Remodelling Flashcards
(66 cards)
1
Q
how can cells behave as communities?
A
- different cell types interact
- make larger structures tissues and then organs
- allows/enables organisms
- ECM allows tissues to form
2
Q
what is the ECM?
A
- extracellular matrix
- forms a home for cells
- fibres surround cells
- interact with ECM through integrins
- eg collagens, fibronectin, iaminium, proteoglycans
3
Q
what are tissues composed of?
A
- cells and often ECM
- epithelial doesnt have it
4
Q
what is the ECM composed of?
A
different proteins and proteoglycans
5
Q
what does the composition of ECM determine?
A
determines the physical properties from hard structures
6
Q
what is the role of the ECM?
A
- not just an inert scaffold, its dynamic
- helps to define the phenotype and behaviour of the cell
- acts as a storage compartment for signalling molecules
- regulates what signals are presented
7
Q
what are some features of collagen?
A
around 25% of the total mammalian proteins
- vitamin c is an essential cofactor for collagen synthesis
- around 30 different types
8
Q
what is the strutcure of collagen?
A
- composed of homo or heterodimers of alpha chains to form a triple helical based structure
- amino acid sequence consists of Gly-x-4
- divided into fibrillary or non-fibrillar
9
Q
what are fibrillar collagens?
A
organised into fibres and provide tensile strength
10
Q
what are non-fibrillar collagens?
A
collagens form networks and sheet like structurs
11
Q
how is collagen organised?
A
- amino acid chain
- alpha chain
- assembled into triple helices
- assembled into collagen fibrils
- finally into collagen fibres
12
Q
why does collagen need gly in the amino acid chain?
A
- ensures every third residue can twist to form the alpha helix
13
Q
what is the triple helix?
A
assembly end to end to make an elongated structure and join through covalent bonds
14
Q
how is collagen synthesised?
A
- initally in the cell but then outside
- ribosome = synthesis of alpha chains (has a pro-peptide domain that can be later cleaved off)
- vitamin C interacts and enables hydroxylation of selected prolines and lysines
- glycosylation events occur in the ER
- assemble into the triple helices aided by disulphide bonds
- packaged into a vesicle and secreted out of the cell
- pro-callgen contains the pro-peptide domain
- cleavage of pro-peptides through pro-collagen peptidases
- get collagen allowing assembly into a collagen fibril
- then aggregates into the fibre
15
Q
what is brittle bone disease?
A
- osteogenesis imperfecta
- mutations in alpha1 or alpha2 genes
- clearest symptom is bone fragility
16
Q
what is dermatosparaxis?
A
- proteolytic processing of procollagen is require for correct assembly into fibrils
- fragile and loose skin with substantial bruising and bleeding
- caused by mutation in the N terminal pro-peptides
17
Q
how do glycosaminoglycans and proteoglycans interact?
A
glycosaminoglycans (GAGs) are covalently attached to a core protein to form proteoglycans (except hylauronan)
18
Q
what do glycosaminoglycans and proteoglycans?
A
provide hydrated, space-filling functions and compressive strength
19
Q
what are GAGs?
A
- 4 classes
- formed by polymerisation of specific disaccharides and modification
- chrondroiton sulfate, hepara sulfate and keratan sulfate (attach to core proteins)
20
Q
what are hyaluronans?
A
can attach to the proteoglycan aggrecan or exists as its own disaccharide polymer
21
Q
what are some examples of proteoglycans?
A
aggrecan (CS KS), Decorin (CS DS), Perlecan, Syndecan
22
Q
what is the process of assembly of GAGs and proteoglycan?
A
- a core protein to which GAGs attach
- sequential addition of GAGs and linking sugars
- have repeating disaccharide repeats
GAGs –> Sugars –> Core protein
23
Q
how does hyaluronan bind?
A
- bind to the aggrecan
- does that through its N terminal hyraluronan binding domain and links proteins
24
Q
how are GAGs and proteoglycans involved into cell signalling?
A
- proteoglycans can regulate cell signalling events
- have a major role in signalling between various secreted signalling molecules
- can inhibit or enhance the signalling activity of growth factors
25
what is FGF signalling?
- fibroblast growth factor
- syndecan is a heparan sulfate proteoglycan (HSPG) that helps to control FGF signalling strneght - membrane bound
- Free FGF can bind heparin sulfate side chains
- syndecan can determine the concentration of FGF at the cell surface
- can have free heparin sulfate proteoglycans
26
what is the role of elastin?
- maintains the elasticity in the skin
- provides elasticity to help regulate tissue function
- allows stretching
- consists of covalently linked monomers
- when relaxed has a coiled sturcture
- found in the lungs and elastic ligaments
27
what is curtix laxa?
- mutations that effect how elastic is produced or organised
- rare inherited disorder
- skin inelastic and hangs loosely, hypermobility of the joints may also feature
28
what is fibronectin?
- large glycoprotein that helps matrix organisation
29
what is the role of fibronectin?
helps matrix organisation
| - has a specific binding domains that can link thing together
30
what is the structure of fibronectin?
- has a very specific binding domain
| - homodimer has binding motifs for proteoglycans, cells and collagen
31
how can you see cells grown on different fibronectin shapes?
