Hardware mechanotherapy in aesthetic medicine: effects of mechanical stress in the skin and prospects for their use in modern times

Abstract

Mechanotherapy is а traditional therapeutic method, better known by the term "massage". The development of science has led to rethinking the role of the skin in the massage process and also contributed to the creation of high-tech mechanotherapy devices. The article considers the biological effects of mechanical stress in the skin and the prospects for their use in aesthetic medicine.

Keywords: mechanotherapy, massage, PIEZO channel, Beautylizer

The development of hardware physiotherapy and cosmetology has led to а new round of popularity of mechanotherapy. Broadly defined, this word means the treatment or health improvement by mechanical stress in the skin – pressure, tapping, vibration, rubbing or stroking. Such methods of treatment, better known under the general name “massage”, are an important part of the traditional medical art of all peoples of the world. In the 20th century, the massage
reached completely new heights due to development of the medical equipment:

• using the devices, it became possible to control the force and time of exposure;
• it became possible to simultaneously expose with several factors, not only mechanical, but also physical, primarily, light and temperature;
• high-precision methods for biological research have appeared allowing studying the effects of mechanical stress at the cellular level.

The study results have led to rethinking the role of the skin in the massage process: the skin is not а passive signal conductor to а diseased organ or tissue. It reacts actively and can even change structurally.

Nowadays, massage procedures are an important part of cosmetic care aimed at improving the skin condition.

In order not to make а mistake in choosing а procedure, you need to clearly imagine the entire sequence of events in the skin – from the reaction of individual cells to exposure to а visible result which is based on structural changes in the skin tissue.

How does the skin react to mechanical stress?

То designate methods of non-invasive mechanotherapy, the general term “massage” is used. It covers different types of exposure on the skin – vibration, negative or positive pressure, kneading of folds which can be done pointwise or in а moving mode, manually, as well as using some tools. But all these types of exposure somehow deform the skin – the bulk structure of the skin is distorted, not only the extracellular space, but also the cells themselves.

Cytoskeleton and extracellular matrix as а point of application of mechanotherapy.

Every living cell has an internal framework of protein microtubules, the cytoskeleton (Figure 1) [1, 2]. The cytoskeleton maintains the cell shape in the resting state and is essential for movement. Distortion of the external space leads to deformation of the cytoskeleton, which triggers а variety of biochemical processes in the cell allowing it to adapt to the external environment. For example, fibroblast. This is the main cell of the dermis layer of the skin, it produces all the necessary structural elements of the dermal matrix:

• hyaluronic acid and polysaccharides – retain water and form an aqueous gel (hydrogel) into which cells and scaffold collagen-elastin fi bers are immersed (Figure 2) [3]; hydrogel is responsible for turgor and skin elasticity;
• collagen and elastin – form а three-dimensional framework that provides strength and elasticity.

FIGURE 1. Fibroblast cytoskeleton (fluorescence micrograph): microtubules (green lines), intermediate fi laments {red lines) [1]

FIGURE 2. Extracellular matrix in healthy skin [3]. А – Schematic diagram of skin layers; the area of the basement membrane (the ВМ) connecting the epidermis to the dermis is highlighted. В – the dominant structural component of the ВМ is collagen type IV, which builds а meshwork with intersperced glycoproteins laminin and fibronectin. Тogether they build the basis Jor keratinocyte attachment via integrins. Collagen type VII reaches into the papillary dermis and stabilizes the dermal-epidermal junction. С – in the dermis collagen type 1 and fibronectin build а fibrillary structure that allows cell adhesion and migration through the matrix. Shown is а fibroblast attaching to collagen and fibronectin via integrins. GAG – glycosaminoglycans; HSPG – heparan sulfate proteoglycan

The hyaluronic acid pool in the dermis layer is renewed within а few days. But collagen and especially elastin are renewed extremely rarely. The time of biological half-renewal of collagen in the skin is considered to be approximately 15 years, and, according to some data, elastin can remain in the skin for almost а lifetime. At the same time, both collagen and elastin can be chemically modified – oxidized, attach sugar groups (this process is called glycation). Glycated proteins are more rigid and less elastic (Figure 3) [4]. As they accumulate, the skin can resist gravity worse, overstretches and sags -gravitational ptosis is developing.

