Collagen is the most abundant protein in the human body, found in the bones, muscles, skin, and tendons.
It is the substance that holds the body together. Collagen forms a scaffold to provide strength and structure.
Endogenous collagen is natural collagen, synthesized by the body. Exogenous collagen is synthetic. It comes from an outside source, such as supplements.
Endogenous collagen has a number of important functions. Breakdown and depletion is linked to a number of health problems.
Exogenous collagen is used for medical and cosmetic purposes, including the repair of body tissues.
Fast facts on collagen
Here are some key points about collagen. More detail is in the main article.
- Collagen occurs throughout the body, but especially in the skin, bones, and connective tissues.
- Some types of collagen fibrils, gram-for-gram, are stronger than steel.
- Collagen production declines with age and exposure to factors such as smoking and UV light.
- Collagen can be used in collagen dressings, to attract new skin cells to wound sites.
- Cosmetic lotions that claim to increase collagen levels are unlikely to do so, as collagen molecules are too large to be absorbed through the skin.
What is collagen?
Collagen has a sturdy structure. Gram-for-gram, some types are stronger than steel.
Collagen is a hard, insoluble, and fibrous protein that makes up one-third of the protein in the human body.
In most collagens, the molecules are packed together to form long, thin fibrils.
These act as supporting structures and anchor cells to each other. They give the skin strength and elasticity.
There are at least 16 different types of collagen, but 80 to 90 percent of them belong to types 1, 2, and 3. These different types have different structures and functions.
The collagens in the human body are strong and flexible.
Type 1 collagen fibrils are particularly capable of being stretched. Gram-for-gram, they are stronger than steel.
Roles: What does collagen do?
Collagen is secreted by various cells, but mainly by connective tissue cells.
It is found in the extracellular matrix. This is an intricate network of macromolecules that determines the physical properties of body tissues. A macromolecule is a molecule containing a large number of atoms.
With age, collagen weakens, leading to wrinkles and cartilage problems.
In the dermis, or the middle layer of skin, collagen helps form a fibrous network of cells called fibroblasts, upon which new cells can grow. It also plays a role in replacing and restoring dead skin cells.
Some collagens act as protective coverings for delicate organs in the body, such as the kidneys.
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.
Uses: Medical and cosmetic
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.
Collagen for medical use can originate from humans, cows, pigs, or sheep.
Collagen injections can improve the contours of the skin and fill out depressions.
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 can help heal:
- chronic wounds that do not respond to other treatment
- wounds that expel bodily fluids such as urine or sweat
- granulating wounds, on which different tissue grows
- necrotic or rotting wounds
- partial and full-thickness wounds
- second-degree burns
- sites of skin donation and skin grafts
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.
Guided tissue regeneration
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.
Treatment of osteoarthritis
Collagen supplements or formulations may help treat osteoarthritis.
A 2006 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.
Not all studies have supported these findings, however.
Collagen creams are unlikely to work, as collagen molecules are too large to pass through the skin.
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.
Preventing collagen loss
Laser therapy can help treat stretch marks, as it can stimulate the growth of collagen, elastin, and melanin.
A healthful diet can help the body produce collagen.
Nutrients that may support collagen formation include:
- Proline: In egg whites, meat, cheese, soy, and cabbage.
- Anthocyanidins: In blackberries, blueberries, cherries, and raspberries.
- Vitamin C: In oranges, strawberries, peppers, and broccoli.
- Copper: In shellfish, nuts, red meat, and some drinking water.
- Vitamin A: Occurring in animal-derived foods and in plant foods as beta-carotene.
What damages collagen?
Some factors can deplete the levels of collagen within the body. Avoiding them could keep the skin healthy for longer.
High sugar consumption: A high-sugar diet increases the rate of glycation, a process where blood sugars attach to proteins to form new molecules called advanced glycation end products (AGEs).
AGEs damage nearby proteins and can make collagen dry, brittle, and weak.
Smoking: Many chemicals present in tobacco smoke damage both collagen and elastin in the skin.
