Normal and Abnormal joints pathogenesis of RA

Question 1

how many cells thick is the synovial membrane

Answer 1

1-3 cells thick

- synoviocytes make up the synovial membrane

Question 2

What are the cells called that make up the synovial membrane

Answer 2

Synoviocytes

Question 3

name the two types of synoviocytes and what they do

Answer 3

Type A bone marrow derived macrophage - immune surveillance - last check to make sure that the synovial fluid is aseptic

Type B fibroblast-like connective tissue cell - make hyaluronic acid

Question 4

what is another word for synovial membrane

Answer 4

Synovium

Question 5

describe the synovial membrane

Answer 5

• 1-3 Synoviocytes cells thick
• no basement membrane
• subintima

Question 6

describe the subintima

Answer 6

Contains dense network fenestrated capillaries - leaky capillaries that allow substances through

fat (loose areolar connective tissue)

Question 7

What type of synoviocytes make hyaluronic acid

Answer 7

Type B= fibroblast-like connective tissue cell - make hyaluronic acid

Question 8

what does the hyaluronic acid do to the synovial fluid

Answer 8

• it makes it more viscous

Question 9

what is the benefit of having no basement membrane in the synovial membrane

Answer 9

this means that there is no barrier for blood plasma that is coming out of the capillary network in the subintima to go into the joint , also means there is no barrier for the synovial fluid passing into the blood

Loose areolar connective tissue allows plasma to move through subintima

No basement membrane between subintima and synoviocytes allows plasma to flow through to joint cavity

Question 10

synovial fluid is the …

Answer 10

ultrafiltrate with blood and added hyaluronic acid

Question 11

describe the downside of having no basement membrane

Answer 11

• the joint can be easily more damaged
• fenestrated capillaries are already more leaky meaning immune cells can leave more easily and enter the joint meaning the joints are at a higher risk of infections and autoimmune problems

Question 12

what does normal synovial fluid look like

Answer 12

• Normal synovial fluid is colourless to pale yellow and clear therefore it is normal

Question 13

what does it mean if the synovial fluid is yellow and cloudy

Answer 13

• this is what it looks like in rheumatoid arthritis

- due to the amount of neutrophils that are present

Question 14

what is present if the synovial fluid looks white/creamy and cloudy/shiny

Answer 14

crystals

Question 15

What is present if the synovial fluid looks colourless to yellow and purulent (lumpy)

Answer 15

means that there is a bacterial infection present

Question 16

what does if mean if the synovial fluid is red and brown

Answer 16

• means that there is haemorrhage into joint which is the result of a direct acute injury

Question 17

What is synovial fluid made out of

Answer 17

• white blood cells = mainly phagocytes
• hyaluronate
• glucose
• protein - albumin (60%) and globulin (40%)
• Lubricin
• lactate and the rions

Question 18

What is the pH of synovial fluid

Answer 18

7.38

Question 19

what does the hyaluronate with the protein form

Answer 19

• they form a gel like substance that separates the articulating surface from each other

Question 20

where is synovial fluid

Answer 20

• small amount occupies all free spaces between articulating surfaces - approximately 50 micrometers

Question 21

what else does synovial fluid do

Answer 21

• seeps into articular cartilages
• this helps nourish articular cartilage
• it is called weeping lubrication

Question 22

What is articular cartilage

Answer 22

Slippery weight-bearing film which reduces friction between cartilages

Question 23

what part of the articular cartilage are compressible

Answer 23

• as you compress down the peripheral zone and transitional zone compress
• water moves out of these zones
• the lower zone is not compressible due to the direction of the collagen fibres

Question 24

what happens to the hyaluronate as you move

Answer 24

as you move it becomes more thicker

• gets thicker between the joints at movement as it becomes more tangled and integrated with the articular proteins
• this acts as a shock absorber

Question 25

describe what happens to the synovial joint and fluid at rest compared to movement

