C2-HC12 Flashcards
3 types of cartilage:
Hyaline cartilage
Elastic cartilage
Fibro cartilage
Hyaline cartilage:
Hyaline cartilage: found in the joints, smooth surface, very lubricating (so that the joint space remains free moving).
Elastic cartilage:
Elastic cartilage: flexible, makes up the external ear and the epiglottis, it adds elastin fibres to its structure to be a bit more flexible than the rest and allows movement.
Fibrocartilage:
Fibrocartilage: resist strong forces of compression and tension (one of the strongest type of cartilage), located in the ribs.
Articular cartilage:
- This is ... cartilage - Functions:
Articular cartilage:
- This is hyaline cartilage
- Functions: shock absorption & lubrication ('smering')
Chondrogenesis:
2 methods:
Chondrogenesis: the process in which cartilage is formed.
Intersitial growth & appositional growth
Interstitial growth:
- Interstitial growth
○ Occurs during endochondral ossification (early embryonic development) as our chondrocytes (derived from the mesoderm) undergo mitosis and start to replicate causing growth of the bone structure. Continues until our epiphyseal plate closes. During puberty the bones stop growing. From there on, there is not more division of the cells in the cartilage and we end up with this single layer that covers the end of long bones.
Appositional growth:
• Appositional growth
○ Matrix is deposited from chondrocytes near edge of cartilage to add some more matrix in the superficial zone, and the cartilage progenitors and the cells in the perichondrium can also differentiate and move into the cartilage from the outside.
This is limited in adults; as soon as we stopped development, cartilage does not regenerate very much upon damage.
Content of cartilage:
Content:
- Collagen (type II): 15-22%
- Proteoglycans: 4-10%
- Water: 65-80%
- Chondrocytes: <5%
Cellular organization in articular cartilage:
Cellular organization in articular cartilage:
- Superficial zone: here you find the only population of progenitor cells, so these cells can still secrete matrix and differentiate towards chondrocytes. - Middle zone: chondrocytes are still a bit in a elongated fashion. - Deep zone: columnar structures. - Calcified zone - Subchondral bone - Cancellous bone
How are the arches called in collagen and what is their function?
The collagen structure is important since collagen is a load bearing tissue that must withstand a huge amount of load. During every step, there is shock absorption. The arches are called Benninghoff Arcades. These arcades are formed as the fibres move from one zone to the other, ending up in the superficial zone which are perpendicular to the rest. Reason: the loads are spread more evenly through the entire cartilaginous layer, allowing even more load bearing.
Components of the meniscus:
Components:
○ Water 72%
○ Collagen (22%, type I most abundant, instead of collagen II like other cartilages)
§ This leads to more fibrous, stronger cartilage that can also withstand a lot of mechanical strength. This is important because it’s a layer between bone and bone contact.
§ It’s a little wedge shaped structure that adds a bit more to the shock absorption.
○ GAGs 17%
○ 2% cells
Treatment methods for osteoarthritis:
microfracture & mosaicplasty
Microfracture:
○ Remove a part of the damage cartilage (biopsy). You drill small parts in the bone and you get some sort of healing by cells from the bone (cells are recruited through the vessel for the blood flow).
○ Disadvantage:
§ Fibrocartilage formation (type I collagen) > not durable. Drilling holes causes scar tissue which effectively covers the defect. This doesn’t have the same mechanical properties as the old cartilage.
§ Small defects only (<2 cm2)
Mosaicplasty:
○ Take cartilage from other areas (low bearing) and use this to fill the damaged areas.
○ Limitations:
§ Donor site morbidity (the architecture of the focal region where you resect will not regenerate, because it’s cartilage. You get different thickness & properties in that region).
§ Small defects that can be sort of, but not completely regenerated.
§ Donor shortage
Meniscal injury:
Meniscal injury:
- Incidence of 60-70 per 100.000 /year (common for athletes). - Caused by axial loading and rotational forces. - Pain, swelling, locking, knee instability. - Increased risk of early osteoarthritis: losing cartilage --> more exposure to cartilage to cartilage --> further damage --> OA.
Current treatments for meniscal injury:
Current treatments for meniscal injury:
- Physical therapy (if the injuries are not severe enough)
- Surgical repair
○ Partial meniscectomy (where you remove a part of the meniscus).
- Meniscal allograft transplantation (cut a little part of the regions of meniscus)
- Meniscus replacement using scaffolds > Collagen Meniscus Implant
Current meniscus replacement do not replicate intricate fiber organization and mechanical properties. The most used scaffold is CMI: made of collagen I, difficult for cells to integrate into the scaffold. The regeneration from this implantation is not nearly enough to actually regain native function. It’s a little sponge that you place between the bones that will do the job. But often it has to be replaced; invasive.
A different types of materials have been developed:
• Biodegradible: try to elicit cell invasion for the cells themselves to start produce minuscus like matrix and eventually replace the scaffold.
• Non degradable/ non resorbable: meant to stay. The results of clinical trials are quite limited. You are not bringing back any biological function.
