Tissue engineering Flashcards
What is tissue engineering, TE?
An interdisciplinary field that applies the principles of engineering and life sciences toward the development of
biological substitutes that restore, maintain, or improve tissue function or a whole organ.
The cell:
Synthesizes matrices of new tissue
The scaffold:
Provides the appropriate environments for cells to be able to effectively accomplish their missions.
The growth factors:
Facilitates and promotes cells to regenerate new tissue.
Can replace structure or metabolism
Nanotechnology
Biotechnology
Medicine
Biomaterials
Develop external or internal devices containing human (animal) tissues for
replacement of the function of diseased internal tissues (artificial liver or pancreas)
Exogenous/endogenous TE
Exogenous:
Design and grow human tissue outside the body for later implantation to repair or replace diseased tissue
Endogenous:
Implant cell-containing or cell-free devices which induce/harness the bodies ability to generate functional human tissue
Principles of TE
Scaffold Tissue development (growth factor, mechanical stimulus) Implantation Biopsy Cell isolation Cell cultivation Cell proliferation
Why TE?
It’s innate: Supporting the body to take care of the problem
Pharmaceuticals and adverse effects
Organ transplant shortage
Technologies allow for more effective, and sustainable therapies
Replenish or Replace- tissue regeneration and whole organ
regeneration
Tissue classification:
Epithelial, muscle, nerve, connective
Epithelial tissue:
Cover the body’s surface and line the internal organs, body cavities, and passageways
Muscle tissues:
Are capable of contraction and form the body’s musculature
Nerve tissues:
Conduct electrical impulses and make up the nervous system
Connective tissues:
Composed of widely spaced cells and large amounts of intercellular matrix and which bind together various body
structures.
TE triad
Scaffold - conductive
Cells - productive
Signaling molecules - inductive
Purpose of a scaffold
Mimic the ECM:
- Cell anchorage
- Structural integrity to tissue
- Channel for signaling molecules
- Reservoir for growth factors
- Tissue remodeling and homeostasis
- Facilitate cell migration
Cell delivery veichle
Scaffold - ECM mimicry
Neotissue - Newly-formed tissue, especially TE around a scaffold
Three basic tools:
- Cell
- Scaffold
- Growth factor
Design factors:
- Polymer type
- Crosslinking density
- Stiffness
- Degradability
- Adhesive motifs
- Growth factors
Factors affecting degradation:
- Degradation activity by cells
- UV light
- pH
- Temperature
- Hydrolysis
- The material’s intrinsic degradability
Scaffold properties
- Clinical feasibility
- Biocompatible
- Biodegradable
- Surface properties
- Mechanical performance
- Porous
Need interconnected micropores => vascular formation and waste transport
Hydrogel
Hydrogel products constitute a group of polymeric materials, the hydrophilic
structure of which renders them capable of holding large amounts of water (more
than 90%) in their three-dimensional networks
- Tunable physical, chemical and biological properties
- High biocompatibility
- Versatility and feasibility in fabrication
- Similarity to native ECM
Bioink - material for 3D printing
Compromises between biocompatibility and printability.
Properties:
- Printability
- Viscoelasticity (Protect cells from shear stress)
- Hydration degree (nutrient diffusion)
- Biocompatibility (High cell viability)
- Viscosity (For uniform cell encapsulation)
- Gelation kinetics (Structural fidelity)
Scaffold free TE
Single cells, cell sheets, microtissues
Problems:
- High cell number
- Long culture time
- Necrosis middle layers
- Delamination of layers
- If single layer: thin sheet, low ECM deposition
Scaffold free TE
Single cells, cell sheets, microtissues
Problems:
- High cell number
- Long culture time
- Necrosis middle layers
- Delamination of layers
- If single layer: thin sheet, low ECM deposition
Stem cells
Undifferentiated cells that are capable of dividing into either new stem cells (proliferation) or specialized cells (differentiation).
Outcomes of differentiation/proliferation:
- Symmetric self-renewal (2 SCs)
- 2 differentiated cells
- Asymmetric self-renewal (1 SC, 1 diff. cell)
Types:
- Adult stem cells: found in many/all tissues.
- Embryonic stem cells (ESC): From blastocysts of fertilized egg (now established cell lines – no ability to form a whole organism)
- Mesenchymal (MSCs): from bone marrow, can differentiate into connective tissue.
- Induced pluripotent stem cells (IPSC): From specialized (adult) cells, pluripotency induced by genetic engineering or soluble factors.
Cellular potency (SCs)
Describes the ability of cells to divide by
mitosis, giving rise to further cell types.
Unipotency:
The ability to give rise to only one cell type.
Multipotency:
The ability to give rise to cells in the tissue from which the cell originated, i.e., adult stem cells.
Pluripotency:
The ability to give rise to all cells in the body, i.e., embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs)
Totipotency:
The ability to give rise to a new organism, i.e., a fertilized egg.
