Extracellular Matrices Flashcards
You are working in a lab to study different cells of the skin. You have isolated fibroblasts from healthy skin and wounded skin.
Why may you purchase collagen? (1) (1/5)
- Fibre-forming molecule (structure to ECM by creating a complex 3D framework of rigid proteins)
- Collagen = most prevalent fibre-forming protein (~77% of fat-free dry weight of human skin)
- Defines the rigidity & elasticity of a T
You are working in a lab to study different cells of the skin. You have isolated fibroblasts from healthy skin and wounded skin.
Why may you purchase hyaluronan? (1) (2/5)
- non fibre-forming molecule
- funct to create a charged, dynamic & osmotically active space
- fills majority of interstitial space
- -ive charge & h.philic nature enables proteoglycans & GAGs to funct in: .. within T
- hydration
- buffering
- force dispersion
- key roles in fibrotic & wound-healing
- ↑ XPS’ion of HA & HA-R (CD44) = associated w/ fibrotic diseases in many T
- human oral fibro & fetal scarless wounds = ass w/ ↑ XPS’ion of HA
- HA exerts FXs via CD44 & ‘receptor for HA-mediated motility’ (RHAMM) receptors
- evidence that this large pericellular molecule can trap TGF-b1, close to fibro
- = +ive FB autocrine loop that contributes to fibro → myofibroblast differentiation
You are working in a lab to study different cells of the skin. You have isolated fibroblasts from healthy skin and wounded skin.
What may you mix with hyaluronan? (1) (3/5)
- HMW HA (>500 kDa) ass w/
-↓ inflammation
-↑ XPS’ion of collagen-III
-↑activity of anti-fibrotic TGG-b3 - fragmented HA (<400 kDa) ass w/
-↑inflammation
-↑↑ XPS’ion of collagen-III
-↑fibro prolif
-↑myofibro differentiation - controversial bc hexameric fragmented HA (~1 kDa)
- improves fibro migration
- promotes wound closure
- decreases myofibro differentiation
- decreases fibrosis
- hexameric may be of interest in healing chronic wounds
You are working in a lab to study different cells of the skin. You have isolated fibroblasts from healthy skin and wounded skin.
Why may you purchase osteonectin? (1) (4/5)
- aka SPARC
- matricellular protein
- group of secreted local proteins that interact in autocrine/paracrine cell-matrix sig
- ≠ contribute to mechanical structure of ECM
- unlike most ECM components that = omnipresent ↷ normal skin & repopulate wounded skin after predicted intervals, matricellular prot can be absent in healthy skin
- XPS’d only after skin wounding
- wound healing
- fibro produce maj of ECM comp, wh/ act simultaneously to mod fibro funct
- interaction of fibro:ECM = thought as autocrine reg that = crucial to wound-healing
- fibro continuously create new ECM-P to heal cutaneous wounds, whilst being reg by prot of its own
- SPARC = found @ ~2d post wound infliction
You are working in a lab to study different cells of the skin. You have isolated fibroblasts from healthy skin and wounded skin.
What may you mix with ostenoectin? (1) (5/5)
- more osteonectin in wound healing fibro, rather than healthy
- fibro grown on collagen-I showed ↑XPS’ion of Alpha_vBeta_3 integrin (binds to vitronectin/FN) & ↑XPS’ion of Alpha_2Beta_1 integrin (binds fibros to collagen, req for migration)
- suggest that as an open would contracts & builds tension via tightening of collagen fibrils, myofibro transition away from collagen-mediated binding → non-collagen protein binding in wounds
- collagen may not be necessary
- in this case a non-collagen fibre-forming protein may be best to use, to still ensure mechanical stability i.e., VN/FN
What are the components of the ECM, and what are their functions?
Fibre-forming molecules (2) (1/3)
Collagen
Fibrin
Fibronectin
Vitronectin
Elastin
Fibrillin
- structural element
- tensile strength
- cell adhesion reg
- support chemotaxis & migration
- directs T development
What are the components of the ECM, and what are their functions?
Non fibre-forming molecules (2) (2/3)
Proteoglycans (HA, decorin, versican, dermatopontin)
GAGs
- hydration
- swelling pressure to the T enabling it to withstand compressional forces
- T homeostasis & struct
- modulators of sig pathways, reg cellular processes
What are the components of the ECM, and what are their functions?
Matricellular proteins (2) (3/3)
Glycoproteins
- laminins: basement membrane
- integrins: receptors
You are working in a lab to study different cells of the skin. You have isolated fibroblasts from healthy skin and wounded skin.
What other factors may be considered? (1) (6/7) (stiffness)
- mechanical prop of ECM have been shown to promote myofibro diff & lung fibrosis
- matrix stiffness-induced myofibro diff, mediated by intrinsic mechanotransduction
You are working in a lab to study different cells of the skin. You have isolated fibroblasts from healthy skin and wounded skin.
