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Regenerative Medicine > Lecture 8 - Tissue Engineering 1 > Flashcards

Lecture 8 - Tissue Engineering 1 Flashcards

1
Q

What is the primary goal of tissue engineering?

A

Replacing diseased or damaged living tissue with living tissue designed and constructed for the needs of each individual.

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2
Q

What are the key steps in the tissue engineering process?

A
  1. Cell isolation and enrichment/purification
  2. Expansion of cell number
  3. Seeding on a suitable scaffold
  4. Maturation of the tissue
  5. Implantation in patient.

  1. Allows proliferation and differentiation.
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3
Q

What are the two primary sources of cells used in tissue engineering?

A
  • Allogeneic (need HLA match)
  • Autologous

  • Autologous, e.g. MSCs, iPSCs, satellite cells, differentiated cells
  • Allogenic, e.g. ES cells, iPS cells, MSCs, differentiated cells.
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4
Q

What techniques are used for cell isolation in tissue engineering?

A
  • Differential adhesion
  • Density centrifugation = size
  • FACS (fluorescence-activated cell sorting) = size, granularity, surface markers)
  • MACS (magnetic-activated cell sorting) = surfacce markers
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5
Q

What are the ideal properties of scaffolds in tissue engineering?

Acts as 3D support for cell growth.

A
  • Biocompatible (HLA)
  • Biodegradable
  • Cytocompatible (adhesive)
  • Porous (growth factors entry, waste removed)
  • Mechanically appropriate (maintain structural viability)
  • Architecturally appropriate (e.g. alignment of cells - muscle fibres contract in same direction)
  • Growth promoting (controlled drug/GF release)
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6
Q

What types of materials are commonly used for scaffolds in tissue engineering?

A
  • Polypeptides
  • Polysaccharides
  • Synthetic polymers.

Polypeptides - collagen, gelatin, fibronectin, fibrin, laminin, silk bibroin
Polysaccharides - hyaluronic acid, alginate, chitosan
Synthetic polymers - poly(caprolactone), poly(lactic acid), PLGA

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7
Q

Fill in the blank: The polymer __________ allows control over degradation, strength, and biological signals.

A

Poly(lactic-co-glycolic acid) - PGLA

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8
Q

What are some methods of scaffold formation in tissue engineering?

A
  • Compression
  • Solvent casting
  • Particle leaching
  • Freeze drying
  • Spinning
  • Electrospinning
  • 3D printing.
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9
Q

What is the significance of scaffold morphology in tissue engineering?

A

It affects tissue homeostasis, formation, and regeneration.

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10
Q

True or False: The expansion of cell number is not necessary before seeding on scaffolds.

A

False.

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11
Q

What are some examples of synthetic polymers used in tissue engineering?

A
  • Poly(caprolactone)
  • Poly(lactic acid)
  • Poly(glycolic acid).
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12
Q

What are the challenges faced in tissue engineering?

A
  • Complexity
  • Vascularization.
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13
Q

What is the purpose of bioreactors in tissue engineering?

A

To provide a controlled environment for cell growth and tissue maturation.

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14
Q

Fill in the blank: Purified cell populations need to be __________ before seeding on scaffolds.

A

expanded

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15
Q

What is the role of growth factors in cell culture conditions?

A

They affect growth and function, and may help preserve ‘stemness’.

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16
Q

What type of cells can be classified as allogeneic?

A
  • ES cells
  • iPS cells
  • MSCs
  • Differentiated cells.
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17
Q

What are hybrid scaffolds?

A

Scaffolds generated from multiple types of materials.

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18
Q

What is the importance of controlling the degradation rate of scaffolds?

A

It affects the timing of tissue integration and regeneration.

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19
Q

What does ‘cytocompatible’ mean in the context of scaffold properties?

A

It means the scaffold supports cell attachment and growth without causing harm.

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20
Q

Fill in the blank: The process of __________ involves using various methods to create scaffolds with specific properties.

A

scaffold formation

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21
Q

What is the significance of receiving signals in three dimensions for cells?

A

Important for correct function of the tissue or organ.

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22
Q

What is a limitation of hydrogels in tissue engineering?

A

While hydrogels provide 3D signalling, they may not be mechanically appropriate.

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23
Q

Name one method used in scaffold morphology for tissue engineering.

A

Electrospinning.

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24
Q

What types of structures can be generated in scaffold morphology?

