Extracellular matrix and fluids, compartements and solutes Flashcards
What is the extracellular matrix? What cells deposit it?
Network of macromolecules - minaly proteins and carbs filling spaces between cells
Deposited by fibroblast cells consisting of both fibrillar and non-fibrillar components
What are the key functions of the ECM?
Provides physical support
Determines mechanical and physiochemical properties of the tissue
Influences the growth, adhesion and differentiation status of the cells and the tissue with which it interacts
Essential for development, tissue function and organogenesis
What are the three types of connective tissues?
Collagens
Type I, II, III (fibrillar)
Type IV (basement membrane
Multi adhesive glycoproteins
fibronectin, fibrinogen
laminins
Proteoglycans
Aggrecan, versican, decorin
perlecan - basement membrane
Explain the structure of type I collagen v type II and II collagen
→ Each collagen molecules has three alpha chains forming a triple helix
→ Type I collagen has chains from two different genes
→ Types II and III have one chain
Every third position in the alpha chains is.glycine
Describe simply how an single collagen α chain forms a collagen fibre
synthesis of pro-α chain → One α chain → hydroxylation and glycosylation → three α chains (self assembly) → Secretion from cell and cleavage of propeptides → collagen fibril (self assembly) → collagen fibre (crosslinking)
What is the purpose of cross-links in collagen?
Provides tensile strength and stability
Both lysine and hydroxy-lysine residues involved
- Crosslinks are tissue specific and change with age
What is the role of lysine and proline hydroxylation in collagen formation?
What is required?
Contribute to interchain hydrogen bond formation
Prolyl and lysyl hydroxylases require Fe2+ and vitamin C - so deficiency leads to underhydroxylated collagens with consequences for tissue stability (scurvy)
What is ehlers-danlos syndrome?
Group of inherited connective tissue disorders whose symptoms include stretchy skin and loose joints
several disorders arise due to mutations in collagen which negatively effect
- collagen production
- collagen structure
- collagen processing
What type of collagens are IX and XII and what do they do?
Fibril-associated collagens
associate with fibrillar collages and regulate organisation of collagen fibrils
What type of collagen is type IV?
Network framing collagen - present in all basement membranes (molecular constitution varies from tissue to tissue)
What are basememt membranes/basal lamina ?
Flexible thin mats of extracellular matrix underlying epithelial sheets and tubes
surround muscle, peripheral nerevs and fat cells
highly specialised extracellular matrices containing distinct repertoire of collagens, glycoproteins and proteoglycans.
How is basement membrane affected in diabetic nephropathy?
Diabetic nephropathy - an accumulation of extracellular matrix leading to a thickened glomerular basement membrane, this restricts renal filtration and lead to renal failure
How is glomerular basement membrane affected in alports syndrome?
mutations in collagen IV result in an abnormally split and laminated GBM which is associated with progressive loss of kidney function and hearing loss
What is the role of elastic fibres in the ecm?
How is extent of their purpose limited
for elasticity of tissues ie as skin, blood vessels and lungs
Collagen and elastic fibres can be interwoven to limit the extent of stretching
Elastic fibres consist of a core made up pf protein elastin and microfibrils which are rich in protein fibrillin
What is protein fibrillin? What does a mutation in this lead to/
The protein in myofibrils around elastic fibres that determines integrity of the elastic fibres
Mutations in fibrillin-1 lead to marfans syndrome leading to disease manifestations in skeletel, ocular and cardiovascular systems - individuals predisposed to aortic ruptures
What is elastin?
- Unusual protein consisting of two types segments that alternate along the polypeptide chain: hydrophobic regions and a-helical regions rich in alanine and lysine
- Many lysine side chains are covalently cross-linked
What is the role of multi-adhesive glycoproteins?
Determine modular architecture of extracellular matrix proteins
Many large modular proteins are multi-adhesive binding various matrix components and cell surface receptors
What are laminins?
How do they interact in the ECM?
What mutations can arise in these?
Heterotrimeric proteins
made up of an α chain, a β chain and a γ chain, which form a large cross shaped molecules
Muti-adhesive proteins - interact with various cell surface receptors including integrins and dystroglycan
self-associate as part of the basement membrane matrix, but also interact with other matrix components like type IV collagen, nidogen and proteoglycans
Mutations in specific chains are associated with inherited diseases such as….
○ Congenital muscular dystrophy can rise from an absence of the alpha-2 chain in laminin 2 - Symptoms include hypotonia (abnormally decreases muscle tension), generalised weakness and deformities of the joints
○ epidermolysis bullosa
What are fibronectins in the ECM? How are they derived
- fibronectins are multi-adhesive proteins glycoproteins, made up of large multidomain molecule linked together by disulphide bonds
- They either exist as an insoluble fibrillar matrix or as a soluble plasma protein
- They are derived from a single gene, with alternate splicing of mRNAs giving rise to the different types
What do fibronectins interact with and what are they important for?
• Fibronectins interact with cell surface receptors and other matrix molecules to regulate cell adhesion and migration in a variety of processes, ie embryogenesis and tissue repair
form a continuum with actin cytoskeleton of many cell types.
