COD Matrix biology Flashcards
Describe the ECM
Highly specialised
Composed of fibrillar and non-fibrillar molecules
Reciprocally influences cellular function
Modulates normal tissue homeostasis and progression of disease
Give an example of some molecules found in the ECM
Collagens Structural proteins Proteoglycans Glycosaminoglycans Glycoproteins Proteinases
Describe collagens
Most abundant and widespread distribution in tissues
28 different collagen types
Construct fibers, networks and filaments in the ECM
Formed from polypeptide alpha chains
These create homo or hetero trimeric triple helices
Typical collagenous domains within alpha chains consist of repeat triplets of amino acids Gly-X-Y
Fibrillar is the most common
FACIT and MACIT
Anchoring and Beaded fillaments are self assembled forming
What are MACIT and FACIT collagens?
MACIT - membrane associated collagens with interrupted triple helices
FACIT - Fibril associated collagens with interrupted triple helices
What are some subclasses of collagen types?
Fibrillar Network forming FACIT MACIT Anchoring filaments Beaded filaments Multiplexin
What are heterotypic fibrils
A mixture of different collagen types
Dermis, tendon and bone - Type I,III,V
Cartilage and Vitreous - Type II,IX,XI
What is Elastin used for?
Structural protein
Lends elasticity and resilience to tissues
What are laminins used for?
Structural protein
Cell-cell assembly
What are fibronectins used for?
Structural protein
A receptor that binds to other ECM molecules
What are the 4 types of glycosaminoglycans?
Carbohydrate attached to a protein core Chondroitin sulphate Dermatan sulphate Heparan sulphate Keratan sulphate
Describe the glycosaminoglycan Hyaluronan
Synthesised and assembled on the plasma membrane
Non-Sulphated
Not attached to a protein core
Found in joint synovial fluids to facilitate joint movement
Describe the glycosaminoglycan Heparin
Prevents clotting
Synthesised and stored in mast cells
Used as an anticoagulant in medicine
Describe glycoproteins
Non structural
Modulate cell function
By interacting with cell surface receptors, hormones, proteases, structural matrix proteins (collagens)
What are some enzyme components of the ECM?
eg heparanases
Matrix Metalloproteinases (MMP) ADAM and ADAMTS proteinases Serine proteases Cathepsins HA-degrading enzymes (Hyaluronidases) Heparanases
Tissues requiring high tensile strength are enriched in what?
Fibrillar collagens eg tendons, bone, ligaments
Tissues requiring compressive properties are enriched in what?
Proteoglycans and hyaluronan eg cartilage
Tissues requiring elastic properties and recoil are enriched in what?
Elastin, eg skin, ligaments, connective tissue of lungs/blood vessels
Matrix stored chemical signals include what?
Growth factors
Cytokines
Where is the mutation in Ehlers-Danlos Syndrome?
Collagen
MMP gene that play key roles in regulating
collagen organization
Describe Ehlers-Danlos Syndrome
Elastic skin
Hyper flexible joints
Valvular heart disease
Invertebral disc disease IVD is a disorder of aging. What impact does this have and what is it attributed to?
Impacts mobility Decreased workplace productivity Attributed to loss of glycosaminoglycans through the loss of aggrecan Decreased hydration Reduced compressibility Increased risk of disc herniation
What are the changes in cell behaviour in IVD disease?
Hypoxia (O2)
Inflammation
Autophagy (Self eating)
Describe fibrosis
Damaging
Can occur as a result of excess formation of
connective tissue in response to injury
Due to a combination of factors such as a disproportionate activity of
matrix enzymes responsible for matrix degradation and reorganization
Hyperactive ligand-mediated receptor signaling via TGF-ß
Activity of mesenchymal cells
Name some common diseases that exhibit fibrosis
Pulmonary fibrosis
Hepatic fibrosis
Renal scarring
Describe osteoarthritis
Bone ends rub together
Thinned cartilage
Describe rheumatoid arthritis
Bone erosion
Swollen inflamed synovial membrane
What is the structure of the knee joint?
Synovial membrane Articular cartilage Fibrous joint capsule Joint cavity filled with synovial fluid Ligaments
Describe the bio mechanical function of articular cartilage
Composite of collagens, proteoglycans and water
Allows tissue to withstand load
Provides a near frictionless surface for joint articulation
Tension, compression, shear, lubrication
What is the morphology of articular cartilage?
