Engineering tissues in 3D Flashcards
Why is tissue engineering necessary?
Prosthetic health over time declines dramatically
Peak performance at start, then goes off
Deteriorate graduallt by corrosion or rejection
What happens when a prosthetic fails?
Have to be removed
This is a very hard process
Enormous implicartions for health services
What is the performance of engineered tissue over time like?
Works mediocre at beginning
Grows with tissue
Functions well with time
What are the main components of engineered tissues?
Living cells
ECM support
Water
Where can the cells needed for engineered tissues be taken from?
Any tissue with undifferentiated cells
Stem cells
Cells from tissue on their way to differentiation
What is the composition of the ECM support?
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
What is the main component of engineered tissues?
Water
What percentage of engineered tissues is water?
60 - 80%
What are the two steps to making engineered tissues?
Cell acquisition
Expansion
How do we acquire cells?
Aspirate bone marrow/ muscle/ fat/ placenta for stem cells
Smash tendons and grow cell types - fractionate cells depending on type
What is the process of expansion of cells to make engineere tissues?
Layers of cells are cultured in robotic tissue machines
What is synthetic polylactate?
Scaffold or template made of synthetic material
Cells grow on this
Produces tissue as cells are cultured and maintained
What are two ways in which we can produce engineered tissues?
Grow them
Fabricate them
What is the process of growing engineered tissues?
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
What is the process of fabricating tissues?
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
What are the advantages of fabricating engineered tissues?
Not all one grows in big lump - requires lots of oxygen and nutrients
Smaller components are easier to perfuse and keep alive
What is an analogy for growing engineered tissues?
Cows - give them optimum conditions so they make milk for us
What is an analogy for fabricating engineered tissues?
Cell phone - all parts are fabricated separately and then assembled
Steps of growing skin
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
If engineering skin
Engineer components separately
Assemble them together
What are 2 uses for engineered tissues?
Clinical and therapeutic implants - replace damaged tissues
Drug testing
How can genetically engineered tissues be used in drug testing?
Make hundreds of genetically identical tissues
Place toxic agent on reproducible discs and test the effect of the drug
What can tissue engineering replace in the drug testing world?
Animal testing
What is cultivation of engineered tissues?
Once assembled all the cells and materials together
Need to place the engineered tissue in a bioreactor
How are the conditions of a bioreactor?
Nutrients for growth
Ideal temperature
Ideal pH
Tissue are perfused and gien GF
What does the bioreactor do to the engineered tissue?
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
Why is 3D printing of biological tissues difficult?
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
What technique can be used to replace 3D printing of tissues?
Collagen layer compression
What are the steps of collagen layer compression?
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
What are the advantages of collagen layer compression?
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
How does collagen layer compression allow us to customise tissues?
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
