Matrix biology Flashcards
What are the 4 types of tissue
connective, epithelial, muscle, nervous
What are some of the types of connective tissue
1 - loose connective - under the skin, contains fibroblasts that produce and secrete the ECM
2 - adipose tissue - storage vessel of fat
3 - blood - liquid ECM
4 - fibrous - containing collagen fibres, contains tenocytes (type of fibroblast) that makes and secretes the ECM
5 - cartilage - matrix with cells in, chondrocytes, found in every synovial joint, found at ends of bones
6 - bone - matrix, cells and osteocytes
What is the ECM
a highly specialised 3D scaffold in which cells reside in tissue. fibrillar (such as collagen) and non-fibrillar (such as proteoglycans) components. influences cellular function, homeostasis and disease progression. composed of collagen, structural proteins, proteoglycans, GAG’s, glycoproteins and proteinases
What are collagens
most abundant, 28 different types. contructs fibres, networks and filaments. formed from 3 polypeptide alpha chains which create homo/hetero trimeric triple helices. alpha chains have repeated triplets of Gly-X-Y that allow the chains to twist around each other
What of the 7 collagen subclasses are the 2 most abundant
FACIT and fibrillar
What are heterotypic fibrils and 2 examples
a mixture of collagen fibres
dermis, tendons and bone tend to have a mixture of type I, III and V
cartilaginous and vitreous tend to have a mixture of type II, IX and XI
List 3 other ECM structural proteins other than collagen
elastin - lends elasticity and resilience to tissues
laminins - cell-cell assembly
fibronectin - a receptor that binds to other ECM molecules
What are proteoglycans (PGs)
a protein core that joins to one or more GAG chains
What are GAG’s
chains that attach covalently to PG’s. examples:
- chondroitin sulphate
- dermatan sulphate
- heparan sulphate
- keratan sulphate
- hyluronan (different because it does not join to the protein core. found in synovial fluids to facilitate movement)
GAGs bind to growth factors, cytokines and water and have a role in cell signalling
What is heparin
component of blood that prevents clotting by binding to anti thrombin III
serglycin (a PG) is a precursor to heparin in mast cells
used as anticoagulant medication
What are glycoproteins and some examples
large, heterogeneous family of non-structural matrix glycoproteins modulate cell function by interacting with cell surface receptors, proteases, hormones, structural matrix proteins. such as thrombospondins and fibulins.
induced during disease and tissue repair. influences cell adhesion, migration, growth and differentiation
what are some functions of the ECM
balance between structural and regulation of cell behaviour. determined by bio mechanical properties of the tissue and its resident cells
If a tissue needs high tensile strength, what will it be enriched in
fibrillar collagens. such as in tendons, ligaments and bone
If a tissue needs compressive properties, what must it be enriched in
proteoglycans and hyluronan. such as in cartilage, intervertebral discs, connective tissue of placenta
If the tissue needs elastic properties what will it be enriched in
elastin, such as in the skin, connective tissues of blood vessels, ligaments and lungs
What is Ehler’s Danilo’s syndrome
mutation in collagen, MMP gene plays roll in regulating collagen organisation. results in hyper flexible joints, elastic skin and valvular heart disease
What is invertabral disc disease
loss of GAGs due to loss of aggrecan. decreased hydration as discs cannot take in water so there is a loss of compressive qualities and increased risk of disc herniation
changes in cell behaviour = hypoxia, inflammation, autophagy
What does fewer CS (GAG) chains on aggrecan and versican result in
decreased compressive resistance
What does abnormal synthesis of HSPG (a class of PG with heparin sulfate GAGs attached) result in
alters growth factor levels and morphogen signalling which alters the cells in the inner core of the invertebral disc (the nucleus pulposus phenotype)
what does fewer and shorter KS (GAG) chains on aggrecan and fibromodulin lead to
abnormal collagen cross-linking fibril formation
What do changes in hyaluronan lead to
impaired aggregation of aggrecan and versican
What is fibrosis and what causes it
excess formation of connective tissues in response to injury. causes disproportionate activity of matrix degradation enzymes. hyperactive ligand-mediated receptor signalling via TGFB. chronic injury to endo/epithelial cells switches on activation of coagulation and platelets. results in persistent activation of myofibroblast precursor cells = highly cross linked, stiff
result in scarring = pulmonary, hepatic or renal
What is osteoarthritis?
Caused by mechanical wear, thinned cartilage so bone ends rub together
What is rheumatoid arthritis?
Autoimmune disease which body’s own immune system attacks the body’s joint, swollen inflamed synovial membrane
What are the ligaments in the knee joint?
Lateral collateral ligament
Curciate ligaments
Medial collateral ligament
What are the bones that articulate at the knee joint?
Femur, tibia, fibula, patella
What is the tendon in the knee joint?
Patella tendon
What cartilage is in the knee joint?
Articular cartilage, meniscus
What is articular cartilage made up of?
Collagen, Proteoglycans and water
What is the morphology of articular cartilage?
No lymphatics, avascular, aneural, hypocellular, no basement membrane
What cell produce collagen?
Chondrocyte
What type of collagen is the major collagen and what does it provide?
Type II- Provides a cartilaginous framework and tensile strength
What is aggrecan
A major proteglycan and gives cartilage compressive stiffness
What are aggrecan aggregates composed of?