Answer 25

Movement - at movement pressure is pressed on the joint - decreases the peripheral and transitional zone of the articular cartilage - the hyaluronate becomes more entangled with proteins and therefore acts as a shock absorber and an energy store Rest - at rest pressure is decreased in the joint - increased elongation of the peripheral and transitional zone back to normal on the articular cartilage - hyaluronate becomes less entangled and more viscous and energy is dissipated as viscous flow

Question 26

How do you test viscosity in the synovial fluid (hyaluronic acid)

Answer 26

- measure the string that originates from the synovial fluid - the longer the string the less oedema fluid and the less hydrolysed the hyaluronic acid - normal string is between 4-6cm - the longer it is the more vicious it is and the better the result - normal synovial fluid is highly vicious

Question 27

What is the mucin clot test used to measure

Answer 27

measures the viscous property of the synovial fluid

Question 28

describe how to do the mucin clot test

Answer 28

- add 2-5% acetic acid - normal synovial fluid will then from a clot surrounded by clear fluid - In RA - the hyaluronate is smaller and not as polymerised therefore clots less this means that the results would show a cloudy view with no clot

Question 29

What is Rheumatoid arthritis

Answer 29

Autoimmune condition that primarily damages the synovial membrane causing synovicitis

Question 30

What and the three things that happen microscopically with rheumatoid arthritis

Answer 30

proliferation of synoviocytes infiltration of inflammatory cells - neutrophils - in the synovial fluid - lymphocytes in the subintima proliferation of fibroblasts in the subinitima causing thickening

Question 31

Where are the neurtrophils and lymphocytes in an inflammatory reaction such as rheumatoid arthritis in the joint

Answer 31

- neutrophils - in the synovial fluid | - lymphocytes in the subinitima

Question 32

describe the inflammatory cells that are associated with rheumatoid arthritis

Answer 32

- the synovial fluid has infiltration of tissue inflammatory cells - B cells inflation which produce autoantibodies that we find in RA as it is an autoimmune condition - the B cells produce the two main autoantibodies associated with RA these are Rheumatoid factor and Anti-Citrullinated protein antibodies (ACPA) - Anti-Citrullinated protein antibodies (ACPA) is thought to be the main antibody associated with RA as they are present in higher quantities - there are also T cells present and mainly TH17 - TH17 produces IL17 int eh synovium - IL-17 causes synonvitis - IL-1, TNF alpha and RANKL are also produced - TNF-alpha is more important peripherally = TNF alpha also helps produce synovial fibroblasts therefore we get proliferation of the synovial membrane - T regulatory cells that should be stopping the T and B cells from targeting our own cells are impaired and don't recognise the problem so therefore do not act - The macrophages within the synovial membrane and the subitnma can swtich and become under the influence of cytokines and osteoclasts – make them switch to become bone destroyers

Question 33

what is the mechanism of action of how the autoimmune reaction happens in RA

Answer 33

Mechanism of action - Neurotrophils are the first responders and take-up an infection and this particular infection has antigens that look like self antigens - therefore our own self antigens are mistaken for the infections - therefore the B cells make antibodies against these self antigens

Question 34

What are the two antibodies that are associated with RA

Answer 34

Rheumatoid factor and Anti-Citrullinated protein antibodies (ACPA) - Anti-Citrullinated protein antibodies (ACPA) is thought to be the main antibody associated with RA as they are present in higher quantities

Question 35

what T cell is more prelevant and what does is produce in RA

Answer 35

- TH17 and IL-17

Question 36

What does IL-17 cause to happen

Answer 36

IL-17 causes synonvitis - induces RANKL on synovial fibroblasts - stimulates local inflammation - activates synovial macrophages to secrete proinflammatory cytokines, such as TNF, IL-1 and IL-6.

