September 16, 2008

Fibroblast Growth Factor Activity

Fibroblast growth factor (FGF) signaling is part of an extensive range of crucial organical activities with differential effects in several cell types. The activity of FGF is modulated by glycosaminoglycans, found both in the extracellular space 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.

With no control 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 conditions that affect people's quality of life, due to high treatment costs and frequent unsatisfactory results.

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

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

Keratinized Cells

During the natural process of scar removal keratinocytes are eliminated and restored continuously from the stratum corneum. The time of transit from the basal layer to the shedding stage is about four weeks, although this can be sped up 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 extends throughout adult life. In addition, stem cells are commonly considered to have the potential to originate differentiated progeny.

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

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

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

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

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