Tissue engineering and stem cells

Question 1

What is tissue engineering?

Answer 1

It uses the methods of biochemistry, cell biology, engineering and materials science to repair, improve or replace biological functions. Its goal is to produce bio-artificial organs and to regenerate injured tissue in the body.

Question 2

Cells for tissue engineering?

Answer 2

• Autologous cells are from the same individual, have fewest problems with rejection and pathogen transmission.
• Allogenic cells come from donor of same species.
• Xenogenic cells are from another species, e.g. cells from pigs have been used to develop cardiovascular implants (valves).
• Syngenic or isogenic cells are from genetically identical organisms.

Question 3

What are scaffolds?

Answer 3

Cells are seeded onto a scaffold (an artificial structure that can be support a 3D tissue. It must:

• Allow cells to attach and move.
• Deliver and retain cells and biological molecules.
• Be porous to allow diffusion of nutrients and waste products.
• Be biodegradable and be absorbed by the surrounding tissues, rate it degrades = rate of tissue formation.

Question 4

What are tissue cultures?

Answer 4

Cells that are grown in tissue culture form cell lines that are clones, as all the cells derived from a single parent cell are genetically identical. Cell lines are used to produce cloned tissue samples or to generate organs.
Production of cloned material = THERAPEUTIC cloning. With this type of cloning a patient is unlikely to reject as using their own cells to clone.
During tissue culture cells must be given oxygen, nutrients, growth factors and pH, humidity, temp, WP.
Special physical or chemical stimuli may be needed for the correct structures to differentiate.

Question 5

What are stem cells?

Answer 5

Stem cells are unspecialised cells and can develop into many different cell types. When a stem cell divides by mitosis, each daughter cell can either remain a stem cell or become another type of cell with a more specialised function, e.g. muscle fibre or RBC.

Question 6

What types of stem cells are there?

Answer 6

• Embryonic stem cell; found in 3-5 day old embryos.
• Some adult tissues; e,g, bone marrow, muscle, brain, can replace cells lost through wear and tear.
• Adult cells can be genetically reprogrammed to become induced pluripotent stem cells which behave as ESCs and can differentiate into any cells.

Question 7

Why do stem cells have huge potential?

Answer 7

• For tissue engineering to regenerate tissues and organs, e.g. bone using cells from bone marrow.
• For cell based therapies to treat disease; need for transplantable tissue and organs far outweighs the available supply.
• To screen new drugs; cancer cell lines have long been used to screen potential anti-tumour drugs.
• To develop model systems to study normal growth and identify the causes of birth defects.
• To investigate the events that occur during human development and how gene switches turn undifferentiated stem cells into differentiated.

Question 8

Advantages of using stem cells?

Answer 8

• Embryonic stem cells can become any cell type but adult stem cells are more limited.
• A blastocyst may contain about 100 ESCs so can be isolated in useful numbers.
• Embryonic stem cells grow easily in culture and large quantities can be readily produced.
• Use of stem cells will make the acute problem of a shortage of organs for transplantation less significant.
• Patient receiving tissue derived from ESCs is likely to need immunosupressive drugs, they may cause side effects, adult is less likely to.

Question 9

Disadvantages to stem cells?

Answer 9

• Techniques for extracting, culturing and manipulating stem cells are still under development and the behaviour of cell cultures is not always predictable.
• Use of stem cells is very new and so long term studies have not yet been possible.