All these external changes are an aesthetic problem for us, but from the point of view of the fibroblast, everything is fine, because the fibers are intact, so there is no need to change them for new ones. Another thing is when the fibers are broken as а result of injury. That’s when the enzymes turn on, which begin to cut the scraps of fibers into even smaller pieces. Some of these pieces (they are called matrikines) bind to special receptors on fibroblasts – and the cell understands that it is urgent to synthesize new structural fibers to replace the broken ones. This is how, through damage to the dermal matrix, remodelling methods of cosmetology work.

But it turned out that fibroblast reacts not only to matrikines, but also to long-term deformation of the matrix. ln order for the skin tissue to resist stretching more effectively, fibroblasts strengthen it by synthesizing new framework collagen-elastin fibers. In this way, they adapt the skin to additional stress.

FIGURE 3. Changes in the collagen fibril arrangement and organization during non-enzymatic glycation: results of collagen gel incubation with ribose (0, 50, 100, 150, 200, and 250 mМ) [4]

PIEZO channels are the key levers of the mechanotherapy.

However, not only the cytoskeleton, but also the outer shell of the cell, the cell membrane, can participate in the perception of а mechanical signal by а cell. The basis of the cell membrane is the lipid bllayer. This is the thinnest flexible film: it bends under the exposure of an external mechanical force, its lateral tension changes. Although this change is not very strong, it maybe enough to change the shape of proteins that are associated with the membrane. For the vast majority of membrane proteins, this is not critical and will not affect the work in any way. But some cells have special proteins that are highly sensitive to membrane deformation.

These proteins which form end-to-end channels for ions were discovered in 2010 by the American scientist Ardem Patapoutian. They were called PIEZO – from the Greek for “press, compression’’. In 2021, Dr. Patapoutian was awarded the Nobel Prize in Physiology and Medicine for the discovery of PIEZO channels. Normally, PIEZO channels are in а closed state; therefore they are also called channels with mechanical opening or channels with stretching. If, under the exposure of an external force, the membrane adjacent to such а protein is stretched, then the protein itself is deformed after it, and the channel opens [5]. Such channels are found on all mechanoreceptors, the endings of sensory (afferent) nerve fibers that respond to various mechanical stimuli, such as touch, pressure, and stretch (Figure 4) [6].

FIGURE 4. Mechanoreceptors in skin [5]. А – In glabrous skin, innocuous touch is mediated by four types of mechanoreceptors: Merkel cells, Ruffini endings, Meissner and Pacinian’s corpuscles; В – in hairy skin – by Аβ-, Аσ- or С low threshold mechanoreceptors (LTMR)

The operation algorithm of PIEZO channels can be represented as follows.

1. When the membrane is mechanically deformed, the channel opens, and charged ions – Са2+, Na+ – begin to enter the cell through it.
2. On the inner side of the membrane, where negative ions are concentrated in the resting state, more positive ions appear, and «–» changes to «+». In the resting state, it is the opposite – minus on the inside of the membrane, plus on the outside. Thus, when а channel is opened that allows positive ions to enter the cell, а short-term change of poles occurs, i.e., membrane depolarization [7].
3. The area of depolarization serves as а kind of epicenter а wave of depolarization (or, as it is called, а nerve impulse) begins to spread from (Figure 5). The impulse goes strictly in one direction: in the case of а sensitive neuron, from the mechanoreceptor along the axon. At some point, а wave of excitation reaches а neighboring nerve cell and passes the baton to it.
4. The nerve impulse reaches the brain [5]. Here, the received information is processed, and а decision is made how to respond to it.
5. Responses also trigger nerve cells, but others are motor (efferent). They receive а command from the central nervous system; in response, they emit various substances that are signals for other skin cells – immunocytes, endotheliocytes, keratinocytes, fibroblasts, adipocytes. Each cell type will respond to а different signal according to its nature.

Indeed, this is а very general and simplified scheme of how external mechanical forces can cause а change in the skin structure. The keyword here is deformation.