- determines how cells adhere to structures by presenting one surface to ahere to
- a teardrop FN
- when the cell is on the FN it occupies the space available
- a lemellipodium forms
- produces structure for migration
- can grow on different shapes
- from this can determine how structures in the cell are organised
32
what is the basement membrane?
- specific ECM barrier
- separates the epidermis and the dermis
- above = has keratinocytes
- bellow = collagen network in underlying dermis
- a flat, sheet structure
33
what is the basement membrane composed of?
- entactin, perlecan, laminin, IV collagen
34
what is entactin?
multi-adhesive matrix protein
35
what is type IV collagen?
- non-fibrillar collagen
36
what is the structure of Type IV collagen?
- triple helical with a C terminal globular domain and N terminal domain
- assemble end to end and laterally
- globular heads come together to form alpha helices
- organise into the alpha helix
- collagen dimerisation through C-Nc trimers
- head to head interactions
37
what does the basement membrane act as?
a selective barrier for cell molecules
38
what are the properties of a stem cell?
to renew and differentiate
39
what is self-renew?
- asymmetric cell division
- one becomes a differentiated cell
- one becomes a stem cell
- maintains the stem cell pool
40
what is the telomerase activity like in stem cells?
- high levels in stem cell
- telomerase added back on the chromosome so its not shortening
- especially in pluripotent
41
what is totipotent?
- have the ability to develop into an entire organism
- very early days of embryogenesis
- fertilised egg up until around day 4 (when the blastocyst is formed)
42
what is pluripotent?
- have the ability to develop into virtually every cell type
- do norm form a placenta and supporting tissues
- ES cell of the inner cell mass (ICM) in the blastocyst are pluripotent
43
what does a teratoma assay determine?
the pluripotency
44
how does a teratoma assay work?
- inject into the back of mice
| - remove an look for a teratoma which should include all 3 germ layers
45
what are the 3 germ layers?
- endoderm
- mesoderm
- ectoderm
46
what transcription factors is pluripotency controlled by?
- Oct-4
- Nanog
- Sox2
47
what are the roles of Oct-4, Nanog and Sox2?
- act collectively to regulate ESC pluripotency
- can activate promoters of self-renewal genes
- silent promoters of developmental genes
- different genes can drive different specific lineage commitment pathways
48
what is the therapeutic potential of stem cells?
- generation of specific cell types and tissue structures to replace worm or disease body parts
- eg neurodegenerative, disease, diabetes corneal defects, cardiovascular disease, musculoskeletal disorders
49
what are the potential difficulties of stem cells as a therapy?
- understanding how specialisation takes place
| - directing differentiation to generate specific tissue types
50
how stem cells been used in experimental therapies for Parkinson's disease?
- directed differentiation of dopaminergic neurons
- NURR1, FGF8 and shh are all required in the normal brain
- look at markers to see if shh and FGF8 have the same markers as DA neurons (this doesnt tell you about functionality)
- then did an in vivo model in a mice model
- DA neurons killed
- test if functions are recovered by transplanted cells
51
how could ES cells be used to treat paralysis?
- differentiated into cells in the spinal cord
- rat recovered to some extent
- some ability to walk
52
what is SCNT?
- somatic cell nuclear transfer
| - fusion of a somatic cell nucleus with an egg emptied of its genetic material
53
how can SCNT be used in therapies?
- therapeutic cloning, generate a blastocyst where pluripotent cells are expanded in vitro
- used to create dolly the sheep
54
what are adult stem cells?
- they are multipotent
- many tissues in the adult can undergo repair and remodelling
- enabled by the presence of stem cells
55
what is multipotent?
differentiate into more than one cell type
- much more restricted
- generates cells of the tissue in which it resides
56
how can multipotent stem cells be used therapetuically?
- patients own cells can be used
- fewer ethical concerns as not using embryos
- fewer safety concerns as a teratoma wont be formed
57
what are heamatopeoitic stem cells used in?
- bone marrow transplants and blood transplants
| - the rate of these kind of transplants are generally increasing
58
what are mesenchymal stem cells?
- found in the bone marrow
- differentiate to bone, fat and cartilage
(make osteoblasts, chondrocytes, adipocytes and stromal cells)
59
where are mesenchymal stem cells targeted>
- at disorders that affect the muscoskeletal system
- can make bone and cartilage
- theoretically be used to regrow
- studies have been successful to some degree
60
how can cornea and limbal stem cells be used?
treat the epithelial structure on the outer surface
| - eg when theres a limbal cell deficiency or a chemically burnt eye
61
what is the limbus?
- round the outside of the cornea
- stem cell niche
- migrate to the epithelial layer which is essential for protecting the cornea
62
how would loss of corneal function be treated with stem cells?
- limbal harvest
- limbal stem cell culture (explant culture or suspension culture)
- culture limbal epithelium on a scaffold
63
what are iPS cells?
induced pluripotent stem cells
| - can express telomerase, ESC surface markers and differentiate into the 3 germ layers
64
how can iPS cells be used?
- introduction of genes associated with ESC pluripotency
- can reprogramme somatic cells to pluripotent stem cells
- introduction of just four factors appear to be sufficient
65
what are the issues with iPS cells?
- reprogramming somatic cells to iPS is inefficient
- use of viral delivery systems
- use of oncogenes (potentially cancer forming)
- epigenetic memory of parent cells
- teratoma risk
66
what are the potential of iPS cells?
- differentiate cells into whatever we need
- personalised medicine
- transplants
