Collagen

Collagens are a family of fibrillar proteins that dominate the extracellular matrix of most connective tissues in mammals. They are the basic proteins responsible for the structure and biochemical properties of connective tissue and in the case of skin, they constitute approximately 70% of its dry weight. These are natural polymers constituting 1/3 of the total mass of proteins in the human body, mainly performing building functions. They are characterised by a unique form that varies depending on their function and place of occurrence. Its presence, e.g., in bone tissue, provides elasticity and strength.

Collagens are a fibrous components of the skin, tendons, ligaments, cartilage, and blood vessel walls. They are also present in bones and teeth and internal organs such as the heart, lungs, and liver.

In terms of structure, collagens are among the most complex natural polymers. More than 20 amino acids may be involved in the construction of these protein molecules. Regardless of the type of collagen, the most abundant amino acids are proline, hydroxyproline, glycine, and hydroxylysine.

Collagen proteins perform various functions in the body. The most important of them are maintaining structural integrity, and being responsible for the processes of cell adhesion, differentiation, growth, survival, and regeneration. Collagen is found in various tissues of the body and its structure varies depending on its location and function.

The basic task of collagen is to connect cells, which is why it is a building block of most organs, especially skin, bones, teeth, cartilage, blood vessels, and the cornea of the eye. At the same time, it protects internal organs such as the kidneys, stomach, and liver, creating a flexible scaffolding around them. It also takes part in regenerative processes and ensures proper hydration of the skin thanks to its ability to bind water. In the immune system, it prevents the entry of pathogenic microorganisms and toxic substances. It ensures the continuity of cell renewal processes in the skin and maintains the appropriate level of hydration, which affects its elasticity, appearance, and condition. It accelerates wound healing, creates scars, and promotes the reconstruction of connective tissue. Collagen increases the absorption of minerals and increases bone density. It stimulates the activity of cartilage cells and supports protective processes within cartilage tissue, providing cartilage with the appropriate shape and resistance to stretching.

It is responsible for the production of synovial fluid and the condition of cartilage. Moreover, it reduces the activity of enzymes responsible for causing inflammation and rheumatic pain. Collagen fibers can also be carriers of some drugs, including Interferon. It provides essential amino acids that nourish hair bulbs and ensure their proper growth. Its proteins also play an important role in the functioning of the circulatory system because they are a component of blood vessel walls.

In a healthy, young body, collagen is regularly replaced—about 3 kg per year—and systematically rebuilt, and over time, the ability to regenerate Collagen fibers disappears. The level in the body begins to decrease from the age of 25, its sharp decline occurs after the age of 50, and after the age of 60, this protein ceases to be synthesized by the body. However, the reduction in endogenous collagen biosynthesis is not limited to adulthood. A decrease in its concentration in the body can also be observed in young people, which is genetically and hormonally determined. This process is also favoured by stress and other external factors, and the Collagen biosynthesis process is also disrupted during menopause.

Collagen constantly changes its structure as a result of external factors. Collagen structures are damaged by factors such as UV radiation, hormonal changes, mechanical loads, vascular changes, and inflammation. Among the factors that damage collagen proteins, we can also distinguish free radicals generated under the influence of stress, drinking alcohol or smoking cigarettes, and an incorrect diet rich in sugar causing glycation of collagen and low in, e.g., flavonoids, i.e., anti-inflammatory factors.

Extracting animal collagen is complex, expensive, and time consuming. ( he main one is beef, especially from cow bones and skin. Due to the occurrence of cow diseases that threaten human life, such as BSE (bovine spongiform encephalopathy), TSE (transmissible spongiform encephalopathies), FMD (fibromuscular dysplasia), and mad cow disease in particular, scientists are looking for an alternative, safer source of collagen) Due to concerns about the occurrence of defence reactions and the occurrence of diseases among land animals, marine sources began to be investigated. Marine Collagen has many advantages over that received from land animals: mainly, lack of diseases, environmental friendliness, better absorption due to lower body temperature (than terrestrial animals), greater absorption due to low molecular weight, minimal presence of biological contaminants and toxic substances (practically negligible), lower immunogenicity, and metabolic compatibility.

The use of collagen fillers is an increasingly developing method in minimally invasive aesthetic medicine and involves levelling the skin surface, i.e., “smoothing” wrinkles and places with, for example, atrophic scars. They are also used to shape lips or face contours. Fillers are substances that can fill soft tissue defects permanently or temporarily and are injected intradermally. We can distinguish synthetic and natural fillers, which are obtained from animal tissues (xenogeneic), human tissues (allogeneic), and our tissues (autogenic). Collagen fillers belong to the group of the oldest tissue fillers.

