lecture 9 - tissue engineering II Flashcards
What are bioreactors used for in tissue engineering?
Providing cues to ensure effective maturation of tissue in vitro (e.g. O2 concentration, fluid flow, forces)
Can be used for scaling up the number of cells we have, as well as generating the mature tissue when we have enough cells
Ensures transfer of nutrients/waste (or necrosis can occur)
What are the differences between tissues produced as a result of static culture, spinner-flask and rotating wall bioreactors?
Tissue produced from static culture shows a lot of necrosis in the middle, as there is not sufficient mass transfer of waste/oxygen
Spinner flask tissue shows necrosis around the edge where the cells have died and are not depositing the matrix
Rotating wall bioreactor - very little/no damage to the cells as these is very good mass transfer of chemicals/gases
How can bioreactors be used in bone defect repair?
Using a natural scaffold and bioreactor technology, a TMJ can be successfully replicated
Nice formation of a calcified deposit can be seen
There is better deposition the bioreactor culture than in the static culture
How can the body be used as a bioreactor and why is it advantageous?
Already contains the correct environment for tissue development - chemical signalling, mechanical forces, etc.
Calcium alginate hydrogel can be injected between the periosteum and tibia in rabbits to create an in vivo bioreactor
The alginate gel disappears until there is nothing left - after 7 days there is an increase in the pereosteal cells
Over time, this becomes more and more like natural bone tissue - the space becomes full of bone matrix
What are some advantages of acellular strategies over engineered tissues?
Can be designed to release cocktails of small and macromolecular drugs and to recruit specific cells
Less expensive
Ideal scenario would be to implant/inject a scaffold and then stimulate the cells in the body to repair that damage
How can tissue engineering be used in bronchial repair?
Patient with narrowing of the bronchus
They took a 7cm section of donor trachea and used DNAse to remove the cellular content from the trachea
They seeded it with epithelial cells from the right bronchus and MSC-derived chondrocytes from the patient
Put in a rotating bioreactor, helping the cells to grow and mature on the scaffold
Implant into patient
No donor antibodies/immunosuppressive drugs needed, because all of the donor antigens have been removed
How can tissue engineering be used in heart repair?
Valves - can use a decellularised valve from an animal and seed the valve with scaffold from the patient
Blood vessels have to withstand large pressures or they can burst
Cardiac muscle - after a heart attack - take elastic substrates, grow stem cells, differentiate them into contractile cardiomyocytes
seed the patient’s cells onto a decellularised heart and then stimulate them in the right way to generate a heart
What is the challenge of complexity with vascularisation and what is a solution?
- Problem: Cells need to be within ~200 µm of a blood vessel to survive in the body – tissue engineered constructs need capillaries which integrate with the patient
- Solutions:
- Seed scaffold with endothelial cells - randomly or using pre-formed channels
- Incorporate VEGF into scaffold
- Build scaffold around vascular bed ex vivo
How can bioprinting methods be used?
Attempts to address the 3D organisation of cells
Need some way of cross linking the bioink
Can photocrosslink - when they are deposited, shining a specific wavelength of light onto the bioink can trap the cells into a specific structure
Or, use a photocrosslinkable polymer - laser is focussed to print a layer of cells and trap them
What are some challenges of tissue engineering?
Cell density, resolution, vascularisation, innervation and mechanical integrity, stem cell differentiation, arrangement of multiple cell types into complex 3D patterns, regeneration
