2
Klf4
C-MyC

Question 14

How was the first iPS cell discovered?

Answer 14

Yamanaka’s team in Kyoto uni selected 24 genes shown to be important to ES cells, virally transfected inot adult mouse fibroblast, deleted genes 1 by 1 and identified 4 essential genes

Question 15

Name 3 applications of stem cells

Answer 15

Bone marrow transplant
Potential therapies in development e.g. neuronal disorders, heart diseases etc.
Tissue engineering

Question 16

What is tissue engineering?

Answer 16

An field that applies the principles of engineering and life sciences toward the development of biological substitutes that restore, maintain or improve tissue function/whole organs

Question 17

What are the 4 basic principles of tissue engineering?

Answer 17

1. Reproduce whole organs or parts of the body for therapeutic use
2. Address the problem of organ donation
3. Remove the problem of organ rejection
4. Produce bespoke organs that are biologically compatible with patient

Question 18

What are the main steps of tissue engineering?

Answer 18

Biopsy
Cell isolation
Cell cultivation
Cell proliferation
Add scaffold
Tissue development (growth factor & mechanical stimulus)
Implantation

Question 19

What 3 factors do most tissue engineering strategies employ?

Answer 19

1. Biological source - the cells
2. Supportive medium - replace extracellular matrix, the scaffold
3. Environmental growth support - the bioreactor

Question 20

Describe the steps of tissue engineering

Answer 20

1. Extract cells from a tissue source e.g. bone
2. Cells seeded onto an appropriate scaffold
3. Grow implant in a bioreactor
4. Reimplantation

Question 21

What are the 4 sources of cells?

Answer 21

Autologous - obtained from the patient who will be reimplanted
Allogenic - from a donor
Xenogenic - from a separate species
Syngenic/isogenic - not currently acheivable

Question 22

What are some advantages of autologous cells?

Answer 22

No risk of immune rejection
Biological activity perfectly matches activity of host
Lower risk of passing on pathogens/disorders

Question 23

What is a disadvantage of using autologous cells?

Answer 23

Number of cells is low due to senescence and loss of function

Question 24

What is senescence?

Answer 24

Cells only divide a certain number of times before stopping, if senescence isn’t functioning cancer occurs

Question 25

What is contact inhibitions?

Answer 25

Cells can inhabit neighbouring growth if no room left, requires cells to be split apart which can cause damage

Question 26

What are some advantages of using allogenic cells?

Answer 26

Greater number of cells | Off the shelf - cryopreservation for use when needed

Question 27

What are some disadvantages of using allogenic cells?

Answer 27

Rejection by host immune system - fibroblasts have been used in skin engineering without rejection Risk of pathogen/disorders being passed to host

Question 28

What are some advantages of using xenogenic cells?

Answer 28

Greater number of cells - potentially limitless - using multiple donor organisms Off the shelf - cryopreservation for use when needed

Question 29

What are some disadvantages of using xenogenic cells?

Answer 29

Rejection by host immune system Risk of pathogen/disorders being passed to host Biocompatibility issues

Question 30

What is the role of the scaffold in tissue engineering?

Answer 30

Provides a supportive structure designed to allow the desired biological mechanisms to occur

Question 31

Name some materials used for scaffold production?

Answer 31

Biological source - extracted ECM or purified matric protein or polysaccharide materials Polymer - wide variety used Metals

Question 32

What are some advantages of using a scaffold?

Answer 32

Doesn't elicit an immune response Many different ways of manufacturing them Bioreabsorption is highly desired - material implanted is degraded over a defined period of time

Question 33

Why is the environmental growth support needed?

Answer 33

Cells and biological constructs cultured in vitro require environmental support e.g. bioreactor

Question 34

What is a bioreactor?

Answer 34

Device designed to support a specific biological processes, cheaper if not used and less chance of harmful things being introduced

Question 35

What is autologous chondrocyte implantation (ACI)?

Answer 35

Type of tissue engineering used to treat cartilage damage (injury not disease)

Question 36

What are some problems associated with tissue engineering?

Answer 36

Replicating complexity Issues of scale Sources of cells - which is best for which organ? Scaffold technology - approaches & materials Economic costs - very expensive