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Tissue Engineering (Scaffolds (Requirements (Easy and cheap to produce to…
Tissue Engineering
Scaffolds
Requirements
Bond to host tissue
without forming scar tissue
Resorption rate = repair rate
Provide signals to cells
Easy and cheap to
produce to ISO standard
sterilisation
Provide suitable
structural environment
for cell growth
e.g. 3D gel for chondrocytes
Similar mechanical properties to host tissue
Materials
Bioactive glass
Polymers
Hydrogels
Composites
Surface topography
Anisotropic materials
Morphology
Pore size
Mimic tissue architecture
Provide SA for cell attachment
Allows vascularisation
Controlled depending on cell
Connected pores aid diffusion
Bone morphogenic proteins
Growth factors promoting bone growth
Expensive
Can be used in scaffolds
No controlled delivery
Experimental Design
Expansion in vivo
Cell ratios
Seeding densities
Differentiation
Cell Source
Passage
Cells become adapted to culture
Decreased phenotypic expression
Reduction in efficacy of treatment
Cells grow until they
fill the available area
90% confluency reached
Liquid drained, enzyme cleaves
cell-cell and cell-matrix bonds
Centrifuge, aspirate
and resuspend
Divided into different flasks
1 generation
Careful monitoring as
cells age
Types of cells
Primary Cells
Derived directly from a media
Cell isolation
Obtain target tissue
Disaggregate tissue using
collagenase and trypsin
Culture individual cells
in correct environment
Antibody coated magnetic
beads can be used to tag cells
Cells migrate from tissue to dish
Slow-growing
Mature Cells
Not as proliferative as stem cells
More prone to loss of phenotype
Cell lines
Highly proliferative
Used to study disease states
Often derived from cancer cells
Stem cells
Types
Adult stem cells
Undifferentiated cells
in a specific tissue
Exist in most organs
Used for repair
Easy to isolate and handle
High phenotypic stability
Limited ethical consequences
Difficult to find
Pluri/monopotent
Induced pluripotent stem cells
Derived from a non-pluripotent cell
Forced expression of specific genes
Long term fate unknown
Embryonic stem cells
Essentially immortal cell line
Greater plasticity and
self-renewal than adult
Totipotent
Cannot be used
directly in cell therapy
Teratoma
Directed differentiation crucial
May not provoke immune response
Ethical questions
Long term effect
Sensitive to culture conditions
Feeder cells required
Not reproducable
Allogeneic
Potential source of all cell types
Potentially grown in culture
Prone to differentiation
Self-renewing
e.g. Chondrocytes
Difficult to obtain
Cadaveric tissue rarely used
Heals poorly
Animal tissue often used
Passage poorly
Require a rounded morphology
General
Strategy
Obtain stem cells
from patient
Cell Expansion
Attachment
to scaffold
Cell proliferation
Cell differentiation
Cells lay down ECM
(creating a biocomposite)
Transplantation
GOAL
Regeneration of tissue
to original state and function