No lymphatics Avascular Aneural Hypocellular No basement membrane
Articular cartilage is highly hydrated with water accounting for WHAT% of its wet weight
65 - 85%
What are chondrocytes?
Resident cells
Produce collagen, proteogylcans and enzymes
What are type II collagens?
Major collagen
Provides a cartilaginous framework and tensile strenght
What proteoglycans?
eg aggrecan
Major proteoglycan
Gives cartilage compressive stiffness
What is the chondrocyte morphology?
eg what are the zones
Superficial zone
Middle (intermediate) zone
Deep zone
Calcified zone
Describe the zones of chondrocytes
eg superficial, intermediate, deep, calcified
Superficial - 600um. Cells flat, collagen Fibrils parallel to articular surface
Intermediate - 1500um. Cells round, collagen fibrils diagonal to articular surface
Deep - Cells round, collagen fibrils perpendicular to articular surfaces
Calcified - 300um, cells round, collagen fibrils perpendicular to articular surface
What are aggrecan aggregates composed of?
30-50 aggrecan monomers 1 Hyaluronan Glycosaminoglycan 30 - 50 Link proteins that stabilise the aggrecan interactions All of these interactions are non-covalent
Describe the glycosaminoglycans charge
Negative charges
Create strong charge repulsive forces
Charge repulsion stiffens proteoglycans in the collagen network
And give cartilage compressive stiffness
Load bearing properties of cartilage are provided by the tensile properties of WHAT?
Of the collagen fiber network and
The osmotic swelling pressure of the high concentration of aggrecan
Aggrecan is immobolised within the matrix by forming WHAT aggrecates with hyaluronan and link protein?
Supramolecular
What 2 phases are there in the biomechanical behaviour of cartilage?
Fluid and solid phase
Describe the fluid phase in the biomechanical behaviour of cartilage
Is under high interstitial fluid pressurisation
Allows for the transmission of load in cartilage
Describe the solid phase in the biomechanical behaviour of cartilage
Low permeability
This is because the proteoglycans PGs resist fluid flow
They are also restricted by the collagen fibril network
WHAT are the major proteinases responsible for matrix turnover in cartilage?
Metalloproteinases
Is cartilage turnover relatively slow or fast in adults?
Slow
MMP (Metalloproteinases) and ADAMTS (A Disintegrin And Metalloproteinase with ThromboSpondin motif) are enzymes that require what for their activity?
Zinc OR
Calcium
(metal ions)
True or false
Matrix proteinases are proteolytic enzymes
True
Collagenases (MMPs) and gelatinases (MMPs) degrade WHAT
The collagen fibers
Aggrecanases (ADAMTS4 and ADAMTS5) degrade WHAT
Aggrecan
Stromelysins (MMP3 and MMP10) degrade WHAT
Non- collagenous matrix proteins
Collagenases (MMP-1 & MMP-13) - degrade WHAT
Gelatinases (MMP-2 & MMP-9) - degrade WHAT
Stromelysins (MMP-3 & MMP-10)-degrade WHAT
triple helical collagens
denatured collagens
non-collagenous matrix proteins (not aggrecan)
What are the 2 classifications of OA?
Primary
Secondary
Describe primary OA
Idiopathic (no known cause)
Describe secondary OA
Post traumatic Metabolic Endocrine disorders Congenital (present at birth) Malposition
What are some risk factors associated with OA?
Age Sex Hereditary Ethnicity Overweight Lifestyle Post menopausal Resective joint surgery
What are symptoms of OA?
Limited movement
Pain
Crepitation (crackling/rattling sound)
Sensitivity to damp or cold
How do you diagnose OA?
X-ray
What is the main hallmark of OA?
Matrix degradation of the articular cartilage
Results in loss of tissue function
In OA, chondrocyte metabolism is altered. Explain how
Mechanical forces (through mechano and osmo sensors embedded in the chrondrocyte plasma membrane)
Inflammatory mediators (cytokines, chemokines, reactive oxygen species, nitric oxide)
Increased synthesis and activation of aggrecanases and MMP through NF kappa signalling pathway
Increased degradation of aggrecan and collagen
What is catabolism?