30-50 aggrecan monomers
1 hylauronan glycosaminoglycan
30-50 link proteins that stabilise the aggrecan interaction
All of these interactions are non covalent
What is the biphasic model
Biomechanical behaviour of cartilage
Fluid phase of water and cations
Solid phase of chrondrocytes, collagen and Proteoglycans
The solid phase has low permeability because PGs resit fluid flow (GAG components affinity for water) and restricted by the collagen fibril network
The fluid phase is under hight interstiial fluid pressurisation and allows for the transmission of load int cartilage
What occurs during cartilage homeostasis?
• in the balance between synthesis and degradation of the extracellular matrix
• Metalloproteinases are the major proteinases responsible for matrix turnover in cartilage
• Cartilage turnover is relativtively slow in adults
What are collagenases and gelatinases?
They degrade collagen fibres
What do aggrecanases do?
Degrade aggrecan
What does stromelysins do?
Degrade non-collagenous matrix proteins
What are the two classifications of Osteoarthiritis?
Primary- idiopathic (no known cause)
• Secondary OA- post traumatic, congenital, malposition, postoperative, metabolic, endocrine disorders, a
Symptoms of osteoarthritis?
Limited movements
• Pain
• Crepitation
• Sensitivity to cold or damp
What are the risk factors of arthritis?
• Age
• Sex
• Heredity
• Ethnic origin
• Post menopausal
• Macrotrauma
• Repetitive micro trauma
• Overweight
• Life styles
• Respective joint surgery
What is the main hallmark of arthritis?
Matrix degradation of articular cartilage - results in loss of tissue function
How is Chondrocyte metabolism altered?
• mechanical forces: through mechanical and osmosensors embedded in the chorocyte plasma membrane
• Inflammatory mediators such as cytokines, chemokines, prostaglandins, reactive oxygen species and nitric oxide
• Increased synthesis and activation of aggrecaanase and MMPs through NF Kappas signalling pathway
• Increased degradation of aggrecan and collagen
What are the treatment for osteoarthritis?
• steroids
• Non steroidal anti-inflammatory drugs (NSAIDs)
• Anti-cytokine antibodies
• Neutraceuticals
• Joint replacement surgery
• Autologous Chondrocyte or mesecnhumal repair
future- drugs to target enzyme activuty
What is the result when aggrecan is lost?
Results in the loss of glycosaminoglycans and the inability to imbibe water
What happens when there is a loss of collagen?
Breakdown of framework of cartilage and the tensile strength of the tissue collagen loss is irreversible
What is tissue regeneration?
The regrowth of a damaged or missing organ part from the remaining tissue.- Complete restoration of original tissue
What are examples of human organs that can regenerate?
Liver and skin
What are the clinical applications of tissue engineering?
• Structural replacement e.g cosmetic reconstruction
• Functional replacement e.g musculoskeletal tissues
• Wound healing e.g autologous skin grafts in burn patients, chronic wounds and corneal replacement
What is regenerative medicine?
Regenerative medicine - is a broad field that includes tissue engineering but also incorporates research on self-healing (tissue regeneration) where the body uses its own systems, sometimes with the help of foreign biological material to repeats cells and rebuild tissues and organs
What are they key ingredients of tissue engineering?
Cell precursors and bioactive molecules
What are cell precursors?
Required to produce ECM and/or synthesis and release bioactive molecules such as growth factors to maintain
What are the three cell sources and define them?
Autologous- from yourself
Allogenic- cell line taken from another person
Xenogeneic- from another species
What are the bioactive molecules?
- Growth factors
Interleukins
Anti-inflammatory molecules
Enzymes
What are scaffolds?
A structural framework made of biomaterials that provide support for cells to adhere, migrate and form functional tissues.
What are common knee sports injuries than can all lead to OA
• Anterior crucial ligament injuries
• Collateral ligament injuries
• Meniscal cartilage tears
• Cartilage lesions e.g osteochondritis dissecans
What is Osteochondosis Dissecans (OCD)
Inflammation of bone and cartilage resulting in the formation of loose fragments
What are symptoms of OCD?
Pain
• Inflammation, Edelman and swelling and soreness in the joint during movement
• Reduced range of motion
• Crepitus, a grating, cracking or popping sound when moving the joint
How does chondrocytes transplantation in the right femoral condyle?
- 300-500 mg cartilage harvest from low
weight bearing region (upper medial
femoral condyle) - Cartilage digested (collagenase &
deoxyribonuclease) to release cells
(range 180,000 to 455,000)
3.Cells seeded into tissue culture flasks at a
cell density of 5000-10,000 cells per cm2
(T25 or T75 Flasks) and maintained in
media containing patient serum
(autologous serum)
- Transplantation 12-14 days after initial
surgery. Chondrocytes trypsin treated,
washed and resuspended in 50-100 µl
volume 2.6- 5 million cells - Chondral lesion excised to surrounding
Normal tissue. Cartilage defect covered with
periosteal flap. Sutured to normal cartilage.
Periosteal flap potential source of growth
factors and stem cells - Autologous Chondrocytes injected beneath
the periosteal flap to initiate repair and
Periosteum provides source of growth factors
What are three theoretical explanations for the repair process?
1) The transplanted cells (chondrocytes) repopulate the area of the defect
producing new cartilage matrix and the periosteum seals the defect.
- The periosteum stimulates the replication of the transplanted chondrocytes,
which produce new cartilage matrix
3.The periosteum and transplanted chondrocytes stimulate chondrocytes in the
surrounding cartilage or cells in the deep noncalcified zone and calcified layers
of the articular cartilage or in the periosteum itself to enter the defect, divide
and repair the defect.
