Tissue Engineering Epithelium Flashcards
What is epithelial tissue?
consists of a flat sheet of closely adhering cells, one or more cells thick, with the upper surface usually exposed to the environment or to an internal space in the body
What is the structure of epithelium?
1) squamous epithelium
2) connective tissue
3) muscle tissue
4) inflammatory cells
What are the key characteristics of epithelium tissue structure?
- Tightly packed epithelial cells. • Strong intracellular junctions. • Can be single layer (simple), or multi layered (stratified).
- Does not contain blood supply • Relies on nutrients from underlying connective tissues
What are the cell types in the simple epithelium?
1) simple squamous
2) simple cuboidal
3) simple columnar
(All epithelial cells form tight cell-cell junctions (eg. Tight junctions, desmosomes)
What are the cell types found in the stratified epithelium?
!) stratifies squamous
2) stratified cuboidal
3) stratified columnar (very rare)
4) pseudostratified columnar
What is a basement membrane?
made of collagen, laminin and fibronectin
What are the functions of the epithelia?
protection, absorption, filtration, excretion, secretion
Why does the structure of the different epithelia vary as a result of their distinct functions?
as a result of their distinct functions and anatomical locations
What are the common characteristics of epithelia?
1) specialised contacts: adjacent cells bound together by cell-cell junctions • Very little extracellular material-comprised of tightly packed cells
2) Polarity – Basal and Apical
3) Basement membrane
4) Regenerative capacity
5) Epithelial/mesenchymal co-dependency
What is the need for tissue engineering epithelia?
- Congenital defects • Surgical resections • Stricture and fibrosis • Cancer excision • Trauma
- Toxicity testing • In vitro disease models • Epithelial biology • Diagnostic development
What are the stages of epithelisation?
• Cell migration • Cell adhesion • Cell proliferation • Cell differentiation
How are epithelial cells grown?
• Normal oral keratinocytes • Isolated from small biopsy • Grown with support cells • Limited proliferation capacity
How are stromal cells grown?
• Human oral fibroblasts • Variable • Different to skin • Needed for keratinocyte attachment
What is the epithelial-mesenchyme inter dependency?
• Keratinocyte limit fibroblast proliferation • Fibroblasts drive epithelial differentiation • Keratinocytes rely on fibroblasts for attachment
What are the different scaffold selection?
- Natural vs synthetic • Mechanical properties • Porosity • Wettability • Degradation
- Fabrication • Surface topography • Growth factors • Storage • Surgical handling
What are the different environments for the cells?
1) bioreactors
2) air-liquid interface
3) animal models
Why is hollow tube tissue engineering important?
Many epithelia line hollow tubes • Inner lumen posses epithelium Eg. Oesophagus, Trachea, Gastrointestinal tract, Bladder, etc
Why produce tissue engineering oral mucosa?
1) disease models
2) reduce use of animals
3) diagnostic technology development
4) biocompatibility testing
5) intra-oral recontruction
How do tissue engineered and in vivo models compare?
IN VIVO MODEL
- limited models of oral disease
- strict controls over in vivo experiments
- genetically different to human disease
TISSUE ENGINEERING MODEL
- tissue engineering models have been developed for a number of oral diseases
- strict control in obtaining primary cells, but once isolated can be expanded and used for many experiments
- grown using human cells or oral origin
What is the method for tissue engineering oral mucosa?
1) waste tissue form oral surgery
2) normal oral fibroblasts + normal oral keratinocytes
3) grown on de-cellularised skin scaffold
4) cultured at air-liquid interface
5) tissue engineered oral mucosa
What is the scaffold choice?
