Extracellular Matrix (ECM) Year 1 PDF

Extracellular matrix (ECM) Year 1 Dr Charlotte Illsley [email protected] PSQ C505 Learning objectives By the end of this session, you should be able to: Explore general features of extracellular matrices of dental/oral comp...

Extracellular matrix (ECM) Year 1 Dr Charlotte Illsley [email protected] PSQ C505 Learning objectives By the end of this session, you should be able to: Explore general features of extracellular matrices of dental/oral complex Recognise the 5 key specific ECM components found in oral tissues Relate ECM changes due to pathological change Establish a foundation of knowledge to be developed with later aspects normal and diseased tissues SIDE NOTE Could you outline the basic structure and function of proteins, carbohydrates, lipids and nucleic acids? If not, you might also find it useful to remind yourself of basic biochemistry: Basic sciences for Dental students (on the reading list!) This session is a very basic overview of the ECM. If you are struggling, go back to the ILOs. What is the ECM? Extracellular matrix (ECM) Non-cellular component present within all tissues and organs Network of macromolecules that occupy the extra-cellular space Proteins, proteoglycans (carbohydrate) & minerals Secreted by cells Forms large % of connective tissue Constituents & organisation vary between different tissues e.g. cartilage mostly ECM https://www.khanacademy.org/science/ap-biology/cell-structure-and- function/membrane-permeability/a/the-extracellular-matrix-and-cell-wall Why is the ECM important? Strength, support, protection Stores & presents growth factors Acts as a scaffold for tissue repair Important in cell adhesion & migration ECM acts as a signal which influences cell function e.g. growth & survival Establishes a tissue microenvironment Rozario & DiSimone (2010) Developmental Biology ; 341(1): 126-140 Examples of ECM Basement membrane (basal lamina) Epithelia, endothelia, muscle, fat, nerves Elastic tissues Skin, lung, large blood vessels Stromal or interstitial matrix Bone, tooth, and cartilage Tendon and ligament What synthesises and maintains the matrix? ECM in dental/oral complex  Extracellular Matrix Molecules 5 classes of macromolecules 1. Collagens 2. Elastic fibres (Elastin and Fibrillin) 3. Proteoglycans 4. Glycosaminoglycans e.g. Hyaluronan 5. Adhesive glycoproteins e.g. Poole, J.J.A.; Mostaço-Guidolin, L.B. Optical Microscopy and the Extracellular Matrix Structure: A laminin and fibronectin Review. Cells 2021, 10, 1760. https://doi.org/10.3390/cells10071760 Derya M, Yilmaz I, Aytekin M (2014) The Role of Extracellular Matrix in Lung Diseases. Biol Med 6:200. doi: 10.4172/0974-8369.1000200 Collagen Main structural protein of extracellular space type I - skin, tendon, bone type II - cartilage, vitreous humour type III - skin, muscle type IV - basal lamina (meshwork) types V-XII - less abundant  Elastic fibres Allows tissues to resume their shape after stretching e.g. artery, lung, skin, bladder Elastic fibres are crosslinked arrays of tropoelastin https://link.springer.com/chapter/10.1007/978-4-431-55139-3_8  Proteoglycans Protein backbone polysaccharide side chains Large branching aggregates retaining H2O Glycosaminoglycans (GAGs): Chondroitin sulphate - hyaline cartilage Heparin sulphate - basement membrane Keratin sulphate - cornea Hyaluronic acid – skin, polysaccharide only Proteoglycans Can be small or large e.g. decorin or aggrecan Bind to proteins e.g. decorin to collagen & can regulate their activities Cell surface proteoglycans e.g. syndecan Act as co-receptors Glycosaminoglycans (GAGs) Hyaluronan (Hyaluronic acid, Hyaluronate) Major component of proteoglycans Extremely long, negatively charged polysaccharide Resists compression Swollen gel creates turgor pressure Forms viscous, hydrated gels Large number of anionic residues on the surface bind water Hyaluronan keeps cells apart from one another Facilitates cell migration Surrounds migrating and proliferating cells Inhibits cell-cell adhesion Adhesive glycoproteins - Fibronectin Large dimer of 2 nearly identical proteins Soluble form in plasma Several regions which bind to other proteins Arg-gly-asp (RGD) mediates cellular binding (through integrins) Adhesive glycoproteins - Laminin Trimeric (cross) structure Binding sites for cells & other proteins Major component of basal lamina (one layer of basement membrane) Cell