Hallmark of OA
Loss of cartilage
Aggrecanase activity is defined by the
specific cleavage between a Glutamate (E)
and an Alanine (A) peptide bond in the
WHAT of Aggrecan
Interglobular Domain (IGD)
The cleavage in the IGD of Aggrecan
allows the WHAT
attachment domains of Aggrecan to
be released from the cartilage
glycosaminoglycan (GAG)
Loss of aggrecan results in the loss of WHAT and the ability to imbibe water
Net loss of compressive properties
glycosaminoglycans
True or false Loss of collagen results in the breakdown of the framework of cartilage and the tensile strength of the tissue. Collagen loss is reversible
FALSE
Collagen loss is irreversible
Name some treatments for OA
Steroids
Non steroidal anti-inflammatory drugs (NSAIDs)
Anti-cytokine antibodies
Neutraceuticals
Joint replacement surgery
Autologous chondrocyte or mesenchymal repair
Future- specific drugs to target enzyme activity
Human adults can regenerate only some organs. Give an example
Skin
Liver
Give an example of human tissues that do not regenerate
Cartilage
Nerve tissue
What is tissue engineering?
Involves the practice of combining scaffolds, cells and biologically active molecules into functional tissues
Tissue engineering Give an example of: Structural replacement Functional replacement Wound healing
Cosmetic reconstruction
Musculoskeletal tissues
Autologous skin grafts in burn patients
What is regenerative medicine?
Research field that includes tissue engineering but also research on self-healing
This is where the body uses its own systems,
Sometimes with the help of foreign biological material
To recreate cells and rebuild tissues and organs
What are ‘key ingredients’ of tissue engineering?
Cell precursors
Autologous, heterologous (allogeneic) or
xenogeneic cells derived from healthy or
pathological tissue
Source of cells (skin biopsy, bone marrow)
Types/origins of cells (embryonic stem cells/mesenchymal stem cells)
Bioactive molecules (enzymes, growth factors,interleukins)
What are cell precursors?
Produce ECM
and/or
synthesis and release bioactive molecules (growth factors)
In tissue engineering, what is used to make ‘scaffolds’?
Natural products
Purified collagens (usually Type I) Fibronectin Fibrin Hyaluronan Silk Plant polysaccharides e.g. cellulose Animal polysaccharides e.g. Chitin
In tissue engineering, what is used to make ‘scaffolds’?
Synthetic biomaterials
Composites
Polylactic acid (PLA) biodegradable • Polyglycolic acid (PGA) biodegradable • Carbon fibres • PLA/Elastin • PLGA/Hyaluronan
What are some common knee sport injuries?
Meniscal Cartilage Tears
Collateral Ligament injuries
Cartilage lesions- e.g.Osteochondritis Dissecans
Describe Osteochondritis Dissecans OCD
Inflammation of bone and cartilage
Results in the formation of loose fragments
Occurs in 15-29 of 100,000 patients
More common in males than females ( between 2:1 and 3:1)
Most common aged 10-20
Common in young athletes
Idiopathic focal joint disorder affecting the subchondral
bone
Knee is the commonly affected joint
A Fragment of cartilage and subchondral bone separates from the articular surface
Due to a lack of blood supply (osteonecrosis) in the underlying bone
Decalcification of the trabecular bone matrix
Left untreated, OCD can lead to the development of degenerative arthritis
What are they symptoms of Osteochondritis Dissecans OCD?
Pain Inflammation Swelling Edema Soreness in the joint Catching and locking in the joint during movement Reduced range of motion Crepitus
How do you diagnose Osteochondritis Dissecans OCD?
Radiographic examination
MRI
Describe simply a chondrocyte transplantation in the right femoral condyle
A lesion in the right femoral condyle is made
There is a biopsy of the healthy cartilage
There is enzymatic digestion
These are cultivated for between 11-21 days
They are treated with trypsin
Suspension of cells
There is an injection of the cultured chondrocytes under the lap in the lesion
A periosteal flap is taken from the medial tibia and sutured over the lesion
When doing a chondrocyte transplantation, how many mgs of cartilage is harvested from low weight bearing region?
300-500mg
Describe Autologous matrix-induced chondrogenesis (MACI)
eg cell precursors and scaffold
Cell precursors- bone marrow and constituents
Scaffold- hydrogel
Describe first generation ACI
Cell precursors- autologous chondrocytes
Scaffold-none- but use of periosteal flap/collagen membrane
Describe second generation ACI (also known as MACI)
Cell precursors: autologous chondrocytes
Scaffolds: hydrogels, fibrous scaffolf, decelluarised ECM
Describe third generation ACI
Cell precursors: allogenic stem cells, autologous stem cells
Scaffolds:hydrogel, fibrous scaffold, decelluraised ECM,
or composite
