Lecture 9

Question 1

3 types of cartilage

Answer 1

1) hyaline : weakest -> joints, nose, ribs
2) fibrous : strongest -> ligament, menisci, intervertebral discs
3) elastic : most flexible -> external ear, epiglottis

Question 2

origin of joint cartilage and craniofacial cartilage

Answer 2

joint -> mesodermal
craniofacial -> neuroectodermal

Question 3

what is the perichondrium ? what does it contain ?

Answer 3

dense connective tissue that covers the cartilage (except joints)

contains :
- nerve supply
- blood vessel
- fibroblasts (produce collagen)
- chondro-progenitors (differentiate into chondroblasts)

Question 4

3 pieces of cartilage in nose

Answer 4

1) septum : separates nose in 2 halves, channel for air
2) lateral cartilage
3) alar cartilage

2 and 3 keep the nostril open, shape of nose, nasal tip and nostrils

Question 5

components of synovial joints

Answer 5

• synovial capsule (collagenous)
• synovial membrane (inner layer), which secretes synovial fluid
• hyaline cartilage (on end of bones)

Question 6

main 3 functions of articular cartilage

Answer 6

1) shock absorption (transmission of loads, compression)

2) lubrication

3) durability

Question 7

difference between bone development and articular cartilage development from MSCs

Answer 7

• differentiation into chondroblasts
  If BMP -> chondroctyes that become hypertrophic and lead to endochondral ossification.
  If no BMP -> maturation into articular chondroctyes

Question 8

dual role of cells in cartilage ? zonal organisation of articular cartilage ?

Answer 8

cells are responsible for regulation of cartilage synthesis and degradation.

1) superficial : flat Ch, collagen parallel, lo PG
2) intermediate : spheroid Ch, random collagen, high PG
3) deep : Ch and collagen in columns, max PG
4) calcified : Ch surrounded by calcifieed ECM

Question 9

3 compartments of matrix ? what happens when we unload cartilage ?

Answer 9

pericellular, territorial, interterritorial

joint unloading causes structural changes in articular cartilage -> degenerative properties

Question 10

how does oxygen reach chondrocytes ?

Answer 10

double diffusion barrier : synovial tissue (and fluid) and cartilage matrix

Question 11

what are the other components of a joint ?

Answer 11

synovial membrane, ligaments, tendons, bursas, menisci, intrapatellar fat pad

Question 12

3 degrees of articular cartilage damages, consequences ?

Answer 12

1)2) chondral defect ; partial or full thickness
3) osteochondral defect (into bone)

1+2 -> no repair, progressive damage
3 -> fibrocartilage (collagen I)

all leads to joint degeneration

Question 13

healing articular cartilage : how, results ?

Answer 13

lavage or arhtroscopic debridement to remove fragments or joint fluid (enzymes, inflammatory mediators).

No repair and only temporary relief

Question 14

articular cartilage regeneration : techniques, result ?

Answer 14

drilling, abrasion, microfracture -> penetrate bone to stimulate bone marrow cells

generation of fibrocartilage -> not an adequate long term replacement

Question 15

articular cartilage substitution : 3 ways to do it, result ?

Answer 15

synthetic matrices, osteochondral autograft or allograft.

but immune reaction and limited availability + donor site morbidity

Question 16

difference between ACI and tissue engineering ? what is better ?

Answer 16

ACI = cells harvested from the joint, grown and then implanted back

TE = same cells but assembled in a functional construct (implant)

TE is better : larger defects, easier handling, more protection of defect

Question 17

what is the problem during 2D expansion of chondrocytes ? how can that be improved ?

Answer 17

de-differentiate into fibroplastic morphology (flat) that don’t produce collagen II -> poor capaciy to re-differentiate

use growth factors, mimick joint environment (= low oxygen)

Question 18

what other cells could we use to repair articular cartilage ?

Answer 18

nasal chondrocytes : also hyaline cartilage, high regenerative capacity (neuroectoderm origin), minimally invasive biopsy

Question 19

what do we need to test for nasal chondrocytes before using them in a knee joint injury ?

Answer 19

test if they’re compatible in a joint environment : mechanical, developmental aspects