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Examining Skin: A Functional Barrier
By: Marie Alice Dibon, PharmD
Posted: March 2, 2012, from the March 2012 issue of GCI Magazine.
page 9 of 13
Because time and maturation speed cannot be considered as an isolated notion, we also have to consider relative speed. If the speed is too great, it becomes a problem unto itself, but it also becomes a relative problem: In perfectly healthy skin, variations in the migration speed exist and are compensated by cell synchronization. Cells talk to one another and make sure that they, more or less, all function on the same rhythms.
Biological rhythms are regulated by a host of systems—a central clock (regulated mainly by light), peripheral clocks (clock genes, individual cellular genes activated by light), light itself and other cues, and the cells themselves, communicating among each other with signaling molecules. And when moving upward to the skin surface, cells move in columns. If two groups of columns move at different speeds, and that difference is too great or if the synchronization systems between cells falter (impaired cell communication is a common characteristic of aging skin), cells will come to the surface in different states and create different zones on the skin. In this case, there is no longer a harmonized synchronization between differentiation and proliferation. And that is the case and cause of blotchy skin. Patches of skin with an immature barrier, and thus an impaired barrier function, are created by the conditions noted.
Largely caused by the loss of synchronization between the cells, the loss of homogeneity in the look of skin is one of the marked signs of aging. Most of the time, areas lacking homogeneity are the result of inflammatory reaction, which could be represented as micro volcanoes: The cells go up very fast just like the lava in the cone of the volcano, pushing the cells outward too fast. The cells in those zones tend to hyper-proliferate and move toward the surface very fast.
But not only will the inflammation create a hyperpigmentation, it also creates an impaired barrier; thus exposing the skin to more inflammation [Editor’s note: Inflammation is further discussed in Inflammation and Aging].
Often, attempts are made to treat hyperpigmentation with exfoliation; this is a losing tactic for multiple reasons—notably when inflammation occurs, it activates a number of immune skin cells, as well as very specific enzymes (metalloproteases) that destroy specific components of the extracellular matrix in the dermis and key elements of the basement membrane/basal layer. Under these conditions, melanocytes, which usually stay above the basal layer, literally fall into the dermis, under the basal layer, where they stay permanently and give rise to an age spot.
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