Questions cluster 1, 2

Question 1

From which embryonic structure are embryonic stem cells (ESCs) derived, and are they totipotent or pluripotent? Motivate your answer.

Answer 1

Inner cell mass
Pluripotent
ESC can form all structures in the embryo but not extra-embryonic tissues.

Question 2

which endothelial progenitor cell type is thought to become a structural part of newly formed blood vessels?

a) Colony-forming units (CFU) -Hill cells
b) Circulating angiogenic cells (CAC)
c) Endothelial colony-forming cells (ECFC)
d) All of the above

Answer 2

c) Endothelial colony-forming cells (ECFC)

Question 3

What is the difference between angiogenesis and vasculogenesis?

Answer 3

Angiogenesis: formation of new blood vessels (capillaries) from pre-existing vessels

Vasculogenesis: formation of new blood vessels de novo (without pre-existing vessels)

Question 4

How can you prove stemness of adult hematopoietic stem cells?

Answer 4

Serial transplantation of bone marrow cells into irradiated mice, and showing that they are capable of forming all blood cell lineages.

Question 5

Epithelial organoid cultures have been derived from many tissues of murine and human origin. Name three of these tissues.

Answer 5

Possible answers: (o)esophagus, colon & rectum, liver, pancreas, salivary gland, skin (epidermis), small intestine, stomach, taste buds, fallopian tube, mammary gland, prostate, lung

Question 6

Which is the first cell type involved in foreign body response?

a) M1 macrophages
b) M2 macrophages
c) Neutrophils
d) Complement system

Answer 6

c) Neutrophils

Question 7

What is an unfavorable side effect of decellularization on tissue?

Answer 7

An unfavorable side effect of decellularization is the loss of important biological/bioactive/structural/functional components that reside in the ECM.

Question 8

What is the main difference between physically and chemically crosslinking methods for hydrogels?

Answer 8

Physical crosslinking: physical bonds are formed (hydrogen bonds, hydrophobic interactions)

Chemical crosslinking: covalent bonds are formed.

Question 9

What is a supramolecular polymer? Give the definition.

Answer 9

A supramolecular polymer is a polymeric array of monomeric units that are brought together by reversible and highly directional non-covalent interactions, resulting in polymeric properties in dilute and concentrated solution as well as in the bulk.

Question 10

Name 3 types of bioink.

Answer 10

Gelatin, collagen, alginate, matrigel, hyaluronic acid, decellularized ECM, PEG

Question 11

Which of the following statements on additive manufacturing technologies is correct?

a) Stereolithographic printing requires the use of shear thinning bioinks
b) The first patented 3D printing technology was fused deposition modelling
c) In fused deposition modelling, a metal filament is melted through a hot end end extruded to build 3D objects
d) Stereolithography prints objects at a slower speed than digital light projection, but provides higher resolution

Answer 11

d) Stereolithography prints objects at a slower speed than digital light projection, but provides higher resolution

Question 12

Why is healing of cartilage defects so ineffective? Name two reasons.

Answer 12

No direct delivery of nutrients through blood vessels

Few active cells present to produce matrix

Compact matrix which does not allow quick cell migration

Question 13

What is the main function of the allogeneic MSCs that are combined with autologous chondrons in the IMPACT trial to treat cartilage defects?

a) they differentiate into chondrocytes and produce cartilage tissue
b) they stimulate the autologous cells to produce new cartilage tissue
c) they modulate the inflammatory response
d) they transdifferentiate into adipocytes to provide lubrication

Answer 13

b) they stimulate the autologous cells to produce new cartilage tissue

Question 14

Name two components that maybe present in extracellular matrix. Briefly describe their roles in the mechanical properties of tissue.

