In the event of a skin lesion, an entire repair system is implemented, with multiple signals and cascades, which
act to fill in the lesion through a cellular migration and the synthesis of components of the dermal extracellular
matrix.
When the skin is damaged, a temporary matrix (made of fibrin) provisionally covers the lesion and then works
as a support for the migration of different cell types (inflammatory, dermal and epidermal cells). This migration
phase of cells towards a matrix which temporarily covers the lesion is one of the key stages in the process of
repair and reconstruction of the skin.
Fibroblasts and keratinocytes, activated by various mediators (including cytokins and growth factors) migrate
from the edges of the lesion to colonise the temporary matrix and proliferate. To migrate, fibroblasts acquire a
myofibroblast contractile phenotype which is characterised in particular by the presence of bundles of
microfilaments or stress fibres. Having acquired this contractile power, these fibroblasts actively participate in
tissue repair by bringing the edges of the lesion together to ensure it closes up.
At the same time, keratinocytes migrate towards the temporary matrix. When the lesion is covered by a single
layer of keratinocytes, they stop their migration, multiply and then differentiate themselves to form a newly
stratified epidermis. Finally, due to the action of various proteases, the matrix begins to be remodelled, causing
the structural, functional and aesthetic qualities of the newly formed tissue to be recuperated.
The dermal temporary matrix is then gradually replaced by a definitive matrix produced by fibroblasts.
Matrikines have an important role in this reconstruction: they are fragments of peptides produced by the
proteolysis of the matrix during the cleansing of the wound before healing. They work as messengers that
regulate the steps needed for proper healing.
Growth factors
“Growth factors” are proteins present in the body that represent an essential element for the growth of cells
and their regeneration, by acting as messengers.
They are secreted in the extracellular environment and are able to transmit instructions for growth, cellular
multiplication and regeneration to the cells, whatever the affected tissue. They work locally, near to the tissue,
where they are secreted.
The discovery of growth factors was the subject of a 1986 Nobel Prize for Medicine and Physiology, awarded to
Rita Levi-Montalcini and Stanley Cohen.
How it works:
In terms of the way it works, the growth factor, which is also called the “first messenger”, binds with a
chemical molecule that is its specific receptor, often located in the external membrane of the cells. The role of
these receptors is to transmit and amplify the signals received externally.
This binding of growth factors to the receptors causes them to be activated and triggers the production of
another chemical molecule called the “second messenger”.
This process in turn triggers a series of chemical reactions which culminate in the synthesis of a so-called
regulator protein, meaning it has the ability to accelerate or slow down certain phenomena.
At the end of this cascade of reactions, this protein binds to the genes involved in the division and
differentiation of cells, thereby altering their degree of activity.
When the body suffers a lesion, the growth factors therefore have the ability to act (by promoting or limiting
it depending on the case) on the synthesis of new tissue as well as its growth and repair. Growth factors
contribute to skin regeneration. More precisely, they communicate directly with the cells and act on the
production of new cells and therefore new tissue. The growth of these cells, their distribution and,
consequently, the repair of damaged tissue are therefore all regulated by growth factors.
There are more than thirty, some of which are still wrongly characterised.
The EGF family, the family of growth factors involved in the normal development of the skin, heart, lungs,
nervous system and breasts, is the best known and the most widely studied:
- EGF or Epidermal Growth Factor.
- TGF or Transforming growth factor alpha.
- But also:
- TGF: Transforming growth factor beta.
- This is one of the most important mediators involved in the skin repair system of the TGF super-family. This
- includes a certain number of sub-families including TGF-, to which activins and TGF-1s belong.
- FGF: Fibroblast growth factor.
- Insulin family: IGF-1, IGF-2
- PDGF family (Platelet derived growth factor):
- PDGF1 and 2
- VEGF: Vascular endothelial growth factor.
This is a key factor in the regulation of neovascularisation. It is a protein that promotes the growth of
new blood vessels.
HGF: Hepatocyte growth factor
This is a mitogenic factor (it promotes cell division) of keratinocytes, also produced in the skin fibroblasts. It
stimulates the proliferation of keratinocytes.
Dermo-aesthetic procedures and techniques and even aesthetic surgery can partially weaken the skin and in
order for the skin to be in good condition, it is important to use cosmetic products that act especially on growth
factors. This approach helps to quickly restore the skin’s intrinsic qualities of comfort and suppleness.