differentiation, adhesion & migration Mutation: junctional epidermolysis bullosa, nephrotic syndrome Basement membrane (BM) Specialised ECM Cell attachment Separates cells e.g. epithelium & connective tissue Cells on the BM can divide i.e. signal Filtration in the kidney  Interactions with the ECM Cells can interact with the ECM through specific membrane bound receptors (integrins) Specific dimer paring determines ligand binding Mediates cellular effects Bidirectional signalling molecules ECM- mineral ECM can be mineralised Calcium hydroxyapatite Bone (65%), dentine (70%), enamel (96%) Mechanical stiffness Modifications of ECM Cells can modify the ECM that surrounds them Proteolytic enzymes e.g. matrix metalloproteinses (MMPs) In cell migration this ‘creates a path’ Creates products which can have biological activity Releases/activates growth factors Altered expression in wound healing & disease e.g. cancer doi: 10.1083/jcb.201102147  MMPs “Old names” collagenases, gelatinases and stromelysin replaced by numbers (e.g. MMP-1) MMP-1 (collagenase-1) cuts triple helical collagens MMP-9, (Gelatinase-B) chops e.g. type IV collagen and laminins MT-MMPs are membrane-bound enzymes Regulate amount of ECM - degradation and remodelling Cell migration, wound healing, angiogenesis Activate other MMPs Release or activate growth factors and other bioactive molecules ECM - mechanics ECM can exist with different stiffness & elasticity Dependent on composition (collagen & elastin) Affects cell behaviour and gene expression Integrins can act as mechanosensors Stiffness changes in disease (fibrosis & cancer) ECM in ageing, wound healing and disease ECM in wound healing ECM & integrin’s in cancer Healthy skin ECM & integrin expression is changed in cancer Normal cell-cell & cell-ECM interactions are disrupted Integrin signalling influences cell growth, Squamous cell carcinoma anoikis & cell migration (& invasion) Targeting ECM and integrins in anti- cancer therapy & imaging Own work Fibronectin binding integrin expression (αvβ6) in oral cancer Tumour metastasis Growth Decrease cell-cell contact BM breakdown Stromal invasion Endothelial BM breakdown Attach & invade stroma Re-grow with angiogenesis MMPs in disease Extensive matrix degradation in disease e.g. in periodontitis, rheumatoid arthritis Tumour cell invasion and metastasis E.g. carcinoma breaks basement membrane and invades surrounding stroma MMP inhibitors tested for therapeutic use https://doi.org/10.3390/ijms21249739 Summary ECM complex mixture of extracellular proteins, proteoglycans and mineral Cell-matrix interactions important regulator of cell behaviour Structural role BUT cells also interact with it and thus it is a signal Composition depends on where you are in the body ECM different in healing and disease Summary Collagens: Triple helical rod and non-collagenous domains. Important structural role. Extensive post-translational modifications Fibronectin: adhesive glycoprotein in matrix and plasma Proteoglycans: GAG-chains attached to core protein. Laminins: major components of basement membranes Matrix metalloproteinases (MMPs): degrade and re-model matrix Integrins: heterodimeric proteins that mediate cell adhesion to extracellular matrix. Learning objectives By the end of this session, you should be able to: Explore general features of extracellular matrices of dental/oral complex Recognise the 5 key specific ECM components found in oral tissues Relate ECM changes due to pathological change Establish a foundation of knowledge to be developed with later aspects normal and diseased tissues Mini Research Task Choose one of the conditions/diseases.... Find Out: What is it? Dentinogenesis imperfecta Papillon-Lefèvre syndrome Symptoms/Condition? Scleroderma Ectodermal dysplasia What part of matrix is affected? Scurvy Ehler’s –Danlos syndrome Oral tissue involvement? Marfan Syndrome (Spend 10 or so minutes on this) Further reading Poole, J.J.A.; Mostaço-Guidolin, L.B. Optical Microscopy and the Extracellular Matrix Structure: A Review. Cells 2021, 10, 1760. https://doi.org/10.3390/cells10071760 https://www.khanacademy.org/science/biology/structure-of-a- cell/cytoskeleton-junctions-and-extracellular- structures/v/extracellular-matrix https://www.frontiersin.org/articles/10.3389/fonc.2018.00431/full https://journals.biologists.com/jcs/article/123/24/4195/31378/The- extracellular-matrix-at-a-glance