Answer 14

• Glycosaminoglycans, proteoglycans (e.g., hyaluronan, chondroitin sulfate, dermatan sulfate, heparin sulfate, keratin sulfate): ground substance for ECM, ‘space filler’, resist compressive loading
• Structural/fibrous proteins (e.g., collagen, elastic fibers/elastin, fibrin): strengthen, organize ECM, maintain ECM integrity, high stiffness
• Glycoproteins (e.g., fibronectin, laminin): facilitate cell attachment/adhesion, organize ECM by facilitating adhesion between various ECM components.

Question 15

What does it mean when a material is anisotropic?

Answer 15

A material is anisotropic when the material properties depend on a direction. This means that if we extract a tissue sample from a piece of material and subject it to a uni-axial stress test, the result depends on the original orientation of the sample in the material. Biological materials are often anisotropic because they contain a large number of highly oriented fibres.

Question 16

What is the difference between stress and strain?

Answer 16

Stress measures the deforming force on an object, while strain is the change in shape triggered by the deforming force. Stress is internally generated but caused by external pressure, while strain is usually generated by the amount of force or stress applied. Strain cannot occur without stress, but stress can occur without strain.

Question 17

Would the thickness of cartilage change, and if so, would it become thinner or thicker, if the collagen network would be damaged? Consider the cartilage in unloaded equilibrium conditions, and assume that the total collagen content and the total proteoglycan content have not changed. Explain your answer in a few words.

Answer 17

Cartilage becomes thicker at the damaged location.

Concentrations are the same, so osmotic pressure remains the same. The collagen network is damaged, and therefore it is less stiff: it has less resistance against swelling. Thus, it will swell, given that the the internal osmotic pressure has increased.

Question 18

The trophectoderm of a blastocyst:

a) Forms the mesoderm
b) Forms the non-maternal part of the placenta
c) Forms the epiblast
d) Forms the neural crest cells

Answer 18

b) Forms the non-maternal part of the placenta

Question 19

During gastrulation:

a) Somites become further differentiated
b) Homeotic transformations take place along the body axis
c) The germ cells are allocated
d) The definitive germ layers are formed

Answer 19

d) The definitive germ layers are formed

Question 20

Hox genes are important for:

a) Postional information in a developing embryo
b) Formation of limbs in an embryo
c) Formation of germ cells during embryogenesis
d) Start of gastrulation

Answer 20

a) Postional information in a developing embryo

Question 21

Name 3 components of extracelllular matrix that you would find in connective tissue.

Answer 21

Collagen, elastin, microfibrillar protein, proteoglycans, hyaluronan, fibronectin, laminin

Question 22

Order the following materials according to their ultimate tensile strength, starting with the material possessing the lowest tensile strength (measured in MPa):
Skin, Hydroxyapatite, Arterial wall, Cortical bone

Answer 22

Arterial wall < Skin < Cortical bone < Hydroxyapatite

Question 23

What are focal adhesions? And what is their function in cell–matrix interaction?

Answer 23

Focal adhesions are clusters of integrins in the cell membrane that are bound to the extracellular matrix on the outside and to intracellular/cytoskeletal structures on the inside. Focal adhesions help the cell to feel/sense their microenvironment and relay external forces to internal signals.

Question 24

Which one of the following statements is true?

a. In a uniaxial stress test the material does not experience shear stresses because the test only uses principal strains
b. In a uniaxial stress test the material does not experience shear stresses because the stress is only applied in one direction, the pulling direction
c. In a uniaxial stress test on an isotropic material the maximum shear strain is found under an angle of +30o with respect to the pulling direction.
d. In a uniaxial stress test on an isotropic material the maximum shear strain is found under an angle of +45o with respect to the pulling direction.
e. Only when an anisotropic material is subjected to a uniaxial stress test we find shear stresses in the material.

Answer 24

d. In a uniaxial stress test on an isotropic material the maximum shear strain is found under an angle of +45o with respect to the pulling direction.

Question 25

Name 3 types of bioink.

Answer 25

Gelatin, collagen, alginate, matrigel, hyaluronic acid, decellularized ECM, PEG