What other factors may be considered? (1) (7/7) (laminin used)
- L-a5 = observed to mod fibro prolif in fibrosis via disruption of the PI3K/Akt/mTOR sig pathway
- downreg of L-a5 = observed to prevent activation of the sig pathway
- PI3K = bridge b/w extra cellular sig & cellular responses
- activated PI3K may promote the transformation of Akt, accelerating phos of downstream mTOR (inhibits cell apoptosis)
Describe the seven different functions of the ECM.
Anchorage, migration barrier/track, signal reservoir (3) (1/2)
Anchorage
- anchorage to the BM = essential for the maintenance of stem cells & establishment of polarity in many T
Migration barrier and track
- context-dependent
- ECM may serve as barrier to or facilitator of cell migration
Signal reservoir
- ECM binding to sig molecules prevents free diffusion
- facilitates establishment of conc gradients
- serves to create reservoir from which they can be liberated during matrix remodelling
Describe the seven different functions of the ECM.
Low affinity co-receptor, signal presenter, biochemical force (3) (2/2)
Low-affinity co-receptor
- ECM comp (e.g., heparan sulfate proteoglycans; HSPG) & ECM receptors (CD44) can bind signalling molecules & serve as co-receptors
Signal presenter
- SAME AS ABOVE
- inv in establishing [growth factor/cytokine] grad → reg their spatial and temporal bioavailability
- fibroblast growth factor family strongly binds to heparan sulfate chains of proteoglycans i.e., perlecan
- HSPG inv in binding, transporting & activation of developmental control factors (Wnt/HH)
- also acts in ligand maturation
- TGF-b = secreted in a latent form & stored in ECM
- activated by MMP-dep proteolysis
Biochemical force
- stiffness exerts profound influence on cells & reg their differentiation
- diff cells/T req diff stiffnesses to grow optimally i.e., bone = one of strongest ECM, neuronal cells grow in elastic modules of 50-209 Pa.
What are the different characteristics in the ECM b/w normal issue & wound healing / fibrotic tissue (4) (1/1)
Normal tissue:
- ECM consists of a basement membrane, interstitial (stromal) ECM
- BM = collagen IV, laminin, fibronectin & several types of proteoglycans
- Role: physical barrier b/w epi cells & connective T (stroma) of the organ, allows gaseous diff & transportation of sig molecules
- normal ECM = highly remodelled after initial set-down = exhibits T-specific composition & organisation
Fibrotic tissue:
- Cancer: rupture of BM permits EMT & migration of epi cells into surrounding stroma → invasion of interstitial ECM
- Epi cells undergoing EMT can activate stromal cells to become pro-tumorigenic, permitting remodelling of the ECM to make a tumour-permissive enviro
- ↑lvls of HA documented in cancer progression & = ass w/ poor prognosis & chemo-resistance
- HA induces EMT by binding CD44 & activating EMT TCF (TWIST-1)
- ↑[HA] has been shown to compromise vascular integrity - imp for metastasis (intravasation & extravasation)
- also shown to be involved in inflam resp that mediate ECM remodelling
- Dermoplasia: linear ECM fibres = observed to provide migratory tracks → cancer cells use to enhance migratory capability
Cell ECM interactions in both norm & fibrotic T are mediated by integrins
Integrins:
- reg CS organisation
- activate intracellular sig path to convey mechanical & chemical signalling
Why are fibroblasts important during wound healing? (5) (1/1)
- pivotal role in reg ECM turnover under norm cond. ∴ in injured T they can be activated = elicit differentiation into myofibroblasts
- they proliferate & chemotax to site of T injury
- Myofibro function during wound healing by ↓size of wound & secreting ECM proteins that elicit appropriate immune resp
- in normal tissue:
- Fibro = stress-shielded by ECM & ≠ develop contractile feat or cell-matrix adhesions
- in injured tissue:
- inflam signals activate fibro to spread into provisional wound matrix → differentiation: TGF-β1 stim proto-myofibroblasts to XPS α-SMA & become differentiated
- myofibros exit cycle when ECM = reconstituted & is able to compensate for the mechanical load (apoptosis when epithelialization completed)
- fibro regulate their collagen & ECM protein syn in resp to mechanical tension:
- ↑mech stress stretches fibros, ↑ing collagen production & ↓ing collagenese production
How is PDGF, IL6, IL13 & eicosanoid leukotrine signalling important in wound healing in fibroblasts? (6) (1/1)
- Cytokines that promote inflammation & development of fibrotic resp.
PDGF
- produced platelets, endothelial cells, smooth muscle cells & macrophages
- acts on mesenchyme & fibroblasts → prolif, differentiation, & ECM production
- imp in wound healing, inflamm, angio, embryonic, fibrosis
IL13
- produced by mast & T-cells
- acts on many cells, inc fibro
- stim TGFβ prod & activation, collagen prod, MMP XPS’ion, fibro proliferation & myofibro differentiation
- TGFβ & other cytokines reg most common molecular mech (EMT) @ the heart of fibrosis
Eicosanoids
- induce fibroblast prolif & ECM production