Nicotine also narrows the blood vessels in the outer layers of the skin. This compromises skin health by reducing the delivery of nutrients and oxygen to the skin.
Sunlight: Ultraviolet rays in sunlight cause collagen to break down more rapidly, damaging collagen fibers and causing abnormal elastin to build up.
The UV rays in sunlight damage the collagen in the dermis, and the skin rebuilds incorrectly, forming wrinkles.
Autoimmune disorders: Some autoimmune disorders cause antibodies to target collagen.
Genetic changes can affect the extracellular matrix. The collagen that is produced can be lower, or it may be dysfunctional, mutated collagen.
The aging process causes collagen levels to deplete naturally over time. There is no way to prevent this.
Avoiding tobacco and excess sun exposure and following a healthful dietary and exercise regime can help reduce visible aging and protect collagen, keeping the skin, bones, muscles, and joints healthy for longer.
Collagen structure deciphered
CAMBRIDGE, Mass.—For the first time, an MIT researcher’s atom-by-atom study of the deformation and fracture of collagen explains Nature’s design of its most abundant protein material. It is due to the basis of the collagen structure that leads to its high strength and ability to sustain large deformation, as relevant to its physiological role in tissues such as bone and muscle. This work, likely to have wide impact on biomedical and engineering applications, appears in the Aug. 15 issue of P. Natl. Acad. Sci. USA (M.J. Buehler, “Nature designs tough collagen: Explaining the nanostructure of collagen fibrils”). Experiment has shown that collagen isolated from different sources of tissues universally displays a design that consists of a staggered assembly of tropocollagen molecules with lengths of approximately 300 nanometers. The reason why strands of amino acids associate to form tropocollagen molecules consistently at this length has been an unexplained phenomenon.
“Our analysis provides – for the first time – a rationalization for the distinctive design features and characteristic length scales found in natural collagen, using a theory that start at the most fundamental, atomistic scale,” says Professor Buehler, Principal Investigator at the Atomistic Mechanics Modeling Laboratory at MIT. Buehler’s work represents a breakthrough in understanding how molecular and tissue properties are linked. The smallest building blocks of collagen, called tropocollagen molecules, are five to ten times stronger than steel, while sustaining enormous tensile strains of up to fifty percent before fracture occurs. In comparison, steel typically sustains only small strains of a few percent before it breaks. Buehler discovered that the characteristic design of collagen displays a clever strategy that enables Nature to take advantage of the nanoscale properties of individual molecules at larger scales, leading to a tough material. This is achieved by arranging tropocollagen molecules into a staggered assembly known as collagen fibrils. “The natural design represents a delicate balance between tensile forces within each tropocollagen molecule and shear forces between the molecules,” says Buehler.
He confirmed his theory using large-scale computer simulations that begin at the atomistic scale treating individual chemical interactions based on quantum mechanical calculations. Previous models of collagen typically involved empirical parameters and lacked a rigorous connection between quantum chemistry, molecular structure, material properties and collagen’s physiological function. Buehler’s model provides a first principles based materials representation. Collagen, an extracellular matrix protein, plays an important role in defining the infrastructure of physiologic tissues under load or strain, and is critical to tissues within the skeletal, muscular and cardiovascular networks. Improved understanding of Nature’s design criteria will help guide material and biomedical engineers to develop enhanced biomimetic polymers. Buehler’s work could contribute to research that may one day develop cures for collagen related diseases such as the Ehler-Danlos syndrome, joint hyperextensibility or Scurvy.
Original publication: Markus J. Buehler Nature designs tough collagen: Explaining the nanostructure of collagen fibrils P. Natl. Acad. Sci. USA, August 15, 2006 Further information: Markus J. Buehler Dept. of Civil and Environmental Engineering (CEE) Massachusetts Institute of Technology 77 Massachusetts Ave, Room 1-272, Cambridge, MA, 02139, USA Tel.: +1 617-452-2750 Mobile: +1 626-628-4087 Fax: +1 617- 258-6775 Email: mbuehler@MIT.EDU