Engineering tissues in 3D

Question 1

Why is tissue engineering necessary?

Answer 1

Prosthetic health over time declines dramatically

Peak performance at start, then goes off

Deteriorate graduallt by corrosion or rejection

Question 2

What happens when a prosthetic fails?

Answer 2

Have to be removed

This is a very hard process

Enormous implicartions for health services

Question 3

What is the performance of engineered tissue over time like?

Answer 3

Works mediocre at beginning

Grows with tissue

Functions well with time

Question 4

What are the main components of engineered tissues?

Answer 4

Living cells

ECM support

Water

Question 5

Where can the cells needed for engineered tissues be taken from?

Answer 5

Any tissue with undifferentiated cells

Stem cells

Cells from tissue on their way to differentiation

Question 6

What is the composition of the ECM support?

Answer 6

Mostly made of collagen I since it has to be designed to be in our bodies

Removable if needed

A lot of work is centered around using artificial temporary scaffolds to grow cells

Question 7

What is the main component of engineered tissues?

Answer 7

Water

Question 8

What percentage of engineered tissues is water?

Answer 8

60 - 80%

Question 9

What are the two steps to making engineered tissues?

Answer 9

Cell acquisition

Expansion

Question 10

How do we acquire cells?

Answer 10

Aspirate bone marrow/ muscle/ fat/ placenta for stem cells

Smash tendons and grow cell types - fractionate cells depending on type

Question 11

What is the process of expansion of cells to make engineere tissues?

Answer 11

Layers of cells are cultured in robotic tissue machines

Question 12

What is synthetic polylactate?

Answer 12

Scaffold or template made of synthetic material

Cells grow on this

Produces tissue as cells are cultured and maintained

Question 13

What are two ways in which we can produce engineered tissues?

Answer 13

Grow them

Fabricate them

Question 14

What is the process of growing engineered tissues?

Answer 14

Indirect engineering

Give cells optimum conditions

Best cues and controls needed

Encourage a living thing to make something for us

Cells make the whole tissue - are in control

Question 15

What is the process of fabricating tissues?

Answer 15

Direct engineering

Make the separate cells and ECM in different cultures

Make the components and assemble them to increase complexity

Tissues have more than one cell type

Cell-independent process

Question 16

What are the advantages of fabricating engineered tissues?

Answer 16

Not all one grows in big lump - requires lots of oxygen and nutrients

Smaller components are easier to perfuse and keep alive

Question 17

What is an analogy for growing engineered tissues?

Answer 17

Cows - give them optimum conditions so they make milk for us

Question 18

What is an analogy for fabricating engineered tissues?

Answer 18

Cell phone - all parts are fabricated separately and then assembled

Question 19

Steps of growing skin

Answer 19

Put all the cell types and ECM together

Incubate the lump of skin

Expect the cells to grow together

Different layers contain different cell types

Question 20

If engineering skin

Answer 20

Engineer components separately

Assemble them together

Question 21

What are 2 uses for engineered tissues?

Answer 21

Clinical and therapeutic implants - replace damaged tissues

Drug testing

Question 22

How can genetically engineered tissues be used in drug testing?

Answer 22

Make hundreds of genetically identical tissues

Place toxic agent on reproducible discs and test the effect of the drug

Question 23

What can tissue engineering replace in the drug testing world?

Answer 23

Animal testing

Question 24

What is cultivation of engineered tissues?

Answer 24

Once assembled all the cells and materials together

Need to place the engineered tissue in a bioreactor

Question 25

How are the conditions of a bioreactor?

Answer 25

Nutrients for growth

Ideal temperature

Ideal pH

Tissue are perfused and gien GF

Question 26

What does the bioreactor do to the engineered tissue?

Answer 26

Mechanical cues are given to the tissue via pulsating tube

Maintained for a long period of time

Cells grow gradually and produce ECM to assemble and enlarge tissue

Question 27

Why is 3D printing of biological tissues difficult?

Answer 27

Have to slow the process down to not damage the cells

Can’t use the techniques used to print plastic - high temperature and dry conditions kills the cells

Matrix is jelly-like so it is difficult to stack on the z-plane

Question 28

What technique can be used to replace 3D printing of tissues?

Answer 28

Collagen layer compression

Question 29

What are the steps of collagen layer compression?

Answer 29

Create gel of native collagen I protein

Gel is very highly hydrated - 99.6% water

Cells are trapped in the collagen - sparsely distributed

Compress the gel - get dense layer of cells and collagen = one x-y plane

Stack the layers to increase the complexity and form tissues

x-y planes build up to form the z-plane

Question 30

What are the advantages of collagen layer compression?

Answer 30

Looks like biological tissue - cutomise complex tissues

Cells survive - no loss in cell viability

Can control cell and matrix density

Can control the positon of cells in the collagen layers

Question 31

How does collagen layer compression allow us to customise tissues?

Answer 31

Can change the position of the x-y plane layers

Can make skins resembling the target tissues you want

Don’t have to settle with whatever grows