It can be found in our skin, bones, muscles, cartilage, ligaments, hair, nails - in short, in almost every tissue in our body. In some places, for example in the skin, collagen proteins form fibrous networks that are very elastic.
But why these networks are so elastic has so far been unclear. Between three and four fiber connections per intersection is ideal.
In fact, more connections make the collagen networks less elastic. The new insights can be used, among other things, to repair damaged or aged tissue, such as cartilage or skin, and to grow new skin tissue for burn victims.
The breaking of a collagen network may sound like an abstract concept. But anyone who has ever broken a bone, torn a muscle, or had a cut in their finger has had experience with it. Collagen is everywhere in our body, and although it is naturally very elastic, there are limits to that elasticity. Disordered networks Collagen organises itself in many different ways. In tendons, for example, the fibres are all aligned in the same direction, like a bundle of rope.
With age, the body produces less collagen. The structural integrity of the skin declines. Wrinkles form, and joint cartilage weakens. Women experience a dramatic reduction in collagen synthesis after menopause.
By the age of 60 years, a considerable decline in collagen production is normal. Collagen is resorbable. This means it can be broken down, converted, and absorbed back into the body.
It can also be formed into compacted solids or lattice-like gels. Its diverse range of functions and the fact that it is naturally occurring make it clinically versatile and suitable for various medical purposes. Fillers that contain collagen can be used cosmetically to remove lines and wrinkles from the face.
It can also improve scars, as long as these do not have a sharp edge. These fillers are sourced from humans and cows. Skin tests should be done before using collagen from cows, to avoid aggravating any allergies. Collagen can fill relatively superficial volumes. More extensive gaps are usually filled with substances such as fat, silicone, or implants.
Collagen can help heal wounds by attracting new skin cells to the wound site. It promotes healing and provides a platform for new tissue growth. Collagen dressings are not recommended for third-degree burns, wounds covered in dry eschar, or for patients who may be sensitive to products sourced from cows. Collagen-based membranes have been used in periodontal and implant therapy to promote the growth of specific types of cell. In oral surgery, collagen barriers can prevent fast-growing cells around the gum from migrating to a wound in a tooth.
This preserves a space where tooth cells have the chance to regenerate. Collagen-based membranes can aid healing in these cases and they are resorbable, so this barrier does not need to be surgically removed after the main operation.
Collagen tissue grafts from donors have been used in peripheral nerve regeneration, in vascular prostheses, and in arterial reconstruction. While collagen prostheses are compatible with the human body, some have been found to be thrombogenic, or likely to cause coagulation of the blood. A review found that supplements containing collagen helped decrease painful symptoms and improving joint function in people with osteoarthritis.
As the supplement was absorbed, collagen accumulated in the cartilage, and this helped to rebuild the extracellular matrix. Many products containing collagen, including creams and powders, claim to revitalize the skin by increasing collagen levels within the body. This is unlikely , however, as collagen molecules are too large to be absorbed through the skin. Any benefit is probably due to the moisturizing effects of these products.
They do not directly increase collagen. Such treatments are also not classified as drugs, so any claims regarding their efficacy do not need to be scientifically proven. Caution is advised when using these products. The sequence is a repeating pattern of glycine-proline-X, where X can be any amino acid.
A special amino acid sequence makes the tight collagen triple helix particularly stable. Every third amino acid is a glycine, and many of the remaining amino acids are proline or hydroxyproline. A classic triple helix is shown here in the image. Notice how the glycine forms a tiny elbow packed inside the helix, and the proline and hydroxyproline smoothly bend the chain back around the helix. In this structure, the researchers placed a larger alanine amino acid in the position normally occupied by glycine, showing that it crowds the neighboring chains.
The collagen helix shown on the right contains a segment of human collagen. Notice that the top half is very uniform, where the sequence is the ideal mixture of glycine and prolines. At the bottom, the helix is less regular, because many different amino acids are placed between the equally-spaced glycines.
Twenty-eight different types of collagen have been identified in vertebrates. Collagen types I to IV are the most prevalent. The unique properties of each type are due to segments in the collagen molecules that disrupt the helical structure. These are caused by the amino acids in the X positions of the polypeptide sequence. Different tissues of the body contain different amounts of each type of collagen.
For example, cartilage contains a lot of type II, whereas type IV is mostly found in basement membranes. Hydroxyproline, which is critical for collagen stability, is created by modifying normal proline amino acids after the collagen chain is built. The reaction requires vitamin C to assist in the addition of oxygen. Vitamin C deficiency slows the production of hydroxyproline and stops the construction of new collagen, ultimately causing scurvy. The symptoms of scurvy — loss of teeth and easy bruising — are caused by the lack of collagen needed to repair the wear-and-tear caused by everyday activities.
A number of diseases are associated with collagen abnormalities or damage. These can be acquired or caused by a genetic mutation.
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