• Deformation of the extracellular matrix leads to deformation of the cytoskeleton, and this triggers biochemical processes in the cell. The most striking example is the fibroblast. It directly feels
  the deformation.
• Deformation of the cell membrane opens PIEZO channels in tactile receptors; they are excited and transmit а signal through sensory nerve fibers to the central nervous system. And from there, in the opposite direction, the command descends to the skin cells in the form of chemical signal substances which are released at the endings of the motor nerve fibers. This is mediated sensitivity.

But one way or another, directly or indirectly, all skin cells become participants in the response to mechanical exposure and contribute to its structural restructuring. But what it will be depends on the parameters of the mechanical stress, such as force, duration, direction (perpendicular to the skin or along the surface).

FIGURE 5. Scheme of functioning of PIEZO channels [6]

Application of massage in cosmetology

In cosmetology, almost all massage options have been used, but some methods have proven to be the most suitable for solving such aesthetic problems as а decrease in tone, skin laxity and local fat deposits.

Note that manual massage for solving these problems is ineffective. But procedures using modern devices that affect the skin simultaneously with several factors and in controlled modes give а good clinical result. What are these factors and how do they affect the skin?

Vibration

First of all, it is а vibration with а frequency of 20 to 200 cycles per second with different amplitude (that is, force) and direction. It is unrealistic to maintain the desired vibration mode with your hands for а given time, but the device can do this.

Strong shaking creates flows of tissue fluid in the extracellular space. On the one hand, it improves the supply of the substances required to the cells. On the other hand, it facilitates the withdrawal of metabolic products. Such assistance is especially essential in case of impaired microcirculation and skin congestion. In particular, this is observed in case of cellulite, when enlarged fat lobules compress the blооd vessels and lymphatic ducts of the skin.

But vibrotherapy works not only as а mechanical shaker of the extracellular fluid. Vibration is felt by living skin cells, because it deforms the skin tissue (Figure 6) [8]. ln the area of vibration, blood vessels and capillaries dilate and blood flow increases. As а result, nutrition and oxygen for cells comes. The lymphatic ducts also dilate and metabolic products begin to be removed through them.

FIGURE 6. Effects of the vibration exposure оn the culture of human fibroblasts [8]. А – control intact fibroblasts; В – fibroblasts following exposure to vibration; there is аn increase in the number of actin fibers, especially near the cytoplasmic тетbrаnе, which indicates reorganization of the fibroblast cytoskeleton. Remodelling of the fibroblast cytoskeleton sequentially mediates the process of cell proliferation and differentiation, which promotes tissue regeneration [8]

Such а plan of exposure on the skin is especially effective in case of cellulite, when stagnation progresses in the skin tissue, there is swelling due to compression of capillaries and lymphatic ducts of the skin by fatty lobules (Figure 7) [9].

The condition of other skin layers on the background of the course of vibrotherapy will also improve. But still, especially striking changes for the better will be precisely in the subcutaneous fat, where the fat lobules are located.

FIGURE 7. Тhermograms of the lateral part of the thigh of а patient with cellulite before the jirst vibration treatment (А), 10 minutes after its completion (В), before the beginning of the 20th session (С) and 10 minutes after (D) [9]

Stretching by compression and decompression

То solve the problems of the dermal matrix, the methods stretching the skin are the most suitable. As we wrote above, fibroblasts that are in the stretch area for а long time – months, react to this exposure by producing collagen to strengthen the skin tissue. This is their adaptive response to an external force.

Skin stretching is а result of vacuum application, when а tubercle of skin tissue is formed by means of negative pressure. This method is called vacuum decompression.

The pressure vector (compression) is directed in the opposite direction – the skin deepens. Or you can form а skin fold by squeezing it from the sides.

Both the one and the other, as well as the third deformation options are used during the massage, but not for the purpose of skin remodeling. The reason is clear: such an exposure, neither manual nor hardware, cannot last for months. But the combination of mechanical methods with each other helps to overcome this natural obstacle.

The first mechanotherapeutic devices that made it possible to achieve real results appeared in the early 1990s.

