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What is Collagen?

27/02/19
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You have probably heard that collagen is a very important and abundant material in the body. But have you ever wondered exactly what it is?

In this article, we take a look at what collagen is and how it is structured, the different types that exist and also touch on how it is used in research.

The nature and structure of collagen

Collagen is a protein present in the areas around and between many of the cells in the body, known as extracellular space. It makes up about 25-35% of the total protein content in most mammals and is the main structural protein in human fibrous connective tissues such as tendons, skin and ligaments.

Collagen plays a number of roles in the body including :

  • giving tissues structure
  • enabling cell adhesion and migration
  • helping to facilitate repairs.

It also filters certain molecules in organs, such as in the kidney for example. Outside of bodily functions, collagen also has various uses in medicine and research.

Collagen is formed of amino acids; basic organic compounds made up primarily of Carbon, Oxygen, Hydrogen and Nitrogen, which are the constituent parts of most proteins. The amino acids are arranged in triple helical chains as shown below, which differ in length and size depending on the type of collagen.

collagen triple helical structure

Collagen triple helical structure (Image source: https://commons.wikimedia.org/wiki/File:Collagen_triple-helical_structure.png).

The different types of collagen

Not every protein with a triple helical structure is classified as a collagen, only those that play an important role in some aspect of tissue assembly or maintenance.

At the time of writing, 28 different types of collagen have been classified. The most common are those present in vertebrate tissues and are denoted with Roman numerals.

The five most prolific are:

  • Type I – present in tendons, skin, various organs and the primary organic component of bone.
  • Type II – the main component of cartilage, playing a key role in joints and other connective tissues.
  • Type III – the main component of reticular fibres; connective tissues that form a mesh-like scaffolding for other cells in several organs such as bone marrow or lymph nodes. Type III collagen is often found alongside type I.
  • Type IV – this type of collagen forms the basal lamina, a layer of extra-cellular matrix that is secreted by the tissue epithelium. Type IV collagen helps affix other cells to the epithelium and control absorption in a number of organs and structures in the body including blood vessels and skin.
  • Type V – as 90% of human collagen Type V is very common material and is the main connective tissue in the body. It also forms a variety of cell surfaces, makes up hair cells, and is a major constituent of placenta.

All 28 types of collagen are found in different amounts across the animal kingdom. Mammals have collagen in many areas of the body and marine animals also contain collagen that gives body parts shape, structure and basic functions.

Collagen doesn’t occur naturally in plants, but it can be created from plant-derived cells through genetic engineering.

The major uses of collagen

As collagen is stable, biocompatible and usually absorbed by living tissue more easily than artificial alternatives, it is used in a number of different settings in research and healthcare, for example:

Medicine – to help heal severe wounds, burns and non-healing ulcers, as well as in some cosmetic procedures.

Dentistry – as an agent for root conditioning, haemostatic processes and wound dressing, as well as forming part of guided tissue regeneration (GTR) membranes.

Supplements – some people take collagen as commercial dietary supplements that claim to have a variety of health effects.

Research – among other uses, collagen is the primary material used in cell culture – a vitally important process in many aspects of medicine, drug discovery, biological testing and more.

As you can see, this versatile material has important biological properties that not only make it useful for healing today, but also able to help researchers uncover the treatments of tomorrow.

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