→ Integrin receptors at the cell surface provide the linkage between the matrix and cytoskeleton
• They are important for wound healing and helping promote clotting (ALS2- haemostasis)
What are proteoglycans?
core proteins to which glycosaminoglycan (GAG) chains are attached
GAGs (repeating disaccharide units) are sulfated or carboxylated so carry a high negative charge
this attracys cloud of cations - Na= included so water is sucked into the ECM
What are the different proteoglycan families and give examples
→ Basement membrane proteoglycans ie perlecan
→ Aggregating proteoglycans (interact with hyaluronan) eg aggrecan
→ Small leucine-rich proteoglycans ie decorin
→ Cell surface proteoglycans ie syndecans 1-4
What is hyaluronan (hyaluronic acid)?
Found in the extracellular matric of soft connective tissue
a carbohydrate chain with no core protein
Unsulfated and made of repeating disaccharides
Can undergo a high degree of polymerisation, creating enormous molecules thus can occupy a large volume
Its typically of high viscosity - vitreous humour of eye and synovial fluid of joints where it protects cartilaginous surface from damage
What is aggrecan in the cartilage matrix suited for?
Resists compressive forces
Under compressive load water is given up, but regained once the load is reduced.
What are two types of disorders of the ECM?
Osteoarthritis
Erosive disease resulting in excessive extracellular matrix degradation
• The cushioning properties of cartilage over the end of bones is lost, so with increasing age aggrecan is cleaved by aggrecanases and metalloproteinases.
• This results in a loss of aggrecan fragments to the synovial fluid
Fibrotic diseases
Arises as a result of excessive production of fibrous connective tissue
What does a histopathologist do?
deals with tissues. She/he will examine sections, noting the architecture of the tissue and asking what it tells us about a particular condition.
works with Biopsies Resection specimens Frozen specimens Post-mortems
What does a cytopatholgist do?
deals with cells. They are often are the individuals responsible for taking the cells from the patient, preparing them for examination and then delivering their expert diagnosis on the cell sample.
Biopsy?
biopsies are small sections of tissues that are removed from the patient and typically placed in a formalin solution which preserves the tissues by cross-linking proteins
mbedded in paraffin wax to allow thin sections to be cut by an instrument known as a microtome
What does the Zieh-Neelsen stain do?
stain acid-fast bacteria red, aiding in the diagnosis of tuberculosis infection
Resected specimens?
Primary used for?
Def- Taken from tissue that has been removed as part of a surgical procedure and can be processed for biopsy
Primarily used to look at the stage of the disease ie cancer
can also be donated to biobanks and used to inform genomic studies of the disease process, with the input of other medical professionals
Frozen sections?
Frozen sections are taken during surgical procedures and are examined by pathologists while the patient is being operated upon - rapid diagnosis in minutes
freshly taken tissue is frozen by a machine known as a cryostat, cut then mounted on glass slides and stained as for biopsies
Fine needle aspirates?
- A fine needle can be used to get into a lesion and aspirate (suck out) the cells which can be analysed as a smear
- powerful technique as the needle can penetrate relatively inaccessible tissues ( thyroid nodule) and assess the suspect mass without the need for surgery
What indicates endothelial cell tumours?
CD31 immunohistochemical staining of a skin biopsy.
Brown colouration indicates CD31 positivity
antibody recognising the endothelial cell marker CD31 on the surface of endothelial cells allows us to define this biopsy as being of an endothelial cell tumour
What are some antibody conjugates and what do they do?
Enzymes - peroxidase, alkaline phosphatase
Fluorescent probes - allow rapid measurement of hte levels of mokecules in a sample
Magnetic beads - purification of cell types
Drugs; ie kadcyla, anti-HER2 antibody linked to emtansine
What are the three uses of manufactures antibodies?
Blood group serology - blood transfusion
Immunoassays - detection of hormones and circulating antibodies/antigens
Immunodiagnosis - infectious diseases, AB levels and IgE hypersensitivity
What precaution is taken to stop donated organ deterioration during transport?
rapid cooling to 4 degrees
Perfused with cold solutions via arterial supply
ie universit of wisconsin solution (UW)
- lack of Na+ and Cl- so no influx possible
- Presence of extracellular impermeant solutes (lactobionate ions, raffinose).
- Presence of a macromolecular colloid (starch)
What is the colloid osmotic pressure?
Higher concentration of plasma proteins inside the capillary than outside generates an osmotic pressure known as the colloid osmotic pressure (COP)
What is inflammatory oedema?
cardinal signs of inflammation
Infectious and inflammatory stimuli often results in oedema
inflammation can be observed around the sites of insect bites which has caused local blood vessels to become leaky. Swelling occurs because the rate of leakage from the vessels is greater than the rate at which the lymphatics can drain it.
What is hydrostatic oedema?
have high blood pressure, which means increased hydrostatic pressure in vessels.
This pushes more fluid out of the vessels, and can lead to accumulation of interstitial fluid
Why does a breast cancer survivor often have oedema in arms?
likely to have had axillary (armpit) lymph nodes removed as part of her diagnosis or treatment
This can remove the pathway of drainage from the upper limb on the affected side, resulting in the accumulation of fluid.
What happens in elephantiasis?
parasitic worms can block lymphatic vessels, thereby preventing drainage of the lymph
Features of marfans syndrome?
long slender limbs, long fingers, a predisposition to aortic ruptures and heart murmur
Features of Ehler’s-Danlos syndrome?
Joint hypermobility and extremely elastic skin
