Fibroblast growth factor (FGF) signaling is part of a wide range of crucial organical activities with differential effects in various 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 injury healing. Such a dynamic process is interactive and depends on the proper regulation of fibroblasts.

With no regulation of these processes, excessive scar tissue develops. As a result of inefficient healing, keloids and hypertrophic scars often become a problem. These are both difficult health problems that alter people's quality of life, due to high treatment costs and often poor results.

A Fibroblast is a kind of cell that stimulates the proliferation of keratinocytes and the creation of reticular and elastic fibers, and glycoproteins found in the extracellular matrix. The proliferation of fibroblasts improves the epidermal morphology.

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

The Healing Process and Keratinized Cells

During the natural process of scar removal keratinocytes are eliminated and replaced continuously from the stratum corneum. The time of transit from the basal layer to the shedding stage is approximately four weeks, although this can be accelerated in conditions of keratinocyte hyperproliferation, such as psoriasis.

We can define a stem cell in an adult organism as any cell with a high capacity 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 characteristics, the epidermis has long been recognized as having a resident stem cell population. The tissue consists of a stratified 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 dead, ultimately differentiated cells of the external cornified layers through the proliferation of cells in the basal layer.

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

Following exposure to appropriate mesenchymal signals, cells of the interfollicular epidermis are capable of originating hair or sebaceous lineages. There is, however, evidence for the presence of distinct stem cell populations within the IFE and sebaceous gland. These findings can be reconciled by afirming that there are different 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 response to signals from the local microenvironment.