week 2 teaching: extracellular matrix and biological scaffolds Flashcards
what is in the extracellular matrix
fibres (solid component) :
collagen
elastic
reticular
ground substance (fluid):
water (& solutes e.g ions)
carbohydrates
-proteoglycans
-Glycosaminoglycans (GAGs)
collagen & characteristics
family of fibrous proteins- 25 members
long, stiff, unbranched, triple helix
formation of collagen protein
alpha chain
three chains self-assemble combine into triple helix - procollagen
procollagen peptidase- self assembles into collagen fibril
combine to from collagen fibre
describe primary chain of collagen
alpha helical peptide chain
routine sequnece gly,x, hydroxyproline
every 3rd amino acid- glycine
produces kink in chain- alphahelical shape
what is procollagen
triple helix with loose ends
what occurs during procollagen peptidase
terminal proteins of procollagen are removed
how do collagen fibrils from collagen fibre
covalent bonds cross link between fibrils
struteral benefit of collagen forming fibres instead of firbrils
strength
elastin fibres & characteristics
750 amino acid protein
allows skin, blood vessels and lungs to stretch
elastin structure
secreted as elastin molecules, assembles into elastin fibres in extracellular space
forms cross-links with neighbouring elastin molecules
glycosaminoglycans
large, unbranched polysacharide chains
70-200 saccharide units
four groups of GAGs
chondroitin/ dermatan sulphate
keratan sulphate
heparin/ heperan sulphate
hyaluronic acid
because GAGs contain sulphate group
SO4 2- :
(except hyaluronic acid)
tend to be negatively charged due to sulphate groups (except hyaluronic acid)
due to their negative charge, GAGs:
interact with water, due to fixed negative charge, strongly hydrophilic
can create an electrochemical gradient, positive ions drawn in
influx of ions/ salts : osmotic gradient
fixed negative charge bound to extracellular matrix GAGs
means water is immobilised
why is it useful that GAGs bind water into tissues
useful to resist compression/ compressive forces
resist deformation in tissue
keeps tissue hydrated
how are GAGs commonly found
proteoglycans
multiple GAGs interacting with central protein
fibronectin
glycoprotein
dimer connected by disulphide bonds
adheres cells to ECM
what is a biological scaffold
structure made out of proteins (e.g collagen) used to support the growth of new tissue
how is a biological scaffold formed
decellurilastion - gently washed to remove cells
leaves only the ECF
overcomes immune system issues- rejecting grafts
how do biological scaffolds work
scaffold immediately replaces damaged tissue
repopulated with patient’s own cells to form new tissue
aims of biological scaffolds
aim to reduce burden of disease by repairing/ replacing natural tissues as they become damaged
