Collagen – Wikipedia – This protein, affected by Ehlers-Danlos and other connective tissue disorders, has multiple critical roles and gives structural support throughout the whole body.
Depending upon the degree of mineralization, collagen tissues may be rigid (bone), compliant (tendon), or have a gradient from rigid to compliant (cartilage).
In muscle tissue, it serves as a major component of the endomysium. Collagen constitutes one to two percent of muscle tissue, and accounts for 6% of the weight of strong, tendinous muscles. The fibroblast is the most common cell that creates collagen.
The name collagen comes from the Greek κόλλα (kólla), meaning “glue“, and suffix -γέν, -gen, denoting “producing”. This refers to the compound’s early use in the process of boiling the skin and tendons of horses and other animals to obtain glue.
So far, 28 types of collagen have been identified and described. The five most common types are:
- Type I: skin, tendon, vascular ligature, organs, bone (main component of the organic part of bone)
- Type II: cartilage (main collagenous component of cartilage)
- Type III: reticulate (main component of reticular fibers), commonly found alongside type I.
Reticular fibers crosslink to form a fine meshwork (reticulin). This network acts as a supporting mesh in soft tissues such as liver, bone marrow, and the tissues and organs of the lymphatic system.
- Type IV: forms basal lamina, the epithelium-secreted layer of the basement membrane.
- Type V: cell surfaces, hair and placenta
The collagen protein is composed of a triple helix, which generally consists of two identical chains (α1) and an additional chain that differs slightly in its chemical composition (α2).
The amino acid composition of collagen is atypical for proteins, particularly with respect to its high hydroxyproline content.
One thousand mutations have been identified in 12 out of more than 20 types of collagen. These mutations can lead to various diseases at the tissue level.
Just two examples:
Ehlers-Danlos syndrome – Six different types of this disorder, which lead to deformities in connective tissue, are known. Some types can be lethal, leading to the rupture of arteries. Each syndrome is caused by a different mutation, for example type four of this disorder is caused by a mutation in collagen type 3.
Osteoporosis – Not inherited genetically, brought on with age, associated with reduced levels of collagen in the skin and bones, growth hormone injections are being researched as a possible treatment to counteract any loss of collagen.
This is the first I’ve heard that osteoporosis also affects the skin.
Tough bundles of collagen called collagen fibers are a major component of the extracellular matrix that supports most tissues and gives cells structure from the outside, but collagen is also found inside certain cells.
More information on collagen’s role in bones:
Collagen and Bone Matrix – American Society for Bone and Mineral Research 2008 – by Susan Ott
Mature bone is composed of proteins and minerals.
Approximately 60% the weight of the bone is mineral, mainly calcium and phosphate.
The rest is water and matrix, which is formed before the mineral is deposited, and can be considered the scaffolding for the bone.
About 90% of the matrix proteins are collagen, which is the most abundant protein in the body.
Collagen is very strong and forms bone, cartilage, skin, and tendons.
Collagen is formed as chains (short pieces of thread) which twists into triple helices (strings). These line up and are bonded together into ropes (fibrils). The fibrils then are arranged in layers, and mineral crystals will deposit between the layers.