They combined vacuum and tensile exposure. Another option is to combine vacuum decompression with vibration. Despite significant clinical effects, the use of vacuum exposure is limited in some cases.

Special contraindications to the use of vacuum massage:

• fragility of blood vessels;
• varicose veins, circulatory disorders;
• tendency to form hematomas;
• increased pain sensitivity.

Another combined mechanotherapy option is deprived of these limitations. Vibration is combined there not with vacuum decompression, but with compression, that is, pressure on the skin.

Beautylizer: а new generation of skin mechanotherapy

We can see а beautiful technical solution in the Beautylizer device. It was developed in Russia, but is already known in other countries. The Beautylizer maniple is made in the shape of an elongated cylinder with 72 silicone spheres inside. They are of the same size and are grouped in 12 longitudinal rows of 6 spheres each. The spheres on adjacent rows are staggered, which increases the coverage area to 140 cm2. This allows treating the entire body in an hour without any loss of еffciency. Spheres of one row are put on а common axis and freely rotate around it. As а result, the maniple glides easily over the skin is already known in other countries. The Beautylizer maniple is made in the shape of an elongated cylinder with 72 silicone spheres inside. They are of the same size and are grouped in 12 longitudinal rows of 6 spheres each. The spheres on adjacent rows are staggered, which increases the coverage area to 140 cm2. This allows treating the entire body in an hour without any loss of efficiency. Spheres of one row are put on а common axis and freely rotate around it. As а result, the maniple glides easily over the skin.

The device provides three types of exposure on tissues.

1. Vibration. The vibration from the cylinder is transmitted to each sphere, which in turn transmits it to the skin during contact.
2. Compression. Firstly, the pressure is exerted by the maniple itself, which is quite heavy (2,350 g). The total weight of the maniple is distributed to the points of contact with the skin – that is, to those spheres that are currently in contact with the skin. It is under them that point compression occurs. Secondly, the pressure can be increased if necessary by simply pressing the maniple from above. The degree of load is shown on the digital display of the device, so that the specialist can adjust it depending on the area and depth of the skin tissue.
3. Red light (650–660 nm). The low-intensity red light is considered to normalize the work of immunocytes, which may be essential in the case of reactive skin with hypersensitivity, and also to stimulate the synthesis of new collagen fibers.The vibrocompression procedure in combination with phototherapy with the Beautylizer device is called RSL-sculpting (Rotation, Spheres, Light). Indications for the RSL sculpting procedure.

When is this procedure recommended? There are several medical areas.

Cosmetology and aesthetic medicine:‍

• excess fat deposits at stages 1 to 2 (Figure 8);
• gynoid lipodystrophy (cellulite at any stage) (Figures 9 and 10);
• sagging and reduced turgor;
• swelling and congestion;
• preparation for plastic surgery and rehabilitation after it.

Sports medicine:‍

• accumulation of lactic acid in the muscles (“ clogged” muscles);
• muscle spasms;
• improvement of blood circulation in muscles and preparation for competitions.

Health medicine:‍

• restorative massage;
• “tired legs” symptom.

Contraindications for the RSL sculpting procedure. As any therapeutic procedure, RSL sculpting also has contraindications:

• oncology with remission up to 5 years;
• pregnancy;
• acute infectious, viral diseases;
• chronic diseases at the acute stage;
• hyperthermia;
• haemophilia;
• epilepsy;
• hepatic, renal, cardiac or respiratory failure in the stage of decompensation;
• dermatological pathologies (extensive localization).

In fact, general contraindications for the massage are meant; this technology has no specific restrictions.

FIGURE 8. Patient, age: 38 years old, fat roll оn the back, stored fat оn the abdomen: А – initial state, В – after 5 RSL sculpting treatment sessions

FIGURE 9. Patient, age: 52 years old, severe cellulite: A – initial state, В – after 15 RSL sculpting treatment sessions taken 2–3 times а week

FIGURE 10. Patient, age: 32 years old, cellulite at stage 3, stretch marks: А – initial state, В – after 10 RSL sculpting treatment sessions taken 2–3 times а week