Oral preparations with collagen or its hydrolysates were mainly intended for people struggling with connective tissue diseases, mainly cartilage and joint changes. However, there are more and more dietary supplements with collagen appearing on the market, the effect of which is to improve the appearance of the skin and delay its aging. Such preparations with aesthetic indications have been popular for a long time, e.g., in Japan, where they constitute a significant category of nutraceuticals, while in Europe they appeared later. Hydrolysed Collagen works in the dermis in two ways: first, free amino acids provide the building blocks for the formation of collagen and elastin fibers, and second, collagen oligopeptides act as ligands—they bind to receptors on the fibroblast membrane and stimulate the production of new CLG, elastin, and hyaluronic acid.

Collagen found in cosmetics applied to the skin is not able to replenish its losses in the skin; its role is to retain and absorb water in the outer layer of the skin, i.e., the epidermis. It will also influence the appropriate level of skin hydration. Cosmetic preparations with natural collagen (native collagen, tropocollagen) penetrate the epidermis, where they actively bind water. They can also penetrate deeper layers—the dermis—combining there with other water-insoluble proteins, creating a hydrophilic layer on the skin surface, successively retaining moisture in the skin’s intercellular spaces. Collagen is a common ingredient in hydrogel forms, which include widely used beauty masks. Such products are supposed to restore skin elasticity, and have anti-aging properties. It can also be used as a thickening agent, but the high price of native Collagen limits this choice, and instead Gelatin, a denatured form of collagen, is used, which is a much cheaper alternative.

Collagen has been used in creams for decades, so it can be argued that it improves the structure of the skin. However, Collagen molecules are too large to penetrate the epidermal barrier when applied to the skin surface. Due to the poor penetration of Collagen, cosmetic products use partially hydrolyzed collagen, i.e., amino acids or peptides that would be able to penetrate the skin, but the properties of hydrolyzed CLG differ from those of native one.

One other example of a product with collagen is serum. It is a cosmetic preparation in concentrated form, contains higher doses of active substances, and is supposed to act stronger and faster than cream. It can be in the form of an emulsion, gel, milk, or oil and has very light consistency, which facilitates the penetration of active ingredients into the skin. Applying the cream over the serum will prevent it from evaporating.

There are also masks, which are preparations in the form of a cream or paste, the main role of which is to provide a high dose of nutritional and regenerative ingredients. They are applied to the cleansed skin of the face, neck, or cleavage and washed off with water or removed completely by removing the elastic layer. The most frequently used masks are regenerating and nourishing ones, e.g., algae masks, moisturising or lifting masks aimed at smoothing the skin, reducing wrinkles, and improving skin tension, thereby improving the face oval and minimizing signs of fatigue. Natural collagen hydrolysate is the main ingredient found in the formulas of Collagen masks, while Collagen flakes soaked in nourishing and moisturizing substances are used to improve the absorption of active substances on facial skin. Collagen masks are also used in anti-aging and moisturising treatments for people struggling with atopic dermatitis, where they appear as dry flakes made of freeze-dried ingredients applied to the skin, activated by soaking in individual active ingredients. They are supposed to have a lifting effect and retain moisture in the skin,

Often, partially hydrolysed Collagen is used, but its properties will differ from those of native Collagen. This protein, after application, remains on the skin surface, preventing water loss, making the skin better hydrated, and, consequently, improving its colour, brightness, and overall appearance. It also has a protective role against microorganisms in the case of injured skin. Thanks to this, it has been used in cosmetics for atopic skin. In order for collagen to be included in a cosmetic product, it must be properly extracted and purified. In order to break the strong crosslinks in its molecule, dilute acids and bases are used. Oral supplements used to improve the appearance of the skin and delay its aging process are becoming more and more popular. The site of their action is the dermis, where free amino acids provide building blocks for the synthesis of collagen and elastin fibers, while Collagen oligopeptides stimulate fibroblasts to produce new collagen, elastin, and hyaluronic acid. If we want to temporarily improve the appearance of the skin or reduce wrinkles, we should use collagen fillers that have the ability to fill soft tissue defects permanently or temporarily.

Numerous studies confirm the effects of Collagen preparations as a result of their use: the depth of wrinkles is reduced, the density and elasticity of the skin improves, trans-epidermal water loss (TEWL) is reduced, and when using oral supplements, it also provides hydration. CLG peptides also prevent damage to the extracellular matrix caused by metalloproteinases.

NOT MY OWN WORK. For more information and further (rather technical ) information, please see the full article:

Jadach B, Mielcarek Z, Osmałek T. Use of Collagen in Cosmetic Products. Current Issues in Molecular Biology. 2024; 46(3):2043-2070. https://doi.org/10.3390/cimb46030132

(Division of Industrial Pharmacy, Chair and Department of Pharmaceutical Technology, Faculty of Pharmacy, Poznan University of Medical Sciences, 3 Rokietnicka, 60-806 Poznan, Poland. Chair and Department of Pharmaceutical Technology, Faculty of Pharmacy, Poznan University of Medical Sciences. Rokietnicka, 60-806 Poznan, Poland)