A
  • Random
  • Aligned
25
What type of cells were used in the study from abdominal muscle biopsies?
Human skeletal muscle cells.
26
What is the role of myoblasts in tissue engineering?
Myoblasts fuse together to generate myotubes.
27
What factor influences the striation of myotubes?
Elasticity of growth substrate.
28
How can mechanical properties of a growth surface influence stem cells?
They can promote self-renewal or influence lineage.
29
What elasticities have been reported to support self-renewal of stem cells?
* 10 kPa * 25 kPa
30
What type of differentiation is assisted by optimal elasticity?
Cardiac differentiation.
31
True or False: Soft gels promote neuronal differentiation.
True.
32
What factors can affect stem cell fate?
* Stiffness * Topography * Patterning
33
What are some types of scaffold topography mentioned?
* Hexagonal * Square * Disordered square * Random ## Footnote Disordered square showed highest efficacy differentiating into osteoblasts.
34
What is a common issue with many biocompatible and biodegradable materials?
They are not particularly cell adhesive or growth promoting.
35
What can scaffolds require to guide cell function and fate?
Certain motifs.
36
How can polyesters be modified in tissue engineering?
Using NaOH or primary amines. ## Footnote Subsequent reaction with coupling reagents can be used to attach bioactive motifs.
37
What is RGD and its significance in tissue engineering?
RGD (Arg-Gly-Asp) is a motif for cell adhesion.
38
What is the function of polydopamine in scaffold modification?
It can increase adhesion. ## Footnote Increase adhesion in muscle foot proteins (Mfps) in mussels due to high amounts of polydopamine.
39
Name one method of incorporating bioactive molecules in scaffolds.
* Adsorption * Direct ligation * Surface entrapment * Ionic interactions * Mineralization
40
What is a unique characteristic of some synthetic polymers in tissue engineering?
They may have bioactive motifs built in.
41
What is the role of hydroxyapatite in tissue engineering?
It can be used for mineralization.
42
How does culture conditions impact stemness?
Culture conditions affect growth and function (e.g. GF cocktails)
43
How does phenotype impact cell isolation and expansion?
Phenotype important (e.g. ES and iPS cells) and may require further purification (e.g. reduce risk of teratoma formation)
44
How are cells usually grown in vitro?
Usually on flasks and seeded onto scaffolds, but this may not be appropiate for clinical application and wide-spread adoption of tissue engineering.
45
Why are typical flasks may not suitable for tissue engineering?
* Low surface area:volume ratio * Does not replicate 3D environment
46
Alternative cell flasks for cell expansion
* Stalked flask * Fluidised bed * Stirred tank * Hollow fibre
47
What are the properties of synthetic polymers?
Control over degradation, stength, chemical functionality, biological signals Reproducibility Bulk processing Interesting properties, e.g. temperature responsiveness These synthetic polymers can be 'tailored' and designed for optimal properties
48
Properties of PGLA?
* Degradation via bulk hydrolysis - occurs throughout whole material * Breakdown products are lactic and glycolid acid which can be metabolised * Molecular weight can be modified - higher Mw = longer longer degradation * Osteinductivity - promote bone regneration ## Footnote Can be brittle and have slow degradation.
49
What inorganic materials can be used for scaffolds?
Bioceramics and bioactive glasses: * Hydroxyaptite * Bioactive glass * Alumina * TiO2 * Calcium phosphates ## Footnote Decellularised tissues can be used - organic content removed (mostly inorganic)
50
What types of scaffolds shapes are there?
* Porous scaffolds - sponge-like to mimic structural of natural tissues * Fibrous scaffolds - provides matrix for cell attachment and growth * Microsphere/microparticle scaffolds - often used for controlled drug delivery or gene therapy ## Footnote Hybrid scaffolds can also be generated.
51
What mechanisms can drive formation of hydrogels? ## Footnote Depending on the polymer.
* Thermal * Ionic, e.g. sodium alginate * UV * Enzymaatic * Covalent
52
What aspects influence scaffold morphology?
* Pore size and porosity * Interconnectedness - transport of fluids * Surface morphology - roughness and topography * 3D structure - cell attachment, proliferation and differentiation * Hierarchical structures - replicates multi-scale organisation of natural tissues
53
Advantages of 3D (collagen gel) scaffold morphology over 2D (collagen-coated glass)
2D: * Soluble gradients absent * Forced apical-basal polarity * Continuous layer of matrix * Unconstrained spreading and migration * Adhesion restricted to x-y plane * High stiffness 3D: * Soluble gradients present * No prescribed polarity * Discrete matrix fibrils * Spreading and migration sterically hindered * Adhesions distributed in all three dimensions * Low stiffness
54
Why is scaffold stiffness important?
Significantly influences cell behaviour, including differentiation, migration and proliferation. ## Footnote Can mimic ECM, machanosensation.
55
Why are myotubes ideal surfaces for myotube growth?
Myotubes exhibit optimal growth and differentiation on surfaces that mimic the in vivo environment, for cell alignment, stiffness and adhesion.
56
What is scaffold modification with polydopamine (PDA) deposition?
Technique used to enhance the bioactivity and performance of scaffolds. Easily deposited on various materials (biocampatible) that can enhance hydrophilicity.
57
58
Scaffold modification methods
* Covalent coupling of laminin using EDC/NHS chemistry into nanofibre mat * Physical absorption of laminin onto nanofibre mat * Electrospun blended laminin-polymer nanofibre mat

Regenerative Medicine (12 decks)

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