Chondrogenesis
Chondrogenesis is the biological process through which cartilage tissue is formed and developed. This intricate and tightly regulated cellular differentiation pathway plays a crucial role in skeletal development, as cartilage serves as a fundamental component of the embryonic skeleton. The term "chondrogenesis" is derived from the Greek words "chondros," meaning cartilage, and "genesis," meaning origin or formation.[1]
Cartilage in fetal development
In
Early in fetal development, the greater part of the skeleton is cartilaginous. This temporary cartilage is gradually replaced by bone (endochondral ossification), a process that ends at puberty. In contrast, the cartilage in the joints remains unossified during the whole of life and is, therefore, permanent.[citation needed]
Mineralization
Adult hyaline articular cartilage is progressively
Adult articular calcified cartilage is penetrated by vascular buds, and new bone produced in the vascular space in a process similar to endochondral ossification at the physis. A cement line demarcates articular calcified cartilage from subchondral bones.[citation needed]
Repair
Once
In a 1994 trial, Swedish doctors repaired damaged knee joints by implanting cells cultured from the patient's own cartilage. In 1999, US chemists created an artificial liquid cartilage for use in repairing torn tissue. The cartilage is injected into a wound or damaged joint and will harden with exposure to ultraviolet light.[3]
Synthetic cartilage
Researchers say their lubricating layers of "molecular brushes" can outperform nature under the highest pressures encountered within joints, with potentially important implications for joint replacement surgery.[4] Each 60-nanometre-long brush filament has a polymer backbone from which small molecular groups stick out. Those synthetic groups are very similar to the lipids found in cell membranes.
"In a watery environment, each of these molecular groups attracts up to 25 water molecules through electrostatic forces, so the filament as a whole develops a slick watery sheath. These sheathes ensure that the brushes are lubricated as they rub past each other, even when firmly pressed together to mimic the pressures at bone joints."[4]
Known as double-network hydrogels, the incredible strength of these new materials was a happy surprise when first discovered by researchers at Hokkaido in 2003. Most conventionally prepared hydrogels - materials that are 80 to 90 percent water held in a polymer network - easily break apart like a gelatin. The Japanese team serendipitously discovered that the addition of a second polymer to the gel made them so tough that they rivaled cartilage - tissue which can withstand the abuse of hundreds of pounds of pressure.[5]
Molecular level
Bone morphogenetic proteins are growth factors released during embryonic development to induce condensation and determination of cells, during chondrogenesis.[6] Noggin, a developmental protein, inhibits chondrogenesis by preventing condensation and differentiation of mesenchymal cells.[6]
The molecule
L-Sox5 and Sox6 share this common role with Sox9. L-Sox5 and Sox6 are thought to induce the activation of the Col2a1 and the Col11a2 genes, and to repress the expression of Cbfa1, a marker for late stage Chondrocytes. L-Sox5 is also thought to be involved primarily in embryonic chondrogenesis, while Sox6 is thought to be involved in post-natal chondrogenesis.[8]
The molecule Indian hedgehog (Ihh) is expressed by prehypertrophic chondrocytes. Ihh stimulates chondrocyte proliferation and regulates chondrocyte maturation by maintaining the expression of PTHrP. PTHrP acts as a patterning molecule, determining the position in which the chondrocytes initiate differentiation.[9]
Research is still ongoing and novel transcription factors, such as ATOH8 and EBF1, are added to the list of genes that regulate chondrogenesis.[10]
Sulfation
The
References
- ^ Chondrogenesis at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
- PMID 10966838.
- ^ "Dictionary, Encyclopedia and Thesaurus - the Free Dictionary".
- ^ a b "Artificial cartilage performs better than the real thing".
- ^ "Study of Tough Hydrogel for Synthetic Cartilage Replacement". Archived from the original on 2009-01-03. Retrieved 2010-06-11.
- ^ PMID 10694419.
- PMID 12154128.
- PMID 11702786.
- PMID 10465785.
- PMID 36987858.
- PMID 11457925.