What is cellular stretching in the skin?
Cellular stretching is the mechanical deformation of cells when subjected to tension or stretching.
The skin is continually subjected to mechanical forces. Facial movements, body movements and natural tissue tension cause deformation to which cells must adapt.
In the dermis, fibroblasts are surrounded by an extracellular matrix composed, in particular, of collagen. They are connected to this matrix and can detect changes in its tension.
When a fibroblast is stretched, its shape and the organisation of its cytoskeleton can change. The activity of certain genes also changes. Research on human fibroblasts has shown that mechanical stretching influences their orientation, migration and various cell signalling pathways.
Cellular stretching is therefore not visible stretching of the skin: it is a cellular response to mechanical forces in the surrounding environment.
What is mechanotransduction?
Mechanotransduction is the mechanism through which a cell converts a mechanical force into a biological response.
A fibroblast does not only respond to hormones, growth factors or molecules in its environment. It can also detect tension exerted on the extracellular matrix surrounding it.
This mechanical information is transmitted inside the cell through various structures, including integrins and the cytoskeleton. It can then change the expression of certain genes and the functioning of the fibroblast.
Mechanotransduction therefore explains how a physical change in a fibroblast's environment can lead to a change in its activity.
What role do fibroblasts play in skin ageing?
Fibroblasts produce a substantial part of the dermal extracellular matrix, including collagen, which contributes to the strength and firmness of the skin.
With age and photoageing, the collagen network fragments and its organisation changes. Fibroblasts then have a different mechanical environment from that of young skin.
A fibroblast's shape and tension influence its function. When the dermal matrix loses some of its integrity, fibroblasts are less stretched and their interactions with collagen fibres change.
Dermal ageing therefore does not depend solely on a reduction in the amount of collagen. Mechanical relationships between fibroblasts and the extracellular matrix also contribute to skin function.
Does stretching fibroblasts stimulate collagen production?
Mechanical stretching can alter collagen production by fibroblasts, but the response depends on the type, intensity and duration of stimulation.
A systematic review with meta-analysis of in vitro studies on human dermal fibroblasts found an overall increase in collagen production in response to mechanical stimulation. However, results varied according to cell age and the characteristics of the stretching applied.
Not all experiments produce the same result. One study on human fibroblasts showed that cyclic stretching changed their migration and several mechanotransduction pathways without increasing collagen synthesis under the conditions studied.
Another study on skin regeneration observed that short-term mechanical stretching promoted the proliferation of certain fibroblasts and extracellular matrix synthesis, whereas prolonged stretching was associated with premature senescence of these cells.
It would therefore be incorrect to summarise this phenomenon as “stretching fibroblasts produces collagen”. The biological response depends on how the mechanical force is applied.
What is the link between cellular stretching and hyaluronic acid injections?
Some research suggests that hyaluronic acid injected into the dermis can exert mechanical tension on the extracellular matrix and restore tension in certain fibroblasts.
This mechanism has notably been studied in photoaged human skin. Following injection of cross-linked hyaluronic acid, researchers observed more stretched fibroblasts around the areas occupied by the product, together with increased collagen production.
The proposed hypothesis is mechanical: by occupying space in the dermis, hyaluronic acid stretches the surrounding collagen fibres. This tension is transmitted to the fibroblasts attached to them and can change their activity.
The authors also identified other mechanisms that may contribute to collagen production. It would therefore be excessive to attribute the entire biological effect of hyaluronic acid to cellular stretching alone.
Do hyaluronic acid injections prevent ageing through cellular stretching?
Cellular stretching is an interesting biological hypothesis for explaining certain dermal effects of hyaluronic acid, but it does not demonstrate that repeated injections prevent skin ageing.
Skin ageing involves many mechanisms: collagen fragmentation, changes in elastic fibres, a reduction in hyaluronic acid, slower cell renewal, oxidative stress and the cumulative effects of ultraviolet radiation.
Mechanical stimulation of a fibroblast cannot prevent all these processes.
Hyaluronic acid injections must therefore retain a specific indication. Skinboosters are mainly used to improve skin hydration and quality. More structural hyaluronic acids are used when a loss of support or volume needs correcting.
Injecting hyaluronic acid solely to “stretch fibroblasts” is not a validated strategy for preventing ageing.
Can facial massage cause anti-ageing cellular stretching?
Facial massage has not been shown to stretch fibroblasts in a way that could slow skin ageing.
Massage does exert mechanical forces on the skin. It can temporarily change local circulation, mobilise tissues and provide a feeling of decongestion or relaxation.
The nature, direction, intensity, duration and frequency of the force influence the cellular response. Experimental studies also show that different mechanical stimuli can produce different biological responses.
The effects of facial massage therefore cannot be equated with cellular stretching studied experimentally in the laboratory.
Can facial exercises stimulate fibroblasts naturally?
There is no robust evidence showing that facial exercises prevent skin ageing by stimulating fibroblasts through cellular stretching.
Facial expressions do indeed exert repeated mechanical stress on the skin. However, they are not considered a method of stimulating collagen synthesis.
On the contrary, repeated contractions of the forehead, glabellar or eye-area muscles gradually contribute to expression lines as the skin loses elasticity.
Is cellular stretching an anti-ageing treatment?
No. Cellular stretching is a biological mechanism studied in mechanobiology; it is not an aesthetic medicine treatment.
Its main value is to improve understanding of how fibroblasts respond to their mechanical environment and how certain interventions can change that environment.
This research shows that dermal cells do not function independently of the structure surrounding them. Extracellular matrix tension can influence their shape, signalling pathways and activity.
However, it does not establish that a technique called “cellular stretching” should be performed to prevent ageing.
The role of cellular stretching in preventing skin ageing
Cellular stretching mainly helps explain certain mechanisms of dermal remodelling; its effectiveness as a standalone anti-ageing strategy has not been demonstrated.
Experimental data show that fibroblasts respond to mechanical forces and that this response can change the production and organisation of the extracellular matrix. Observations following hyaluronic acid injection also suggest that restoring mechanical tension in fibroblasts in photoaged skin may contribute to new collagen production.
These findings are useful for understanding the biology of certain treatments.
Cellular stretching should therefore be considered a biological mechanism that may contribute to the effects of certain treatments, rather than a method of preventing skin ageing.
Article written by Dr Valeria Romano
Dr Valeria Romano supports each patient through a comprehensive approach to facial, body and intimate aesthetics, as well as skin and hair quality. Every treatment is based on a personalised medical assessment.
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