- Acellular dermis • Retains native ECM
- Retains basement membrane proteins
- Can be stored in glycerol
- Collagen gels lack basement membrane
- High level of contraction
- Collagen lacks organisation
What are the pros and cons of acellular dermis as a scaffold choice?
pros: biologically relevant
cons: disease transmission
limited quantities
variability
What are the pros and cons of collagen as a scaffold choice?
pros: good cell attachment
cons: batch to batch variability
animal origin
expensive
What are the pros and cons of fibrin as a scaffold choice?
pros: good cell attachment
cons: variability
animal origin
What are the pros and cons of synthetic polymeric scaffold as a scaffold choice?
pros: adjustable properties
scale up
no disease risk
cons: cell adhesion can be an issue
What are the pros and cons of autologous cells as a cell choice?
pros: non-immunogenic for in vivo applications
conc: expensive variability
What are the pros and cons of cell lines (eg TR146, OKF6) as a cell choice?
pros: reproducible
cons: not suitable for in vivo applications
cancer derives or immortalised
What are the pros and cons of mesenchymal stem cells (MSC) as a cell choice?
pros: shown to improve wound healing around dental implants
cons: cannot form epithelial cells
What are the pros and cons of induced pluripotent stem cells (iPSCs) as a cell choice?
pros: patient derived cells
cons: still very new
What is the clinical need for bladder tissue engineering>
- Congenital abnormalities (eg spinal bifida)
- Cancer
- Neurogenic bladder disease (spinal cord injury)
What is the current treatment for bladder?
- Replacement with bowel segments
* Transplants are not done (require catheterisation)
What are the tissues of bladder tissue engineering?
- Infection
- Compliance
- Fibrosis
- Malignancy
- Bowel obstruction
- Perforation
- Metabolic function
- Mucus production
- Bladder stones
What should a tissue engineered bladder provide?
- a complete regeneration of bladder wall, (i.e., urothelial, muscular and adventitial layers
- rapid tissue reconstitution to prevent early urine leakage or bladder rupture
- safe, long-term evolution (particularly in the context of oncological risks)
What does Tony’s Atala’s tissue engineered bladder consist of?
320 x106 urothelial cells
320 x106 smooth muscle cells
Bladder shaped PLGA:PLA copolymer
What materials have been looked at for bladder tissue engineering?
• Polymers (eg PLGA and PLA) • Silk • Decellularised tissues • Animal derived proteins
What cell spurces have been considered for bladder tissue engineering?
• Urothelial cells • Smooth muscle cells • Autologous cells hard from patients with bladder disease. • MSCs • iPSCs
What is the problem with bladder tissue engineering?
main cause is cancer, therefore autonomous cell cannot be used
What are the challenged faces with bladder tissue engineering?
- Vascularisation
- Urine toxicity
- Cancer relapse
- Fibrosis
- Innervation
Where are we currently with bladder tissue engineering?
Clinical trials: • No studies in humans with oncological bladder disease
• Small pilot studies conducted for neurogenic bladder disorders.
• 2 studies showed limited improvements to leak pressure and bladder capacity
• Disappointing urodynamic results.
• Serious adverse effects have been reported in at least 2 of 5 human studies (bladder rupture, bowel obstruction)
How is gastric cancer often treated?
requires full gastrectomy to remove all cancerous tissue
What are the complications associated with full gastrectomy?
• Malnutrition, • Weight loss, • Reflux esophagitis, • Anaemia Reduced food intake and loss of endocrine function
What is SIS?
small intestine submucosa eg Surgisis
- decelluarised porcine sub mucosa
What is SIS?
small intestine submucosa eg Surgisis
- decelluarised porcine sub mucosa
What are the cell choices for stomach tissue engineering?
- Gastric glands are heterogeneous
- Rapidly differentiate in culture
- Oncological risk
- Limited autologous material
- Exocrine (gastric acid) and endocrine functions (gastrin, somatostatin)
page 58 - 63 need to be noted
• Tissue engineered stomachs tested in vivo (mice) • No serious adverse effects but clinical outcomes not improved vs gastrectomy. • No improvement in weight gain or total protein and cholesterol. • May improve vitamin B12 levels
What was achieved through stomach tissue engineering?
- Columnar epithelium
- Vascularized tissue (by growing in omentum for 3 weeks)
- Extracellular matrix
- Smooth muscle–like cells
- Good anastomosis to oesophagus and intestine
- Secretions
What were the fall backs of stomach tissue engineering?
- No submucosal layer was evident
- No parasympathetic innervation
- Impaired peristalsis
- Time consuming
- Only suitable for autologous implantatio
