lecture 8 - tissue engineering

Question 1

What are the basic concepts of tissue engineering?

Answer 1

Replacing diseased or damaged living tissue designed and constructed for the needs of each individual
The cells are differentiated and seeded onto a scaffold, allowing the tissue to mature as a result of specific cues
The final step is to implant the tissue into the patient

Question 2

What are autologous and allogenic cells?

Answer 2

Allogenic cells are from a donor (e.g. iPS cells), whereas autologous cells come from the patient (e.g. MSCs)

Question 3

How can cell isolation and expansion be carried out?

Answer 3

Since stem cells are quite rare, we need to enrich the population for the therapeutic cell we want to use
some techniques include:
differential adhesion - some cells will stick to surfaces more effectively than others, so cells that are loosely bound can be washed off
FACS (fluorescence-activated cell sorting - enrich cell based on specific antigens on the surface of the cells
MACS - magnetic-activated cell sorting
scaling up the cells is one of the main issues with tissue engineering

Question 4

What are the ideal characteristics of a scaffold?

Answer 4

Biocompatible, biodegradable, cut-compatible, porous, mechanically appropriate, architecturally appropriate and growth promoting
the ideal scaffold will degrade at the same rate as the tissue produced on it

Question 5

What are some of the types of scaffold material that can be used?

Answer 5

Polypeptides (e.g. collagen, gelatin, fibronectin)
Synthetic polymers (e.g. bioactive glass, decellularised tissues and calcium phosphates)

Question 6

What are the advantages of synthetic scaffolds?

Answer 6

Can design them to have the characteristics you want - degradation, strength, chemical functionality and biological signals
they have a higher reproducibility and are able to be bulk processed, which is not the case for animal-derived materials

Question 7

What are some of the methods of scaffold formation?

Answer 7

Compression, solvent casting, particle leaching, freeze drying, spinning, electrospinning and 3D printing

Question 8

How can formation of hydrogels be driven?

Answer 8

Ionic - can be cross linked ionically, UV - generate free radicals that crosslink the chains
enzymatic - to covalently link groups together

Question 9

What are the differences in morphology between a collagen-coated glass (2D) and a collagen gel (3D)?

Answer 9

2D:
- no soluble gradient
- high stiffness
- forced apical-basal polarity
- continuous layer of matrix
- adhesions restricted to x-y plane
- continuous layer of matrix

3D:
- soluble gradients present
- low stiffness
- no prescribed polarity
- discrete matrix fibrils
- adhesions distributed in all three dimensions
- spreading and migration statically hindered

Question 10

How can aligned fibres be generated?

Answer 10

The scaffold can be rotated - it can be electrospun and collected on a rotating collector
the faster it rotates, the more aligned the fibres are along the axis of rotation - this helps guide the formation of cells
can get better engineered muscle with the aligned fibres than the random ones

Question 11

What are some scaffold modifications that can be carried out?

Answer 11

NaOH or primary amines
subsequent reaction with coupling reagents can be used to attach bioactive motifs (or whole proteins)
Incubating with diamine – will interact with the esters and create amines on the surface – these can be used as chemical handles for further reactions
- In particular, can modify with peptides or proteins that will increase the adhesion of cells