Articles

Fibroblast growth factor (FGF) signaling is part of an extensive range of important organical activities with differential actions in various cell types. The activity of FGF is modulated by glycosaminoglycans, located both in the extracellular matrix and on the cell surface.

These molecules are crucial in wound healing. Such a dynamic mechanism is interactive and depends on an adequate regulation of fibroblasts.

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

A Fibroblast is a kind of cell that stimulates the proliferation of keratinocytes and the creation of reticular and elastic fibers, and glycoproteins located 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, undergoing gradual differentiation until they join the stratum corneum where they create a layer of enucleated, flattened, strongly keratinized cells named squamous cells. This layer creates an effective barrier to the entry of foreign matter and infectious agents in the body and minimizes humidity loss.

The Healing Process and Keratinized Cells

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

The simplest definition of a stem cell in an adult organism is any cell with an elevated capability for self-renewal that remains throughout adult life. In addition, stem cells are commonly considered to have the potential to produce differentiated progeny.

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

The IFE supports constant turnover and there is always a need to replace the dead, ultimately specialized cells of the external cornified layers through the proliferation of cells in the basal layer.

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

After exposure to appropriate mesenchymal signals, cells of the interfollicular epidermis are capable of giving rise to hair or sebaceous descendants. There is, nevertheless, evidence for the presence of distinct stem cell populations within the IFE and sebaceous gland. These findings can be reconciled by verifying that there are separate stem cell populations within the hair, sebaceous gland and IFE.

Each of these can create daughters that differentiate along any of the epidermal lineages. In steady conditions, however, the stem cells usually give rise to a more selected repertoire in response to signals from the local microenvironment.