The skin is the most visible organ, yet the least understood, with a magnificent array of chemical reactions taking place within it on a molecular and cellular level. Addressing skin biochemistry is key in combatting the effects of ageing.
The skin never lies – literally – as sensory, nerve, temperature, blood flow, perspiration and pore dilation activities are assessed during lie detection tests. With this in mind, it’s apparent that we have to understand who we are and what our cells are made of, as we recognise ourselves by our skin. Human skin is a complex living material but reveals its homogeneous nature in biomechanical tests. Our environment can directly influence who we are and the skin reacts immediately and directly to the outside environment. The skin and subcutaneous tissue provide a protective covering of the body, capable of stretching and contracting. Skin thickness measurements are used to evaluate skin characteristics, and biomechanical skin parameters change with time. The process of ageing is the reason why the skin becomes thinner, stiffer, less tense and less flexible.
Flexibility and reactivity
Human skin can be stretched to several times its original size and still maintain its original phenotypic properties. Such impressive expansion is possible because the skin is a highly specialised mechanical structure, responding through a network of interconnected cascades of chemical reactions, with the participation of extracellular, cytoplasmic and nuclear membranes. When the skin is stretched above its physiological limit, a series of reactions activating ion channels, integrins, growth factor receptors and G-receptors conjugated with protein reactions takes place. These reactions aim to restore the homeostatic balance. The skin also comprises a network of immune cells and antimicrobial peptides that increase in response to microbial invasion. In order to achieve cellular longevity and amplified cellular energy, cell metabolic activity should function at an optimal state. The main source of cellular energy is the mitochondrion. A skin cell, such as a fibroblast or a keratinocyte, can typically contain anything between 100 to 2 000 mitochondria that produce the molecule adenosine triphosphate, which provides energy for a cell during mitotic activity and enhances cell turnover time. Mechanical activation of the skin initiates the signalling pathways, which in turn activate the transcription of factors stimulating gene expression, causing a cascade of events that result in increased mitotic activity and collagen synthesis. Changes in the skin tissue that occur during dermatological and surgical treatments initiate these paths, also increasing mitotic activity and the synthesis of collagen. However, if external stimuli such as mechanical stress reach sufficiently large values, they may cause irreversible deformation and damage to the skin.
Incorrect pH imbalances ionic activity to the skin, which may inherently degrade or destabilise proteins.
The right biochemical and dermatological interventions
Biomechanical tests of the human skin help to quantify the effectiveness of dermatological products, detect skin diseases, and help to schedule and plan surgical and dermatological interventions and treatments. One person’s skin metabolic profile differs from another according to social and environmental pressures, and the biomechanical parameters of the skin alter over the course of one’s life. During the ageing process, the skin becomes thinner, stiffer, less tense and less flexible, and protective functions against mechanical injuries decrease. Due to the complex importance of cell kinetics, the active ingredients of topical products should therefore comprise specific pharmacokinetic properties that assist against mechanical injury. Particular compounds and molecules need to be applied to the demanding skin in order to assist and supplement a homeostatic balance at all times, even when the skin is exposed to social and environmental stressors. A product with measurable quality, safety and efficacy standards should be considered. The overall architectural building blocks of the skin – such as macromolecule kinetic pathways, cell permeability and cell polarity – should be assessed carefully when products are applied topically. Applying products with stereo chemical properties of the active and inactive ingredients to the skin is explicitly important. This means that the chemical characteristics of a compound, for instance vitamin C (ascorbic acid), should be thoroughly understood in order to ensure that a therapeutic and biological benefit is obtained on a cellular level. Molecular weight is important, as the compound applied topically should be dramatically smaller than the target skin cell macromolecule it needs to bind with, in order to stimulate a biological response. There are various derivatives and compound by-products available on the market that ultimately only apply more metabolic strain on a skin cell. Products should stimulate ample membrane ion channelling in order to activate and increase transient ATP production and not arouse an inflammatory response. It has been found that mitochondria from skin cells cannot be isolated thoroughly with solutions at neutral or alkaline pH levels, which highlights the importance of an acidic milieu in the skin. Incorrect pH provides an imbalanced ionic activity to the skin, which may inherently degrade or destabilise proteins. A product with the correct pH should thus contribute or absorb hydrogen atoms to or from the skin, rather than reacting with extracellular proteins. Ionic activity enables optimal transdermal absorption and therapeutic protein binding both inside and outside the cell, indicating the important role pH plays in skin chemistry. The “conductivity” and “polarity” of product ingredients promotes product absorption by means of ion channelling, hydrophobic and hydrophilic properties, isotonic, hypertonic and hypotonic activity. The aforementioned are all considerations for an ageing or injured skin that requires specific topical exposure or dermatological intervention to accommodate the biochemical changes of skin over time.