Lecture 3 - tissue engineering Flashcards
Define tissue engineering.
Tissue engineering is the in vitro development of tissues or organs to replace or support the function of defective or injured body parts.
Describe the three types of cellular communication.
The first one is soluble signal, it is comprised of small proteins (15-20KDa) which are chemically stable with long half lives. They bind to membrane receptors usually with high affinity.
The second one is cell to cell contact. Some of the membrane are adhesive molecules such as adherent junctions and desmosomes. The other membranes serve to create gap junctions of 1.5-2nm which allow transport
The third one is the cell and ECM interactions. The ECM provide a substrate that allow communication to the cells. Examples of the receptors that allow cell-ECM communication are integrin and CD44.
What is a scaffold role?
It is a substrate material that must be inserted to aid in organisation of the cells in three dimensions.
What are the types of biomaterial scaffold materials and provide examples.
Polymeric (Chitosan, alginate)
Natural (Fibrin, collagen, elastin)
Ceramic (Calcium phosphate)
What is the purpose of scaffold?
They provide temporary structural support to maintain the shape. They can be have surface coating which enhances the cellular microenvironment by providing a large surface area, ECM secretion, better integrin expression and it facilitate cell migration.
State the properties that would make the ideal scaffold.
- 3-dimensional
- Porous
- cross-linked
- Biodegradable
- Proper surface chemistry
- Matching mechanical strength (5-23 KPa)
- Biocompatible
- Promote self healing
- Accessibility
- Commercial feasability
Define mechanotransduction.
It is the conversion of a mechanical stimulus into a biochemical synthesis.
State the three types of cell culture.
- monolayer (adherent cells)
- suspension (non adherent cells)
- three dimensional (Scaffold or template)
What are the requirement for culturing cells?
Culture media should have the right chemical environment (pH, osmolarity, ionic strength, buffering agents) and the right nutritional environment (nutrients, amino acids, vitamins, minerals, growth factors). It should have the right growth conditions to stimulate physiological environment (pH 7.4, 5% CO2, 37 C, 95% relative humidity. Should also have sterilisation method such as UV light, 70% ethanol, steam autoclave, gamma radiation, ethylene oxide gas.
State the different cell sources for tissue engineering.
The cells used should be autologous to prevent any immunological complications. The three classes of cells are primary cells, passage cells and stem cells. The primary cells are differentiated cell acquired form the patient. But these primary cells have a low cellular yield and can have age related problems. The passaged cells are serial expansion of primary cells but they have a tendency to lose potency. Last are stem cells, these are undifferentiated cells, they have a self renewal capability. They can be differentiated into functional cell types. However they can be very rare
Give the lineage of stem cells and how they differ.
The two lineages of stem cell are mesenchymal and hematopoietic. The mesenchymal cell gives rise to connective tissues such as bones and cartilage. The hematopoietic stem cells give rise to blood cells and lymphocytes. These are both normally isolated from the bone marrow. The ratio of mesenchymal cell to myeloid cell is 1 to 1000 000 and ratio of hematopoietic to myeloid is 1 to 100 000.
Define graft.
A skin graft is a tissue of epidermis and varying amount of dermis that is detached from its own blood supply and placed in a new area with new blood supply.
Define flap.
It is defined as any tissue that has been used for reconstruction or wound closure that retains all of it original blood supply after it has been moved to the recipient location.
State the classification of grafts.
- Autografts - tissue transferred from one part of the body to another
- Homografts - tissue transferred from one individual to another of the same species
- Xenografts - tissue transferred from one individual to another individual of a different species.
State the types of grafts.
types of grafts depends on the thickness or depths.
- Split thickness consists of 100% epidermis and a portion of the dermis
- Full thickness consists of 100% epidermis and dermis.