Question 37

What does TNF alpha do

Answer 37

TNF alpha also helps produce synovial fibroblasts therefore we get proliferation of the synovial membrane

Question 38

Why are synovial joints susceptible to inflammatory injury

Answer 38

- Presence of rich network of fenestrated capillaries that are more leaky to begin with - limited ways that it can respond - pro-inflammatory cytokines induce proliferation and or direct osteoclast differentiation

Question 39

What is a Pannus

Answer 39

- Synovial membrane at the end of proliferation that is abnormal - grows over the surface of joints and covers the cartilage

Question 40

describe what a pannus results in

Answer 40

- Pannus contains osteoclasts - the osteoclasts erode and remove bone - therefore they erode the cartilage that the Pannus overhangs - they cause the cartilage to soften and the chondrocytes to become stressed and produce a tide mark - the pannus also secretes cytokines - CD4 T helper lymphocytes collect around small blood vessels and form lymphoid nodules

Question 41

What happens if you remove the Pannus

Answer 41

- if you remove the Pannus it will regrow

Question 42

What does anti-citrullinated protein antibodies stimulate

Answer 42

- osteoclast differentiation from monocytes leading to intimal bone loss

Question 43

describe the autocrine feedback of osteoclasts

Answer 43

- Osteoclasts produce IL 8 that induces more osteoclasts by autocrine feedback - IL 8 also sensitises nociceptors and may contribute to increased pain

Question 44

what contributes to the pain felt in RA

Answer 44

- IL 8 also sensitises nociceptors and may contribute to increased pain

Question 45

what does synovitis lead to

Answer 45

Synovitis at start of clinical disease leads to production of cytokines, which stimulate osteoclast proliferation and differentiation - causes the production of RANKL this enhances osteoclast differentiation and causes more bone erosion

Question 46

what molecule does synovitis lead to the expression of

Answer 46

RANKL

Question 47

Describe what established RA looks like

Answer 47

- Large bone erosions filled with inflamed synovial derived pannus tissue

Question 48

What is Citrullination

Answer 48

changing arginine to citrulline by deamination by peptidyl arginine deiminase occurs during apoptosis

Question 49

what is the hallmark of RA pathogenesis

Answer 49

CD4+ T-cell infiltration is a hallmark of RA pathogenesis (TH17 cells)

Question 50

what does inflammation within synovial tissue induces

Answer 50

- Osteoclast proliferation and differentiation | - causes increased expression of RANKL by pro inflammatory cytokines which synergies with RANKL

Question 51

what do cytokine induce

Answer 51

Cytokines induce expression of Dkk-1 by synovial fibroblasts which inhibits directly osteoblast differentiation

Question 52

What does DKK-1 do

Answer 52

inhibits directly osteoblast differentiation | - induces the expression of sclerotin by osteocytes which inhibits osteoblasts therefore reducing osteoblast activity

Question 53

how is synovial fluid affected in RA

Answer 53

- increased amount of neutrophils - synovial fluid is less viscous due to shorter hyaluronic acid strands - increased volume due to leakier vessels from the release of cytokines

Question 54

what is the most numerous cells in inflammatory synovial effusion

Answer 54

Neutrophils

Question 55

describe how much fluid expands in the knee in RA

Answer 55

Normal knee 2 ml in RA can remove 20ml from knee

Question 56

what do neutrophils do in the synovial fluid

Answer 56

Direct damage - present in the early or active stages of the disease - they produce superoxide anion free radical - therefore there is free radical damage which directly damages hyaluronic acid Indirect damage - they also secrete B cell activating factor - this activates the B cell to produce more antibody - B cells stimulate osteoclasts

Question 57

describe the difference between RA and OA in synovial fluid analysis - colour - clarity - viscosity - white cell count - neutrophils - crystals - bacteria

Answer 57

OA - colour - colourless - clarity - clear - viscosity - high to medium (1-2cm string) - white cell count - 100-2000 - neutrophils - <5 - crystals - 5% have pyrophosphate crystals - bacteria - no RA - colour - yellow - clarity - cloudy - viscosity - low, less than 1cm - white cell count - 2000-50,000 - neutrophils- 30-80 - crystals - no - bacteria - no