Fibroblast growth factor (FGF) signaling is involved in a wide range of crucial organical activities with differential actions in several cell types. The activity of FGF is modulated by glycosaminoglycans, found both in the extracellular matrix and on the cell surface.

These molecules are crucial in wound healing. Such a dynamic process is interactive and depends on the proper regulation of fibroblasts.

Without regulation of these processes, excessive scar tissue develops. Because of impaired healing, keloids and hypertrophic scars often become a problem. These are both serious health problems that affect people's quality of life, due to high treatment costs and often poor results.

A Fibroblast is a kind of cell that promotes the production of keratinocytes and the synthesis of collagens, and glycoproteins found in the extracellular matrix. The production of fibroblasts improves the epidermal morphology.

Keratinocytes originate in the basal layer from the mitosis of keratinocyte stem cells. They are pushed up through the cells of the epidermis, experiencing gradual differentiation until they join the stratum corneum where they form a layer of enucleated, flattened, highly keratinized cells called squamous cells. This layer forms an efficient barrier to the entry of foreign matter and infectious agents in the body and reduces moisture loss.

Stem Cells and Skin Health

Typically occurring during the process of scar removal keratinocytes are shed and replaced continuously from the stratum corneum. The time of transit from the basal layer to the elimination stage is about one month, although this can be accelerated in conditions of keratinocyte hyperproliferation, like psoriasis.

We can define a stem cell in an adult organism as any cell with a high capability for self-renewal that remains throughout adult life. In addition, stem cells are commonly considered to possess the potential to produce differentiated progeny.

According to these criteria, the skin has long been recognized as having a resident stem cell stock. The tissue consists of a layered squamous epithelium (interfollicular epidermis; IFE) with associated capillary follicles and glandular structures (the sebaceous glands and sweat glands).

The IFE supports continuous renovation and there is a never failing need to replace the devitalized, terminally differentiated cells of the external cornified layers through the production of cells in the basal layer.

It is now well accepted that stem cells within the epidermis are multipotent and capable of producing daughter cells that specialize along several lineages. Stem cells inside the hair follicle bulge can create progeny that differentiate not only in all the capillary follicle lineages, but also in sebocytes and the interfollicular epidermis.

Following exposure to adequate mesenchymal signals, cells of the interfollicular epidermis are able of originating hair or sebaceous lineages. There is, however, evidence for the existence of distinct stem cell populations within the IFE and sebaceous gland. These findings can be reconciled by afirming that there are separate stem cell populations within the hair, sebaceous gland and IFE.

Each of these has the capacity to generate daughters that differentiate along any of the skin lineages. Under steady conditions, however, the stem cells usually give rise to a more restricted repertoire in reaction to signals from the local microenvironment.